Radiant chills: the revolutionary science of laser cooling

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- Physics world.

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Hello and welcome to the
Physics World Stories Podcast.

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I'm Andre Gluster. And
to take us on a journey

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through the stories of laser
cooling, here's our guest.

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- My name's Chad Zel.

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I'm a professor at Union College
in Schenectady, New York.

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And, uh, I'm also for my sins,

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the chair of the department at the moment.

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- The discovery of laser cooling
has transformed the field

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of atomic physics and led to
a number of Nobel Prize wins

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and real world applications
through atomic clocks,

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GPS technology, and now
laying the foundations

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for quantum computing.

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In addition to his research
in atomic, molecular

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and optical physics, Chad has been an

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accomplished science communicator.

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He's a prolific blogger

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and author of several books, including How

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to Teach Quantum Physics to Your Dog.

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Chad has been exploring the
story so far of laser cooling

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with his trilogy of features
for physics world At the time

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that this podcast goes live,

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the first two articles are
already available on physics

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world.com, entitled Cold and Colder,

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and the final installment
called Coldest will be available

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from early January, 2024.

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- Yeah, laser cooling, right?

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It, it sounds like something
that is just, you know,

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air conditioning the laser lab
or, or something like that.

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Uh, but in fact, it's,

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it's a wonderfully
counterintuitive area of physics,

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which is you can make a gas of atoms cold

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by shining laser light on it.

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That seems like the

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exact opposite of what you expect, right?

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You think lasers shining on things.

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You think things getting
really hot, things exploding,

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you know, the death star whatever.

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Um, but in fact, uh,

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what you can do is you can use
carefully arrange laser beams

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to slow down the motion of atoms

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from something approximately
the speed of sound, uh,

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for a gas of atoms at room
temperature, down to a speed

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of a few centimeters per second of a,

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a rapidly moving insect.

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Um, and you can do that, uh,

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by using forces exerted by laser light.

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So just shining light on a gas

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of atoms can make those
atoms move slowly, slower.

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Motion is equal to lower temperature,

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and so lasers can cool a gas of atoms.

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- You've done it now, 'cause
you mentioned Star Wars,

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but why is it then that
if we fire a laser at

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the death star, then it blows up?

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I mean, maybe unsatisfactorily
and it's able to be rebuilt

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and everything, but why
doesn't it just call it down?

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- Uh, what happens if you're
talking about something like a,

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a macroscopic object, right?

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And you shine light on it, it'll absorb

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light over a very broad
range of frequencies,

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and it picks up the energy
that was carried by the light,

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and then that energy goes
into vibrations of, of things.

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It heats up the, the system

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and it gets, gets transferred there.

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Um, and so that, that
energy just comes in and,

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and doesn't, uh, go back out.

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Um, in, in the same form.

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It, it changes from energy
carried by the light

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to energy in the, the kinetic
energy of, of the atoms

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and molecules making a thing up.

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And, you know, if you have enough,

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you dump enough energy in, it'll,

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it'll heat up significantly
and, and blow up.

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Um, if you're talking
about, uh, atoms though,

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atoms are very simple
and they'll only absorb

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and emit very particular
frequencies of light,

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and there's nowhere for that energy to go.

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Once it's in the atom, right?

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The atom, uh, has a
photon of light come in,

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it gets some amount of energy, it puts

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that energy into the orbit of the electron

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around the nucleus.

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Uh, and then sometime later it
will remit that, that light,

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uh, at more or less the same frequency

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that it, that it came in.

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There's nowhere for that energy
to go, generally speaking.

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So, uh, whatever comes in, goes
right back out, uh, in terms

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of the internal states of the atom.

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Now, the light can also
affect the external states

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of the atom, right?

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So because the photon carries,
uh, energy, the photon is,

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you can think of it as
a little bundle of some,

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some very tiny amount of
energy carried in the light

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by Einstein's relativity.

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That also means it has some momentum.

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And when the atom absorbs the, the photon,

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that momentum gets trans
transferred to the atom as well.

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So the energy mostly goes
into, um, increasing the,

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the energy of the electron and its orbit.

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But this momentum goes
into how the, the nucleus,

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how the entire atom is moving.

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Now, if an atom is sitting still

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and absorbs a photon, it'll
heat up exactly like you expect

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to, because, you know,
it's just sitting there.

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It gets a kick from this,
uh, photon coming in,

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and that sends it off
moving in some direction.

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But if the atom is
moving toward the laser,

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when it absorbs the the
photon, it will slow down.

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It gets that same kick that
momentum is transferred,

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but that momentum acts to reduce

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the speed at which the atom
is moving, which, you know,

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slows down its motion
and slow equals cold.

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The reason we want atoms to
be moving more slowly is,

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is the primary way we know
about what's going on inside

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of atoms is doing spectroscopy,
looking at the colors

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of the light that they absorb and emit,

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and the colors of the
light that they absorb

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and emit are shifted by
the doppler effect, right?

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The doppler effect is this
change in the frequency

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of waves from a moving source

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that's most familiar in the
case of, of sound waves, right?

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If you, if you watch,
you know, you know, any,

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any toddler can tell you, right?

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The noise that a, that
a race car makes, right?

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Is that no noise as as it goes by.

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That's the Doppler effect.

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As the car is coming toward
you, the engine sound is shifted

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to a higher frequency.

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And, uh, as it goes away
from you, it's shifted

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to a lower frequency,

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and it changes very rapidly from one

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to the other as it goes by.

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Um, that doppler effect,
uh, also happens with light.

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So an atom that's moving
at something like the speed

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of sound has a fairly
substantial Doppler effect, uh,

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changing the frequency of
the light that it absorbs,

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and the light that it emits,
which limits our ability to,

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to study the properties of, of atoms.

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If we can reduce that velocity,

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if we can take it from the speed
of sound down to, you know,

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centimeter per second speeds,

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then we can do incredibly
precise spectroscopy of the,

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the states of, of these atoms,

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because they're moving

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so slowly in the doppler shift
is essentially eliminated.

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Uh, this is most important in
the case of atomic clocks, uh,

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which are really in some
sense light clocks, right?

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Uh, the definition of a second is it's

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9,192,631,770

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oscillations of the
microwaves that are absorbed

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and emitted in making a
transition between two states

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and a cesium atom, right?

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Our ability to measure
that is constrained by

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how fast those cesium atoms are moving.

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So the very best atomic clocks
made today use cesium atoms

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that are laser cooled to a
small fraction of a degree

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above absolute zero speeds
of centimeters per second.

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At which point we can
measure that, that frequency

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with amazing precision, uh, the best, uh,

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atomic clocks using laser
cooled atoms are good to around,

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uh, a second and a billion years, right?

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If you had two of these clocks, uh,

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two identical clocks running next

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to each other would take
a billion years, give

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or take, for them to drift
apart by, by one second.

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Um, and we can do even better than that

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with experimental clocks
that are, that are good to,

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you know, a second in more
than the age of the universe.

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Uh, so, uh,

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and these, again, use these,
these laser cooled atoms

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to make these incredibly precise
spectroscopic measurements.

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- Okay? But why does that
matter to people on the street?

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- It turns out to matter
enormously to people on the street

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who want to know where they're going, uh,

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because the, the basis of, uh, a lot

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of modern navigation, right?

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If you use one of those, the Google Maps

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or Apple Maps, whatever,
whatever app you use to navigate,

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um, those are relying on the
global positioning system,

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which is a set

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of atomic clocks on satellites up in space

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that are broadcasting the time.

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And your, your receiver, uh,

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detects the time signal from
several different satellites

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and uses that to determine

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how long it took the radio
signal from the satellite to get

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to you, which tells you
your distance, the distance

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between you and the satellite,
um, which allows you

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to determine your position on
the, the surface of the earth.

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If you know several of these,
these travel times, um,

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that allows you to
determine your position, uh,

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but it's, your position is
only as good as the, the clocks

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that you have, uh, and light travels.

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Uh, it's the, the one case where, uh,

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American units are superior,

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light travels about one
foot in a nanosecond.

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And, um, that, that means
that if you wanna know

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where you are on the earth
to within, say, a meter,

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you need the timing to within

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a little more than three nanoseconds.

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Um, and for that you need atomic clocks.

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And the better the atomic
clocks, the better the timing,

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which means the better you can do

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with things like the global position. So

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- How was all this discovered?

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You know, what, what were
the beginnings of this as a

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- Science?

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The story of laser cooling
really starts in the,

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the 1960s when people first,
you know, invented lasers and,

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and started playing around with them.

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And, and, uh, they noticed that,
that you would see sort of,

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uh, specks of dust sort of
popping in and out of the beam,

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and it looked like they
were kind of getting pushed

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around by the light.

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Uh, so a guy named Art
Ashkin, uh, did some back

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of the envelope calculations and,

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and worked out that, you know,
you could actually use light

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to exert, uh,

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fairly substantial forces
on very small objects.

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Um, and this had actually been measured

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before in the, in the thirties.

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Uh, there's, uh, uh, a fabulous set of,

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of very early experiments, uh,
done that, that demonstrated

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that you could use light
to exert forces on atoms,

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that you could transfer this
momentum from photons to,

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to atoms and deflect
them by a tiny amount.

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But nobody could really do
anything with it until you,

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you had a laser, which allows
you to throw, you know,

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an essentially infinite
number of photons at,

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uh, at something.

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So, uh, art Ashkin at Bell
Labs started playing around

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with this and demonstrated
that they could, uh, use this,

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these forces from light to,
to manipulate small, uh,

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beads basically, uh, and,

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and push them around, uh, with
these, these light forces.

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Um, which, you know,
then it's a new way to,

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to manipulate microscopic objects.

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And, and they started doing
this in the, the early

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to mid 1970s.

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Um, this gets, uh, connected
up to, to Adams, uh, thanks to,

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to two, uh, people who are
now at, at NIST in, in the us.

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Um, uh, one of them is, is Dave
Weinland, uh, who's one of,

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uh, four people who, who, um, were part

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of the original proposals
of, of doing, uh,

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00:11:12,055 --> 00:11:13,605
laser cooling of atoms.

246
00:11:13,665 --> 00:11:15,685
Uh, it's, it's Dave Weinland

247
00:11:15,685 --> 00:11:19,645
and his, his PhD advisor, Hans
Day Melt, wrote a paper on,

248
00:11:19,945 --> 00:11:21,605
um, using these light forces

249
00:11:21,785 --> 00:11:23,725
to manipulate specifically Adams.

250
00:11:24,345 --> 00:11:27,085
Uh, and the other is, uh, art Sallow

251
00:11:27,265 --> 00:11:30,845
and, uh, Ted Hench, uh,
Theodore Hench won a Nobel Prize

252
00:11:31,425 --> 00:11:35,645
for, uh, work on, on, um,
high frequency lasers.

253
00:11:37,235 --> 00:11:39,495
Uh, they also had a, a
proposal both of these in a,

254
00:11:39,495 --> 00:11:42,975
around 1975, looking at the
idea of using these forces

255
00:11:43,535 --> 00:11:45,855
specifically to cool atoms and,

256
00:11:45,915 --> 00:11:47,935
and selectively slow the motion of atoms.

257
00:11:48,555 --> 00:11:52,535
Um, so in the, in the mid 1970s,
uh, weinland and day melt,

258
00:11:52,535 --> 00:11:53,685
and, uh, Shiloh

259
00:11:53,685 --> 00:11:56,405
and hench, uh, come up
with this, this idea

260
00:11:56,545 --> 00:11:59,165
of using these forces to slow down atoms.

261
00:11:59,625 --> 00:12:02,605
Uh, and then, uh, wineland went to the,

262
00:12:02,755 --> 00:12:05,605
then the National Bureau of
Standards, now NIST in Boulder,

263
00:12:06,105 --> 00:12:09,125
to, uh, start doing these,
these experiments, uh,

264
00:12:09,125 --> 00:12:11,005
which was a, a side project to

265
00:12:11,555 --> 00:12:13,125
what he was actually hired to do.

266
00:12:13,185 --> 00:12:15,245
But they, they brought
him in with the promise

267
00:12:15,275 --> 00:12:17,365
that he could do some of his own thing.

268
00:12:18,065 --> 00:12:21,365
Uh, and, uh, around the same
time, a few years later,

269
00:12:21,435 --> 00:12:24,765
bill Phillips, um, ended
up going to, uh, the,

270
00:12:24,785 --> 00:12:26,005
the other National Bureau

271
00:12:26,005 --> 00:12:27,685
of Standards Lab in
Gaithersburg, Maryland.

272
00:12:28,305 --> 00:12:31,845
And he also was hired with
the promise that he could, uh,

273
00:12:31,905 --> 00:12:34,645
do some side projects
of, of his own choosing,

274
00:12:34,785 --> 00:12:36,565
and decided to pursue laser cooling.

275
00:12:37,245 --> 00:12:40,525
Wineland did, uh, laser
cooling of, of ions,

276
00:12:40,525 --> 00:12:42,805
because that's what he
had been working on, uh,

277
00:12:42,805 --> 00:12:46,725
for his thesis is, is trapping
these, uh, charged particles.

278
00:12:47,385 --> 00:12:50,525
And so he looked at, at
ways to use, uh, lasers to,

279
00:12:50,545 --> 00:12:51,765
to slow the motion of those.

280
00:12:52,265 --> 00:12:55,365
Uh, Phillips, uh, looked
at at doing neutral atoms.

281
00:12:55,365 --> 00:12:58,565
He had been studying, uh,
properties of atoms as part of,

282
00:12:58,625 --> 00:12:59,645
uh, of his thesis.

283
00:12:59,825 --> 00:13:01,565
And so he said, you know, we
could do the same thing with,

284
00:13:01,565 --> 00:13:03,045
with, uh, neutral atoms.

285
00:13:03,505 --> 00:13:05,645
And there are pros and
cons to, to both of those.

286
00:13:05,985 --> 00:13:07,725
But, um, that's really,

287
00:13:07,905 --> 00:13:12,485
or where the, the, the study
of this, uh, applying this

288
00:13:12,485 --> 00:13:14,405
to Adams really, really gets going. You

289
00:13:14,405 --> 00:13:16,845
- Mentioned the Nobel Prize,
and it's an area of physics

290
00:13:16,995 --> 00:13:19,925
that has actually won quite a few of them.

291
00:13:20,655 --> 00:13:21,725
There are a few stories

292
00:13:21,725 --> 00:13:24,445
that you share in your three features.

293
00:13:24,785 --> 00:13:26,205
Do you have a particular favorite,

294
00:13:27,035 --> 00:13:29,045
- Like my, my favorite story relating

295
00:13:29,045 --> 00:13:31,925
to Nobel Prizes in this
is a, a story that, that,

296
00:13:31,925 --> 00:13:33,325
that Bob Drollinger told.

297
00:13:33,465 --> 00:13:36,245
He was a colleague of, of
Dave Weinland's at, uh,

298
00:13:36,785 --> 00:13:38,445
at NIST in, in Boulder.

299
00:13:38,825 --> 00:13:40,525
And, uh, they were
working together on this.

300
00:13:40,555 --> 00:13:43,605
They had, uh, Wineland was
doing the vacuum system,

301
00:13:44,225 --> 00:13:48,125
and, uh, the ion trap to, to,
you know, initially hold the,

302
00:13:48,125 --> 00:13:50,645
the sample of atoms and
dinger was the laser guy.

303
00:13:50,985 --> 00:13:54,085
He was, he put together a
laser system that could,

304
00:13:54,255 --> 00:13:56,925
could do the extremely
inconvenient frequencies

305
00:13:56,925 --> 00:13:59,645
that you needed to, to
do to, to cool these,

306
00:13:59,645 --> 00:14:00,925
these trap ions.

307
00:14:01,545 --> 00:14:05,505
Um, and so they were, uh,
they were working on this,

308
00:14:05,505 --> 00:14:07,465
and they, they set up
their first experiment

309
00:14:07,685 --> 00:14:10,585
and, uh, they're, they're
in the lab late at night

310
00:14:10,585 --> 00:14:13,985
because these first experiments
always happen late at night.

311
00:14:14,565 --> 00:14:16,985
And, uh, they, they turn on the laser

312
00:14:17,085 --> 00:14:18,585
and they saw exactly the signal.

313
00:14:18,585 --> 00:14:21,345
They expected they had this
sample of trapped ions.

314
00:14:21,575 --> 00:14:23,225
They could measure the temperature by

315
00:14:23,225 --> 00:14:25,905
how much electrical noise
these, these ions were making.

316
00:14:26,165 --> 00:14:29,025
And they turned on the laser,
the noise level went down,

317
00:14:29,025 --> 00:14:31,425
which told you the, the
ions were getting cold

318
00:14:31,685 --> 00:14:33,865
and worked exactly as
they expected, exactly

319
00:14:33,865 --> 00:14:35,105
where they expected it to be.

320
00:14:35,685 --> 00:14:38,545
Um, and so Dinger says
that they're in the lab,

321
00:14:38,895 --> 00:14:41,465
it's late at night,
they've just done this.

322
00:14:41,605 --> 00:14:42,745
And he said, you know, like,

323
00:14:42,745 --> 00:14:45,145
there's this wonderful
feeling of excitement.

324
00:14:45,525 --> 00:14:47,705
He said, but I didn't know
what we were gonna do next.

325
00:14:48,285 --> 00:14:53,045
And so, you know, I said to
Dave, what do we, you know,

326
00:14:53,045 --> 00:14:54,045
where do we go from here?

327
00:14:54,505 --> 00:14:57,365
And he said, he looked across
the, the laser table at,

328
00:14:57,365 --> 00:15:00,565
at wineland is lit only by the,
the, the glow of the lasers.

329
00:15:00,945 --> 00:15:03,405
And he said, this, this
smile comes over his face,

330
00:15:03,425 --> 00:15:05,605
and he says, Stockholm, oh,

331
00:15:05,805 --> 00:15:06,805
- <laugh>.

332
00:15:07,265 --> 00:15:10,005
- So, 'cause they knew right
away that they had something

333
00:15:10,195 --> 00:15:12,405
that was, that was just
absolutely fantastic.

334
00:15:12,825 --> 00:15:14,325
- But it took a while, didn't it, for them

335
00:15:14,345 --> 00:15:15,445
to actually win the prize.

336
00:15:15,945 --> 00:15:19,525
- It took a while to, to get
the, the Nobel Prizes, uh, the,

337
00:15:19,705 --> 00:15:23,685
the first of the Nobel Prizes
actually went to, to Phillips

338
00:15:24,025 --> 00:15:25,205
and Steve Chu

339
00:15:25,465 --> 00:15:29,085
and Claude Cohen to Nugi for
laser cooling of, of neutrals.

340
00:15:29,625 --> 00:15:33,325
Um, Wineland, uh, got
the, got the prize, uh,

341
00:15:33,325 --> 00:15:36,645
several years later, uh, for,
for his experiments with ions.

342
00:15:37,065 --> 00:15:39,205
Uh, and the, the ion
experiments are really amazing

343
00:15:39,445 --> 00:15:41,605
'cause they can get down to, to, you know,

344
00:15:41,605 --> 00:15:43,005
incredibly low temperatures

345
00:15:43,005 --> 00:15:47,525
and trapping these single ions
that are now a platform for,

346
00:15:47,665 --> 00:15:48,925
for quantum computing.

347
00:15:48,945 --> 00:15:52,805
And really completely revolutionized
that, that whole field

348
00:15:52,865 --> 00:15:54,125
of, of, of things.

349
00:15:54,795 --> 00:15:58,205
- Okay. So we have quantum
computers such as they are

350
00:15:58,785 --> 00:16:00,925
at the moment, and such as
they will be because of this

351
00:16:01,345 --> 00:16:02,345
- In part.

352
00:16:02,345 --> 00:16:03,925
Yeah. One of the big
things that, that, uh,

353
00:16:04,095 --> 00:16:08,365
kicks off the field of, of
quantum computing is it's, it's

354
00:16:08,365 --> 00:16:10,445
around 1994, I think.

355
00:16:10,445 --> 00:16:13,925
There's, uh, a paper by, uh, RAC

356
00:16:14,105 --> 00:16:17,565
and Solar, uh, that it's
a theoretical study,

357
00:16:17,625 --> 00:16:20,445
but they looked at the, the
trapped ion system that Wineland

358
00:16:20,445 --> 00:16:22,565
and his, his team had built in Boulder,

359
00:16:22,705 --> 00:16:25,285
and they said, Hey, you
know, if you had several

360
00:16:25,385 --> 00:16:28,965
of these ions in a trap,
uh, there's this, uh,

361
00:16:28,965 --> 00:16:32,485
collective motion of the,
the several ions back

362
00:16:32,485 --> 00:16:35,245
and forth that you can use to
connect the states together,

363
00:16:35,305 --> 00:16:38,165
and you can actually do the
operations you need to do

364
00:16:38,185 --> 00:16:40,085
to make a quantum
computer with this system.

365
00:16:40,705 --> 00:16:45,085
And, uh, the, the ability to
laser cool these to the lowest

366
00:16:45,645 --> 00:16:48,085
possible energy state gives you just this

367
00:16:48,155 --> 00:16:50,365
unprecedented fidelity for, for this.

368
00:16:50,365 --> 00:16:52,365
And they can do all of
these manipulations.

369
00:16:53,465 --> 00:16:54,885
The, um, RAC

370
00:16:54,885 --> 00:16:56,525
and solar paper on this really gets

371
00:16:57,105 --> 00:17:00,605
people thinking very seriously about, uh,

372
00:17:00,655 --> 00:17:03,205
about quantum computing
specifically in ions.

373
00:17:03,425 --> 00:17:05,085
And, and they start weinland

374
00:17:05,085 --> 00:17:08,005
and his group really start
pursuing that, that field

375
00:17:08,065 --> 00:17:11,965
and that that's become one of
the, the, the best areas of,

376
00:17:12,305 --> 00:17:15,165
of, uh, quantum computing
in terms of, you know,

377
00:17:15,165 --> 00:17:17,605
your ability to manipulate
these, these cubits and,

378
00:17:17,825 --> 00:17:20,085
and read out the, the signal and all that.

379
00:17:21,185 --> 00:17:24,205
- It is tempting to think of,
you know, Nobel Prize winners

380
00:17:24,205 --> 00:17:26,685
of as getting all the
science right, you know,

381
00:17:26,685 --> 00:17:27,685
from the get go.

382
00:17:27,685 --> 00:17:31,125
But there are a couple of
fun stories in your features

383
00:17:31,695 --> 00:17:33,205
about, you know, the,

384
00:17:33,265 --> 00:17:35,525
the experiments not
necessarily going wrong,

385
00:17:35,705 --> 00:17:38,765
but could you just share a couple with me?

386
00:17:39,465 --> 00:17:41,005
- Oh, yeah. There, there, there's,

387
00:17:41,005 --> 00:17:42,805
there's two different
versions of that there.

388
00:17:42,805 --> 00:17:46,885
There's, uh, the, uh, so
there's, there's one with, uh,

389
00:17:46,885 --> 00:17:49,840
Wineland and, and Dinger
were doing the experiment.

390
00:17:49,840 --> 00:17:50,980
And they were, they were using, uh,

391
00:17:50,980 --> 00:17:52,965
magnesium ions is what
they were trying to trap.

392
00:17:53,625 --> 00:17:55,485
And, you know, the first
time they, they set it up,

393
00:17:55,485 --> 00:17:57,565
they've got this trapped
ion signal, they can see

394
00:17:57,565 --> 00:17:59,845
that the ions are kind
of hot from the amount

395
00:17:59,845 --> 00:18:01,565
of electrical noise
that they're picking up.

396
00:18:01,675 --> 00:18:04,165
They turn on the laser, the
ions get cold, it's great.

397
00:18:04,825 --> 00:18:07,485
Um, they do it the, the next day.

398
00:18:07,785 --> 00:18:09,725
And, uh, they turn on the ions

399
00:18:09,745 --> 00:18:11,325
and the, the lasers get colder,

400
00:18:11,585 --> 00:18:14,085
but not as cold as they
did the first time around.

401
00:18:14,145 --> 00:18:15,885
And they're like, oh,
that's, that's weird.

402
00:18:16,185 --> 00:18:18,285
And then they try it again
and it doesn't work at all.

403
00:18:19,145 --> 00:18:22,725
And, um, so they end up
and, and nothing worked.

404
00:18:22,865 --> 00:18:26,205
And they, uh, they end up
tearing the whole system apart,

405
00:18:26,485 --> 00:18:27,565
rebuilding it from the ground up.

406
00:18:27,905 --> 00:18:30,445
Uh, dinger says he, he, he is convinced

407
00:18:30,445 --> 00:18:32,765
that Weinland thought
he had just completely

408
00:18:32,765 --> 00:18:34,085
screwed up the laser system.

409
00:18:34,565 --> 00:18:37,365
'cause Dave, uh, you know,
had built the ion traps

410
00:18:37,365 --> 00:18:38,765
and knew what he was
doing with the ion traps,

411
00:18:38,765 --> 00:18:41,205
and knew that that was
working, uh, perfectly.

412
00:18:41,785 --> 00:18:45,005
Um, and so, but they rebuilt
both systems completely.

413
00:18:45,705 --> 00:18:47,765
And, uh, when they turned
it back on, they had a,

414
00:18:47,845 --> 00:18:48,925
a much better laser system,

415
00:18:48,925 --> 00:18:50,645
and they knew the laser
was in exactly the right

416
00:18:50,645 --> 00:18:51,845
place, and it still didn't work.

417
00:18:52,465 --> 00:18:53,925
And it turned out that they had used,

418
00:18:54,115 --> 00:18:55,845
they had used up all of the magnesium.

419
00:18:55,845 --> 00:18:57,005
They, they were, they had,

420
00:18:57,065 --> 00:18:59,725
and were, in fact, they
had heated up the, the oven

421
00:18:59,725 --> 00:19:02,765
that produced the ions so
much that they were boiling

422
00:19:03,505 --> 00:19:04,645
sodium out of the glass,

423
00:19:04,905 --> 00:19:06,445
and they could trap sodium ions,

424
00:19:06,445 --> 00:19:08,445
which are about the
same mass as magnesium.

425
00:19:08,785 --> 00:19:11,485
So it looked like they
had ions in the trap, uh,

426
00:19:11,545 --> 00:19:13,125
but they were the completely
the wrong element.

427
00:19:13,185 --> 00:19:14,885
And so the lasers didn't
affect them at all.

428
00:19:15,385 --> 00:19:18,085
Um, and so it wasn't D Jinger's
fault with the laser system.

429
00:19:18,105 --> 00:19:20,245
It was, uh, it was, they'd
run outta magnesium,

430
00:19:20,665 --> 00:19:22,845
and so they got more magnesium, they put,

431
00:19:22,845 --> 00:19:23,885
they reloaded the system,

432
00:19:23,885 --> 00:19:25,725
and then it worked great
from there, there on.

433
00:19:26,565 --> 00:19:30,425
Um, the other version of that
is, is, uh, Phillips, uh,

434
00:19:30,455 --> 00:19:33,025
bill Phillips and Hal
Metcalf were doing, uh,

435
00:19:33,865 --> 00:19:35,625
magnetic trapping of sodium atoms.

436
00:19:35,625 --> 00:19:37,905
So they, they had a laser,
they're slowing down a beam

437
00:19:37,905 --> 00:19:40,905
of sodium atoms, and then they
would turn on this collection

438
00:19:40,905 --> 00:19:44,025
of magnetic fields that
would trap the, the atoms.

439
00:19:44,565 --> 00:19:47,145
Uh, and, and then they, you
know, they'd hold them there

440
00:19:47,145 --> 00:19:48,745
for a while, and then,
then they, you know,

441
00:19:48,755 --> 00:19:50,185
flash on some light, and they would see

442
00:19:50,185 --> 00:19:52,425
that these atoms are sticking
around for a very long time.

443
00:19:53,515 --> 00:19:56,215
And they were, uh, they,
they were working on this,

444
00:19:56,355 --> 00:19:57,895
and, you know, they, they got a signal.

445
00:19:57,965 --> 00:20:00,855
They saw these, these,
these atoms trapped.

446
00:20:01,395 --> 00:20:04,255
And then, uh, and then just
nothing worked for a while.

447
00:20:04,395 --> 00:20:06,615
And, and it, uh, it, it wasn't working.

448
00:20:06,675 --> 00:20:09,415
And they said, you know,
okay, this is, you know,

449
00:20:09,635 --> 00:20:10,815
uh, something's wrong here.

450
00:20:10,815 --> 00:20:12,215
We gotta go think about this. So they went

451
00:20:12,215 --> 00:20:13,775
and they got, they got fast food.

452
00:20:13,965 --> 00:20:15,375
They turned everything off in the lab.

453
00:20:15,375 --> 00:20:17,015
They went out, they got a,

454
00:20:17,095 --> 00:20:19,455
a very late dinner at like McDonald's

455
00:20:19,515 --> 00:20:20,655
or someplace like that.

456
00:20:21,195 --> 00:20:23,655
Uh, and they came back, uh,
you know, an hour or so later,

457
00:20:23,715 --> 00:20:25,015
and they turned everything on

458
00:20:25,015 --> 00:20:27,615
and they get this fabulous
signal of trapped atoms.

459
00:20:28,075 --> 00:20:30,015
Uh, and they're like, you know, hooray.

460
00:20:30,015 --> 00:20:31,975
And then the signal slowly
got worse over a couple hours.

461
00:20:32,035 --> 00:20:33,975
And what it turns out is, uh, they were,

462
00:20:34,125 --> 00:20:35,815
they were heating the system up.

463
00:20:36,395 --> 00:20:39,095
Uh, so they were laser cooling
the atoms successfully.

464
00:20:39,275 --> 00:20:41,295
And they were, they were
getting 'em to the area,

465
00:20:41,755 --> 00:20:44,575
but the, the, to make the
magnetic trap, they had to run

466
00:20:44,635 --> 00:20:47,845
so much current through the,
the coils that they were,

467
00:20:47,875 --> 00:20:49,365
they were heating the whole system.

468
00:20:49,545 --> 00:20:53,605
And then the vacuum, uh,
system would degrade, uh,

469
00:20:53,705 --> 00:20:55,525
to the point where they, they, uh,

470
00:20:55,825 --> 00:20:58,645
had all this stray background gas in there

471
00:20:58,835 --> 00:21:01,245
that would knock the, the
sodium atoms out of the trap.

472
00:21:01,245 --> 00:21:02,285
And they couldn't trap anything.

473
00:21:02,365 --> 00:21:03,365
'cause the vacuum was terrible.

474
00:21:04,025 --> 00:21:06,445
Um, and so they, they figured that out,

475
00:21:06,465 --> 00:21:08,005
and they got it, got it fixed up,

476
00:21:08,025 --> 00:21:10,525
and they, they ended up,
um, they ended up working

477
00:21:10,525 --> 00:21:12,565
through the night getting this, this data

478
00:21:12,665 --> 00:21:15,165
and showing that they were,
they were magnetically trapping

479
00:21:15,165 --> 00:21:16,365
these, these sodium atoms.

480
00:21:16,365 --> 00:21:19,525
And then, uh, the, the, the
story they tell is that, uh,

481
00:21:19,785 --> 00:21:20,965
you know, they, they worked all night

482
00:21:20,965 --> 00:21:22,485
and they're like, at six
in the morning, they go

483
00:21:22,485 --> 00:21:24,685
to Bill's house and they root

484
00:21:24,685 --> 00:21:26,925
around in the refrigerator
looking for something to eat,

485
00:21:26,945 --> 00:21:29,005
and they just end up eating ice cream.

486
00:21:29,225 --> 00:21:31,285
And so it's in the morning, uh,

487
00:21:31,395 --> 00:21:34,085
bill Phillips' wife comes
down and, and her husband

488
00:21:34,305 --> 00:21:36,445
and Hal Metcalf are sitting
in the, in the kitchen,

489
00:21:36,985 --> 00:21:38,085
uh, eating ice cream.

490
00:21:38,085 --> 00:21:39,165
And she's like, what, what are you doing?

491
00:21:39,235 --> 00:21:41,285
It's six in the morning and
that ice cream is for the kids.

492
00:21:41,385 --> 00:21:44,085
And they're like, no, no,
no, no, we had a good night

493
00:21:44,445 --> 00:21:45,445
- <laugh>.

494
00:21:45,445 --> 00:21:47,885
- So, you know, so they're
celebrating that, you know, what,

495
00:21:47,885 --> 00:21:49,725
what turned into a Nobel Prize Later on.

496
00:21:54,925 --> 00:21:56,325
- I hope you're enjoying this conversation

497
00:21:56,325 --> 00:21:57,845
with Chad Azel so far.

498
00:21:58,025 --> 00:22:00,845
And just a reminder that he has
written a three part feature

499
00:22:00,925 --> 00:22:03,565
series for Physics World,
all about the history

500
00:22:03,745 --> 00:22:04,805
of laser cooling.

501
00:22:05,225 --> 00:22:06,845
In the first part of this conversation,

502
00:22:06,915 --> 00:22:11,205
Chad mentioned Stephen Chu,
who shared the 1997 Nobel Prize

503
00:22:11,205 --> 00:22:15,285
with Bill Phillips and
Claude Coi, not content

504
00:22:15,285 --> 00:22:16,805
with reaching this pinnacle of science.

505
00:22:17,365 --> 00:22:20,165
Chu also went on to
serve as the US Secretary

506
00:22:20,165 --> 00:22:23,365
of Energy from 2009 to 2013

507
00:22:23,745 --> 00:22:26,445
during Barack Obama's
first presidential team.

508
00:22:27,195 --> 00:22:30,485
Perhaps part of Chu's
suitability to politics is

509
00:22:30,485 --> 00:22:32,845
that he built a reputation as the guy

510
00:22:32,945 --> 00:22:35,125
who gets difficult experiments. Done.

511
00:22:35,635 --> 00:22:40,285
- Yeah. So, uh, so Steve
Chu comes in, he was, uh,

512
00:22:40,645 --> 00:22:43,165
a colleague of Art Kin's at, at Bell Labs.

513
00:22:43,385 --> 00:22:46,125
And, and Ashkin had this, uh, idea of,

514
00:22:46,825 --> 00:22:48,485
of doing laser cooling

515
00:22:48,585 --> 00:22:52,285
and using, um, you know,
did the first demonstrations

516
00:22:52,285 --> 00:22:54,845
of using light to push
around microscopic objects.

517
00:22:54,845 --> 00:22:57,885
But he is using these like
little glass beads and,

518
00:22:57,945 --> 00:23:01,125
and things like that, uh,
to, to push stuff around.

519
00:23:01,595 --> 00:23:04,565
Then they had the idea to
do some of this with Adams,

520
00:23:04,565 --> 00:23:08,365
but he particularly wanted
to do, um, trapping, uh,

521
00:23:08,415 --> 00:23:10,165
using only light, right?

522
00:23:10,305 --> 00:23:14,125
And so using, using just the
forces from laser beams to trap

523
00:23:14,655 --> 00:23:17,005
Adams, um, and, and cool them.

524
00:23:17,825 --> 00:23:19,365
And, uh, that turns out to be a,

525
00:23:19,525 --> 00:23:20,965
a really tricky thing to do.

526
00:23:21,345 --> 00:23:25,165
Um, Ashkin and, and his colleague
John Olm worked on this,

527
00:23:25,225 --> 00:23:27,125
and they did some, some
preliminary experiments,

528
00:23:27,265 --> 00:23:29,325
but they didn't really have
the, the setup to do it.

529
00:23:29,325 --> 00:23:31,645
And, and in fact, their
bosses at Bell Labs started

530
00:23:31,645 --> 00:23:34,205
to tell them, you know,
okay, this has been fun,

531
00:23:34,265 --> 00:23:36,445
but do do something else, right?

532
00:23:36,545 --> 00:23:38,805
Uh, stop, stop working on this so much.

533
00:23:39,345 --> 00:23:43,125
But, um, Chu uh, got transferred into, uh,

534
00:23:43,405 --> 00:23:45,685
a different Bell Labs research facility,

535
00:23:45,975 --> 00:23:48,765
ended up in an office next
to Ashkin and started talking

536
00:23:48,785 --> 00:23:51,285
and then said, no, you know,
I think we can make this work.

537
00:23:51,665 --> 00:23:54,685
And so he was instrumental
in, in really, uh,

538
00:23:54,685 --> 00:23:56,685
taking the ideas that that Ashkin

539
00:23:56,685 --> 00:23:58,525
and Bjork home had had put together

540
00:23:58,665 --> 00:24:02,445
and, you know, building up a,
a much fancier vacuum system

541
00:24:02,665 --> 00:24:04,285
to, to really contain these.

542
00:24:04,385 --> 00:24:07,965
And coming up with, uh, the
idea of, of what they dubbed,

543
00:24:07,965 --> 00:24:09,485
um, optical molasses.

544
00:24:09,715 --> 00:24:13,445
This, uh, idea of overlapping
laser beams going in,

545
00:24:13,465 --> 00:24:16,845
in opposite directions that
will slow down atoms no matter

546
00:24:16,845 --> 00:24:18,045
what direction they're moving in.

547
00:24:18,585 --> 00:24:21,125
And, uh, that gives
you the ability to, to,

548
00:24:21,265 --> 00:24:22,685
to really cool the atoms.

549
00:24:22,685 --> 00:24:25,405
The atoms feel like
they're in a viscous fluid,

550
00:24:25,675 --> 00:24:28,885
thus optical molasses
a very colorful term.

551
00:24:29,265 --> 00:24:31,325
And, um, and,

552
00:24:31,425 --> 00:24:33,485
and it was true that that really got that,

553
00:24:33,515 --> 00:24:35,525
that whole thing working experimentally.

554
00:24:36,105 --> 00:24:40,565
Um, so he was, uh, he had been
doing some experiments on,

555
00:24:40,785 --> 00:24:41,925
uh, positrons

556
00:24:41,925 --> 00:24:44,645
and positron in, uh, in other systems,

557
00:24:44,645 --> 00:24:46,405
something very different, uh,

558
00:24:46,905 --> 00:24:49,205
but got interested in this, in this idea.

559
00:24:49,345 --> 00:24:53,005
And one of the, the neat
things, you know, bell Labs, uh,

560
00:24:53,705 --> 00:24:58,565
had this, this very open
culture at the time of, uh,

561
00:24:58,645 --> 00:25:01,605
I think it's Bjork home, who,
who put it that, you know,

562
00:25:01,705 --> 00:25:04,725
you could work on anything
you wanted as long

563
00:25:04,725 --> 00:25:06,685
as it was world class, right?

564
00:25:06,865 --> 00:25:09,365
So whatever you wanted to study, you were,

565
00:25:09,425 --> 00:25:11,445
you were pretty much
free to study anything

566
00:25:11,445 --> 00:25:12,965
that seemed interesting, as long

567
00:25:12,965 --> 00:25:14,645
as you were gonna be one of
the best in the world at it.

568
00:25:15,145 --> 00:25:18,285
And so they were, they were
able to, to take on this,

569
00:25:18,305 --> 00:25:20,885
you know, this idea of laser
cooling doesn't really seem

570
00:25:20,885 --> 00:25:22,805
like it has much to do
with, you know, bell Labs

571
00:25:22,865 --> 00:25:25,525
as a telecommunications
company doesn't seem directly

572
00:25:25,525 --> 00:25:28,605
connected to that, but at the
time, they were allowed to,

573
00:25:28,625 --> 00:25:30,125
to do kind of whatever they wanted.

574
00:25:30,385 --> 00:25:33,045
And that freedom really
helped launch things.

575
00:25:33,925 --> 00:25:37,105
Uh, something very similar at
the NIST too, I should say.

576
00:25:37,105 --> 00:25:38,585
The, the National Bureau of Standards.

577
00:25:38,725 --> 00:25:41,385
You know, they hired
Dave Weinland in Boulder.

578
00:25:41,495 --> 00:25:45,545
They hired Bill Phillips
in, uh, in, in Gaithersburg.

579
00:25:45,925 --> 00:25:48,065
Uh, both of them were hired
to work on other things.

580
00:25:48,285 --> 00:25:51,065
Uh, Weinland's job was
to, to help evaluate

581
00:25:51,085 --> 00:25:54,065
and improve an existing
cesium atomic clock.

582
00:25:54,685 --> 00:25:56,505
Uh, but he was told he could spend some

583
00:25:56,505 --> 00:25:59,985
of his time on doing these
experiments with trapped ions.

584
00:26:00,525 --> 00:26:04,825
Um, and Phillips was hired
to, to do some, uh, uh,

585
00:26:05,265 --> 00:26:08,065
electrical measurements that
eventually, uh, became the,

586
00:26:08,065 --> 00:26:09,825
the new standard for the, the volt,

587
00:26:09,825 --> 00:26:11,745
and then the, the kilogram on.

588
00:26:11,765 --> 00:26:12,905
He was hired to work on that,

589
00:26:12,925 --> 00:26:16,465
but again, was told he could
have some, some time to do, uh,

590
00:26:16,885 --> 00:26:18,225
you know, his own thing when,

591
00:26:18,245 --> 00:26:20,705
and do these laser cooling
of, of neutral atoms.

592
00:26:21,125 --> 00:26:24,585
Uh, and they were pretty much,
uh, left alone to, to do,

593
00:26:24,585 --> 00:26:27,425
they, they both cite their,
you know, their initial bosses

594
00:26:27,685 --> 00:26:31,105
as being extremely supportive
of, of exploring, you know,

595
00:26:31,345 --> 00:26:33,025
whatever they were, they
were most interested in.

596
00:26:33,525 --> 00:26:37,105
Uh, and later on, they both,
uh, particularly praised, um,

597
00:26:37,175 --> 00:26:40,465
Katherine Gebe, who was
eventually the director

598
00:26:40,465 --> 00:26:43,065
of the physics laboratory
at, at nist, and,

599
00:26:43,185 --> 00:26:46,045
and had a really good, uh, line about, um,

600
00:26:46,475 --> 00:26:49,045
that really captures sort
of the ethos of, of that,

601
00:26:49,335 --> 00:26:52,965
which was she felt that her
job was to, to hire good people

602
00:26:52,985 --> 00:26:57,595
and stay out of their way so
that, uh, you know, really, uh,

603
00:26:57,625 --> 00:27:02,115
supported, uh, Wineland and
Phillips and, and Jan Hall

604
00:27:02,375 --> 00:27:05,555
and, uh, some other people
to, to really explore

605
00:27:06,145 --> 00:27:09,915
very broadly into exciting,
uh, areas of research.

606
00:27:10,255 --> 00:27:11,275
And that's really paid off.

607
00:27:11,695 --> 00:27:13,195
- That's an interesting thing, isn't it?

608
00:27:13,195 --> 00:27:17,875
Because that freedom giving
great researchers freedom

609
00:27:17,975 --> 00:27:22,155
to do their work led to,
as you say, you know,

610
00:27:22,285 --> 00:27:24,075
Nobel Prize winning physics.

611
00:27:24,695 --> 00:27:25,915
Is that freedom something

612
00:27:25,915 --> 00:27:28,035
that we're seeing today in physics still?

613
00:27:28,385 --> 00:27:30,515
- It's certainly, um, you know, that

614
00:27:30,515 --> 00:27:32,235
that still exists in a lot of places.

615
00:27:32,385 --> 00:27:36,195
There's still, the, the
NISTs are still very much run

616
00:27:36,195 --> 00:27:40,035
that way, that they have,
uh, you know, people in the,

617
00:27:40,035 --> 00:27:42,835
in the physics labs
that are exploring, uh,

618
00:27:42,895 --> 00:27:45,755
really exotic things in,
in, in a lot of ways.

619
00:27:46,245 --> 00:27:48,155
There, there's a bit less of that now.

620
00:27:48,335 --> 00:27:51,035
Uh, the, certainly the,
you know, industrial

621
00:27:51,585 --> 00:27:54,275
labs like Bell Labs are, are, you know,

622
00:27:54,275 --> 00:27:55,915
there's still a Bell Labs around,

623
00:27:56,015 --> 00:27:58,075
but it's, it's a shell of

624
00:27:58,075 --> 00:28:01,355
what it was in the glory days
when they were really, uh,

625
00:28:01,815 --> 00:28:04,995
you know, operating in kind
of the infinite money limit

626
00:28:05,165 --> 00:28:06,635
where they could, could go off

627
00:28:06,635 --> 00:28:08,835
and explore literally
anything that they wanted to.

628
00:28:09,375 --> 00:28:12,995
Um, but there's, there's still
a lot of that, that really,

629
00:28:13,535 --> 00:28:17,555
the pursuit of basic fundamental
science that's foundational

630
00:28:17,855 --> 00:28:20,035
to so many other things, uh,

631
00:28:20,175 --> 00:28:24,115
but it does, it, it, it gets
a lot of times, uh, sort

632
00:28:24,115 --> 00:28:26,315
of disparaged, people will
talk about, well, you know,

633
00:28:26,375 --> 00:28:28,235
why are you, why are you studying that?

634
00:28:28,235 --> 00:28:29,795
That's so arcane and,

635
00:28:30,095 --> 00:28:31,555
and weird that nobody's,

636
00:28:31,555 --> 00:28:32,875
that's never gonna be useful for anything.

637
00:28:33,415 --> 00:28:35,875
Uh, but in fact, a lot of
the times, that's the stuff

638
00:28:35,875 --> 00:28:37,795
that turns out to be foundational to

639
00:28:38,455 --> 00:28:40,435
the next leap forward, right?

640
00:28:40,435 --> 00:28:42,075
Where, you know, somebody goes out

641
00:28:42,075 --> 00:28:43,915
and figures out a way to make atoms cold,

642
00:28:43,935 --> 00:28:46,835
and then suddenly we've
got, you know, atomic clocks

643
00:28:46,835 --> 00:28:49,635
that are factors of a
hundred or a thousand better.

644
00:28:49,695 --> 00:28:51,635
And then we've got these, you know, this,

645
00:28:51,635 --> 00:28:55,315
these ultra cold b Einstein
condensates firmi gasses

646
00:28:55,315 --> 00:28:58,195
that you can study these
really weird exotic, uh,

647
00:28:58,195 --> 00:28:59,515
condensed matter phenomenon.

648
00:28:59,735 --> 00:29:02,235
- So, Einstein plays a role in all this

649
00:29:02,615 --> 00:29:06,395
and features in the third
installment of your features,

650
00:29:06,605 --> 00:29:10,395
which is called, well, in brief, coldest.

651
00:29:10,935 --> 00:29:12,075
Can you tell us a bit about that?

652
00:29:12,375 --> 00:29:16,195
- The idea of, of, uh,
Bose Einstein condensate is

653
00:29:16,425 --> 00:29:19,115
that there's this, this
very strange phenomenon

654
00:29:19,115 --> 00:29:22,435
that happens, uh, as you
approach absolute zero.

655
00:29:22,975 --> 00:29:26,595
Uh, so, you know, one way to
think about temperature is to,

656
00:29:26,655 --> 00:29:31,075
to think of, of temperature
as, you know, the average speed

657
00:29:31,215 --> 00:29:32,435
of an atom and a gas,

658
00:29:32,535 --> 00:29:33,715
and they're all moving in random

659
00:29:33,715 --> 00:29:35,395
directions and, and that sort of thing.

660
00:29:35,855 --> 00:29:38,515
But, um, as you get colder
and colder and colder, right?

661
00:29:38,515 --> 00:29:39,875
Quantum mechanics kicks in,

662
00:29:39,875 --> 00:29:41,405
and these things behave like waves.

663
00:29:42,025 --> 00:29:45,845
And the proper way to think
about, um, a collection

664
00:29:45,845 --> 00:29:48,845
of things that behave
like waves is to think

665
00:29:48,845 --> 00:29:51,685
of them in terms of, of
discrete allowed states.

666
00:29:52,305 --> 00:29:54,685
And this is what happens
in an atom, right?

667
00:29:54,685 --> 00:29:56,565
You have an atom, you have
an electron that's going

668
00:29:56,565 --> 00:29:58,245
around the, the nucleus of the atom.

669
00:29:58,385 --> 00:30:02,805
It can only go around at cer
in certain orbits, right?

670
00:30:02,945 --> 00:30:04,925
Um, very, very loosely.

671
00:30:04,925 --> 00:30:06,845
You can think about it as,
you know, if it's going

672
00:30:06,845 --> 00:30:09,045
around in an orbit, the wave associated

673
00:30:09,045 --> 00:30:12,205
with the electron has to come
back to where it started, uh,

674
00:30:12,205 --> 00:30:13,765
when it, when it completes an orbit.

675
00:30:13,765 --> 00:30:16,245
And that gets you the right i basic idea.

676
00:30:17,065 --> 00:30:19,645
Uh, same thing happens if
you have a bunch of atoms

677
00:30:19,645 --> 00:30:22,125
that you're just holding
in a, in a trap, right?

678
00:30:22,145 --> 00:30:24,445
You can think of that as
a, as a whole bunch of,

679
00:30:24,505 --> 00:30:28,605
of discreet states that have,
uh, very particular energies.

680
00:30:28,745 --> 00:30:30,405
So there's only a limited number

681
00:30:30,425 --> 00:30:33,085
of possible energies the
atoms in the trap can have.

682
00:30:33,905 --> 00:30:36,045
So one way to think about the
temperature is you can think

683
00:30:36,365 --> 00:30:38,005
about the temperature as the,

684
00:30:38,145 --> 00:30:40,085
the speeds at which the atoms are moving.

685
00:30:40,085 --> 00:30:43,125
Another way you can think
about it is it's a distribution

686
00:30:43,305 --> 00:30:47,085
of atoms over all of these
possible energy states in a trap.

687
00:30:47,755 --> 00:30:50,455
Um, and, you know, as you
lower the temperature,

688
00:30:50,455 --> 00:30:51,935
either you're lowering the average speed,

689
00:30:51,955 --> 00:30:54,695
or you're, you're decreasing
the number of states

690
00:30:54,765 --> 00:30:57,015
that these, these atoms can occupy.

691
00:30:57,665 --> 00:31:01,605
Um, what happens is, as you
get really, really cold,

692
00:31:02,235 --> 00:31:04,405
then there's another property of the atoms

693
00:31:04,405 --> 00:31:07,525
that comes into play, which
is this thing called spin, uh,

694
00:31:07,525 --> 00:31:11,445
which is an intrinsic,
uh, ag angular momentum

695
00:31:11,445 --> 00:31:13,045
that's associated with these atoms.

696
00:31:13,345 --> 00:31:16,125
Purely quantum mechanical
thing, not predicted

697
00:31:16,125 --> 00:31:17,285
by any classical theory,

698
00:31:17,585 --> 00:31:20,485
and I am legally required to note

699
00:31:20,485 --> 00:31:22,285
that they're not literally spinning.

700
00:31:22,705 --> 00:31:27,245
Um, but, uh, the, uh, atoms
have this property called spin.

701
00:31:27,265 --> 00:31:31,285
And if the spin is, uh, an integer value,

702
00:31:31,465 --> 00:31:35,205
an integer multiple of plunks
constant, then these atoms,

703
00:31:35,385 --> 00:31:37,165
uh, are called boons.

704
00:31:37,165 --> 00:31:39,245
They have this property
that, that allows them

705
00:31:39,345 --> 00:31:41,165
to be in the same energy state.

706
00:31:41,945 --> 00:31:44,645
Uh, and then what
happens is you get colder

707
00:31:44,645 --> 00:31:45,645
and colder, the number

708
00:31:45,645 --> 00:31:48,045
of states they can
possibly occupy decreases.

709
00:31:48,545 --> 00:31:52,645
And then at some point, it,
it reaches a, a situation

710
00:31:52,645 --> 00:31:55,745
where the atoms are so close to each other

711
00:31:55,855 --> 00:31:58,385
that they're aware of the
presence of other atoms,

712
00:31:58,445 --> 00:32:02,705
and they all will condense
into a single energy state,

713
00:32:02,735 --> 00:32:05,065
generally the lowest state
that's available to them.

714
00:32:05,945 --> 00:32:07,965
Uh, and this is just
because, you know, they,

715
00:32:07,965 --> 00:32:10,485
they realize collectively
that, wait a minute,

716
00:32:10,515 --> 00:32:13,085
like if we were all in
the lowest energy state,

717
00:32:13,085 --> 00:32:16,605
that would be a big drop in
the, the energy of, of the gas.

718
00:32:16,705 --> 00:32:19,245
And we're always looking to, to, you know,

719
00:32:19,345 --> 00:32:21,405
go in the lowest possible state.

720
00:32:22,265 --> 00:32:25,485
So, uh, this is a phenomena
called Bo Einstein condensation.

721
00:32:25,485 --> 00:32:29,285
It's predicted by the, um, Indian, uh,

722
00:32:29,285 --> 00:32:30,445
mathematical physicist.

723
00:32:30,545 --> 00:32:35,205
Uh, RA Na Bose, uh, came up with this, uh,

724
00:32:35,545 --> 00:32:38,205
in thinking about a way to,
to understand the spectrum

725
00:32:38,225 --> 00:32:40,005
of light emitted by a hot object.

726
00:32:40,585 --> 00:32:43,205
Um, he couldn't get his
paper published, uh,

727
00:32:43,275 --> 00:32:46,685
because he was, you know,
nobody in, in India.

728
00:32:47,185 --> 00:32:51,725
Uh, and so he sent, uh, a
copy of the paper to Einstein,

729
00:32:51,745 --> 00:32:55,085
who he had met once before,
uh, Einstein read it

730
00:32:55,085 --> 00:32:58,485
and said, this is
amazing, and also realized

731
00:32:58,635 --> 00:33:00,485
that this condensation thing would happen.

732
00:33:00,985 --> 00:33:03,165
Uh, and so he wrote it a paper of his own

733
00:33:03,185 --> 00:33:05,645
and sent the both of
them to Zeit for physics

734
00:33:06,265 --> 00:33:07,365
and said, publish these.

735
00:33:07,905 --> 00:33:10,525
And so this, this, um, got published,

736
00:33:10,705 --> 00:33:14,365
and this is why these, uh, atoms

737
00:33:14,365 --> 00:33:16,485
with integer spin are called boons.

738
00:33:16,485 --> 00:33:18,005
It's an honor of, of Bose.

739
00:33:18,465 --> 00:33:21,005
And this phenomenon is
Bose Einstein condensation,

740
00:33:21,005 --> 00:33:23,965
because Einstein took Bose's idea and,

741
00:33:24,065 --> 00:33:27,085
and pointed out that, Hey, you
can do this thing where all

742
00:33:27,085 --> 00:33:29,685
of the atoms will collapse
into a single state.

743
00:33:29,745 --> 00:33:31,005
And that's pretty, pretty neat.

744
00:33:31,425 --> 00:33:33,245
And it, it's a purely quantum thing.

745
00:33:33,265 --> 00:33:35,085
It has nothing to do with interactions

746
00:33:35,115 --> 00:33:37,125
between the, the atoms at all.

747
00:33:37,625 --> 00:33:41,205
Uh, just the, the fact that
they're there and their waves

748
00:33:41,265 --> 00:33:44,085
and those waves sort of
overlap with each other, um,

749
00:33:44,405 --> 00:33:45,925
triggers this, this process

750
00:33:45,925 --> 00:33:48,845
because of this quantum
statistical character of this spin

751
00:33:48,845 --> 00:33:51,005
that they have, uh,
will put them into this,

752
00:33:51,115 --> 00:33:52,725
this low energy state.

753
00:33:53,025 --> 00:33:55,325
- You say that they have
awareness of each other,

754
00:33:55,465 --> 00:33:58,045
but they, they're not aware
of each other, are they?

755
00:33:58,045 --> 00:34:00,605
Because atoms don't have awareness? Yeah,

756
00:34:00,795 --> 00:34:03,365
- It's, uh, you know, it,
it, we, we have a tendency

757
00:34:03,365 --> 00:34:06,765
to anthropomorphize, uh,
you know, microscopic

758
00:34:07,275 --> 00:34:08,805
inanimate objects, uh,

759
00:34:08,825 --> 00:34:10,285
and say that, you know, they want

760
00:34:10,385 --> 00:34:12,605
to be in the lowest energy state and,

761
00:34:12,705 --> 00:34:15,125
and whatnot, um, that kind of thing.

762
00:34:15,185 --> 00:34:17,645
But yeah, they, they,
you know, that's, that's

763
00:34:17,645 --> 00:34:18,885
how we tend to talk about it.

764
00:34:18,905 --> 00:34:21,645
The, the, um, the presence

765
00:34:21,645 --> 00:34:24,365
of these different things
becomes, uh, significant.

766
00:34:24,435 --> 00:34:26,165
- Well, as we've said,
it takes a little time

767
00:34:26,345 --> 00:34:28,765
for the Nobel Prize to come to people

768
00:34:28,865 --> 00:34:30,605
for the work that they've done.

769
00:34:31,225 --> 00:34:36,205
Um, are there discoveries that
have been made that will win

770
00:34:36,785 --> 00:34:41,405
future or may win future Nobel
Prize physics for this area?

771
00:34:42,265 --> 00:34:44,565
Is, are those discoveries
already happened,

772
00:34:44,945 --> 00:34:46,005
- Uh, in this field?

773
00:34:46,005 --> 00:34:49,285
Yeah, I think there's probably
a, a, a few future ones.

774
00:34:49,505 --> 00:34:52,925
The, the Nobel Prizes in laser cooling

775
00:34:53,305 --> 00:34:56,845
and, uh, related fields are
actually, uh, on the scale

776
00:34:56,905 --> 00:34:59,285
of Nobel Prizes pretty quick, right?

777
00:34:59,545 --> 00:35:03,685
The, uh, the stuff that,
uh, Phillips did is,

778
00:35:04,505 --> 00:35:08,125
uh, happens in the, the early 1980s, uh,

779
00:35:08,385 --> 00:35:11,725
around 1983, is the magnetic trapping and,

780
00:35:11,745 --> 00:35:13,325
and Zaman slowing, uh,

781
00:35:13,465 --> 00:35:16,005
and he gets a share of the Nobel in 1997.

782
00:35:16,665 --> 00:35:20,445
Uh, Weinland's Nobel is in,

783
00:35:20,905 --> 00:35:22,445
I'm forgetting the, the year now.

784
00:35:22,825 --> 00:35:24,085
Uh, let me look this up.

785
00:35:24,225 --> 00:35:26,605
Uh, Weinland's Nobel is
a, is a little later.

786
00:35:26,715 --> 00:35:28,565
It's in, uh, 2012.

787
00:35:29,265 --> 00:35:32,005
Um, and the work that,
that he is being rewarded

788
00:35:32,025 --> 00:35:35,325
for starts in, in 1978.

789
00:35:35,785 --> 00:35:37,285
Um, so that's, you know,

790
00:35:37,625 --> 00:35:40,445
that's relatively quick on
the scale of Nobel Prizes.

791
00:35:40,705 --> 00:35:44,685
Um, the, the Bo Einstein
common State Nobel is in 2001.

792
00:35:45,305 --> 00:35:48,085
Um, and that's for, for
stuff that was done only,

793
00:35:48,315 --> 00:35:51,805
only like six years
earlier in, uh, in 1995.

794
00:35:52,025 --> 00:35:53,685
So that, that happened really fast

795
00:35:54,225 --> 00:35:55,405
on the scale of these things.

796
00:35:55,945 --> 00:35:57,885
- Why was that one so fast? Well,

797
00:35:57,955 --> 00:36:00,285
- It's fast on the
experimental side, right?

798
00:36:00,285 --> 00:36:04,685
The experiments that that
did it, uh, were in 1995,

799
00:36:04,825 --> 00:36:08,005
that's Cornell and Wyman
and, and Ketley, uh,

800
00:36:08,025 --> 00:36:09,685
and they get the Nobel in 2001.

801
00:36:09,905 --> 00:36:13,325
You know, the prediction
of B Einstein condensation

802
00:36:13,325 --> 00:36:16,445
that this ought to be
possible is made in, in 1924.

803
00:36:17,145 --> 00:36:20,565
So, uh, so it's, you know,
the, it's a realization

804
00:36:20,565 --> 00:36:23,245
of a theory that had been
around for a very long time,

805
00:36:23,905 --> 00:36:25,485
and that makes it a little,

806
00:36:25,745 --> 00:36:26,885
you know, come a little bit faster.

807
00:36:27,745 --> 00:36:31,245
- So, what's the physics that's
going on today that might be

808
00:36:31,885 --> 00:36:33,445
worthy of a Nobel Prize in the future?

809
00:36:34,225 --> 00:36:37,365
- Uh, there are these
experiments with optical latts

810
00:36:37,545 --> 00:36:41,565
and optical lattice clocks
where they, they, uh, take atoms

811
00:36:41,565 --> 00:36:45,685
and they trap them in, um,
in light, you know, uh,

812
00:36:45,685 --> 00:36:46,965
arrangements of light beams

813
00:36:46,965 --> 00:36:48,885
that are lasers going
in opposite directions.

814
00:36:49,155 --> 00:36:52,685
They interfere with each other
to make a, a periodic array

815
00:36:52,685 --> 00:36:54,005
of bright and dark spots.

816
00:36:54,705 --> 00:36:58,485
Uh, and if you arrange this
very cleverly, you can, uh,

817
00:36:58,635 --> 00:37:00,445
trap atoms in the bright spots

818
00:37:00,665 --> 00:37:02,765
or trap atoms in the dark spots in this.

819
00:37:03,305 --> 00:37:06,325
Um, and, uh, this turns out
to be a really good way to,

820
00:37:06,465 --> 00:37:10,365
to make, uh, atomic
clocks with neutral atoms.

821
00:37:10,465 --> 00:37:12,765
You can hold them very,
very tightly in these.

822
00:37:12,785 --> 00:37:14,525
So they're not moving at all, really.

823
00:37:15,065 --> 00:37:17,365
Uh, they stick around
for a very long time,

824
00:37:17,585 --> 00:37:21,365
so you can interrogate them,
um, over, over long periods

825
00:37:21,365 --> 00:37:23,765
of time and make incredibly
precise measurements.

826
00:37:23,765 --> 00:37:26,125
These are the, these are
the clocks that are good to,

827
00:37:26,345 --> 00:37:29,805
you know, one second in more
than the age of the universe.

828
00:37:30,585 --> 00:37:32,765
And, uh, that's a, uh,

829
00:37:32,785 --> 00:37:35,165
that's been some really
spectacular work in,

830
00:37:35,225 --> 00:37:36,365
in those fields.

831
00:37:36,515 --> 00:37:39,525
That is probably the kind of thing that,

832
00:37:39,525 --> 00:37:42,845
that down the road would be,
uh, would be Nobel worthy.

833
00:37:43,585 --> 00:37:47,465
Um, there's also, uh, a lot of, of,

834
00:37:47,685 --> 00:37:50,305
of work in, uh, these, uh,

835
00:37:50,315 --> 00:37:54,825
degenerate fermi gasses is
another area that is, um,

836
00:37:55,205 --> 00:37:57,105
so the other category of things,

837
00:37:57,105 --> 00:38:00,545
you have b Einstein condensation
happens if you have atoms

838
00:38:00,875 --> 00:38:03,785
whose spin is an integer
multiple of plan constant.

839
00:38:04,445 --> 00:38:08,065
Um, you also have, uh, this pheno this,

840
00:38:08,685 --> 00:38:12,665
the other possibility is you
can have atoms whose spin is,

841
00:38:12,885 --> 00:38:14,945
uh, a half integer multiple.

842
00:38:14,965 --> 00:38:18,065
So one AVEs, one and a half, you know, two

843
00:38:18,065 --> 00:38:20,305
and a half times plunks constant.

844
00:38:20,645 --> 00:38:22,945
And those particles are called phons,

845
00:38:22,945 --> 00:38:25,505
and those are absolutely
forbidden from being

846
00:38:25,505 --> 00:38:26,585
in the same energy state.

847
00:38:27,245 --> 00:38:31,305
And so they can be, um, they
can also be cooled down,

848
00:38:31,405 --> 00:38:33,465
and as you cool them,
you, you limit the number

849
00:38:33,465 --> 00:38:34,905
of states they can, can be in.

850
00:38:35,385 --> 00:38:38,285
But unlike the boons, they
fill up the states, right?

851
00:38:38,475 --> 00:38:41,805
Once there's one phon in,
uh, in a allowed state,

852
00:38:42,265 --> 00:38:44,045
no other phons can occupy that.

853
00:38:44,425 --> 00:38:46,845
So at some point, as the
temperature gets cold enough,

854
00:38:47,265 --> 00:38:48,525
you reach a point where all

855
00:38:48,525 --> 00:38:50,885
of the available states
are already occupied,

856
00:38:51,305 --> 00:38:54,525
and, uh, no more atoms can go in there.

857
00:38:54,945 --> 00:38:57,165
Uh, and at that point,
the, the system sort

858
00:38:57,165 --> 00:38:59,205
of in some sense stops cooling, right?

859
00:38:59,205 --> 00:39:01,245
It can't get any more compressed.

860
00:39:01,385 --> 00:39:04,085
It can't get any, get any
smaller, it can't get any colder

861
00:39:04,085 --> 00:39:07,165
because all of the available
states are, are occupied.

862
00:39:07,745 --> 00:39:10,165
Um, and this is, uh, phenomenon.

863
00:39:10,165 --> 00:39:13,925
It's, it's closely related to
what happens in metals, in,

864
00:39:13,945 --> 00:39:16,125
in solids that determines
whether something's, uh,

865
00:39:16,525 --> 00:39:20,525
a conductor or an insulator,
uh, determines, is determined

866
00:39:20,525 --> 00:39:23,205
by this same physics, this
filling up of energy states.

867
00:39:23,625 --> 00:39:25,845
But you can demonstrate, it
doesn't depend on interactions

868
00:39:25,845 --> 00:39:26,885
between the particles at all.

869
00:39:26,885 --> 00:39:29,165
You can demonstrate it
with, with ultra cold atoms.

870
00:39:29,785 --> 00:39:34,445
Uh, and this is done in 1999
by, uh, at, at NIST in Boulder

871
00:39:35,065 --> 00:39:39,245
by, uh, Debbie Gin, uh,
who was, uh, a new, uh,

872
00:39:39,245 --> 00:39:41,085
staff scientist at, at nist.

873
00:39:41,505 --> 00:39:44,485
And, uh, her grad student,
Brian DeMarco, um,

874
00:39:44,745 --> 00:39:47,205
got this lab up and running to do, uh,

875
00:39:47,495 --> 00:39:49,125
degenerate Fermi gasses.

876
00:39:49,305 --> 00:39:52,285
And, and looking at, at
potassium atoms, they were able

877
00:39:52,285 --> 00:39:53,485
to cool them down to the point

878
00:39:53,485 --> 00:39:55,645
where they stopped getting any colder,

879
00:39:56,145 --> 00:39:58,925
and they could show the other category

880
00:39:59,065 --> 00:40:00,565
of weird quantum things

881
00:40:00,565 --> 00:40:02,645
that happens at ultralow temperatures,

882
00:40:02,735 --> 00:40:06,725
which is this degenerate amiga
behavior where the, the, all

883
00:40:06,725 --> 00:40:08,365
of the available states are full

884
00:40:09,565 --> 00:40:12,705
and that, uh, that changes
the properties of materials.

885
00:40:13,325 --> 00:40:15,785
Um, and so there's a, there's
a huge amount of work out of

886
00:40:15,785 --> 00:40:18,425
that that's also, uh, really interesting.

887
00:40:18,445 --> 00:40:22,305
And, um, you know, probably,
uh, Nobel worthy someday.

888
00:40:22,645 --> 00:40:26,105
Uh, it is very sad that, uh, Debbie Gin

889
00:40:26,565 --> 00:40:28,265
who pioneered all this and,

890
00:40:28,365 --> 00:40:30,345
and was, uh, really, uh,

891
00:40:30,665 --> 00:40:32,185
enormously influential in the field.

892
00:40:32,565 --> 00:40:34,905
Uh, unfortunately she passed away, uh,

893
00:40:34,905 --> 00:40:36,905
several years ago of, of cancer.

894
00:40:37,605 --> 00:40:41,185
Uh, and so she's not around
to, to get the, the Nobel,

895
00:40:41,285 --> 00:40:43,785
or would certainly be on the
short list of people that,

896
00:40:44,055 --> 00:40:45,625
that are expected to win one.

897
00:40:46,005 --> 00:40:47,985
Um, but this is a really important area

898
00:40:47,985 --> 00:40:52,505
because, uh, these phons, uh, the,

899
00:40:52,525 --> 00:40:54,905
the other kind of part
really important particle

900
00:40:54,905 --> 00:40:56,465
that are phons are electrons

901
00:40:56,485 --> 00:40:58,265
and electrons in a solid, right?

902
00:40:58,265 --> 00:41:02,865
I said it determines this,
this, uh, this filling up

903
00:41:02,865 --> 00:41:05,785
of states determines the
properties and materials.

904
00:41:06,245 --> 00:41:09,625
Um, if you do this with, with
atoms, you can make a system

905
00:41:09,625 --> 00:41:14,025
that's analogous to, uh, any
kind of, of, you know, metals

906
00:41:14,045 --> 00:41:17,185
or superconductors or
semiconductors, things like that.

907
00:41:17,205 --> 00:41:18,305
And you can study the behavior

908
00:41:18,575 --> 00:41:21,425
with atoms taking on
the role of electrons.

909
00:41:21,565 --> 00:41:23,665
And the nice thing about
that is atoms are, you know,

910
00:41:24,105 --> 00:41:27,785
thousands to millions of
times heavier than electrons,

911
00:41:27,785 --> 00:41:29,065
so they move a lot slower.

912
00:41:29,645 --> 00:41:33,565
So you can watch phenomena
that happen with electrons

913
00:41:34,235 --> 00:41:37,405
that happen far too quickly
to to be tracked directly.

914
00:41:37,865 --> 00:41:39,685
You can set up an analog of that

915
00:41:39,735 --> 00:41:42,565
where atoms are playing
the roles of the electrons

916
00:41:42,825 --> 00:41:45,085
and watch them move
around and interact and,

917
00:41:45,225 --> 00:41:49,725
and, um, you know, study these
transport properties, uh,

918
00:41:50,145 --> 00:41:51,685
at timescales where you can,

919
00:41:51,705 --> 00:41:53,525
you can really follow this in real time

920
00:41:53,665 --> 00:41:57,125
and see how these things, uh,
shift around, uh, which is a,

921
00:41:57,205 --> 00:41:59,805
a whole new regime for
studying these interesting

922
00:41:59,805 --> 00:42:01,405
properties of material. Yeah,

923
00:42:01,405 --> 00:42:02,845
- It's fascinating, isn't it?

924
00:42:02,925 --> 00:42:04,365
I mean, it, it's a funny one for me

925
00:42:04,365 --> 00:42:06,645
because it's not something
that I've thought about

926
00:42:06,645 --> 00:42:10,405
that's coming to my life
really knowingly, at least.

927
00:42:10,475 --> 00:42:13,565
Yeah. Until I read your features.

928
00:42:13,705 --> 00:42:15,885
And when I read that,

929
00:42:16,425 --> 00:42:17,845
and, you know, when I've said to people,

930
00:42:18,025 --> 00:42:20,805
I'm gonna be doing this
interview about laser cooling,

931
00:42:20,805 --> 00:42:23,125
their reaction is laser cooling.

932
00:42:23,155 --> 00:42:24,245
That doesn't make sense.

933
00:42:24,305 --> 00:42:26,965
And it's that this all, it's
not even a little thing, is it

934
00:42:26,965 --> 00:42:31,445
that peculiar nature of this
means that they're going

935
00:42:31,445 --> 00:42:33,525
to listen to this podcast,
you know, they are going

936
00:42:33,525 --> 00:42:36,365
to be interested in this
because of that peculiar thing.

937
00:42:36,365 --> 00:42:38,365
Is it always something
that's interested you?

938
00:42:38,915 --> 00:42:42,285
- It's, I, you know, I, I
had exactly the, the reaction

939
00:42:42,285 --> 00:42:43,325
that you described, right?

940
00:42:43,405 --> 00:42:44,605
I, I got into this field

941
00:42:44,605 --> 00:42:48,485
because in, um, kind of the winter of, of

942
00:42:49,005 --> 00:42:53,925
19 91, 92, um, I heard, uh,
Claude Cohen Nugi give a,

943
00:42:54,085 --> 00:42:57,245
a talk about, uh, laser cooling.

944
00:42:57,385 --> 00:42:59,845
He, he came to the, the
small college where I was an,

945
00:42:59,845 --> 00:43:01,485
an undergrad, and he gave this talk.

946
00:43:01,505 --> 00:43:04,085
And, and, uh, Cohen Nugi is just,

947
00:43:04,305 --> 00:43:06,405
he is a magnificent public speaker,

948
00:43:06,535 --> 00:43:11,085
gives these just incredibly
clear, um, you know,

949
00:43:11,165 --> 00:43:13,565
coherent talks, uh, about things.

950
00:43:13,665 --> 00:43:15,885
And it, and it absolutely blew my mind.

951
00:43:16,105 --> 00:43:17,925
The, the idea that, you know, this,

952
00:43:17,925 --> 00:43:20,725
this counterintuitive notion
that I've got a gas of atoms,

953
00:43:20,765 --> 00:43:22,405
I shine laser light on it,

954
00:43:22,825 --> 00:43:26,245
and suddenly I can make
these, these atoms move at,

955
00:43:26,625 --> 00:43:27,885
you know, centimeter per second,

956
00:43:28,205 --> 00:43:29,645
millimeter per second speeds.

957
00:43:29,985 --> 00:43:32,685
Uh, get this down to,
to millionth of a degree

958
00:43:32,685 --> 00:43:35,485
above absolute zero was just,
just absolutely incredible.

959
00:43:36,025 --> 00:43:38,565
And then I found out that one
of my professors had a lab

960
00:43:38,565 --> 00:43:41,245
where he was trying to set up
an experiment to, to do that.

961
00:43:41,865 --> 00:43:44,565
And I was like, I'm
in, like, I sign me up.

962
00:43:44,725 --> 00:43:46,325
I wanna be part of this. Uh,

963
00:43:46,545 --> 00:43:48,645
and so it, it was, it was really cool.

964
00:43:48,745 --> 00:43:52,005
And, and it's exactly that
counter intuitiveness that

965
00:43:52,005 --> 00:43:54,405
that really drew me into
the, into the field.

966
00:43:54,705 --> 00:43:57,005
And I was lucky enough
to, to go to grad school.

967
00:43:57,005 --> 00:44:00,245
And I worked for Bill
Phillips, uh, at, at NIST in,

968
00:44:00,345 --> 00:44:03,925
in Gaithersburg, uh, doing
laser cooling experiments for,

969
00:44:03,985 --> 00:44:05,045
for my PhD thesis.

970
00:44:05,465 --> 00:44:08,605
And so, you know, I was
incredibly fortunate to be around,

971
00:44:09,145 --> 00:44:12,205
uh, some of these, these
really exceptional people, uh,

972
00:44:12,205 --> 00:44:14,045
doing this, this exceptional science.

973
00:44:14,705 --> 00:44:18,325
- And you can read much more
about Chad Zell's conversations

974
00:44:18,345 --> 00:44:21,885
and explorations of this topic
on the physics world website

975
00:44:22,035 --> 00:44:25,285
with his three features, the first cold,

976
00:44:25,785 --> 00:44:27,845
how physicists learn to manipulate

977
00:44:27,905 --> 00:44:30,285
and move particles with laser cooling.

978
00:44:31,105 --> 00:44:35,285
The second Calder, how physicists
beat the theoretical limit

979
00:44:35,625 --> 00:44:36,685
for laser cooling

980
00:44:36,825 --> 00:44:39,405
and laid the foundations
for a quantum revolution,

981
00:44:40,025 --> 00:44:43,245
and the third, at the time
of recording, known only

982
00:44:43,465 --> 00:44:45,925
and not yet published as coldest.

983
00:44:46,345 --> 00:44:47,725
But by the time you are listening,

984
00:44:47,945 --> 00:44:50,845
or certainly soon enough,
you'll be able to read

985
00:44:50,845 --> 00:44:53,405
that third part on physics world.com.

986
00:44:53,985 --> 00:44:56,845
Before that, settle in and read part one

987
00:44:57,025 --> 00:45:01,165
and part two of the Cold,
colder, and Coldest trilogy.

988
00:45:01,785 --> 00:45:04,005
I'd like to thank Chad Zel for
joining me for this episode

989
00:45:04,005 --> 00:45:05,245
of the Physics World Stories Podcast.

990
00:45:05,665 --> 00:45:08,405
And of course, I'd like
to thank you very much

991
00:45:08,705 --> 00:45:09,285
for listening,

992
00:45:13,915 --> 00:45:15,045
physics World.