William Phillips: Nobel laureate talks about his passion for quantum physics

1
00:00:08,240 --> 00:00:11,199
Hello, and welcome to the Physics World weekly

2
00:00:11,199 --> 00:00:11,699
podcast.

3
00:00:12,240 --> 00:00:14,900
This episode is part of our ongoing

4
00:00:15,684 --> 00:00:16,184
celebration

5
00:00:16,484 --> 00:00:19,925
of the International Year of Quantum Science and

6
00:00:19,925 --> 00:00:20,425
Technology,

7
00:00:21,204 --> 00:00:24,984
and it features the Nobel Laureate William Phillips

8
00:00:25,364 --> 00:00:26,024
in conversation

9
00:00:26,644 --> 00:00:28,904
with Physics World's Margaret Harris.

10
00:00:29,629 --> 00:00:32,530
This episode is supported by Atlas Technologies.

11
00:00:33,630 --> 00:00:36,289
Atlas custom aluminum and titanium

12
00:00:36,670 --> 00:00:39,489
vacuum chambers and hermetically sealed,

13
00:00:39,789 --> 00:00:41,570
bonded bimetal components

14
00:00:42,109 --> 00:00:44,129
are used in quantum applications,

15
00:00:44,954 --> 00:00:46,895
physics labs, and semiconductor

16
00:00:47,354 --> 00:00:47,854
fabs.

17
00:00:48,234 --> 00:00:50,655
And they are built in a fully integrated

18
00:00:50,875 --> 00:00:54,015
facility with on-site design, development,

19
00:00:54,395 --> 00:00:55,375
and manufacturing

20
00:00:55,835 --> 00:00:56,335
capabilities.

21
00:00:57,289 --> 00:01:00,829
Let Atlas help you solve your next engineering

22
00:01:01,210 --> 00:01:01,710
challenge.

23
00:01:02,250 --> 00:01:06,750
Learn more at atlasuhv.com.

24
00:01:07,209 --> 00:01:08,430
Here's that conversation

25
00:01:08,890 --> 00:01:10,189
with Bill Phillips.

26
00:01:10,594 --> 00:01:12,614
He talks about quantum entanglement,

27
00:01:13,234 --> 00:01:14,295
atomic clocks,

28
00:01:14,594 --> 00:01:16,534
the future of quantum technologies,

29
00:01:17,155 --> 00:01:18,454
and much more.

30
00:01:26,209 --> 00:01:28,129
It's the International Year of Quantum Science and

31
00:01:28,129 --> 00:01:30,450
Technology. I'm speaking with a real pioneer in

32
00:01:30,450 --> 00:01:33,489
this field. Bill Phillips shared the 1997

33
00:01:33,489 --> 00:01:35,649
Nobel Prize in Physics for his contributions to

34
00:01:35,649 --> 00:01:38,530
laser cooling, which uses light from precisely tuned

35
00:01:38,530 --> 00:01:40,689
laser beams to slow atoms down and reduce

36
00:01:40,689 --> 00:01:43,394
their temperature to just above absolute zero. Hello,

37
00:01:43,394 --> 00:01:44,614
Bill. Welcome to the podcast.

38
00:01:45,155 --> 00:01:46,134
Glad to be here.

39
00:01:46,594 --> 00:01:48,754
So how did you first become interested in

40
00:01:48,754 --> 00:01:51,155
quantum physics? Well, I guess that,

41
00:01:51,474 --> 00:01:52,375
as an undergraduate,

42
00:01:52,754 --> 00:01:54,269
I was invited by,

43
00:01:55,310 --> 00:01:57,709
one of the, the professors at the college

44
00:01:57,709 --> 00:01:59,170
I went to, a small college.

45
00:02:00,030 --> 00:02:02,509
There was only four physics majors who graduated

46
00:02:02,509 --> 00:02:05,090
with me. But I was invited to participate

47
00:02:05,149 --> 00:02:06,929
in research that he was doing

48
00:02:07,334 --> 00:02:09,655
on what we called electron spin resonance. In

49
00:02:09,655 --> 00:02:11,354
other words, what we were doing was

50
00:02:11,735 --> 00:02:12,235
using

51
00:02:12,775 --> 00:02:13,275
the,

52
00:02:14,615 --> 00:02:15,995
flipping of of,

53
00:02:16,694 --> 00:02:19,574
unpaired spins in a in this case, in

54
00:02:19,574 --> 00:02:20,235
a solid,

55
00:02:21,439 --> 00:02:23,860
sample as a way of investigating

56
00:02:24,240 --> 00:02:25,460
the the structure

57
00:02:25,919 --> 00:02:26,419
behavior

58
00:02:26,800 --> 00:02:27,280
of,

59
00:02:27,599 --> 00:02:28,419
of a particular,

60
00:02:29,280 --> 00:02:29,780
compound.

61
00:02:30,319 --> 00:02:33,615
And this is a fundamentally quantum mechanical thing.

62
00:02:33,935 --> 00:02:36,814
The the direction in which the spins can

63
00:02:36,814 --> 00:02:38,435
point is a quantized,

64
00:02:39,375 --> 00:02:39,875
quantity.

65
00:02:40,254 --> 00:02:41,474
It, unlike

66
00:02:41,855 --> 00:02:44,335
a spinning top, which in principle, you could

67
00:02:44,335 --> 00:02:47,259
have the axis pointing any direction you want.

68
00:02:47,560 --> 00:02:49,819
Spins, electron spins, or any other,

69
00:02:50,680 --> 00:02:53,819
spins, proton spins can only have certain

70
00:02:54,360 --> 00:02:56,360
directions in which they can spin. A spin,

71
00:02:56,360 --> 00:02:58,120
what we call spin one half. That is

72
00:02:58,120 --> 00:03:00,544
something that has the the smallest amount of

73
00:03:00,544 --> 00:03:02,164
angular momentum allowed,

74
00:03:02,944 --> 00:03:05,745
by by quantum mechanics. And that kind of

75
00:03:05,745 --> 00:03:07,264
a spin only has two different,

76
00:03:07,824 --> 00:03:08,724
possible orientations.

77
00:03:09,185 --> 00:03:12,944
Itself, a pretty weird thing. Why why is

78
00:03:12,944 --> 00:03:14,384
this? It's it's one of the things that

79
00:03:14,384 --> 00:03:15,044
I found

80
00:03:15,739 --> 00:03:16,719
really fascinating,

81
00:03:17,659 --> 00:03:19,819
at the beginning of my scientific career, the

82
00:03:19,979 --> 00:03:22,539
this what we called space quantization, the fact

83
00:03:22,539 --> 00:03:24,859
that, that you could only have two possible

84
00:03:24,859 --> 00:03:25,359
directions.

85
00:03:25,819 --> 00:03:27,519
So I was beginning

86
00:03:27,979 --> 00:03:30,799
to to be part of the quantum adventure

87
00:03:31,215 --> 00:03:33,295
as as an undergraduate. And in a certain

88
00:03:33,295 --> 00:03:33,795
sense,

89
00:03:34,735 --> 00:03:37,215
everything is quantum mechanical. I mean, we wouldn't

90
00:03:37,215 --> 00:03:37,955
be here.

91
00:03:38,254 --> 00:03:40,435
We wouldn't be able to have this conversation.

92
00:03:40,895 --> 00:03:43,215
There wouldn't even be rocks around if it

93
00:03:43,215 --> 00:03:44,594
wasn't for quantum mechanics.

94
00:03:45,769 --> 00:03:48,169
Matter as we know it could not exist

95
00:03:48,169 --> 00:03:51,289
without quantum mechanics. So to to say, you

96
00:03:51,289 --> 00:03:52,889
know, how did I get started in quantum

97
00:03:52,889 --> 00:03:53,789
mechanics? Well,

98
00:03:55,370 --> 00:03:57,150
that's all there is. But

99
00:03:57,495 --> 00:03:58,715
interestingly then,

100
00:03:59,655 --> 00:04:00,534
I I did a,

101
00:04:02,055 --> 00:04:05,435
a semester study at, Argonne National Laboratory,

102
00:04:06,215 --> 00:04:08,775
outside of Chicago and working on the same

103
00:04:08,775 --> 00:04:09,629
kind of thing,

104
00:04:10,669 --> 00:04:11,169
with,

105
00:04:12,030 --> 00:04:13,650
scientists who became my mentors,

106
00:04:14,750 --> 00:04:15,250
two,

107
00:04:16,350 --> 00:04:17,970
physicists from Argentina

108
00:04:18,430 --> 00:04:20,910
who became my my mentors for that that

109
00:04:20,910 --> 00:04:21,410
semester,

110
00:04:21,949 --> 00:04:24,884
also working on on electron spin resonance

111
00:04:25,585 --> 00:04:27,504
essentially full time. You know, this is my

112
00:04:27,504 --> 00:04:28,324
first introduction

113
00:04:28,865 --> 00:04:30,564
to people who are doing research,

114
00:04:31,345 --> 00:04:34,324
full time. And then I was invited by

115
00:04:34,785 --> 00:04:37,264
the the man who became my thesis adviser

116
00:04:37,264 --> 00:04:38,725
at MIT, Dan Kleppner,

117
00:04:39,769 --> 00:04:40,329
an amazing physicist.

118
00:04:43,209 --> 00:04:45,230
He taught me so much, really taught me

119
00:04:45,769 --> 00:04:47,230
how to think like a physicist.

120
00:04:47,850 --> 00:04:48,350
And,

121
00:04:49,769 --> 00:04:51,230
again, doing resonance,

122
00:04:52,170 --> 00:04:53,689
in different ways in different,

123
00:04:54,685 --> 00:04:57,584
systems, but using this quantum mechanical,

124
00:04:58,524 --> 00:04:59,665
idea of,

125
00:05:00,365 --> 00:05:03,245
of quantum mechanical spins in a different way.

126
00:05:03,245 --> 00:05:06,444
And it was in his laboratory that I

127
00:05:06,444 --> 00:05:07,745
first encountered

128
00:05:08,279 --> 00:05:09,259
tunable lasers,

129
00:05:10,040 --> 00:05:11,740
another wonderful tool

130
00:05:12,199 --> 00:05:12,699
for

131
00:05:13,160 --> 00:05:15,339
using the the quantum properties

132
00:05:15,639 --> 00:05:16,379
of matter

133
00:05:16,759 --> 00:05:19,879
to to explore what's what's going on at

134
00:05:19,879 --> 00:05:21,100
the atomic level.

135
00:05:21,535 --> 00:05:23,375
That was the thing that that led me

136
00:05:23,375 --> 00:05:24,355
to laser cooling.

137
00:05:24,975 --> 00:05:27,214
Now you mentioned that the idea that spin

138
00:05:27,214 --> 00:05:28,895
is quantized is not like a clock, that

139
00:05:28,895 --> 00:05:30,654
it can only have, you know, spin up,

140
00:05:30,654 --> 00:05:31,395
spin down.

141
00:05:31,775 --> 00:05:33,314
You mentioned that being sort of counterintuitive.

142
00:05:33,615 --> 00:05:35,455
A lot of people come across quantum mechanics

143
00:05:35,455 --> 00:05:37,319
and think, oh, this is this is so

144
00:05:37,319 --> 00:05:39,240
weird. This is so strange. Did you did

145
00:05:39,240 --> 00:05:42,040
you find it strange? Well, probably not at

146
00:05:42,040 --> 00:05:42,699
the beginning.

147
00:05:43,160 --> 00:05:45,259
That is the my my first introductions

148
00:05:45,720 --> 00:05:48,120
to quantum mechanics I mean, certainly the the

149
00:05:48,120 --> 00:05:50,545
the spin quantization is strange, but probably the

150
00:05:50,545 --> 00:05:52,964
things that are most weird about quantum mechanics,

151
00:05:53,824 --> 00:05:55,204
superposition and entanglement

152
00:05:55,584 --> 00:05:57,425
were not the first things that I learned

153
00:05:57,425 --> 00:05:59,824
about, quantum mechanics. Now the fact of the

154
00:05:59,824 --> 00:06:01,764
matter is I'm the kind of person

155
00:06:02,160 --> 00:06:04,420
that is just enthralled by everything.

156
00:06:05,199 --> 00:06:06,420
My my colleagues,

157
00:06:07,680 --> 00:06:10,259
sometimes joke that I'm I'm I'm just

158
00:06:10,879 --> 00:06:13,360
so entranced by everything that happens in the

159
00:06:13,360 --> 00:06:16,474
natural world. You know, drop something. Oh, wow.

160
00:06:16,474 --> 00:06:17,375
It's accelerating.

161
00:06:19,034 --> 00:06:19,194
Yeah.

162
00:06:20,154 --> 00:06:22,474
So so I guess that that when I

163
00:06:22,474 --> 00:06:25,115
first was introduced to quantum mechanics as a

164
00:06:25,115 --> 00:06:26,175
boy reading,

165
00:06:26,949 --> 00:06:29,589
books about about quantum mechanics. I was I

166
00:06:29,589 --> 00:06:32,310
was enthralled with with the ideas, but I

167
00:06:32,310 --> 00:06:33,689
don't think it was until

168
00:06:34,389 --> 00:06:36,490
it wasn't until I was in graduate school

169
00:06:36,709 --> 00:06:37,610
that I understood

170
00:06:38,470 --> 00:06:40,409
the deeply weird nature

171
00:06:40,709 --> 00:06:40,870
of,

172
00:06:41,735 --> 00:06:43,814
of quantum mechanics. And I don't think even

173
00:06:43,814 --> 00:06:45,995
in graduate school did I understand

174
00:06:46,295 --> 00:06:47,274
how strange,

175
00:06:48,295 --> 00:06:51,514
entanglement is. Only when I started to study,

176
00:06:52,375 --> 00:06:53,435
what John Bell

177
00:06:53,814 --> 00:06:55,735
had done. Okay. Maybe I should back up

178
00:06:55,735 --> 00:06:58,639
a little bit. Nineteen thirty five, Einstein with

179
00:06:58,639 --> 00:07:00,800
two of his friends, Podolsky and Rosen, write

180
00:07:00,800 --> 00:07:02,979
a paper in which they claim

181
00:07:03,439 --> 00:07:05,939
quantum mechanics just can't be the whole story.

182
00:07:06,560 --> 00:07:08,100
Because if it were,

183
00:07:08,795 --> 00:07:11,115
then things would be just so weird it

184
00:07:11,115 --> 00:07:13,754
couldn't possibly you couldn't possibly believe that the

185
00:07:13,754 --> 00:07:15,514
world was this weird. And what they were

186
00:07:15,514 --> 00:07:16,654
talking about was

187
00:07:17,035 --> 00:07:19,115
they they said, here's here's a a system

188
00:07:19,115 --> 00:07:20,095
in which two

189
00:07:20,395 --> 00:07:22,795
quantum objects are are entangled. What do we

190
00:07:22,795 --> 00:07:23,774
mean by entangled?

191
00:07:24,149 --> 00:07:27,430
Okay. When you measure something quantum mechanic, let's

192
00:07:27,430 --> 00:07:28,410
say it's a spin.

193
00:07:29,110 --> 00:07:30,790
It could be either up or down. But

194
00:07:30,790 --> 00:07:33,269
the wonderful and amazing thing about quantum mechanics

195
00:07:33,269 --> 00:07:35,529
is it can be in a superposition state

196
00:07:35,589 --> 00:07:37,670
of being up and down. Now how I

197
00:07:37,670 --> 00:07:38,564
describe that

198
00:07:39,125 --> 00:07:40,805
is very difficult to do because there's no

199
00:07:40,805 --> 00:07:43,685
classical analog. Sometimes I say it's both up

200
00:07:43,685 --> 00:07:45,064
and down at the same time.

201
00:07:45,444 --> 00:07:47,685
I have colleagues who say the right way

202
00:07:47,685 --> 00:07:49,764
to describe it is to say it's neither

203
00:07:49,764 --> 00:07:50,745
up nor down.

204
00:07:51,444 --> 00:07:53,519
But but in any case, somehow or other,

205
00:07:53,519 --> 00:07:55,139
it's not up or down.

206
00:07:55,839 --> 00:07:56,979
It has the potential

207
00:07:57,279 --> 00:07:59,360
for being either when I measure it. And

208
00:07:59,360 --> 00:08:01,360
when I measure it, it will be one

209
00:08:01,360 --> 00:08:03,599
or the other. And there's no way that

210
00:08:03,599 --> 00:08:04,819
I could predict beforehand

211
00:08:05,279 --> 00:08:07,680
which one it'll be if I initially prepare

212
00:08:07,680 --> 00:08:09,754
it in this state we call a superposition,

213
00:08:10,134 --> 00:08:13,014
which is hard to describe because it's quantum

214
00:08:13,014 --> 00:08:14,875
mechanical, and we don't have an analog

215
00:08:15,414 --> 00:08:16,154
in our

216
00:08:16,694 --> 00:08:17,194
ordinary

217
00:08:17,574 --> 00:08:19,435
everyday classical world.

218
00:08:19,894 --> 00:08:21,914
But the but the cool thing about entanglement

219
00:08:21,975 --> 00:08:24,660
is that you can have two particles that

220
00:08:24,660 --> 00:08:25,720
are in a state

221
00:08:26,259 --> 00:08:27,720
such that when measured,

222
00:08:28,420 --> 00:08:30,259
if you measure one of the particles to

223
00:08:30,259 --> 00:08:33,700
be up, the other particle will necessarily be

224
00:08:33,700 --> 00:08:34,200
down.

225
00:08:34,575 --> 00:08:36,254
But before you do it, you have no

226
00:08:36,254 --> 00:08:38,014
idea whether that first particle is gonna be

227
00:08:38,014 --> 00:08:39,855
up or down. But once you've measured that

228
00:08:39,855 --> 00:08:41,774
one, you know what the other one's gonna

229
00:08:41,774 --> 00:08:43,795
be even though beforehand,

230
00:08:44,175 --> 00:08:45,855
you'd have no way of predicting what that

231
00:08:45,855 --> 00:08:48,670
other one would be and even though there's

232
00:08:48,670 --> 00:08:49,570
no connection

233
00:08:50,190 --> 00:08:52,269
between those two particles, they could be so

234
00:08:52,269 --> 00:08:55,230
far apart that no signal traveling at the

235
00:08:55,230 --> 00:08:57,790
speed of light could get from one particle

236
00:08:57,790 --> 00:09:00,610
to the other to tell that second particle,

237
00:09:00,750 --> 00:09:02,529
you'd better be down now,

238
00:09:03,055 --> 00:09:05,134
because the other the first one was measured

239
00:09:05,134 --> 00:09:05,875
to be up.

240
00:09:06,415 --> 00:09:06,915
So

241
00:09:08,014 --> 00:09:10,735
Einstein and Podolsky and Rosen had a not

242
00:09:10,735 --> 00:09:12,115
exactly that situation,

243
00:09:12,815 --> 00:09:14,035
but a similar situation

244
00:09:14,575 --> 00:09:15,715
and showed,

245
00:09:16,320 --> 00:09:18,399
in in their paper that this is just

246
00:09:18,399 --> 00:09:21,139
too weird. How could nature be like this?

247
00:09:21,920 --> 00:09:23,139
Bohr wrote a response

248
00:09:23,840 --> 00:09:26,180
that everybody agrees was totally inadequate,

249
00:09:26,960 --> 00:09:28,639
saying no. This is just the way things

250
00:09:28,639 --> 00:09:29,139
are.

251
00:09:29,654 --> 00:09:33,014
And what Bell did was he said, look.

252
00:09:33,014 --> 00:09:36,054
Let's make some very simple assumptions. Let's make

253
00:09:36,054 --> 00:09:38,394
the assumption that the property of an object

254
00:09:39,174 --> 00:09:40,954
exists before you measure it.

255
00:09:41,334 --> 00:09:43,034
Seems like a reasonable assumption.

256
00:09:43,389 --> 00:09:45,149
You know, permanence of objects that we learn

257
00:09:45,149 --> 00:09:47,870
as babies, you know, that, that things exist

258
00:09:47,870 --> 00:09:49,570
even though we're not looking at them.

259
00:09:50,029 --> 00:09:52,429
And then let's also assume that I only

260
00:09:52,429 --> 00:09:53,649
need to understand

261
00:09:54,190 --> 00:09:57,409
what happens in the immediate vicinity of something

262
00:09:57,514 --> 00:09:59,274
in order to know everything I need to

263
00:09:59,274 --> 00:10:01,115
know about that. In other words, if I'm

264
00:10:01,115 --> 00:10:03,375
gonna be making some measurements in the next

265
00:10:03,674 --> 00:10:04,174
microsecond,

266
00:10:04,634 --> 00:10:07,294
I don't need to know what's going on

267
00:10:07,835 --> 00:10:10,654
more than a microsecond away traveling at the,

268
00:10:10,875 --> 00:10:13,500
the speed of light. Those two things sound

269
00:10:13,500 --> 00:10:15,200
like perfectly reasonable ideas.

270
00:10:16,059 --> 00:10:17,980
And what Bell showed was that if you

271
00:10:17,980 --> 00:10:18,879
made those assumptions,

272
00:10:19,500 --> 00:10:20,240
you would

273
00:10:20,700 --> 00:10:23,259
predict results that were in contradiction to quantum

274
00:10:23,259 --> 00:10:23,759
mechanics.

275
00:10:24,379 --> 00:10:26,539
So now it was basically what Einstein had

276
00:10:26,539 --> 00:10:29,464
already done, but in a very clear way

277
00:10:29,684 --> 00:10:32,904
that could capture the attention of every physicist.

278
00:10:33,365 --> 00:10:36,084
The trouble with Einstein's nineteen thirty five paper,

279
00:10:36,084 --> 00:10:38,084
what we call the EPR paper for Einstein

280
00:10:38,084 --> 00:10:41,549
Podolsky Rosen, was that most people thought, this

281
00:10:41,549 --> 00:10:44,750
is some technical thing. It's it's a very

282
00:10:44,750 --> 00:10:46,990
subtle point. We don't need to worry about

283
00:10:46,990 --> 00:10:48,610
this. Well, Bell said, look,

284
00:10:50,110 --> 00:10:51,950
if you believe in quantum mechanics, then that

285
00:10:51,950 --> 00:10:54,769
means you can't believe in these completely reasonable

286
00:10:54,830 --> 00:10:55,330
ideas.

287
00:10:55,855 --> 00:10:58,654
And I think that captured people's attention in

288
00:10:58,654 --> 00:11:01,215
a way that that Einstein's paper had not

289
00:11:01,215 --> 00:11:02,894
because people said we don't have to worry

290
00:11:02,894 --> 00:11:04,654
about this. This is a technicality. It's not

291
00:11:04,654 --> 00:11:06,975
gonna affect us. But the amazing thing was

292
00:11:06,975 --> 00:11:08,674
that nobody had yet done an experiment,

293
00:11:09,879 --> 00:11:10,779
to show

294
00:11:11,320 --> 00:11:13,820
whether quantum mechanics was right in this situation

295
00:11:13,879 --> 00:11:16,759
or whether what we call local realism was

296
00:11:16,759 --> 00:11:18,600
right. That what I've described you is basically

297
00:11:18,600 --> 00:11:21,000
a way of of of describing what we

298
00:11:21,000 --> 00:11:22,059
call local realism.

299
00:11:23,285 --> 00:11:25,684
There's a perfectly reasonable idea that quantum mechanics

300
00:11:25,684 --> 00:11:26,665
says isn't true.

301
00:11:27,045 --> 00:11:28,825
And now we have the experiments

302
00:11:29,205 --> 00:11:31,705
done by first John Clauser and then by

303
00:11:31,845 --> 00:11:34,965
Alan Aspey and then all sorts of extra

304
00:11:34,965 --> 00:11:35,764
things by,

305
00:11:36,165 --> 00:11:37,225
Anton Zeilinger.

306
00:11:37,600 --> 00:11:39,360
And I mentioned those three because the three

307
00:11:39,360 --> 00:11:41,519
of them got the Nobel Prize in, what,

308
00:11:41,519 --> 00:11:42,820
2022,

309
00:11:43,759 --> 00:11:47,600
for their experiments basically proved that Einstein was

310
00:11:47,600 --> 00:11:50,980
wrong. Nature, yes, is indeed that weird.

311
00:11:51,284 --> 00:11:53,204
I didn't understand that even as a graduate

312
00:11:53,204 --> 00:11:55,144
student. How how

313
00:11:55,605 --> 00:11:57,784
deliciously weird nature is

314
00:11:58,245 --> 00:11:59,544
because of quantum mechanics.

315
00:12:00,324 --> 00:12:02,164
Would you say that entangled then was the

316
00:12:02,164 --> 00:12:04,264
most challenging concept in quantum

317
00:12:05,329 --> 00:12:07,269
mechanics you've come across in your work?

318
00:12:07,730 --> 00:12:11,029
Most challenging? Let's say the most deliciously weird,

319
00:12:11,809 --> 00:12:14,070
because it's it's easy enough to describe.

320
00:12:14,610 --> 00:12:16,850
I can write down an entangled state. It's

321
00:12:16,850 --> 00:12:18,389
pretty easy. But to understand

322
00:12:18,745 --> 00:12:21,325
how weird that is, that's the thing that's,

323
00:12:22,024 --> 00:12:24,125
that's really, I think, so impressive

324
00:12:24,585 --> 00:12:26,925
about quantum mechanics is that it's so deliciously

325
00:12:26,985 --> 00:12:28,764
weird. So it's not like it's that hard

326
00:12:29,384 --> 00:12:31,065
to it's not that hard to understand in

327
00:12:31,065 --> 00:12:32,039
a formal sense,

328
00:12:33,000 --> 00:12:35,079
but it's hard to get your mind wrapped

329
00:12:35,079 --> 00:12:37,159
around it because it is so weird and

330
00:12:37,159 --> 00:12:37,659
so

331
00:12:38,199 --> 00:12:40,379
distinct from the kinds of things that we,

332
00:12:42,039 --> 00:12:44,714
experience on a day to day basis. And

333
00:12:45,495 --> 00:12:48,154
the the thing that it violates, local realism,

334
00:12:48,294 --> 00:12:49,195
is so reasonable.

335
00:12:49,815 --> 00:12:51,654
You know, Einstein said, are you telling me

336
00:12:51,654 --> 00:12:53,575
the moon doesn't exist when I when I

337
00:12:53,575 --> 00:12:55,355
don't look at it? You know, it

338
00:12:56,695 --> 00:12:59,259
What quantum principle would you say has had

339
00:12:59,259 --> 00:13:01,980
the biggest impact on your own turning from

340
00:13:01,980 --> 00:13:05,339
your your university experiences onto the work you've

341
00:13:05,339 --> 00:13:06,700
done and the work you continue to do

342
00:13:06,700 --> 00:13:08,539
now? For me, look, the things that I've

343
00:13:08,539 --> 00:13:11,279
done with laser cooling are pretty garden variety

344
00:13:11,419 --> 00:13:12,399
compared to,

345
00:13:13,134 --> 00:13:14,335
entanglement and,

346
00:13:14,975 --> 00:13:16,034
and and superposition.

347
00:13:16,654 --> 00:13:17,154
So

348
00:13:17,455 --> 00:13:19,774
laser cooling, I would say it's just, you

349
00:13:19,774 --> 00:13:22,095
know, the quantization of energy levels. That's the

350
00:13:22,095 --> 00:13:24,034
thing that that has driven,

351
00:13:24,815 --> 00:13:26,274
the idea of laser cooling,

352
00:13:26,809 --> 00:13:28,190
but it has enabled

353
00:13:28,809 --> 00:13:30,190
laser cooling has enabled

354
00:13:30,809 --> 00:13:32,110
the creation of,

355
00:13:32,649 --> 00:13:36,089
atomic clocks of incredible precision. And these atomic

356
00:13:36,089 --> 00:13:36,589
clocks

357
00:13:36,889 --> 00:13:40,110
fundamentally use superposition. It's the bread and butter

358
00:13:40,524 --> 00:13:41,584
of atomic clocks.

359
00:13:42,044 --> 00:13:44,865
The process known as, Ramsey spectroscopy

360
00:13:46,044 --> 00:13:48,384
uses entanglements. It's one of the early

361
00:13:49,325 --> 00:13:49,825
practical,

362
00:13:50,524 --> 00:13:51,825
applications of entanglement.

363
00:13:52,284 --> 00:13:55,084
So you take, an atomic system that has

364
00:13:55,084 --> 00:13:56,225
two energy levels.

365
00:13:58,230 --> 00:14:00,649
And the Ramsey method, what it does is

366
00:14:00,870 --> 00:14:03,610
it you put in a pulse of, say,

367
00:14:03,990 --> 00:14:06,730
radio frequency or microwaves or laser light,

368
00:14:07,110 --> 00:14:07,850
in more

369
00:14:08,230 --> 00:14:09,909
the more modern way of doing it and

370
00:14:09,909 --> 00:14:12,284
put the atom into a superposition of these

371
00:14:12,284 --> 00:14:12,944
two states.

372
00:14:13,804 --> 00:14:16,764
What that means is that the the atomic

373
00:14:16,764 --> 00:14:19,324
system will evolve in a certain sense. That

374
00:14:19,324 --> 00:14:20,944
is something is pulsating

375
00:14:21,245 --> 00:14:23,404
or rotating in the atomic system if you

376
00:14:23,404 --> 00:14:23,904
like,

377
00:14:24,444 --> 00:14:27,009
at a frequency that is equal to the

378
00:14:27,009 --> 00:14:29,490
frequency difference between those two states. And then

379
00:14:29,490 --> 00:14:31,490
after a certain length of time, the longer

380
00:14:31,490 --> 00:14:34,129
the better, you give it another pulse. And

381
00:14:34,129 --> 00:14:38,175
depending upon the phase of of that pulse,

382
00:14:38,175 --> 00:14:40,175
be it a, you know, radio frequency or

383
00:14:40,175 --> 00:14:42,735
light or whatever, it's some oscillating thing. The

384
00:14:42,735 --> 00:14:44,754
phase of that thing compared to the phase

385
00:14:44,975 --> 00:14:47,875
of the atomic system, you'll either promote,

386
00:14:48,495 --> 00:14:49,075
the atom

387
00:14:49,690 --> 00:14:51,129
to the state different from the one you

388
00:14:51,129 --> 00:14:52,570
started in or put it back in the

389
00:14:52,570 --> 00:14:54,649
state that you started with. And the longer

390
00:14:54,649 --> 00:14:56,110
you wait, the more

391
00:14:56,490 --> 00:14:56,990
precisely

392
00:14:57,370 --> 00:14:58,269
you'll know

393
00:14:58,970 --> 00:15:00,889
how much the phase was different. So this

394
00:15:00,889 --> 00:15:02,269
is the principle behind

395
00:15:02,595 --> 00:15:03,095
Ramsey's

396
00:15:03,714 --> 00:15:05,495
method for, making an atomic

397
00:15:06,034 --> 00:15:08,274
clock, and that's the way almost all atomic

398
00:15:08,274 --> 00:15:09,334
clocks work today.

399
00:15:09,714 --> 00:15:10,695
And my work

400
00:15:11,394 --> 00:15:13,074
and the work of my my group and

401
00:15:13,074 --> 00:15:15,495
other groups around the world who have contributed

402
00:15:15,634 --> 00:15:17,735
to this whole laser cooling enterprise

403
00:15:18,240 --> 00:15:19,860
has made atomic clocks

404
00:15:20,240 --> 00:15:21,860
of just incredible precision

405
00:15:22,240 --> 00:15:22,740
possible.

406
00:15:23,120 --> 00:15:25,299
And so I feel a a real kinship

407
00:15:25,679 --> 00:15:27,779
to the idea of of superposition

408
00:15:28,240 --> 00:15:31,059
because the major application of laser cooling

409
00:15:31,404 --> 00:15:34,225
in which I've been so so privileged to

410
00:15:34,445 --> 00:15:37,085
to to be a part of is, is

411
00:15:37,085 --> 00:15:37,904
using this,

412
00:15:38,684 --> 00:15:40,524
superposition principle. So let me tell you a

413
00:15:40,524 --> 00:15:42,705
story. Mhmm. Sure. When I first

414
00:15:43,164 --> 00:15:46,129
came to NIST, where I am now, the

415
00:15:46,429 --> 00:15:48,670
the National Institute of Standards and Technology, at

416
00:15:48,670 --> 00:15:50,110
that time, it was called the National Bureau

417
00:15:50,110 --> 00:15:50,769
of Standards.

418
00:15:51,230 --> 00:15:54,190
And, when I first came to to to

419
00:15:54,190 --> 00:15:58,129
our metrology institute in, 1978,

420
00:15:58,764 --> 00:16:01,084
The very best clock in the world was

421
00:16:01,084 --> 00:16:04,125
in our laboratories in Boulder, Colorado. Now Boulder,

422
00:16:04,125 --> 00:16:06,384
Colorado is about a kilometer and a half

423
00:16:06,524 --> 00:16:08,684
above sea level, and here I am in

424
00:16:08,684 --> 00:16:10,544
Washington close to sea level.

425
00:16:11,324 --> 00:16:12,784
Because of Einstein's

426
00:16:13,559 --> 00:16:15,340
theory of general relativity,

427
00:16:16,440 --> 00:16:19,340
he showed that clocks would run slower

428
00:16:19,720 --> 00:16:22,059
if they're deeper in a gravitational potential.

429
00:16:22,600 --> 00:16:24,379
The effect is not very big.

430
00:16:25,160 --> 00:16:27,639
At a kilometer and a half, it would

431
00:16:27,639 --> 00:16:28,379
be about

432
00:16:29,034 --> 00:16:30,394
one and a half parts in 10 to

433
00:16:30,394 --> 00:16:31,134
the 13.

434
00:16:32,235 --> 00:16:34,794
The very best clock operating in Boulder at

435
00:16:34,794 --> 00:16:36,475
an at a an altitude of one and

436
00:16:36,475 --> 00:16:37,294
a half kilometers

437
00:16:37,835 --> 00:16:39,195
was good to a part in 10 to

438
00:16:39,195 --> 00:16:39,855
the 13.

439
00:16:40,154 --> 00:16:41,674
So what that means is if you had

440
00:16:41,674 --> 00:16:44,159
two such clocks that were at the very

441
00:16:44,159 --> 00:16:46,079
best level, which we didn't have two such

442
00:16:46,079 --> 00:16:47,839
clocks, only had one. But if you had

443
00:16:47,839 --> 00:16:50,319
two such clocks, one at sea level and

444
00:16:50,319 --> 00:16:51,120
one at,

445
00:16:51,679 --> 00:16:53,620
the height of our Boulder labs,

446
00:16:54,159 --> 00:16:56,399
you would just barely not be able to

447
00:16:56,399 --> 00:16:57,434
resolve the difference.

448
00:16:58,315 --> 00:17:00,475
Today, we can resolve a difference of less

449
00:17:00,475 --> 00:17:01,375
than a millimeter

450
00:17:02,154 --> 00:17:03,774
with the clocks that exist

451
00:17:04,154 --> 00:17:04,654
today

452
00:17:05,194 --> 00:17:07,994
due in part to laser cooling and in

453
00:17:07,994 --> 00:17:09,914
part due to any number of other developments

454
00:17:09,914 --> 00:17:11,755
that have happened along the way. I just

455
00:17:11,755 --> 00:17:13,880
find that so amazing. Turning now to the

456
00:17:13,880 --> 00:17:15,400
present, actually. What are you working on now?

457
00:17:15,400 --> 00:17:17,160
Are you still involved in atomic clocks or

458
00:17:17,160 --> 00:17:18,759
in laser cooling or Well, not so much

459
00:17:18,759 --> 00:17:21,000
involved in atomic clocks. I I think of

460
00:17:21,000 --> 00:17:22,059
of our laboratory

461
00:17:22,599 --> 00:17:23,339
as having

462
00:17:24,359 --> 00:17:25,339
been a generator

463
00:17:25,640 --> 00:17:28,964
of ideas and techniques that could be used

464
00:17:28,964 --> 00:17:30,744
by people who make atomic clocks

465
00:17:31,605 --> 00:17:32,744
and that we're continuing

466
00:17:33,204 --> 00:17:34,964
to do that that that kind of thing

467
00:17:34,964 --> 00:17:37,365
to doing some of the fundamental work that

468
00:17:37,365 --> 00:17:39,765
enables other people to do some amazing things

469
00:17:39,765 --> 00:17:42,085
that that, that they're doing. So one of

470
00:17:42,085 --> 00:17:43,609
those people is,

471
00:17:44,309 --> 00:17:46,710
Junyi at in our laboratories out in Boulder

472
00:17:46,710 --> 00:17:49,509
making these clocks that are good to better

473
00:17:49,509 --> 00:17:51,289
than a part in 10 to the 18.

474
00:17:51,990 --> 00:17:53,829
Okay? But the same kind of work is

475
00:17:53,829 --> 00:17:56,444
going on at the National Physical Laboratory. So

476
00:17:56,444 --> 00:17:58,845
there's atomic clock groups there where they're doing

477
00:17:58,845 --> 00:18:00,944
microwave clocks and optical clocks

478
00:18:01,404 --> 00:18:01,904
and,

479
00:18:02,444 --> 00:18:06,284
just amazing, amazing things. Again, using laser cooling

480
00:18:06,284 --> 00:18:06,784
techniques.

481
00:18:07,244 --> 00:18:10,304
But but we're doing all kinds of,

482
00:18:11,299 --> 00:18:14,019
adventures using ultra cold atoms. So ultra cold

483
00:18:14,019 --> 00:18:16,819
atoms is the main theme of what our

484
00:18:16,819 --> 00:18:18,200
research group is doing,

485
00:18:18,980 --> 00:18:21,859
which came from laser cooling, but other tricks

486
00:18:21,859 --> 00:18:22,519
as well.

487
00:18:22,835 --> 00:18:24,994
So after you laser cool it, the coldest

488
00:18:24,994 --> 00:18:27,714
temperatures we get using laser cooling is a

489
00:18:27,714 --> 00:18:28,214
mere

490
00:18:28,674 --> 00:18:31,335
one millionth of a degree above absolute zero.

491
00:18:32,035 --> 00:18:34,434
So I know that sounds pretty cold, but

492
00:18:34,434 --> 00:18:37,289
by today's standards, it's not that cold. It's

493
00:18:37,289 --> 00:18:38,910
where the atomic clocks,

494
00:18:39,529 --> 00:18:41,870
that define what we mean by a second

495
00:18:42,170 --> 00:18:44,590
today are operating at that temperature.

496
00:18:45,049 --> 00:18:45,549
But

497
00:18:46,330 --> 00:18:49,690
those clocks, which are based on a microwave

498
00:18:49,690 --> 00:18:50,910
transition in cesium,

499
00:18:51,825 --> 00:18:53,024
They're good to about a part in 10

500
00:18:53,024 --> 00:18:54,384
of the 16. I mean, you might say,

501
00:18:54,384 --> 00:18:55,924
well, part in 10 of the 16.

502
00:18:56,784 --> 00:18:58,464
Who needs to do better than that? And

503
00:18:58,464 --> 00:19:00,784
the answer is we are never satisfied. We

504
00:19:00,784 --> 00:19:03,505
always wanna do better. And so people are

505
00:19:03,505 --> 00:19:04,944
making clocks at a part in 10 of

506
00:19:04,944 --> 00:19:06,750
the 18, but not with cesium,

507
00:19:07,130 --> 00:19:07,529
with,

508
00:19:08,009 --> 00:19:10,910
atoms like strontium or ytterbium, depending on what,

509
00:19:12,170 --> 00:19:14,109
lab you're in, aluminum ions.

510
00:19:14,650 --> 00:19:16,650
So people all over the world are making

511
00:19:16,650 --> 00:19:17,630
atomic clocks

512
00:19:18,194 --> 00:19:21,154
using laser cooling techniques, using other techniques that

513
00:19:21,154 --> 00:19:22,934
have developed in our laboratories

514
00:19:23,315 --> 00:19:24,534
and in other laboratories

515
00:19:24,835 --> 00:19:27,075
that are that are good to on the

516
00:19:27,075 --> 00:19:28,274
order of a part in 10 to the

517
00:19:28,274 --> 00:19:30,434
18. So in other words, two orders of

518
00:19:30,434 --> 00:19:31,575
magnitude better

519
00:19:32,179 --> 00:19:34,920
than the the cesium clocks, but cesium

520
00:19:35,460 --> 00:19:38,119
is the definition of the second. That is

521
00:19:38,259 --> 00:19:41,380
the formal internationally agreed upon definition of the

522
00:19:41,380 --> 00:19:43,400
second is a certain number of oscillations

523
00:19:43,859 --> 00:19:45,240
of a cesium atom.

524
00:19:45,634 --> 00:19:47,875
That's the definition of the second. And that

525
00:19:47,875 --> 00:19:48,375
definition

526
00:19:48,994 --> 00:19:50,454
is two orders of magnitude

527
00:19:50,994 --> 00:19:53,315
worse than what we can do with a

528
00:19:53,315 --> 00:19:55,254
ton of clocks. So what that means is

529
00:19:55,554 --> 00:19:57,954
we're gonna redefine what we mean by a

530
00:19:57,954 --> 00:19:58,454
second.

531
00:19:58,909 --> 00:20:01,230
And I am serving on a committee along

532
00:20:01,230 --> 00:20:04,049
with people from from all over the world

533
00:20:04,429 --> 00:20:04,929
to

534
00:20:05,230 --> 00:20:05,730
decide

535
00:20:06,109 --> 00:20:07,329
or to recommend

536
00:20:07,710 --> 00:20:09,710
to the international bodies that make the final

537
00:20:09,710 --> 00:20:10,210
decisions

538
00:20:10,509 --> 00:20:12,829
what should be the new definition of the

539
00:20:12,829 --> 00:20:13,329
second.

540
00:20:13,644 --> 00:20:14,144
And

541
00:20:15,325 --> 00:20:17,484
there's no question. The new definition of the

542
00:20:17,484 --> 00:20:19,105
second is going to be

543
00:20:19,484 --> 00:20:20,304
the oscillations

544
00:20:20,765 --> 00:20:22,304
of some atom,

545
00:20:22,684 --> 00:20:25,744
maybe some set of atoms at optical frequencies,

546
00:20:25,804 --> 00:20:28,144
not at microwave frequencies, not at nine

547
00:20:28,684 --> 00:20:29,184
gigahertz,

548
00:20:29,700 --> 00:20:30,359
but at

549
00:20:31,140 --> 00:20:32,659
something on the order of 10 to the

550
00:20:32,659 --> 00:20:33,720
15 hertz.

551
00:20:34,179 --> 00:20:36,179
Now why? I mean, when it's going so

552
00:20:36,179 --> 00:20:37,159
much more rapidly,

553
00:20:37,460 --> 00:20:39,380
it means that a lot of errors are

554
00:20:39,380 --> 00:20:42,179
much smaller as a fraction. So that's one

555
00:20:42,179 --> 00:20:43,880
of the reasons why we wanna do,

556
00:20:45,265 --> 00:20:48,305
optical quarks as as we say. And, and

557
00:20:48,305 --> 00:20:50,085
so instead of microwave

558
00:20:50,865 --> 00:20:53,265
shining onto atoms, we're gonna be shining lasers

559
00:20:53,265 --> 00:20:54,565
onto atoms. Lasers

560
00:20:54,945 --> 00:20:56,404
that have a stability

561
00:20:57,345 --> 00:20:58,085
that is

562
00:20:58,519 --> 00:21:01,960
so amazing compared to what was possible when

563
00:21:01,960 --> 00:21:04,059
I first got into the laser business.

564
00:21:04,519 --> 00:21:07,579
These lasers are are stable to

565
00:21:07,880 --> 00:21:09,099
a tiny fraction

566
00:21:09,559 --> 00:21:12,275
of a cycle per second when the light

567
00:21:12,275 --> 00:21:13,015
is oscillating

568
00:21:13,634 --> 00:21:16,295
at 10 to the 15 cycles per second.

569
00:21:17,474 --> 00:21:19,575
It's just it's just amazing. And

570
00:21:20,115 --> 00:21:20,615
so

571
00:21:20,994 --> 00:21:21,894
we have

572
00:21:22,434 --> 00:21:22,934
contributed

573
00:21:23,474 --> 00:21:25,474
to the laser cooling part of that. We've

574
00:21:25,474 --> 00:21:28,019
contributed to some of the ways in which

575
00:21:28,019 --> 00:21:30,019
the atoms are trapped because you gotta hold

576
00:21:30,019 --> 00:21:31,140
on to these atoms. If,

577
00:21:32,819 --> 00:21:34,419
if you let go of the atoms, they'll

578
00:21:34,419 --> 00:21:36,740
just fall in the gravitational field. Now we

579
00:21:36,740 --> 00:21:38,819
actually use that in the cesium clock. We

580
00:21:38,819 --> 00:21:41,345
toss the atoms up and they fall back

581
00:21:41,345 --> 00:21:42,724
down after about a second.

582
00:21:43,184 --> 00:21:44,724
But we want something

583
00:21:45,345 --> 00:21:46,484
longer than that,

584
00:21:46,865 --> 00:21:48,944
so we hold them in traps. And these

585
00:21:48,944 --> 00:21:51,105
traps have to be very carefully arranged so

586
00:21:51,105 --> 00:21:52,004
that they don't

587
00:21:52,759 --> 00:21:53,899
themselves distort

588
00:21:54,279 --> 00:21:56,539
the the ticking frequency of the atoms.

589
00:21:57,159 --> 00:21:59,879
But we're doing other things like, quantum information.

590
00:21:59,879 --> 00:22:01,579
So this is one of the big deals

591
00:22:01,960 --> 00:22:03,179
in current day,

592
00:22:03,879 --> 00:22:05,980
investigations having to do with quantum mechanics,

593
00:22:06,285 --> 00:22:07,025
is using

594
00:22:07,725 --> 00:22:10,545
single atoms or other single quantum

595
00:22:11,085 --> 00:22:11,585
entities

596
00:22:12,205 --> 00:22:13,664
as what we call qubits.

597
00:22:14,205 --> 00:22:15,184
Quantum bits,

598
00:22:16,125 --> 00:22:17,585
ordinary digital information

599
00:22:18,205 --> 00:22:20,684
is stored and processed using what we call

600
00:22:20,684 --> 00:22:22,109
bits. And those bits

601
00:22:22,569 --> 00:22:23,869
represent a mathematical

602
00:22:24,250 --> 00:22:26,269
zero or one that in binary,

603
00:22:27,369 --> 00:22:29,069
mathematics is the thing that

604
00:22:29,529 --> 00:22:32,349
allows you to store and and process information.

605
00:22:33,130 --> 00:22:35,914
And now we're gonna make those zeros or

606
00:22:35,914 --> 00:22:36,414
ones

607
00:22:36,795 --> 00:22:39,695
be represented by, say, for example, a spin

608
00:22:39,994 --> 00:22:42,555
that points up or down. The two spin

609
00:22:42,555 --> 00:22:44,174
states that we talked about earlier

610
00:22:44,634 --> 00:22:47,055
fit very nicely into the idea of binary

611
00:22:47,115 --> 00:22:50,099
logic. But the beauty is or the the

612
00:22:50,099 --> 00:22:50,599
amazingly

613
00:22:50,980 --> 00:22:54,099
difficult thing is that they can be zero

614
00:22:54,099 --> 00:22:55,779
or one, but they could be in this

615
00:22:55,779 --> 00:22:58,500
superposition state, which is neither zero or one

616
00:22:58,500 --> 00:23:00,579
or both zero or one depending on how

617
00:23:00,579 --> 00:23:02,355
you wanna describe it, which we don't really

618
00:23:02,355 --> 00:23:04,134
know how to do in classical terms.

619
00:23:04,914 --> 00:23:06,134
Sounds like a disaster

620
00:23:06,755 --> 00:23:09,015
because one of the great strengths

621
00:23:09,394 --> 00:23:10,055
of binary

622
00:23:10,755 --> 00:23:11,894
information is

623
00:23:12,355 --> 00:23:12,855
that,

624
00:23:13,634 --> 00:23:16,829
the things that store those those bits are

625
00:23:16,829 --> 00:23:18,049
things like a transistor

626
00:23:18,509 --> 00:23:20,269
that is turned on or off like a

627
00:23:20,269 --> 00:23:20,769
switch,

628
00:23:21,150 --> 00:23:24,750
a spot on a, a DVD that's burned

629
00:23:24,750 --> 00:23:25,809
or not burned,

630
00:23:26,109 --> 00:23:28,130
a patch on a magnetic

631
00:23:28,509 --> 00:23:29,009
disc

632
00:23:29,390 --> 00:23:31,970
that is magnetized in one direction

633
00:23:32,424 --> 00:23:35,164
or another. These are the things that store

634
00:23:35,704 --> 00:23:38,125
classical information, and they're so good

635
00:23:38,585 --> 00:23:41,164
that you can be really, really confident

636
00:23:41,625 --> 00:23:43,545
that this thing is one thing or the

637
00:23:43,545 --> 00:23:44,445
other. No

638
00:23:45,160 --> 00:23:46,920
uncertainty. The the the uncertainties

639
00:23:47,559 --> 00:23:49,480
the the the errors where you might get

640
00:23:49,480 --> 00:23:51,960
something that was, you know, only half burned

641
00:23:51,960 --> 00:23:53,559
or or some so you wouldn't be able

642
00:23:53,559 --> 00:23:56,200
to tell what it was. That's so tiny.

643
00:23:56,200 --> 00:23:57,884
It's just it's just ridiculous.

644
00:23:58,664 --> 00:24:00,285
And that's a wonderful strength

645
00:24:00,904 --> 00:24:01,484
of binary

646
00:24:02,424 --> 00:24:02,924
information.

647
00:24:03,305 --> 00:24:05,305
And now I'm telling you, we wanna make

648
00:24:05,305 --> 00:24:07,644
it so so nobody could know

649
00:24:08,105 --> 00:24:10,424
what the state of this thing is before

650
00:24:10,424 --> 00:24:12,285
you measure. That sounds like a disaster,

651
00:24:13,369 --> 00:24:14,269
but it's not.

652
00:24:15,609 --> 00:24:17,529
If you do the right kinds of things

653
00:24:17,529 --> 00:24:19,470
for certain kinds of problems,

654
00:24:20,409 --> 00:24:21,309
the ability

655
00:24:21,609 --> 00:24:24,970
to put the bits, now quantum bits, into

656
00:24:24,970 --> 00:24:25,470
superpositions

657
00:24:26,414 --> 00:24:28,434
means that you can do the problem

658
00:24:28,894 --> 00:24:30,755
in a lot fewer operations

659
00:24:31,775 --> 00:24:32,914
than would be

660
00:24:33,215 --> 00:24:35,295
needed to do that same problem if you

661
00:24:35,295 --> 00:24:37,875
used a classical computer with ordinary bits.

662
00:24:38,335 --> 00:24:41,315
So one of the first examples of that

663
00:24:41,849 --> 00:24:42,349
was,

664
00:24:42,809 --> 00:24:44,670
done by a guy named Peter Shor,

665
00:24:45,049 --> 00:24:47,450
nineteen ninety five. He came up with an

666
00:24:47,450 --> 00:24:47,950
algorithm

667
00:24:48,970 --> 00:24:49,470
that

668
00:24:49,769 --> 00:24:51,710
showed it was possible to factor

669
00:24:52,250 --> 00:24:52,750
numbers

670
00:24:53,289 --> 00:24:54,910
using a quantum mechanical

671
00:24:55,529 --> 00:24:56,025
approach

672
00:24:56,585 --> 00:24:59,065
in a time that would be much shorter

673
00:24:59,065 --> 00:25:00,605
or at least the number of operations

674
00:25:00,904 --> 00:25:02,984
that would be much smaller than the number

675
00:25:02,984 --> 00:25:04,285
of operations needed

676
00:25:04,904 --> 00:25:06,605
by an ordinary classical computer.

677
00:25:07,305 --> 00:25:09,705
Factoring is what is technically known as a

678
00:25:09,705 --> 00:25:10,525
hard problem.

679
00:25:11,230 --> 00:25:13,470
What that means is that the number of

680
00:25:13,470 --> 00:25:16,190
operations required to do that problem, to solve

681
00:25:16,190 --> 00:25:17,970
that problem grows exponentially

682
00:25:18,429 --> 00:25:21,549
with the size of the number. So if

683
00:25:21,549 --> 00:25:22,529
I want to

684
00:25:22,909 --> 00:25:24,690
factor a hundred digit number,

685
00:25:25,674 --> 00:25:27,355
that the time it takes to do that

686
00:25:27,355 --> 00:25:29,674
grows exponentially with how long how many digits

687
00:25:29,674 --> 00:25:30,654
that number has.

688
00:25:31,195 --> 00:25:33,275
But if you do it quantum mechanically, it

689
00:25:33,275 --> 00:25:36,154
doesn't grow exponentially, so it becomes an easy

690
00:25:36,154 --> 00:25:38,335
problem. This is absolutely amazing

691
00:25:38,650 --> 00:25:41,470
that changing the hardware on which you do

692
00:25:41,690 --> 00:25:42,429
the calculation

693
00:25:43,049 --> 00:25:45,950
has changed what we call the complexity class

694
00:25:46,410 --> 00:25:48,170
of a problem. Now I have to be

695
00:25:48,170 --> 00:25:50,109
careful because nobody's ever proved

696
00:25:50,744 --> 00:25:51,244
that

697
00:25:51,545 --> 00:25:52,285
a classical

698
00:25:52,744 --> 00:25:53,964
calculation of,

699
00:25:54,424 --> 00:25:54,924
factoring

700
00:25:55,464 --> 00:25:57,325
is exponentially hard.

701
00:25:58,105 --> 00:26:00,744
It might be that some clever mathematician will

702
00:26:00,744 --> 00:26:01,644
find an algorithm

703
00:26:02,184 --> 00:26:03,805
that makes it easy.

704
00:26:04,744 --> 00:26:07,679
Nobody thinks that's gonna happen. Everybody thinks that

705
00:26:07,679 --> 00:26:09,140
this problem is gonna remain

706
00:26:09,599 --> 00:26:11,919
exponentially hard, and that's one of the reasons

707
00:26:11,919 --> 00:26:12,419
why

708
00:26:13,359 --> 00:26:14,900
certain kinds of encryption

709
00:26:15,839 --> 00:26:16,339
are

710
00:26:16,640 --> 00:26:19,119
used with a lot of confidence. So let's

711
00:26:19,119 --> 00:26:21,784
back up. Why was it so important that

712
00:26:21,784 --> 00:26:23,325
Shor came up with this algorithm?

713
00:26:23,625 --> 00:26:26,265
And the reason is that something called public

714
00:26:26,265 --> 00:26:27,005
key encryption,

715
00:26:27,544 --> 00:26:29,384
which you may not know what that is,

716
00:26:29,384 --> 00:26:31,325
but you use it every day.

717
00:26:32,184 --> 00:26:33,244
Public key encryption

718
00:26:33,960 --> 00:26:34,940
depends upon

719
00:26:35,480 --> 00:26:37,559
the fact that it's hard to factor numbers

720
00:26:37,559 --> 00:26:40,779
but easy to multiply them. So this process,

721
00:26:41,400 --> 00:26:43,660
multiplication, is the inverse of factoring.

722
00:26:44,119 --> 00:26:45,500
And the fact that it's asymmetric

723
00:26:47,095 --> 00:26:49,335
leads to the possibility of what we call

724
00:26:49,335 --> 00:26:50,394
public key encryption.

725
00:26:51,015 --> 00:26:53,674
So let's say you buy something online. Now

726
00:26:54,054 --> 00:26:55,894
your credit card has to go to the

727
00:26:55,894 --> 00:26:57,674
company that's selling it to you.

728
00:26:58,054 --> 00:27:01,829
So your computer actually, that company sends your

729
00:27:01,829 --> 00:27:02,329
computer

730
00:27:03,269 --> 00:27:04,009
a number,

731
00:27:04,549 --> 00:27:05,690
a a big integer,

732
00:27:06,309 --> 00:27:08,089
and they know the factors

733
00:27:08,549 --> 00:27:11,349
and nobody else does because they don't know

734
00:27:11,349 --> 00:27:13,109
how to factor big numbers because it would

735
00:27:13,109 --> 00:27:15,555
take too long. It would take years or

736
00:27:15,555 --> 00:27:17,954
centuries to factor this big number, so nobody

737
00:27:17,954 --> 00:27:19,555
knows the factor. But they know the factors

738
00:27:19,555 --> 00:27:21,795
because they took two smaller numbers and multiplied

739
00:27:21,795 --> 00:27:23,335
them together, and that was easy.

740
00:27:23,634 --> 00:27:25,634
That number is then used to encrypt your

741
00:27:25,634 --> 00:27:26,694
credit card number.

742
00:27:27,529 --> 00:27:31,130
And the encryption is easy for the person

743
00:27:31,130 --> 00:27:33,369
who knows what the factors are and essentially

744
00:27:33,369 --> 00:27:35,529
impossible for the person who doesn't. So that

745
00:27:35,529 --> 00:27:37,230
means somebody trying to intercept

746
00:27:37,690 --> 00:27:38,190
the,

747
00:27:38,649 --> 00:27:41,714
transmission between your computer and the the computer

748
00:27:41,714 --> 00:27:43,335
at the ecommerce company

749
00:27:43,795 --> 00:27:45,894
can't get any useful information.

750
00:27:46,515 --> 00:27:48,934
Now what if that evil doer

751
00:27:49,474 --> 00:27:50,694
had a quantum computer?

752
00:27:51,634 --> 00:27:53,654
Then that evil doer could factor

753
00:27:54,350 --> 00:27:56,350
the the number and figure out what your

754
00:27:56,350 --> 00:27:58,990
credit card number is and then steal it

755
00:27:58,990 --> 00:28:01,490
and use it to buy, you know, TVs

756
00:28:01,549 --> 00:28:04,529
or whatever the, you know, evil doers buy.

757
00:28:05,390 --> 00:28:08,285
Now the fact of the matter is that

758
00:28:08,744 --> 00:28:09,244
probably

759
00:28:09,625 --> 00:28:12,105
you don't have enough money in your bank

760
00:28:12,105 --> 00:28:13,884
account to make it worthwhile

761
00:28:14,505 --> 00:28:17,305
for some criminal who made a quantum computer.

762
00:28:17,305 --> 00:28:18,984
We don't have quantum computers that can do

763
00:28:18,984 --> 00:28:20,825
this yet. Okay? It's not easy to make

764
00:28:20,825 --> 00:28:21,805
a quantum computer,

765
00:28:22,105 --> 00:28:24,490
even one that can do very simple problems,

766
00:28:24,490 --> 00:28:27,070
let alone one that can factor big numbers.

767
00:28:27,369 --> 00:28:28,910
But if somebody did that,

768
00:28:29,210 --> 00:28:30,670
then they could decrypt

769
00:28:31,609 --> 00:28:32,509
secret messages

770
00:28:33,130 --> 00:28:34,430
that really do matter.

771
00:28:35,369 --> 00:28:36,269
So, for example,

772
00:28:37,130 --> 00:28:37,869
the diplomatic

773
00:28:39,505 --> 00:28:40,005
communications

774
00:28:40,384 --> 00:28:40,884
between,

775
00:28:41,265 --> 00:28:43,924
say, diplomatic offices of some country

776
00:28:44,625 --> 00:28:45,605
often contain

777
00:28:46,305 --> 00:28:46,805
secrets

778
00:28:47,505 --> 00:28:50,785
that people don't want revealed for decades, that

779
00:28:50,785 --> 00:28:52,690
it would be it it would it would

780
00:28:52,690 --> 00:28:53,190
matter

781
00:28:53,730 --> 00:28:54,630
to the security

782
00:28:55,009 --> 00:28:55,509
of

783
00:28:55,889 --> 00:28:58,309
of of a country if if these diplomatic

784
00:28:58,369 --> 00:29:01,829
secrets were revealed even decades from now. Military

785
00:29:01,970 --> 00:29:02,470
secrets,

786
00:29:03,250 --> 00:29:05,525
intelligence secrets, you know, who

787
00:29:06,144 --> 00:29:08,884
is the spy and who have they

788
00:29:09,265 --> 00:29:09,765
contacted?

789
00:29:10,305 --> 00:29:12,164
These these could be devastatingly

790
00:29:12,545 --> 00:29:15,045
dangerous things if they were were revealed

791
00:29:15,585 --> 00:29:17,744
even decades from the time that they were

792
00:29:17,744 --> 00:29:19,845
first happened. And so people worry

793
00:29:20,450 --> 00:29:22,690
that sometime in the future, you're gonna have

794
00:29:22,690 --> 00:29:23,750
a quantum computer

795
00:29:24,369 --> 00:29:25,190
that could

796
00:29:25,890 --> 00:29:29,029
reveal secrets because people could wiretap

797
00:29:29,490 --> 00:29:31,410
communications, but it wouldn't do them any good

798
00:29:31,410 --> 00:29:34,025
because it's encrypted. Okay? But if you had

799
00:29:34,025 --> 00:29:36,204
a quantum computer, you could decrypt things.

800
00:29:37,224 --> 00:29:37,724
So

801
00:29:38,105 --> 00:29:40,585
what are you gonna do? Well, quantum mechanics

802
00:29:40,585 --> 00:29:41,565
comes to the rescue.

803
00:29:42,105 --> 00:29:43,964
You can have quantum communications

804
00:29:44,744 --> 00:29:48,184
that cannot be eavesdropped upon because of something

805
00:29:48,184 --> 00:29:48,684
called

806
00:29:48,990 --> 00:29:50,369
the no cloning theorem.

807
00:29:51,069 --> 00:29:51,809
An eavesdropper

808
00:29:52,349 --> 00:29:54,369
could not intercept the message,

809
00:29:54,829 --> 00:29:56,670
make a duplicate of the message, send it

810
00:29:56,670 --> 00:29:58,130
on so that the person

811
00:29:58,509 --> 00:30:01,230
receiving the message doesn't realize that the message

812
00:30:01,230 --> 00:30:01,950
has been,

813
00:30:02,349 --> 00:30:04,934
intercepted and then use that intercepted message. That's

814
00:30:04,934 --> 00:30:05,674
not allowed

815
00:30:05,974 --> 00:30:07,974
by the laws of physics. So we're very

816
00:30:07,974 --> 00:30:08,474
confident

817
00:30:09,095 --> 00:30:10,554
that these quantum,

818
00:30:11,174 --> 00:30:12,315
communication methods

819
00:30:12,694 --> 00:30:14,774
would work, and people are actually using them.

820
00:30:14,774 --> 00:30:17,095
There are places where, I'm not sure they

821
00:30:17,095 --> 00:30:19,335
need to, but they can say, look, our

822
00:30:19,335 --> 00:30:22,850
bank communicates with other banks using quantum,

823
00:30:23,549 --> 00:30:27,090
cryptography. So we know that our our transactions

824
00:30:27,549 --> 00:30:28,930
are, are secure.

825
00:30:29,470 --> 00:30:31,630
So that's one way. Another way is a

826
00:30:31,630 --> 00:30:33,789
classical approach where you come up with new

827
00:30:33,789 --> 00:30:34,850
encryption algorithms

828
00:30:35,265 --> 00:30:36,404
called post quantum

829
00:30:36,705 --> 00:30:39,365
encryption that are not dependent upon

830
00:30:39,664 --> 00:30:41,904
this asymmetry of factoring and,

831
00:30:42,545 --> 00:30:43,525
and and multiplying.

832
00:30:43,904 --> 00:30:45,904
And then these will not be able to

833
00:30:45,904 --> 00:30:48,005
be attacked by a quantum computer

834
00:30:48,785 --> 00:30:50,160
as far as we know.

835
00:30:50,720 --> 00:30:51,940
No one has proved

836
00:30:52,640 --> 00:30:54,019
that these new algorithms

837
00:30:54,320 --> 00:30:55,140
can't be

838
00:30:55,599 --> 00:30:57,680
attacked by some quantum computer. It's just that

839
00:30:57,680 --> 00:30:59,299
nobody has figured out how.

840
00:30:59,759 --> 00:31:02,000
And very clever people have been working on

841
00:31:02,000 --> 00:31:04,704
it to try to figure out ways of

842
00:31:04,704 --> 00:31:06,305
doing this and have failed. And so we

843
00:31:06,305 --> 00:31:08,085
think these things are pretty secure.

844
00:31:08,785 --> 00:31:10,704
But with so many like, with so many

845
00:31:10,704 --> 00:31:12,085
things, we're not sure.

846
00:31:13,265 --> 00:31:15,825
So this is places where quantum mechanics puts

847
00:31:15,825 --> 00:31:18,179
us in danger and quantum mechanics comes to

848
00:31:18,179 --> 00:31:20,819
the rescue. And so in my lab, we're

849
00:31:20,819 --> 00:31:23,779
not making quantum computers, but we're doing some

850
00:31:23,779 --> 00:31:24,599
of the things

851
00:31:25,059 --> 00:31:25,799
that will

852
00:31:26,259 --> 00:31:26,759
enable

853
00:31:27,140 --> 00:31:29,460
new kinds of quantum computers to be,

854
00:31:30,179 --> 00:31:32,125
to be to be made. Mhmm.

855
00:31:32,825 --> 00:31:34,625
So let's talk about quantum computers. You need

856
00:31:34,744 --> 00:31:36,825
you mentioned that you can make a quantum

857
00:31:36,825 --> 00:31:39,244
computer or a quantum processor with cold atoms.

858
00:31:39,705 --> 00:31:41,144
You can make it there's other types of

859
00:31:41,144 --> 00:31:43,945
qubits out there, trapped ions, super connecting circuits,

860
00:31:43,945 --> 00:31:44,759
that sort of thing.

861
00:31:45,240 --> 00:31:46,599
Do you have a view about which of

862
00:31:46,599 --> 00:31:49,000
these platforms is likely to succeed or which

863
00:31:49,240 --> 00:31:50,920
Yeah. Well, this this this has been a

864
00:31:51,079 --> 00:31:53,799
an ongoing question. What's the what's the winning

865
00:31:53,799 --> 00:31:54,299
platform?

866
00:31:55,000 --> 00:31:56,220
And my attitude

867
00:31:56,759 --> 00:31:59,339
from the beginning and still today is

868
00:31:59,880 --> 00:32:01,724
that it's too early

869
00:32:02,345 --> 00:32:04,845
to settle on one particular platform.

870
00:32:06,744 --> 00:32:09,464
And it may very well be that the

871
00:32:09,464 --> 00:32:10,765
final quantum computer

872
00:32:11,144 --> 00:32:13,704
that does things like factor numbers, it's not

873
00:32:13,704 --> 00:32:15,404
even clear that that's the most important

874
00:32:16,319 --> 00:32:17,700
problem that you want to do,

875
00:32:19,119 --> 00:32:21,220
is likely to be a hybrid

876
00:32:22,319 --> 00:32:22,819
where

877
00:32:23,279 --> 00:32:23,779
computations

878
00:32:24,079 --> 00:32:25,460
are done on one platform

879
00:32:25,759 --> 00:32:26,579
and storage

880
00:32:27,200 --> 00:32:29,619
is done on another platform. So superconducting

881
00:32:30,000 --> 00:32:32,554
quantum computers are really nice and fast,

882
00:32:33,015 --> 00:32:35,994
but they can't store information for very long,

883
00:32:36,375 --> 00:32:39,414
whereas atoms and ions can store information for

884
00:32:39,414 --> 00:32:41,275
a really long time. They're very

885
00:32:41,734 --> 00:32:42,954
robust, very

886
00:32:43,494 --> 00:32:45,034
isolated from the environment,

887
00:32:45,829 --> 00:32:46,970
but they're kinda slow

888
00:32:47,430 --> 00:32:49,609
in the in the computation process.

889
00:32:50,309 --> 00:32:52,150
So it might very well be that you

890
00:32:52,150 --> 00:32:53,849
wanna use the best features

891
00:32:54,390 --> 00:32:57,589
of different platforms in different in in in

892
00:32:57,589 --> 00:33:00,755
different parts of your of your quantum computer.

893
00:33:00,815 --> 00:33:03,134
But, you know, what do I know? It's,

894
00:33:03,455 --> 00:33:04,994
I think we're a long way,

895
00:33:05,455 --> 00:33:07,215
and this is not a majority view or

896
00:33:07,215 --> 00:33:08,815
at least is not a universal view. We're

897
00:33:08,815 --> 00:33:10,755
a long way from having quantum computers

898
00:33:11,134 --> 00:33:12,839
that can do interesting problems

899
00:33:13,559 --> 00:33:14,059
that,

900
00:33:14,639 --> 00:33:16,440
a lot faster than what,

901
00:33:17,000 --> 00:33:17,980
classical computers

902
00:33:18,359 --> 00:33:20,299
can do. You've probably heard

903
00:33:20,599 --> 00:33:22,700
that somebody used a quantum computer

904
00:33:23,000 --> 00:33:23,740
to do

905
00:33:24,119 --> 00:33:26,299
a a problem that would take a classical

906
00:33:26,359 --> 00:33:26,859
computer,

907
00:33:27,184 --> 00:33:28,085
you know, a septillion

908
00:33:29,105 --> 00:33:31,285
years to do. Maybe so,

909
00:33:32,224 --> 00:33:32,724
but

910
00:33:33,984 --> 00:33:34,884
it's a little misleading.

911
00:33:36,144 --> 00:33:36,884
They chose

912
00:33:37,265 --> 00:33:38,005
a problem.

913
00:33:38,785 --> 00:33:40,625
It was easy for a quantum computer to

914
00:33:40,625 --> 00:33:42,625
do and hard for a classical computer to

915
00:33:42,625 --> 00:33:44,670
do, and it's a problem nobody cares about.

916
00:33:45,130 --> 00:33:48,190
Nobody's gonna make any money solving that problem.

917
00:33:48,490 --> 00:33:51,549
People definitely gonna make money factoring numbers. People

918
00:33:52,090 --> 00:33:53,789
probably are gonna make money

919
00:33:54,170 --> 00:33:54,670
by,

920
00:33:55,450 --> 00:33:56,670
doing quantum chemistry,

921
00:33:57,214 --> 00:33:59,075
learning how some

922
00:33:59,535 --> 00:34:01,695
molecule that either you haven't made yet or

923
00:34:01,695 --> 00:34:04,035
you haven't tested yet, how it would behave.

924
00:34:05,134 --> 00:34:07,134
That's the sort of thing that could very

925
00:34:07,134 --> 00:34:08,195
well lead to

926
00:34:08,494 --> 00:34:10,494
to things that people care about that that,

927
00:34:11,510 --> 00:34:13,369
are gonna make a difference in our lives.

928
00:34:13,829 --> 00:34:15,130
That hasn't happened yet,

929
00:34:15,670 --> 00:34:17,909
but we may not be that far from

930
00:34:17,909 --> 00:34:18,409
it.

931
00:34:19,269 --> 00:34:21,190
Just to give you an idea of how

932
00:34:21,190 --> 00:34:22,010
far away

933
00:34:22,550 --> 00:34:23,929
we are from this,

934
00:34:24,305 --> 00:34:24,805
I

935
00:34:25,664 --> 00:34:26,164
proposed,

936
00:34:26,704 --> 00:34:28,644
a bet with a colleague of mine.

937
00:34:29,184 --> 00:34:31,184
His name is Carl Williams. He's well known

938
00:34:31,184 --> 00:34:31,925
in the quantum

939
00:34:32,385 --> 00:34:32,885
business.

940
00:34:33,265 --> 00:34:34,405
And the bet is,

941
00:34:35,585 --> 00:34:37,905
at a certain future date, will we or

942
00:34:37,905 --> 00:34:40,059
will we not have a quantum computer that

943
00:34:40,059 --> 00:34:41,119
can factor numbers

944
00:34:41,420 --> 00:34:42,319
that a

945
00:34:43,019 --> 00:34:45,839
classical computer of that future time

946
00:34:46,299 --> 00:34:46,799
cannot

947
00:34:47,179 --> 00:34:47,679
factor?

948
00:34:48,059 --> 00:34:48,559
Okay?

949
00:34:49,179 --> 00:34:49,679
And

950
00:34:50,139 --> 00:34:53,359
he proposed the the date of 2045,

951
00:34:53,934 --> 00:34:54,594
which is

952
00:34:54,894 --> 00:34:57,135
only about twenty years from now. Right? Why

953
00:34:57,135 --> 00:34:59,635
2045? It's about fifty years after

954
00:35:00,255 --> 00:35:02,275
Shor and after the first demonstration

955
00:35:02,734 --> 00:35:05,694
of a quantum gate by Dave Wineland and

956
00:35:05,694 --> 00:35:06,355
his group

957
00:35:06,719 --> 00:35:08,820
at our NIST laboratories in Boulder.

958
00:35:09,599 --> 00:35:12,079
And and it's a well defined problem and

959
00:35:12,079 --> 00:35:13,300
not an easy one.

960
00:35:14,079 --> 00:35:14,579
And,

961
00:35:15,039 --> 00:35:16,559
I'm taking the point of view that, no,

962
00:35:16,559 --> 00:35:18,159
we will not have a computer that can

963
00:35:18,159 --> 00:35:20,244
do that, And he's taking the point of

964
00:35:20,244 --> 00:35:22,485
view that, yes, we will. And we'll put

965
00:35:22,485 --> 00:35:24,885
up some money and it'll go into some

966
00:35:24,885 --> 00:35:27,684
fun for a scholarship or a prize depending

967
00:35:27,684 --> 00:35:29,925
upon who wins. And I expect to be

968
00:35:29,925 --> 00:35:32,440
dead by then. But, what I hope

969
00:35:32,739 --> 00:35:35,319
is that this bet will encourage people

970
00:35:35,699 --> 00:35:38,339
to work hard on solving the problems that

971
00:35:38,339 --> 00:35:40,179
need to be solved in order to,

972
00:35:41,299 --> 00:35:43,219
to make this work like error correction. We

973
00:35:43,219 --> 00:35:44,760
haven't talked about error correction,

974
00:35:45,085 --> 00:35:47,265
but that's the big thing because

975
00:35:47,724 --> 00:35:50,385
these quantum processes are prone to errors

976
00:35:51,244 --> 00:35:53,744
much more so than the classical computers.

977
00:35:54,204 --> 00:35:56,204
So you've got to be doing something to

978
00:35:56,204 --> 00:35:58,224
fix that, and that's called quantum error correction.

979
00:35:58,525 --> 00:36:00,785
And people are starting to do that, and

980
00:36:01,139 --> 00:36:03,059
we need more of that. And so that's

981
00:36:03,059 --> 00:36:04,579
one of the reasons for having a bet

982
00:36:04,579 --> 00:36:06,519
like this. When I talk to people,

983
00:36:07,219 --> 00:36:09,940
other scientists working in the field, and ask

984
00:36:09,940 --> 00:36:12,019
them which side of the bet they would

985
00:36:12,019 --> 00:36:14,454
like to be on, it's about fifty fifty.

986
00:36:14,515 --> 00:36:16,535
So I think this is a great bet

987
00:36:16,675 --> 00:36:17,655
that that

988
00:36:17,954 --> 00:36:20,614
we could expect that in about twenty years,

989
00:36:20,675 --> 00:36:22,054
we're gonna have

990
00:36:22,755 --> 00:36:24,755
or, you know, it'll be of that order

991
00:36:24,755 --> 00:36:25,494
of time

992
00:36:25,875 --> 00:36:27,175
where we'll have

993
00:36:27,579 --> 00:36:30,460
really competent quantum computers that can do that

994
00:36:30,460 --> 00:36:31,659
kind of thing. Now as I said, I

995
00:36:31,659 --> 00:36:34,059
don't think factoring is the most important thing.

996
00:36:34,059 --> 00:36:36,380
What I want is a quantum computer that

997
00:36:36,380 --> 00:36:37,599
can do quantum mechanics.

998
00:36:38,940 --> 00:36:39,255
This,

999
00:36:40,295 --> 00:36:42,795
this exponential growth that I described for factoring

1000
00:36:42,855 --> 00:36:45,174
is also true of many problems in quantum

1001
00:36:45,174 --> 00:36:45,674
mechanics.

1002
00:36:46,054 --> 00:36:47,755
Let's say that you've got

1003
00:36:48,214 --> 00:36:48,875
a model

1004
00:36:49,815 --> 00:36:53,174
that is trying to describe magnetism. Magnetism is

1005
00:36:53,174 --> 00:36:54,875
one of our favorite subjects

1006
00:36:55,289 --> 00:36:57,849
in, in quantum mechanics. So let's imagine it's

1007
00:36:57,849 --> 00:37:01,369
a chain, a one dimensional chain of spin.

1008
00:37:01,369 --> 00:37:03,530
So on each link of the chain, there's

1009
00:37:03,530 --> 00:37:06,510
a spin, a quantum mechanical spin. And magnetism

1010
00:37:07,210 --> 00:37:09,789
is all about how do these spins interact

1011
00:37:10,014 --> 00:37:10,755
to produce

1012
00:37:11,215 --> 00:37:13,054
certain kinds of states, like all the spins

1013
00:37:13,054 --> 00:37:14,655
pointing in the same direction. That's what we

1014
00:37:14,655 --> 00:37:15,394
call ferromagnetism.

1015
00:37:16,255 --> 00:37:18,974
Every other spin pointing in opposite directions. That's

1016
00:37:18,974 --> 00:37:20,114
what we call antiferromagnetism.

1017
00:37:21,295 --> 00:37:21,795
And

1018
00:37:22,255 --> 00:37:23,155
quantum magnetism

1019
00:37:23,809 --> 00:37:25,670
is, at least in some circumstances,

1020
00:37:27,250 --> 00:37:28,309
a hard problem

1021
00:37:28,849 --> 00:37:29,349
because

1022
00:37:30,610 --> 00:37:33,489
the number of possible states of all these

1023
00:37:33,489 --> 00:37:35,269
spins pointing up and down

1024
00:37:35,969 --> 00:37:36,469
is

1025
00:37:37,010 --> 00:37:38,690
let's say that the spin can only point

1026
00:37:38,690 --> 00:37:40,925
up or down and you've got n spins.

1027
00:37:41,224 --> 00:37:44,344
There's two to the power n number of

1028
00:37:44,344 --> 00:37:46,684
ways you could do this on a chain.

1029
00:37:47,385 --> 00:37:49,785
And if you add one more spin to

1030
00:37:49,785 --> 00:37:51,164
the chain, you've doubled

1031
00:37:51,590 --> 00:37:54,090
the number. That's what we mean by exponential

1032
00:37:54,150 --> 00:37:54,650
growth.

1033
00:37:55,269 --> 00:37:57,929
So that means that any reasonable size chain

1034
00:37:58,309 --> 00:37:59,130
is impossible

1035
00:37:59,989 --> 00:38:02,329
for a classical computer to do.

1036
00:38:02,630 --> 00:38:04,489
Once you've got a few tens

1037
00:38:05,984 --> 00:38:06,724
of spins,

1038
00:38:07,025 --> 00:38:09,764
a classical computer cannot do a brute force

1039
00:38:09,905 --> 00:38:13,045
calculation, but a quantum computer could. And so

1040
00:38:13,744 --> 00:38:14,244
having

1041
00:38:14,625 --> 00:38:17,125
a quantum computer that can,

1042
00:38:17,664 --> 00:38:18,885
reliably calculate

1043
00:38:19,505 --> 00:38:20,719
tens of

1044
00:38:21,980 --> 00:38:22,719
of of qubits

1045
00:38:23,099 --> 00:38:25,340
that represent the spins, this will be a

1046
00:38:25,340 --> 00:38:26,000
big deal.

1047
00:38:26,300 --> 00:38:29,280
Now you've probably heard that these quantum computers

1048
00:38:29,420 --> 00:38:30,880
already have that many qubits.

1049
00:38:31,179 --> 00:38:32,239
Yeah. But

1050
00:38:32,875 --> 00:38:34,974
they're not what we call logical qubits.

1051
00:38:35,675 --> 00:38:37,355
You see, the thing is that because of

1052
00:38:37,355 --> 00:38:39,855
these errors, you're not gonna get a reliable

1053
00:38:39,994 --> 00:38:42,795
answer from the kinds of of quantum computers

1054
00:38:42,795 --> 00:38:45,114
we have today. You have to do error

1055
00:38:45,114 --> 00:38:47,369
correction. The way you do error correction is

1056
00:38:47,690 --> 00:38:48,190
you

1057
00:38:48,570 --> 00:38:51,849
assemble a number of physical qubits into what

1058
00:38:51,849 --> 00:38:54,250
we call a logical qubit. And then by

1059
00:38:54,250 --> 00:38:56,590
making measurements on the logical qubit

1060
00:38:57,450 --> 00:38:58,269
that are

1061
00:38:58,730 --> 00:39:00,970
not determining what the state of the logical

1062
00:39:00,970 --> 00:39:02,269
qubit is, but determining

1063
00:39:02,644 --> 00:39:04,565
what the relationship is between some of the

1064
00:39:04,565 --> 00:39:05,065
qubits

1065
00:39:05,364 --> 00:39:07,605
without learning what the state because you can't

1066
00:39:07,605 --> 00:39:09,125
learn what the state is because that would

1067
00:39:09,125 --> 00:39:11,925
destroy the superposition state. But you can determine

1068
00:39:11,925 --> 00:39:15,045
whether an error has happened and and fix

1069
00:39:15,045 --> 00:39:17,444
that error. That's what quantum what quantum error

1070
00:39:17,444 --> 00:39:19,589
correction is about, and people are just starting

1071
00:39:19,589 --> 00:39:21,429
to do this. And this is what one

1072
00:39:21,429 --> 00:39:23,190
of the things that's just so exciting right

1073
00:39:23,190 --> 00:39:25,130
now is that people are making

1074
00:39:25,510 --> 00:39:26,010
computers

1075
00:39:26,389 --> 00:39:29,929
that have logical qubits and doing error correction.

1076
00:39:30,230 --> 00:39:32,765
It's not good enough yet, but it's getting

1077
00:39:32,765 --> 00:39:33,265
there.

1078
00:39:35,325 --> 00:39:37,485
So would you say that's one development that

1079
00:39:37,485 --> 00:39:39,644
our listeners, this podcast, should look out for

1080
00:39:39,644 --> 00:39:40,925
in this field? You know? Who are the

1081
00:39:40,925 --> 00:39:42,605
people to watch in this area? What are

1082
00:39:42,605 --> 00:39:44,765
the things we should be seeing happen in

1083
00:39:44,765 --> 00:39:47,659
the between now and 2045, let's say Yeah.

1084
00:39:47,659 --> 00:39:49,179
I think when the bet's gonna happen? Right.

1085
00:39:49,179 --> 00:39:50,460
So I think the thing you should be

1086
00:39:50,460 --> 00:39:53,579
looking for is things like how many logical

1087
00:39:53,579 --> 00:39:54,079
qubits

1088
00:39:54,859 --> 00:39:55,679
you've got

1089
00:39:57,339 --> 00:39:59,894
that can be entangled with each other. And

1090
00:39:59,894 --> 00:40:01,015
this is one of the things that some

1091
00:40:01,015 --> 00:40:01,914
recent news,

1092
00:40:02,454 --> 00:40:04,855
has shown that this number is starting to

1093
00:40:04,855 --> 00:40:07,355
become larger than it was in the past.

1094
00:40:08,215 --> 00:40:09,755
And how long

1095
00:40:10,534 --> 00:40:12,235
or for how many operations

1096
00:40:13,015 --> 00:40:14,554
can these logical qubits

1097
00:40:15,170 --> 00:40:15,670
maintain

1098
00:40:16,369 --> 00:40:16,869
their

1099
00:40:17,489 --> 00:40:18,869
coherence? That is their

1100
00:40:19,170 --> 00:40:20,470
their quantum ness,

1101
00:40:21,329 --> 00:40:21,829
without,

1102
00:40:22,769 --> 00:40:24,769
having some sort of an error with and

1103
00:40:24,769 --> 00:40:28,094
that those errors occur because they're connected weekly,

1104
00:40:28,094 --> 00:40:30,255
we hope, to the environment. The environment comes

1105
00:40:30,255 --> 00:40:32,974
in and and and messes things up, and

1106
00:40:32,974 --> 00:40:35,135
that's what we have to correct by quantum

1107
00:40:35,135 --> 00:40:37,135
error correction. First, we have to prevent it.

1108
00:40:37,135 --> 00:40:39,215
That's one of the things that using cold

1109
00:40:39,215 --> 00:40:41,900
atoms allows you to do is to prevent

1110
00:40:41,900 --> 00:40:44,300
the connection to the environment, but it's never

1111
00:40:44,300 --> 00:40:44,800
perfect,

1112
00:40:45,340 --> 00:40:45,840
and

1113
00:40:46,140 --> 00:40:48,380
correct it when when the environment does mess

1114
00:40:48,380 --> 00:40:50,000
you up. And it's that correction.

1115
00:40:50,460 --> 00:40:51,360
How long

1116
00:40:52,140 --> 00:40:53,820
is the coherence of this,

1117
00:40:54,140 --> 00:40:55,360
of this state lasting?

1118
00:40:55,925 --> 00:40:57,844
What I often say the thing we need

1119
00:40:57,844 --> 00:40:59,864
is an immortal qubit,

1120
00:41:00,244 --> 00:41:03,144
something that is not killed by the environment

1121
00:41:03,364 --> 00:41:04,105
that lasts

1122
00:41:04,965 --> 00:41:06,105
throughout the whole

1123
00:41:06,965 --> 00:41:07,465
calculation

1124
00:41:08,005 --> 00:41:10,650
and and for a calculation that's long enough

1125
00:41:10,809 --> 00:41:13,049
to do interesting things. So those are the

1126
00:41:13,049 --> 00:41:14,510
the things you wanna be,

1127
00:41:14,969 --> 00:41:16,989
looking for is how many operations

1128
00:41:17,849 --> 00:41:20,029
can you do and still maintain

1129
00:41:20,569 --> 00:41:23,369
the the quantumness of of that qubit, and

1130
00:41:23,369 --> 00:41:24,105
how many,

1131
00:41:24,744 --> 00:41:27,385
logical qubits can you have. Those are are

1132
00:41:27,385 --> 00:41:28,605
some of the key things

1133
00:41:28,984 --> 00:41:31,625
that are gonna determine whether you really have

1134
00:41:31,625 --> 00:41:32,125
a,

1135
00:41:32,585 --> 00:41:34,204
a competent quantum computer.

1136
00:41:34,744 --> 00:41:36,105
And what about in the other areas we

1137
00:41:36,105 --> 00:41:39,449
talked about in quantum information and, optical clocks?

1138
00:41:39,849 --> 00:41:41,869
Yeah. So so optical clocks

1139
00:41:42,489 --> 00:41:43,550
are already wonderful

1140
00:41:44,089 --> 00:41:46,329
and getting better all the time. One of

1141
00:41:46,329 --> 00:41:49,530
the things that recently came up was a

1142
00:41:49,530 --> 00:41:50,670
nuclear clock.

1143
00:41:51,289 --> 00:41:54,105
So now, I mean, it's optical if you

1144
00:41:54,105 --> 00:41:54,605
call,

1145
00:41:55,144 --> 00:41:55,965
sort of far

1146
00:41:56,265 --> 00:41:56,765
ultraviolet

1147
00:41:57,144 --> 00:41:58,204
optics. Okay?

1148
00:41:58,505 --> 00:41:59,885
I mean, it's not so

1149
00:42:00,344 --> 00:42:02,265
far. Okay. So let me back up and

1150
00:42:02,265 --> 00:42:04,445
say why nuclear clocks are so wonderful.

1151
00:42:04,985 --> 00:42:06,925
There's one nucleus, thorium,

1152
00:42:07,980 --> 00:42:10,380
that I forget which isotope it is, that

1153
00:42:10,380 --> 00:42:10,880
has

1154
00:42:11,340 --> 00:42:12,239
an isomer

1155
00:42:12,539 --> 00:42:13,039
state,

1156
00:42:13,739 --> 00:42:15,360
an excited state of the nucleus

1157
00:42:15,820 --> 00:42:17,820
that is only a little bit above the

1158
00:42:17,820 --> 00:42:18,639
ground state.

1159
00:42:18,940 --> 00:42:20,699
It's low enough in energy. I think it's

1160
00:42:20,699 --> 00:42:23,765
about eight electron volts, whereas, like, optical things

1161
00:42:23,765 --> 00:42:26,005
like two electron volts. So it's not not

1162
00:42:26,005 --> 00:42:28,244
not not so far above, which means that

1163
00:42:28,244 --> 00:42:31,305
we can use well known techniques to produce

1164
00:42:31,525 --> 00:42:34,965
what is effectively laser light to shine on

1165
00:42:34,965 --> 00:42:37,280
the nucleus and have it make a transition.

1166
00:42:38,059 --> 00:42:39,440
Most nuclear states

1167
00:42:40,059 --> 00:42:42,460
are kilovolts or more above the ground state,

1168
00:42:42,460 --> 00:42:43,980
and we just don't have any way of

1169
00:42:43,980 --> 00:42:44,480
making

1170
00:42:44,860 --> 00:42:45,360
laser

1171
00:42:45,660 --> 00:42:49,099
like light at those energies. But, you know,

1172
00:42:49,099 --> 00:42:51,515
eight electron volts, yeah, we can do it

1173
00:42:51,515 --> 00:42:53,375
and have done it. That's the thing.

1174
00:42:53,835 --> 00:42:56,414
So in the just in the past year,

1175
00:42:57,675 --> 00:42:58,175
starting

1176
00:42:58,715 --> 00:43:01,994
at PTB, they they used a broadband laser

1177
00:43:01,994 --> 00:43:02,735
to excite,

1178
00:43:04,260 --> 00:43:06,820
the state for the first time. Now starting

1179
00:43:06,820 --> 00:43:08,039
to really pin down

1180
00:43:08,340 --> 00:43:10,260
what the energy was because people didn't even

1181
00:43:10,260 --> 00:43:12,739
know what the energy was. This is amazing

1182
00:43:12,739 --> 00:43:14,440
thing. So a guy at PTB,

1183
00:43:15,380 --> 00:43:17,380
I don't know, two decades ago said this

1184
00:43:17,380 --> 00:43:18,920
looks like a really great idea.

1185
00:43:19,284 --> 00:43:21,784
They didn't even know what the energy was

1186
00:43:22,005 --> 00:43:23,784
to within a factor of two.

1187
00:43:25,204 --> 00:43:27,125
And now they know what it is to

1188
00:43:27,125 --> 00:43:28,664
to some really fine,

1189
00:43:29,364 --> 00:43:30,965
level. I forget what, but, you know, many,

1190
00:43:30,965 --> 00:43:31,704
many digits.

1191
00:43:32,244 --> 00:43:34,344
So so this has been a huge

1192
00:43:34,650 --> 00:43:36,750
improvement over the years. And just this year,

1193
00:43:36,889 --> 00:43:39,210
laser excitation at PTB and then a couple

1194
00:43:39,210 --> 00:43:40,109
of other groups,

1195
00:43:40,489 --> 00:43:41,549
one of them being,

1196
00:43:41,929 --> 00:43:44,489
our NIST laboratories in Boulder, have done it

1197
00:43:44,489 --> 00:43:46,589
with with really narrow band lasers.

1198
00:43:46,994 --> 00:43:49,494
So this is the beginning of the possibility

1199
00:43:49,554 --> 00:43:52,375
of a nuclear clock. It's still years,

1200
00:43:53,234 --> 00:43:55,634
in the future, but the beauty is really

1201
00:43:55,634 --> 00:43:58,214
high frequency. So that means, again,

1202
00:43:59,394 --> 00:44:01,734
various perturbations are gonna be a smaller

1203
00:44:02,400 --> 00:44:02,900
fraction,

1204
00:44:03,280 --> 00:44:06,819
but a nucleus. The nucleus is much less

1205
00:44:06,880 --> 00:44:07,380
susceptible

1206
00:44:08,400 --> 00:44:09,380
to outside

1207
00:44:09,679 --> 00:44:10,179
influences

1208
00:44:11,039 --> 00:44:12,579
than the atom

1209
00:44:13,119 --> 00:44:15,440
where its outer electrons are the ones that

1210
00:44:15,440 --> 00:44:18,235
are doing the work. And those outer electrons

1211
00:44:18,375 --> 00:44:19,594
are basically exposed

1212
00:44:20,775 --> 00:44:23,255
to all kinds of bad things that might

1213
00:44:23,255 --> 00:44:26,074
happen. Whereas the nucleus is protected. It's sitting

1214
00:44:26,135 --> 00:44:28,934
sitting in deep inside the atom with lots

1215
00:44:28,934 --> 00:44:31,139
of electrons around it sort of protecting it.

1216
00:44:31,460 --> 00:44:31,960
And,

1217
00:44:32,420 --> 00:44:34,339
and the hope is that you'd be able

1218
00:44:34,339 --> 00:44:36,019
to make a clock that is much less

1219
00:44:36,019 --> 00:44:36,519
susceptible

1220
00:44:37,059 --> 00:44:39,139
to the kinds of things that that mess

1221
00:44:39,139 --> 00:44:42,260
up our our atomic clock, but probably not

1222
00:44:42,260 --> 00:44:43,239
for some decades.

1223
00:44:43,940 --> 00:44:46,405
Is it gonna be good enough that it's

1224
00:44:46,405 --> 00:44:48,324
really gonna compete with the part in 10

1225
00:44:48,324 --> 00:44:50,164
of the 18 atoms that are going on?

1226
00:44:50,164 --> 00:44:51,364
So one of the things you're gonna look

1227
00:44:51,364 --> 00:44:54,025
for is is the international community gonna

1228
00:44:54,324 --> 00:44:55,304
come to a decision

1229
00:44:55,684 --> 00:44:57,545
about what is gonna be the new,

1230
00:44:58,804 --> 00:45:01,550
the new definition of the second? What atom

1231
00:45:01,610 --> 00:45:03,769
is it gonna be? We haven't even decided

1232
00:45:03,769 --> 00:45:05,369
whether it's gonna be a single atom or

1233
00:45:05,369 --> 00:45:07,630
whether it's gonna be a bunch of atoms.

1234
00:45:07,930 --> 00:45:09,690
I'm very much in favor of the single

1235
00:45:09,690 --> 00:45:10,510
atom approach

1236
00:45:11,210 --> 00:45:14,170
because Simpler. Simpler. Everybody knows what you mean

1237
00:45:14,170 --> 00:45:15,849
when you say this is what a second

1238
00:45:15,849 --> 00:45:17,034
is. So,

1239
00:45:17,434 --> 00:45:19,295
but we'll see. You know, there's there's,

1240
00:45:20,315 --> 00:45:21,534
arguments to be made,

1241
00:45:22,474 --> 00:45:24,815
on, on both sides of that. And,

1242
00:45:25,355 --> 00:45:27,755
so that's another thing to watch, and those

1243
00:45:27,755 --> 00:45:29,579
things are getting better all the time. So

1244
00:45:29,820 --> 00:45:32,860
here's one of the the really wonderful things

1245
00:45:32,860 --> 00:45:34,800
that's being done with these

1246
00:45:35,420 --> 00:45:36,960
incredibly accurate clocks.

1247
00:45:37,340 --> 00:45:39,980
One of the the really fundamental questions we

1248
00:45:39,980 --> 00:45:41,039
might ask ourselves

1249
00:45:41,739 --> 00:45:42,800
about the way

1250
00:45:43,180 --> 00:45:46,565
nature works is, are the fundamental constants of

1251
00:45:46,565 --> 00:45:47,065
nature,

1252
00:45:47,684 --> 00:45:48,344
in fact,

1253
00:45:48,644 --> 00:45:49,144
constant?

1254
00:45:50,324 --> 00:45:52,905
Now the things for which this is important

1255
00:45:52,964 --> 00:45:55,204
are not things like, say, the charge of

1256
00:45:55,204 --> 00:45:56,984
the electron or Planck's constant,

1257
00:45:57,639 --> 00:45:58,139
because

1258
00:45:59,159 --> 00:46:01,739
the value of these constants depends upon

1259
00:46:02,280 --> 00:46:04,139
what we choose for our,

1260
00:46:05,000 --> 00:46:06,380
unit system of units.

1261
00:46:07,239 --> 00:46:08,380
In fact, right now,

1262
00:46:08,760 --> 00:46:09,980
the charge in the electron

1263
00:46:10,440 --> 00:46:11,820
and Planck's constant

1264
00:46:12,359 --> 00:46:14,605
cannot change because it would be illegal.

1265
00:46:15,224 --> 00:46:15,724
Those

1266
00:46:16,025 --> 00:46:18,284
constants have been set by international agreement.

1267
00:46:18,664 --> 00:46:20,824
The things that matter are things like the

1268
00:46:20,824 --> 00:46:22,844
fine structure constant. What is that?

1269
00:46:23,224 --> 00:46:25,625
It's a combination of constants like the charge

1270
00:46:25,625 --> 00:46:27,005
electron Planck's constant

1271
00:46:27,304 --> 00:46:29,750
and the, what's called the, electric,

1272
00:46:30,210 --> 00:46:30,710
permittivity

1273
00:46:31,010 --> 00:46:32,150
of of the vacuum,

1274
00:46:32,849 --> 00:46:34,929
and the speed of light all combined together

1275
00:46:34,929 --> 00:46:37,030
to create a constant that is dimensionless.

1276
00:46:37,890 --> 00:46:38,949
It is a dimensionless

1277
00:46:39,329 --> 00:46:40,230
way of describing

1278
00:46:40,690 --> 00:46:41,510
how strong

1279
00:46:42,014 --> 00:46:45,534
electric interactions or electromagnetic interactions are. And we

1280
00:46:45,534 --> 00:46:46,275
have similar

1281
00:46:46,815 --> 00:46:49,714
dimensionless constants that describe how strong nuclear,

1282
00:46:50,654 --> 00:46:54,355
interactions are, strong force, weak force. Well, anyway,

1283
00:46:54,734 --> 00:46:56,594
the the the fine structure constant

1284
00:46:56,894 --> 00:46:57,394
describes

1285
00:46:57,989 --> 00:46:58,489
how,

1286
00:46:58,949 --> 00:47:01,349
how strong electrical interactions are, and that means

1287
00:47:01,349 --> 00:47:02,170
it's basically

1288
00:47:02,630 --> 00:47:04,329
the thing that sets the scale

1289
00:47:04,710 --> 00:47:07,269
for almost everything that's part of our daily

1290
00:47:07,269 --> 00:47:09,369
lives. Chemistry, which is,

1291
00:47:09,750 --> 00:47:12,090
you know, basically what makes our bodies work,

1292
00:47:12,375 --> 00:47:14,375
is defined with the kinds of things that

1293
00:47:14,375 --> 00:47:16,635
are possible defined by the fine structure constant.

1294
00:47:17,494 --> 00:47:19,574
Some people pointed out that if fine structure

1295
00:47:19,574 --> 00:47:21,355
constant were different by 10%,

1296
00:47:21,414 --> 00:47:22,394
we couldn't exist.

1297
00:47:22,695 --> 00:47:24,934
Our body chemistry wouldn't work in the way

1298
00:47:24,934 --> 00:47:27,110
that it does. So, you know, it's kind

1299
00:47:27,110 --> 00:47:29,670
of a either a happy accident or, you

1300
00:47:29,670 --> 00:47:31,050
know, some divine

1301
00:47:31,349 --> 00:47:33,190
intervention that makes our,

1302
00:47:33,910 --> 00:47:36,630
our body chemistry work. Or we won the

1303
00:47:36,630 --> 00:47:39,045
cosmic lottery and there's 10 of the 500

1304
00:47:39,045 --> 00:47:41,284
other universes where the flying structure comes in

1305
00:47:41,284 --> 00:47:44,264
something different and there's nobody interesting there.

1306
00:47:45,125 --> 00:47:45,625
But

1307
00:47:46,085 --> 00:47:48,264
one of the questions we could ask ourselves

1308
00:47:48,324 --> 00:47:48,824
is,

1309
00:47:49,125 --> 00:47:51,144
does it change with time?

1310
00:47:51,489 --> 00:47:52,230
Well, now

1311
00:47:53,010 --> 00:47:55,489
because of these atomic clocks, we could have

1312
00:47:55,489 --> 00:47:58,309
two atomic clocks that operate on different atoms

1313
00:47:58,530 --> 00:48:00,769
or maybe on different transitions even within the

1314
00:48:00,769 --> 00:48:01,430
same atom

1315
00:48:01,969 --> 00:48:04,450
that depend upon the fine structure constant in

1316
00:48:04,450 --> 00:48:07,005
different ways. So depending on what the transition

1317
00:48:07,005 --> 00:48:08,844
is, it could depend very strongly on the

1318
00:48:08,844 --> 00:48:11,085
fine structure constant or very weakly on the

1319
00:48:11,085 --> 00:48:13,324
fine structure constant. So if you've got two

1320
00:48:13,324 --> 00:48:14,144
such clocks

1321
00:48:14,844 --> 00:48:15,984
and you

1322
00:48:16,364 --> 00:48:19,025
just let them, you know, compare their frequencies

1323
00:48:19,750 --> 00:48:21,369
year after year,

1324
00:48:22,150 --> 00:48:24,070
you can determine whether from one year to

1325
00:48:24,070 --> 00:48:26,250
the next the fine structure constant is changing.

1326
00:48:26,390 --> 00:48:28,170
And this has allowed us to say

1327
00:48:28,470 --> 00:48:30,630
that we know the fine structure constant is

1328
00:48:30,630 --> 00:48:32,390
not changing by about a part in 10

1329
00:48:32,390 --> 00:48:33,769
to the eighteenth per year.

1330
00:48:34,224 --> 00:48:36,464
And as the clocks get better, we'll be

1331
00:48:36,464 --> 00:48:37,764
able to put a finer,

1332
00:48:39,264 --> 00:48:42,304
determination on that, or you might find that

1333
00:48:42,304 --> 00:48:44,644
indeed it does change. That would change everything.

1334
00:48:44,704 --> 00:48:46,880
We would have to change our our view

1335
00:48:46,880 --> 00:48:49,119
of of the way the world works. Another

1336
00:48:49,119 --> 00:48:51,300
thing which is really exciting is

1337
00:48:51,760 --> 00:48:52,260
Einstein's

1338
00:48:52,800 --> 00:48:56,000
theory of general relativity tells us that if

1339
00:48:56,000 --> 00:48:57,140
we have two clocks

1340
00:48:58,000 --> 00:48:58,500
and

1341
00:48:58,880 --> 00:49:00,105
that are of different sorts

1342
00:49:00,664 --> 00:49:03,005
and we move them together in a gravitational

1343
00:49:03,065 --> 00:49:04,744
field. And these are clocks that don't depend

1344
00:49:04,744 --> 00:49:06,744
on gravity, so a pendulum clock wouldn't be

1345
00:49:06,744 --> 00:49:08,905
the right the right thing, but an atomic

1346
00:49:08,905 --> 00:49:11,864
clock would be. If we move them into

1347
00:49:11,864 --> 00:49:12,364
different,

1348
00:49:12,824 --> 00:49:15,005
places in a gravitational potential,

1349
00:49:15,900 --> 00:49:18,219
those two clocks better stay in the same

1350
00:49:18,219 --> 00:49:18,719
ratio.

1351
00:49:19,019 --> 00:49:21,179
If they don't, it means that the most

1352
00:49:21,179 --> 00:49:24,699
fundamental principle of general relativity is wrong, what

1353
00:49:24,699 --> 00:49:26,239
we call the equivalence principle.

1354
00:49:27,980 --> 00:49:29,744
So putting two such clocks,

1355
00:49:30,305 --> 00:49:31,985
maybe one in a satellite, one on the

1356
00:49:31,985 --> 00:49:34,385
earth, maybe two of them together in a

1357
00:49:34,385 --> 00:49:37,664
satellite with an eccentric orbit, this would really

1358
00:49:37,664 --> 00:49:39,985
be be exciting. I mean, we've done this

1359
00:49:39,985 --> 00:49:42,305
to some extent, but but with these new

1360
00:49:42,305 --> 00:49:42,750
clocks,

1361
00:49:43,309 --> 00:49:44,989
we could do this in in a way

1362
00:49:44,989 --> 00:49:47,469
that has been unparalleled in the past. And

1363
00:49:47,469 --> 00:49:49,010
so we could

1364
00:49:49,309 --> 00:49:49,809
test

1365
00:49:50,110 --> 00:49:52,449
this feature of general relativity,

1366
00:49:53,070 --> 00:49:55,329
at a level that's never been possible before.

1367
00:49:55,795 --> 00:49:58,534
This is really important because we don't know

1368
00:49:58,994 --> 00:50:01,554
how to have a unified theory of quantum

1369
00:50:01,554 --> 00:50:02,934
mechanics in general relativity.

1370
00:50:03,235 --> 00:50:04,775
Well, if we could find out

1371
00:50:05,235 --> 00:50:05,735
that

1372
00:50:06,355 --> 00:50:08,215
the equivalence principle fails

1373
00:50:08,799 --> 00:50:11,440
in this particular way, it might give us

1374
00:50:11,440 --> 00:50:12,260
some insight

1375
00:50:12,719 --> 00:50:15,380
into how we can we can solve this

1376
00:50:15,599 --> 00:50:18,559
great unsolved problem, this great challenge of our

1377
00:50:18,559 --> 00:50:21,599
current time of how do we reconcile quantum

1378
00:50:21,599 --> 00:50:23,699
mechanics with, with gravity.

1379
00:50:24,894 --> 00:50:26,434
There's a lot of big things there.

1380
00:50:27,375 --> 00:50:28,735
Taking it back to your own career just

1381
00:50:28,735 --> 00:50:30,735
for a moment, reflecting on your career so

1382
00:50:30,735 --> 00:50:31,235
far,

1383
00:50:31,535 --> 00:50:33,055
what are you most proud of?

1384
00:50:33,535 --> 00:50:34,035
Well,

1385
00:50:34,894 --> 00:50:37,875
back in around 1988,

1386
00:50:38,940 --> 00:50:39,679
we accidentally

1387
00:50:40,139 --> 00:50:40,639
discovered

1388
00:50:41,659 --> 00:50:42,159
that

1389
00:50:42,619 --> 00:50:43,119
the

1390
00:50:43,500 --> 00:50:44,000
temperature

1391
00:50:44,460 --> 00:50:46,639
to which you could laser cool atoms

1392
00:50:47,659 --> 00:50:48,559
was lower

1393
00:50:49,179 --> 00:50:49,920
than what

1394
00:50:50,219 --> 00:50:53,119
everybody said was possible based on the theory

1395
00:50:53,484 --> 00:50:54,464
of laser cooling

1396
00:50:54,764 --> 00:50:55,664
at that time.

1397
00:50:56,045 --> 00:50:57,724
And it was an accidental discovery. I mean,

1398
00:50:57,724 --> 00:51:00,045
we were not looking for this. We were

1399
00:51:00,045 --> 00:51:01,824
just fooling around in the lab

1400
00:51:02,364 --> 00:51:04,764
trying to to see whether laser cooling was

1401
00:51:04,764 --> 00:51:06,364
working the way it was supposed to, and

1402
00:51:06,364 --> 00:51:08,489
the first indications was it looks every like,

1403
00:51:08,489 --> 00:51:11,130
everything's great. And then we started to see

1404
00:51:11,130 --> 00:51:11,789
some problems,

1405
00:51:12,170 --> 00:51:14,409
like, everything wasn't great. And we started to

1406
00:51:14,409 --> 00:51:17,369
pound on that and eventually learned that the

1407
00:51:17,369 --> 00:51:17,869
temperature

1408
00:51:18,570 --> 00:51:20,489
was was too low. And that was the

1409
00:51:20,489 --> 00:51:22,764
thing that made people pay attention. There's other

1410
00:51:22,764 --> 00:51:25,164
little things, things weren't working out. You know,

1411
00:51:25,164 --> 00:51:27,485
there's some detail. We'll figure it out. But

1412
00:51:27,485 --> 00:51:30,125
when the temperature started to be lower, you

1413
00:51:30,125 --> 00:51:31,724
see I mean, the whole idea of laser

1414
00:51:31,724 --> 00:51:33,164
cooling is to make the temperature as low

1415
00:51:33,164 --> 00:51:35,179
as you can. And we had apparently made

1416
00:51:35,179 --> 00:51:36,880
it lower than you can.

1417
00:51:37,179 --> 00:51:39,579
So that got people excited. And then people

1418
00:51:39,579 --> 00:51:42,460
came up with explanations. Our our our friends

1419
00:51:42,460 --> 00:51:45,179
in Paris at the Ecole Normale came up

1420
00:51:45,179 --> 00:51:48,284
with, with explanations for what was what was

1421
00:51:48,284 --> 00:51:50,125
going on. Steve Chu, who was at that

1422
00:51:50,125 --> 00:51:51,025
point at Stanford,

1423
00:51:51,644 --> 00:51:53,344
was also working on on

1424
00:51:53,644 --> 00:51:56,364
understanding the the the theory behind it, and

1425
00:51:56,364 --> 00:51:59,344
that really changed things in an important way.

1426
00:51:59,804 --> 00:52:01,105
It made possible

1427
00:52:01,900 --> 00:52:04,619
laser cooled atomic clocks. So all the laser

1428
00:52:04,619 --> 00:52:07,199
cooled atomic clocks that use cesium today

1429
00:52:07,579 --> 00:52:08,079
use,

1430
00:52:09,019 --> 00:52:11,420
that feature that the temperature is lower than

1431
00:52:11,420 --> 00:52:13,659
what the original theory of laser cooling said

1432
00:52:13,659 --> 00:52:14,320
it was.

1433
00:52:14,765 --> 00:52:17,265
You know, even these optical clocks can be,

1434
00:52:18,684 --> 00:52:20,285
made to work pretty well with that, but

1435
00:52:20,285 --> 00:52:22,605
there's other techniques. And it made those other

1436
00:52:22,605 --> 00:52:24,364
techniques like, I haven't even talked about Bose

1437
00:52:24,364 --> 00:52:25,265
Einstein condensation.

1438
00:52:26,204 --> 00:52:28,224
An amazing process that happens

1439
00:52:28,760 --> 00:52:31,420
because of a purely quantum mechanical feature

1440
00:52:32,119 --> 00:52:34,859
that makes atoms of the same kind

1441
00:52:35,480 --> 00:52:38,440
fundamentally indistinguishable. And this is a feature that

1442
00:52:38,440 --> 00:52:40,920
that quantum mechanics gave us, this idea of

1443
00:52:40,920 --> 00:52:41,420
indistinguishability,

1444
00:52:41,880 --> 00:52:43,099
which was not something

1445
00:52:43,464 --> 00:52:45,324
that that was understood before

1446
00:52:45,704 --> 00:52:48,505
before quantum mechanics. In fact, in 2024,

1447
00:52:48,505 --> 00:52:50,925
a hundred years ago, Satyendra Bose

1448
00:52:51,464 --> 00:52:53,005
came up with the idea

1449
00:52:53,464 --> 00:52:55,005
that photons were indistinguishable

1450
00:52:55,385 --> 00:52:56,844
and therefore the statistical

1451
00:52:57,224 --> 00:52:58,525
mechanics of photons

1452
00:52:58,869 --> 00:52:59,769
would be different

1453
00:53:00,309 --> 00:53:03,510
from the usual statistical mechanics that Boltzmann or

1454
00:53:03,510 --> 00:53:04,010
Maxwell

1455
00:53:04,630 --> 00:53:07,369
and and and such people came up with

1456
00:53:07,670 --> 00:53:10,150
because of the fact that the particles are

1457
00:53:10,150 --> 00:53:10,650
indistinguishable.

1458
00:53:11,204 --> 00:53:13,045
And the way you count the number of

1459
00:53:13,045 --> 00:53:14,825
possible states is different

1460
00:53:15,445 --> 00:53:15,945
because,

1461
00:53:16,405 --> 00:53:18,405
if you interchange the particles, that's not a

1462
00:53:18,405 --> 00:53:19,144
new state

1463
00:53:19,445 --> 00:53:19,945
because,

1464
00:53:20,805 --> 00:53:22,025
because of the indistinguishability.

1465
00:53:23,204 --> 00:53:23,704
And

1466
00:53:24,164 --> 00:53:24,985
that indistinguishability

1467
00:53:25,525 --> 00:53:27,569
has led to this new

1468
00:53:28,269 --> 00:53:29,630
what some people call a new state of

1469
00:53:29,630 --> 00:53:32,269
matter called a Bose Einstein condensate where all

1470
00:53:32,269 --> 00:53:34,670
of the atoms almost all the atoms are

1471
00:53:34,670 --> 00:53:37,329
in the same quantum state. Well, that was

1472
00:53:37,789 --> 00:53:38,289
facilitated

1473
00:53:39,230 --> 00:53:40,530
by this discovery

1474
00:53:41,025 --> 00:53:42,944
that the, that the temperature could be so

1475
00:53:42,944 --> 00:53:45,025
much lower because it meant in order to

1476
00:53:45,025 --> 00:53:47,344
get this state of Bose Einstein condensation, you've

1477
00:53:47,344 --> 00:53:47,924
got to

1478
00:53:48,224 --> 00:53:50,085
cool the atoms to a very low temperature.

1479
00:53:50,385 --> 00:53:52,625
You've got to have a high density of

1480
00:53:52,625 --> 00:53:53,844
atoms, and

1481
00:53:54,385 --> 00:53:56,039
you start off in a better place

1482
00:53:57,000 --> 00:53:59,160
if if the atoms are colder. And and

1483
00:53:59,160 --> 00:53:59,980
our accidental

1484
00:54:00,280 --> 00:54:00,780
discovery

1485
00:54:01,559 --> 00:54:03,820
allowed that that to happen.

1486
00:54:04,440 --> 00:54:06,119
So that's probably the thing that I'm most

1487
00:54:06,119 --> 00:54:09,239
proud of. But we also accidentally discovered what

1488
00:54:09,239 --> 00:54:10,539
are called optical losses.

1489
00:54:11,344 --> 00:54:13,505
Now I shouldn't say that we accidentally discovered

1490
00:54:13,505 --> 00:54:15,444
it because people already had the idea.

1491
00:54:16,065 --> 00:54:17,525
In fact, one of the earliest

1492
00:54:17,984 --> 00:54:21,025
ideas of laser trapped atoms was was in

1493
00:54:21,025 --> 00:54:22,704
fact 1968.

1494
00:54:22,704 --> 00:54:23,519
So this is

1495
00:54:24,640 --> 00:54:27,039
laser cooling. The idea wasn't even came out

1496
00:54:27,039 --> 00:54:29,440
until '75, and it wasn't even demonstrated until

1497
00:54:29,440 --> 00:54:32,559
'78, '10 years later. But in 1968,

1498
00:54:32,559 --> 00:54:33,219
a Russian,

1499
00:54:33,920 --> 00:54:34,960
physicist named,

1500
00:54:36,079 --> 00:54:39,135
Vladland Litokov came up with the idea of

1501
00:54:39,614 --> 00:54:42,514
trapping atoms in a standing wave of light.

1502
00:54:42,974 --> 00:54:44,275
And in that way,

1503
00:54:44,974 --> 00:54:47,215
eliminating the Doppler shift because the atoms would

1504
00:54:47,215 --> 00:54:50,034
be trapped in over such a small distance

1505
00:54:50,335 --> 00:54:52,655
that effectively the thing called, there's a thing

1506
00:54:52,655 --> 00:54:54,255
called Dicke narrowing that,

1507
00:54:54,690 --> 00:54:56,609
that that gets rid of the Doppler shift.

1508
00:54:56,609 --> 00:54:58,070
And so this would be great.

1509
00:54:59,409 --> 00:55:01,650
Ten years before there was even laser cooling

1510
00:55:01,650 --> 00:55:03,089
that would allow you to put the atoms

1511
00:55:03,089 --> 00:55:05,329
in such a thing, that just wasn't possible,

1512
00:55:05,329 --> 00:55:07,724
but he had the idea. Well, that's exactly

1513
00:55:07,784 --> 00:55:09,784
what Junyi does in his lab. He puts

1514
00:55:09,784 --> 00:55:12,105
the atoms in an optical lattice and holds

1515
00:55:12,105 --> 00:55:13,704
them in place and then uses that as

1516
00:55:13,704 --> 00:55:16,425
an atomic clock. Well, okay. So everybody knew

1517
00:55:16,425 --> 00:55:18,905
this was a was was a thing, but

1518
00:55:18,905 --> 00:55:19,405
we

1519
00:55:20,425 --> 00:55:21,804
saw that process

1520
00:55:22,139 --> 00:55:24,940
of the atoms being trapped in the optical

1521
00:55:24,940 --> 00:55:25,440
lattice

1522
00:55:26,139 --> 00:55:28,380
in our laser cooled samples when we weren't

1523
00:55:28,380 --> 00:55:29,359
looking for it.

1524
00:55:29,739 --> 00:55:32,079
We were trying to measure the temperature

1525
00:55:32,859 --> 00:55:33,760
of the atoms

1526
00:55:34,460 --> 00:55:35,519
in the,

1527
00:55:35,900 --> 00:55:37,359
the laser cooling configuration

1528
00:55:38,214 --> 00:55:41,014
Instead of turning lasers off and just letting

1529
00:55:41,014 --> 00:55:41,994
the atoms expand

1530
00:55:42,454 --> 00:55:44,775
and measuring the temperature from the distribution of

1531
00:55:44,775 --> 00:55:47,014
velocities, instead, we wanted to measure what the

1532
00:55:47,014 --> 00:55:49,755
temperature was while they were being laser cooled.

1533
00:55:51,094 --> 00:55:52,920
And the idea we came up with was,

1534
00:55:53,159 --> 00:55:55,339
let's look at the Doppler shift

1535
00:55:55,719 --> 00:55:57,799
induced by the scattered light. So light comes

1536
00:55:57,799 --> 00:55:59,960
in, and if it bounces off an atom

1537
00:55:59,960 --> 00:56:02,119
that's moving, there'll be a Doppler shift, and

1538
00:56:02,119 --> 00:56:03,880
we can measure that Doppler shift and see

1539
00:56:03,880 --> 00:56:06,440
what the distribution of velocities was. So we

1540
00:56:06,440 --> 00:56:09,255
did that, and the distribution of velocities just

1541
00:56:09,255 --> 00:56:11,755
floored us. It was so odd.

1542
00:56:12,054 --> 00:56:14,554
Instead of being a nice smooth broad distribution

1543
00:56:14,695 --> 00:56:15,675
showing the distribution

1544
00:56:16,215 --> 00:56:16,875
of of velocities,

1545
00:56:17,335 --> 00:56:19,755
it was that with a big sharp peak

1546
00:56:20,010 --> 00:56:20,989
right in the middle.

1547
00:56:22,409 --> 00:56:23,710
So what is this peak?

1548
00:56:24,170 --> 00:56:24,650
And,

1549
00:56:25,050 --> 00:56:27,369
and and and we fought for a very

1550
00:56:27,369 --> 00:56:29,210
short period of time. Did we accidentally make

1551
00:56:29,210 --> 00:56:30,110
a Bose condensate?

1552
00:56:30,570 --> 00:56:33,050
Because this is before peep anybody made a

1553
00:56:33,050 --> 00:56:35,390
Bose condensate, but people were talking about it.

1554
00:56:35,875 --> 00:56:37,394
Then we realized, no. No. That's not what

1555
00:56:37,394 --> 00:56:39,555
we did at all. What we're doing is

1556
00:56:39,555 --> 00:56:41,954
we're trapping the atoms so the Doppler shift

1557
00:56:41,954 --> 00:56:43,954
goes away. So this thing that we were

1558
00:56:43,954 --> 00:56:46,434
trying to learn about, the Doppler shift, was

1559
00:56:46,434 --> 00:56:49,210
partly being canceled because the atoms were being

1560
00:56:49,210 --> 00:56:51,130
held in what we now call an optical

1561
00:56:51,130 --> 00:56:51,630
lattice.

1562
00:56:51,930 --> 00:56:52,590
And then

1563
00:56:53,130 --> 00:56:55,789
people started to do it everywhere, and,

1564
00:56:56,329 --> 00:56:58,570
and now it's led to these wonderful clocks

1565
00:56:58,570 --> 00:57:00,905
that have the atoms in the optical lattice.

1566
00:57:00,905 --> 00:57:02,364
So that was another case.

1567
00:57:02,664 --> 00:57:03,965
It wasn't nearly as

1568
00:57:04,505 --> 00:57:05,005
astounding

1569
00:57:05,704 --> 00:57:08,744
as the sub Doppler laser cooling because it

1570
00:57:08,744 --> 00:57:10,824
was expected. It's just that we weren't looking

1571
00:57:10,824 --> 00:57:12,264
for it at the time that we saw

1572
00:57:12,264 --> 00:57:13,409
it, but that

1573
00:57:15,089 --> 00:57:17,989
theme of learning about things accidentally

1574
00:57:19,089 --> 00:57:21,010
has seems like it's been a recurring theme

1575
00:57:21,010 --> 00:57:21,829
in our laboratory.

1576
00:57:22,130 --> 00:57:23,969
And I think it's an important thing for

1577
00:57:23,969 --> 00:57:24,469
people

1578
00:57:25,089 --> 00:57:27,089
to understand about the way that science is

1579
00:57:27,089 --> 00:57:27,909
done. Often,

1580
00:57:28,385 --> 00:57:31,585
science is done not because people are looking

1581
00:57:31,585 --> 00:57:33,045
for a particular goal

1582
00:57:33,344 --> 00:57:36,545
and working towards that, but it happens because

1583
00:57:36,545 --> 00:57:37,844
they're fooling around

1584
00:57:38,385 --> 00:57:39,525
and see something

1585
00:57:39,824 --> 00:57:41,045
that wasn't expected.

1586
00:57:42,359 --> 00:57:44,059
And we have to

1587
00:57:44,599 --> 00:57:45,099
have

1588
00:57:45,799 --> 00:57:46,699
a lot of

1589
00:57:47,079 --> 00:57:48,299
that kind of activity.

1590
00:57:48,920 --> 00:57:51,480
If all of our science activity is directed

1591
00:57:51,480 --> 00:57:51,980
toward

1592
00:57:52,440 --> 00:57:54,859
specific goals, we're gonna miss

1593
00:57:55,364 --> 00:57:57,684
a lot of really important stuff that allows

1594
00:57:57,684 --> 00:57:59,144
us to get to those goals.

1595
00:57:59,525 --> 00:58:02,164
And this idea of what is sometimes called

1596
00:58:02,164 --> 00:58:03,704
curiosity driven research

1597
00:58:04,405 --> 00:58:05,704
just fooling around,

1598
00:58:06,485 --> 00:58:09,364
is so important to the development of science.

1599
00:58:09,364 --> 00:58:11,599
And and without it, we're just not gonna

1600
00:58:11,599 --> 00:58:12,980
get to where we need to go.

1601
00:58:14,559 --> 00:58:17,280
So final question, maybe the most nebulous one

1602
00:58:17,280 --> 00:58:20,500
of all. What does quantum mean to you?

1603
00:58:20,800 --> 00:58:21,300
Yeah.

1604
00:58:21,920 --> 00:58:22,739
So interestingly,

1605
00:58:23,039 --> 00:58:25,680
I was on a panel a couple of

1606
00:58:25,680 --> 00:58:26,420
years ago

1607
00:58:27,144 --> 00:58:28,844
that was run out of Oxford,

1608
00:58:30,184 --> 00:58:32,364
in which they had gathered

1609
00:58:33,065 --> 00:58:35,324
a handful of Nobel laureates together

1610
00:58:35,784 --> 00:58:36,444
in physics

1611
00:58:36,744 --> 00:58:38,744
to answer the question, what was the most

1612
00:58:38,744 --> 00:58:39,884
important discovery

1613
00:58:41,269 --> 00:58:43,050
of twentieth century physics?

1614
00:58:43,829 --> 00:58:44,329
And

1615
00:58:45,429 --> 00:58:46,969
most of us said quantum mechanics.

1616
00:58:48,550 --> 00:58:49,050
And

1617
00:58:49,429 --> 00:58:51,429
so when it was my turn, I said

1618
00:58:51,429 --> 00:58:52,250
quantum mechanics.

1619
00:58:52,710 --> 00:58:54,250
You know, what is quantum mechanics?

1620
00:58:54,550 --> 00:58:56,625
Just the I said, it's it's

1621
00:58:57,105 --> 00:58:59,525
the fact that particles behave like waves,

1622
00:58:59,985 --> 00:59:01,684
which we haven't even talked about here,

1623
00:59:01,985 --> 00:59:05,905
and waves behave like particles. This wave particle

1624
00:59:05,905 --> 00:59:08,804
duality is at the heart of quantum mechanics.

1625
00:59:08,945 --> 00:59:10,164
And that understanding,

1626
00:59:11,460 --> 00:59:12,579
which a lot of people would say was

1627
00:59:12,579 --> 00:59:14,440
sort of the ordinary part of quantum mechanics,

1628
00:59:14,739 --> 00:59:15,480
that understanding

1629
00:59:16,579 --> 00:59:19,000
led to a technological revolution

1630
00:59:19,380 --> 00:59:20,359
that completely

1631
00:59:20,659 --> 00:59:22,519
changed our daily lives.

1632
00:59:22,900 --> 00:59:24,704
We all walk around with

1633
00:59:25,184 --> 00:59:26,164
mobile phones

1634
00:59:26,465 --> 00:59:27,285
that wouldn't

1635
00:59:27,664 --> 00:59:29,925
exist were it not for quantum mechanics. Semiconductor

1636
00:59:30,305 --> 00:59:33,744
electronics depends upon the quantum mechanical nature of

1637
00:59:33,744 --> 00:59:35,985
electrons. And I'm just looking around at the

1638
00:59:35,985 --> 00:59:36,625
kind of,

1639
00:59:37,025 --> 00:59:39,750
electronic devices that you're using for for for

1640
00:59:39,750 --> 00:59:40,969
this, and and

1641
00:59:41,269 --> 00:59:43,829
it's it's all quantum mechanics. So for me,

1642
00:59:43,829 --> 00:59:45,769
quantum mechanics is this idea

1643
00:59:46,150 --> 00:59:48,650
that waves are particles and particles are waves

1644
00:59:48,710 --> 00:59:51,449
and that this has led to a technology

1645
00:59:51,829 --> 00:59:53,750
that has changed our daily lives in a

1646
00:59:53,750 --> 00:59:54,809
fundamental way.

1647
00:59:55,644 --> 00:59:56,465
Steve Weinberg

1648
00:59:57,325 --> 00:59:59,425
was also on this panel.

1649
00:59:59,805 --> 01:00:02,285
And when it came time for him to

1650
01:00:02,285 --> 01:00:02,785
say

1651
01:00:03,244 --> 01:00:05,405
to answer this question, what is quantum mechanics?

1652
01:00:05,405 --> 01:00:08,465
He says, well, quantum mechanics is the departure

1653
01:00:08,684 --> 01:00:09,184
from

1654
01:00:09,690 --> 01:00:12,670
classical mechanics where we thought of particles

1655
01:00:13,289 --> 01:00:15,530
as having a position and a momentum, and

1656
01:00:15,530 --> 01:00:16,349
we described

1657
01:00:16,889 --> 01:00:18,030
the state of something

1658
01:00:18,329 --> 01:00:20,650
by saying what the position and momentum was

1659
01:00:20,650 --> 01:00:22,734
of all the particles in the system. In

1660
01:00:22,734 --> 01:00:23,554
quantum mechanics,

1661
01:00:24,094 --> 01:00:25,635
it's a vector in Hilbert space.

1662
01:00:27,295 --> 01:00:28,974
And I thought this is the difference between

1663
01:00:28,974 --> 01:00:30,675
an experimentalist and a theorist.

1664
01:00:32,335 --> 01:00:34,914
And, of course, Hilbert space behaves differently from

1665
01:00:35,090 --> 01:00:35,590
from

1666
01:00:35,969 --> 01:00:38,849
regular space, and so everything behaves differently. But

1667
01:00:38,849 --> 01:00:40,789
but the perspective you see,

1668
01:00:41,489 --> 01:00:43,090
both of which are, of course, are true

1669
01:00:43,090 --> 01:00:44,949
and both of which I think embody

1670
01:00:45,809 --> 01:00:46,309
the

1671
01:00:47,170 --> 01:00:49,429
the the wonder of of quantum mechanics.

1672
01:00:50,894 --> 01:00:52,575
But but we had very different points of

1673
01:00:52,575 --> 01:00:54,594
view about what quantum mechanics was.

1674
01:00:55,695 --> 01:00:57,135
Bill Phillips, thank you so much. It's been

1675
01:00:57,135 --> 01:00:58,735
really wonderful to talk to you. It's been

1676
01:00:58,735 --> 01:00:59,315
a pleasure.

1677
01:01:06,750 --> 01:01:10,190
That was the Nobel laureate William Phillips in

1678
01:01:10,190 --> 01:01:13,010
conversation with Physics World's Margaret Harris.

1679
01:01:13,549 --> 01:01:15,389
I'm afraid that's all the time we have

1680
01:01:15,389 --> 01:01:16,609
for this week's podcast.

1681
01:01:17,015 --> 01:01:19,594
Thanks to Bill and Margaret for a fascinating

1682
01:01:19,655 --> 01:01:20,155
discussion,

1683
01:01:20,535 --> 01:01:22,155
and also to our producer,

1684
01:01:22,454 --> 01:01:23,434
Fred Isles.

1685
01:01:23,735 --> 01:01:26,235
And a very special thank you to Atlas

1686
01:01:26,295 --> 01:01:26,795
Technologies

1687
01:01:27,175 --> 01:01:29,835
for their generous support of this episode.

1688
01:01:30,680 --> 01:01:32,760
We'll be back again next week, but in

1689
01:01:32,760 --> 01:01:35,500
the meantime, do check out the latest episode

1690
01:01:35,640 --> 01:01:37,900
of the Physics World Stories podcast.

1691
01:01:38,360 --> 01:01:41,740
Host Andrew Glester is joined by three expert

1692
01:01:41,800 --> 01:01:42,300
guests

1693
01:01:42,614 --> 01:01:45,514
to explore the impact of artificial intelligence

1694
01:01:46,135 --> 01:01:46,875
on discovery,

1695
01:01:47,494 --> 01:01:49,914
research, and the future of physics.

1696
01:01:50,534 --> 01:01:53,655
That episode is called AI and the future

1697
01:01:53,655 --> 01:01:54,315
of physics,

1698
01:01:54,614 --> 01:01:56,534
and you can find it on the Physics

1699
01:01:56,534 --> 01:01:57,355
World website

1700
01:01:57,840 --> 01:02:00,660
or at your favorite podcast provider.

1701
01:02:01,760 --> 01:02:04,980
Atlas Technologies is happy to support this episode

1702
01:02:05,280 --> 01:02:08,260
and the exciting work being done in quantum

1703
01:02:08,320 --> 01:02:08,820
science.

1704
01:02:09,440 --> 01:02:12,500
Atlas helps solve engineering challenges everywhere.

1705
01:02:13,074 --> 01:02:14,135
Particle colliders,

1706
01:02:14,594 --> 01:02:16,135
space missions, quantum,

1707
01:02:16,515 --> 01:02:17,015
cryogenics,

1708
01:02:17,554 --> 01:02:18,295
and more.

1709
01:02:18,835 --> 01:02:22,775
Custom vacuum chambers and bimetal flanges and fittings

1710
01:02:23,074 --> 01:02:26,614
are built in Atlas' fully integrated facility

1711
01:02:27,010 --> 01:02:28,550
with on-site design,

1712
01:02:28,849 --> 01:02:29,349
development,

1713
01:02:29,650 --> 01:02:31,510
and manufacturing capabilities.

1714
01:02:32,450 --> 01:02:36,470
Learn more at atlasuhv.com.