Timing the Quantum World: How Spin Reveals the Speed of Atomic Events

<v Speaker 1>Welcome to the quark Side Quantum Physics Podcast, an exploration
<v Speaker 1>of the fundamental structure of reality, where quantum laws govern matter, energy,
<v Speaker 1>and information. Here, uncertainty is a feature, not a flaw,
<v Speaker 1>and understanding begins at the smallest scales.
<v Speaker 2>Hello and welcome. It is February sixth, twenty twenty six.
<v Speaker 2>I want to start today with the little thought experiment.
<v Speaker 2>Just you know, humor me for a second. I want
<v Speaker 2>you to imagine a clock, a simple analog clock on
<v Speaker 2>a wall.
<v Speaker 3>Okay, got it.
<v Speaker 2>Now, imagine that clock starts to melt. The numbers are
<v Speaker 2>dripping down the wall like something out of a surrealist painting.
<v Speaker 2>Or maybe the gears inside start spinning so fast they liquefy,
<v Speaker 2>or they start going backwards, or somehow exist in two places.
<v Speaker 3>At the same time, a quantum clock.
<v Speaker 2>Exactly, because we are starting today's conversation with a question
<v Speaker 2>has I mean, it's kept philosophers up at night for
<v Speaker 2>centuries and has pushed physicists to the absolute edge. What
<v Speaker 2>is time?
<v Speaker 3>It's the big one, isn't it. It is the one
<v Speaker 3>constant we all experience, but the one thing nobody can
<v Speaker 3>really define. I think Augustin had that famous quote about it.
<v Speaker 2>Oh right, what was that?
<v Speaker 3>It was something like, what then is time? If no
<v Speaker 3>one asks me? I know, if I wish to explain
<v Speaker 3>it to one who asks, I know not. It's just it.
<v Speaker 3>It's the water we're swimming in, but we can't grab
<v Speaker 3>a handful of it.
<v Speaker 2>It feels so absolute to us, you know, day in
<v Speaker 2>day out, But we know from physics, from relativity, that
<v Speaker 2>it isn't. It's flexible. And when you go small, really
<v Speaker 2>really small, it gets even stranger.
<v Speaker 3>It really does. It stops being this sort of universal
<v Speaker 3>metronomes background beat for reality, and it becomes a property
<v Speaker 3>of the system itself.
<v Speaker 2>It becomes a variable, and that is exactly where we're
<v Speaker 2>headed today. We're looking at a pretty incredible breakthrough coming
<v Speaker 2>out of EPFL, the Equal Polytechnique federalde Lausanne over in Switzerland.
<v Speaker 3>A fantastic to constitution.
<v Speaker 2>They've managed to do something that honestly sounds impossible. They
<v Speaker 2>figured out a way to measure time on the smallest
<v Speaker 2>possible scale. But and this is the part that really
<v Speaker 2>got me, they discovered that the speed of time actually
<v Speaker 2>changes it depends on the shape of the matter it's.
<v Speaker 3>In, which is a huge deal because Normally, when you
<v Speaker 3>bring quantum mechanics into the discussion about time, the problem
<v Speaker 3>gets harder, not easier. Time is notoriously slippery in the
<v Speaker 3>quantum world.
<v Speaker 2>Right, because we tend to think of quantum events, these
<v Speaker 2>little jumps and electron makes as being instant Right, it's
<v Speaker 2>in one place, one energy level, and then poof, it's
<v Speaker 2>in another.
<v Speaker 3>Exactly like a teleport. We often treat them as instantaneous,
<v Speaker 3>partly because the math is a lot cleaner that way,
<v Speaker 3>but also because honestly, measuring any duration has been next
<v Speaker 3>to impossible.
<v Speaker 2>It's just too fast to see.
<v Speaker 3>But this new research it basically pulls back that curtain.
<v Speaker 3>It says, no, it's not a magic trick, it's not instantaneous.
<v Speaker 3>There is a duration. It's a process. And what's really
<v Speaker 3>amazing is that the length of that process is controlled
<v Speaker 3>by geometry.
<v Speaker 2>So that's our mission for today. We're going to unpack
<v Speaker 2>this whole thing. We're going to figure out how on
<v Speaker 2>Earth you can clock a quantum event without an actual clock,
<v Speaker 2>because using one apparently messes up the whole experiment. And
<v Speaker 2>then we're going to get into this really mind bending
<v Speaker 2>finding that the symmetry of a material it's actual atomic
<v Speaker 2>architecture can warp how fast time passes for the electrons
<v Speaker 2>living inside it.
<v Speaker 3>It's this beautiful place where geometry, quantum theory, and the
<v Speaker 3>very philosophy of time all intersect. Reallyically makes you question
<v Speaker 3>if time is this fundamental thing flowing everywhere, or if
<v Speaker 3>it's more of a local effect generated by the environment itself.
<v Speaker 2>Okay, so let's get into it Part one, the scale
<v Speaker 2>and the struggle. Before we talk about timing something, we
<v Speaker 2>need to be really clear on what it is. When
<v Speaker 2>you say a quantum event, what were the researchers actually measuring?
<v Speaker 3>So they were looking at one of the most fundamental
<v Speaker 3>processes in quantum mechanics. It's called a quantum transition. The
<v Speaker 3>classic example is the photoelectric effect, which Einstein won his
<v Speaker 3>no Bell for.
<v Speaker 2>That's where light hits a metal and knocks an electron out.
<v Speaker 3>Precisely, a photon, which is a particle of light, comes
<v Speaker 3>in and smacks into an electron that's bound inside a material.
<v Speaker 3>The electron absorbs the energy from that photon, gets super
<v Speaker 3>excited and uses that energy to well make a run
<v Speaker 3>for it. It escapes the material entirely. It's a prison break,
<v Speaker 3>a quantum prison break. Yes, it's transitioning from being bound
<v Speaker 3>to the material to being a free particle. And the
<v Speaker 3>huge question has always been how long does that take?
<v Speaker 3>Is the escape instant, the moment the photon hits, is
<v Speaker 3>the electron out or is there a delay a kind
<v Speaker 3>of reaction time?
<v Speaker 2>And I'm guessing we're not talking about seconds here or
<v Speaker 2>even nanosecond Oh, not even close.
<v Speaker 3>We are operating in the realm of the attosecond.
<v Speaker 2>The attosecond, it's one of those words that sounds fast
<v Speaker 2>just saying it. But help us, you know, get a
<v Speaker 2>handle on this. The number ten to the minus eighteen
<v Speaker 2>seconds is just us. It's an abstraction, a decimal point
<v Speaker 2>seventeen zeros than a one. How do we even begin
<v Speaker 2>to visualize that?
<v Speaker 3>It is almost impossible to wrap your head around. You're right.
<v Speaker 3>The analogy the researchers from epfl use is probably the
<v Speaker 3>best one I've heard.
<v Speaker 2>Okay, lay it on us, all right.
<v Speaker 3>Think about light, The fastest thing there is. It travels
<v Speaker 3>in about three hundred thousand kilometers per second. It can
<v Speaker 3>zip around the entire Earth more than seven times in
<v Speaker 3>a single second.
<v Speaker 2>The ultimate speed limit.
<v Speaker 3>Right now, imagine a very very small virus, and at
<v Speaker 3>a second is so short that in that amount of time,
<v Speaker 3>a beam of light can't even make it across the
<v Speaker 3>width of that single tiny virus.
<v Speaker 2>Wait, hold on, say that again, light the cosmic speed
<v Speaker 2>limit cannot cross a virus in one atto second.
<v Speaker 3>That's correct. Let's break it down even more. A small
<v Speaker 3>virus might be say twenty nanometers across. A nanometer is
<v Speaker 3>a billionth of a meter, So already that's incredibly.
<v Speaker 2>Small, invisible to us completely.
<v Speaker 3>But for a photon, which is a particle of light
<v Speaker 3>traveling at its breakneck speed, it still takes a measurable
<v Speaker 3>amount of time to cross that twenty nanometers discs and
<v Speaker 3>that time is roughly sixty to seventy auto seconds.
<v Speaker 2>Okay, so the time it takes light to cross a
<v Speaker 2>germ is about seventy out a second roughly.
<v Speaker 3>Yes. Now consider the events they measured in this experiment.
<v Speaker 3>For material like copper, the quantum transition we're talking about
<v Speaker 3>the electrons escape took about twenty six autoseconds.
<v Speaker 2>So the entire process of the electron getting hit, getting excited,
<v Speaker 2>and completing its transition happens in less than half the
<v Speaker 2>time it takes light to cross a single virus exactly.
<v Speaker 3>It's not that the electrons moving faster than light, of course,
<v Speaker 3>nothing does that. But the duration of the event, the
<v Speaker 3>time it takes for its entire quantum state, its wave
<v Speaker 3>function to evolve from stuck to free, is shorter than
<v Speaker 3>that light crossing time.
<v Speaker 2>That's just absurd. It feels like trying to measure the
<v Speaker 2>duration of a single thought, but then scaling that down
<v Speaker 2>by a factor of a billion.
<v Speaker 3>It gives you a sense of the fundamental clock speed
<v Speaker 3>of reality. If you could stretch a single second to
<v Speaker 3>be as long as the entire age of the universe
<v Speaker 3>about thirteen point eight billion year, an attosecond would be
<v Speaker 3>just a few seconds in comparison.
<v Speaker 2>Wow. Okay, So that brings us to the next obvious
<v Speaker 2>and I imagine, very difficult question. If it's happening that fast,
<v Speaker 2>how on earth do you measure it? You can't just
<v Speaker 2>you know, click a stopwatch.
<v Speaker 3>You absolutely cannot. And this gets us right to the
<v Speaker 3>heart of the problem in this field, what we can
<v Speaker 3>call the external clock issue. It's a massive challenge in
<v Speaker 3>quantum physics, the measurement problem, yes, a version of it.
<v Speaker 3>Professor Hugo. Dill, who is The lead on this study
<v Speaker 3>is very clear about this. If you try to bring
<v Speaker 3>in any kind of external tool to time the event,
<v Speaker 3>say an ultra fast laser pulse that acts like a
<v Speaker 3>flash on a camera, that tool itself is going to
<v Speaker 3>interact with the electron you're trying to measure.
<v Speaker 2>It's the classic observer effect. Right by looking at something
<v Speaker 2>quantum you change it.
<v Speaker 3>It's exactly that, but in a very physical, very direct way.
<v Speaker 3>It's more than just looking. I think the best analogy
<v Speaker 3>is when they hint at in the paper. Imagine you
<v Speaker 3>have a tiny thimble full of water and you want
<v Speaker 3>to measure its temperature with perfect accuracy. Okay, but the
<v Speaker 3>only thermometer you have is a giant industrial one fresh
<v Speaker 3>out of a furnace, glowing red hot.
<v Speaker 2>Right, if I stick that enormous hot poker into my
<v Speaker 2>tiny thimble of water, I'm just going to boil the
<v Speaker 2>water away.
<v Speaker 3>Precisely, you're not measuring the water's original temperature. You're measuring
<v Speaker 3>the temperature of water that you just flash boiled with
<v Speaker 3>your tool. The very act of measuring has completely disported
<v Speaker 3>the reality you wanted to observe.
<v Speaker 2>Your measurement created a new reality.
<v Speaker 3>It induced artifacts that's the technical term for it.
<v Speaker 2>Can you explain what an artifact is in this physics context,
<v Speaker 2>because it makes me think of finding old pottery, not data.
<v Speaker 3>It is a great question. In experimental science. An artifact
<v Speaker 3>is any signal in your data that looks like it's
<v Speaker 3>a real phenomenon, but it was actually created by your
<v Speaker 3>measurement process or your equipment.
<v Speaker 2>So it's a ghost in the machine.
<v Speaker 3>A ghost in the machine. Perfect. Yeah. Imagine you're taking
<v Speaker 3>a photo of a sprinter at the finish line, but
<v Speaker 3>your camera has a really slow shutter and you use
<v Speaker 3>a brake flash when you look at the photo, so
<v Speaker 3>the sprinter might look blurry, or maybe they look like
<v Speaker 3>they have two heads because they moved while the shutter
<v Speaker 3>was still open.
<v Speaker 2>And if I didn't know anything about photography, I might
<v Speaker 2>publish a paper saying, incredible discovery, humans grow a second
<v Speaker 2>head when they run at high speed.
<v Speaker 3>Exactly, you'd be misinterpreting an artifact at the camera as
<v Speaker 3>a real biological event. In the quantum world, when you
<v Speaker 3>use these intense laser pulses as an external clock, the
<v Speaker 3>laser's own electric field starts yanking the electron around it pushes,
<v Speaker 3>I pulls on.
<v Speaker 2>It, So it's not just a passive observer, it's actively interfering.
<v Speaker 3>Actively. You might measure a certain wobble in the electron's
<v Speaker 3>path and say, ah, huh, I've discovered the natural wobble
<v Speaker 3>of an escaping electron. But you haven't. You've discovered the
<v Speaker 3>wobble caused by your laser. It's an artifact and Professor
<v Speaker 3>Dill's whole point is that any external reference, any outside clock,
<v Speaker 3>carries this huge risk of distortion.
<v Speaker 2>And this is even with the amazing technology that won
<v Speaker 2>the twenty twenty three Nobel Prize in Physics, which was
<v Speaker 2>for generating these out of second laser pulses. So even
<v Speaker 2>those tools are too clumsy, too loud for this kind
<v Speaker 2>of work.
<v Speaker 3>They are brilliant for creating the at asecond scale light.
<v Speaker 3>They give us access to that world, but for this
<v Speaker 3>specific task measuring the intrinsic time it takes for an
<v Speaker 3>electron to evolve on its own, using them as the
<v Speaker 3>stopwatch is like using a sledgehammer to perform brain surgery.
<v Speaker 3>You need something more subtle.
<v Speaker 2>We needed a stealth mode.
<v Speaker 3>We needed a way to ask the electron how long
<v Speaker 3>its journey took without it knowing we were even there.
<v Speaker 2>Okay, so that sets up the conflict perfectly. We need
<v Speaker 2>to time a race that's over in the time it
<v Speaker 2>takes light to not even cross a virus. But we
<v Speaker 2>can't be at the finish line with a stopwatch because
<v Speaker 2>just our presence there completely screws up the race. So
<v Speaker 2>what do they do.
<v Speaker 3>Well, if you can't bring a clock to the electron.
<v Speaker 2>You use a clock that's already there.
<v Speaker 3>You use the clock that's already there. This is the
<v Speaker 3>core of their breakthrough. The team led by Hugo Dill
<v Speaker 3>and the first author Fagwo, They figured out how to
<v Speaker 3>use a fundamental property of the electron itself as the
<v Speaker 3>internal timing mechanism, and that property is its spin.
<v Speaker 2>Okay, spin, This is one of those quantum terms that
<v Speaker 2>we hear all the time, but it's really slippery. Is
<v Speaker 2>the electron actually spinning like a tiny basketball on its axis?
<v Speaker 3>It's a great question, and the honest answer is not. Really.
<v Speaker 3>It's not a classical spinning ball, but it has a
<v Speaker 3>property that is mathematically identical to angular momentum. It has
<v Speaker 3>a magnetic orientation of sort of north and south pole.
<v Speaker 3>For our purposes, the crucial thing is that this spin
<v Speaker 3>state can hold information.
<v Speaker 2>It's like a tiny compass needle built into the electron.
<v Speaker 3>That's a very good way to think of it. And
<v Speaker 3>when that electron absorbs a photon and starts its prison
<v Speaker 3>break out of the material that compass needle it moves.
<v Speaker 3>The spin state evolves during the journey.
<v Speaker 2>So the spin is like the electrons black box recorder.
<v Speaker 2>It's flight data recorder. It's logging the trip.
<v Speaker 3>That is a fantastic analogy. Yes, Fay Guo, the lead author, says,
<v Speaker 3>their experiments yield the timescale required for a wave function
<v Speaker 3>of the electron to evolve the final direction of that
<v Speaker 3>compass needle. The spin state, when it comes out, tells
<v Speaker 3>you exactly what happened during the trip.
<v Speaker 2>You mentioned wave function, Just to refresh, that's the mathematical
<v Speaker 2>cloud of probabilities that describes the electron, right, It's not
<v Speaker 2>a point, it's a field of possibilities.
<v Speaker 3>It is, and this is where it gets really really
<v Speaker 3>weird and interesting. When the photon hits the electron, the
<v Speaker 3>electron doesn't just pick one exit door and run through it.
<v Speaker 3>This is quantum mechanics.
<v Speaker 2>It does everything at once.
<v Speaker 3>It takes all the doors at once. It follows several
<v Speaker 3>different quantum roots simultaneously. It's in a superposition of all
<v Speaker 3>possible paths out of the atom.
<v Speaker 2>That's like something out of a science fiction movie. It
<v Speaker 2>takes the highway and the side streets and tunnels under
<v Speaker 2>the city all at the same time.
<v Speaker 3>In essence, yes, and each of those different paths has
<v Speaker 3>something called a phase. You can think of the phase
<v Speaker 3>as the ticking hand on a tiny clock that each
<v Speaker 3>version of the electron is carrying. As an electron wave
<v Speaker 3>travels along a path, its little clockhand rotates. If it
<v Speaker 3>takes a very short direct path, the hand might only
<v Speaker 3>rotate a little bit. It takes a longer, more convoluted path,
<v Speaker 3>the hand rotates a lot more.
<v Speaker 2>And all these different versions of the electron, with their
<v Speaker 2>clocks all pointing in different directions, they all meet up
<v Speaker 2>at the exit.
<v Speaker 3>They do, and they interfere with each other. This is
<v Speaker 3>just like ripples in a pond. If you throw two
<v Speaker 3>stones in, the waves spread out and overlap. Where two
<v Speaker 3>crests meet, you get a bigger wave. That's constructive interference.
<v Speaker 3>Where crest meets a trough that cancel out and you
<v Speaker 3>get flat water. That's destructive interference.
<v Speaker 2>Okay, I'm with you.
<v Speaker 3>The electrons different paths do the same thing. They all
<v Speaker 3>converge and their phases add up or cancel out, and
<v Speaker 3>this final complex interference pattern gets imprinted directly onto the
<v Speaker 3>electron spin. The final direction of that compass needle is
<v Speaker 3>the sum of all those spinning clock hands.
<v Speaker 2>Okay, let me try to put this into an analogy
<v Speaker 2>and make sure I've got it. It's like I'm a
<v Speaker 2>detective trying to figure out how long a hiker spent
<v Speaker 2>in a dense, foggy forest. I can't fall of them
<v Speaker 2>because my presence would change their.
<v Speaker 3>Path, right, you'd scare off the wildlife. They'd take a
<v Speaker 3>different route exactly.
<v Speaker 2>So instead I wait for them to come out the
<v Speaker 2>other side, and instead of looking at a watch, I
<v Speaker 2>look at their shoes. By examining the unique pattern of
<v Speaker 2>mud scuffs and worn down tread the interference pattern from
<v Speaker 2>all the little paths they took inside, I can work
<v Speaker 2>backwards and calculate exactly how long they must have been walking.
<v Speaker 3>That is an excellent, excellent analogy. The wear and tear
<v Speaker 3>on the shoes is the final spin state, and by
<v Speaker 3>reading that you can deduce the duration of the journey.
<v Speaker 3>The hiker brings their own clock printed on their.
<v Speaker 2>Shoes, and as Fegwo said, the method does not require
<v Speaker 2>an external reference. There's no outside clock. It's all internal.
<v Speaker 3>It completely removes the risk of those artifacts of the
<v Speaker 3>hot thermometer problem. We aren't imposing a clock on the system.
<v Speaker 3>We're learning to read the diary the system road itself.
<v Speaker 2>That's brilliant. Okay, So they have the theory the spin
<v Speaker 2>is the clock. But now you need a machine, a
<v Speaker 2>device that can act actually catch these electrons as they
<v Speaker 2>fly out and read that incredibly subtle spin state. The
<v Speaker 2>source mentioned in acronym SARPs.
<v Speaker 3>It does sound a bit like a congbook villain, doesn't
<v Speaker 3>it kneel before SARPs?
<v Speaker 2>It really does, but it sounds for something much more complicated.
<v Speaker 3>It does. It's spin an angle resolved photo emission spectroscopy.
<v Speaker 2>WHOA, Okay, that is a mouthful. Let's break that down
<v Speaker 2>piece by piece. Photo emission spectroscopy. That's the part where
<v Speaker 2>you use light photons to knock electrons out.
<v Speaker 3>Right, correct, that's the core of the technique. Let's just
<v Speaker 3>walk through it first. You need an incredibly powerful and
<v Speaker 3>precise light source for this. They go to a synchrotron facility.
<v Speaker 2>These are those huge circular particle accelerators building sized machines exactly.
<v Speaker 3>They generate extremely intense beams of light. So step one,
<v Speaker 3>you fire this intense synchrotron light at your material sample.
<v Speaker 2>Step two, the photons hit the electrons, giving them that
<v Speaker 2>energy boost for the prison.
<v Speaker 3>Break, right, They get excited to a higher energy state. Three.
<v Speaker 3>With enough energy, they are forced to completely leave the material.
<v Speaker 3>They get ejected out into a high vacuum chamber.
<v Speaker 2>And this is where SARPs the machine is waiting for them.
<v Speaker 3>Yes, and this is the resolved part of the name.
<v Speaker 3>As the electrons fly out, the detector measures three key
<v Speaker 3>things about each one simultaneously, it measures its final energy,
<v Speaker 3>it measures its direction of travel or its angle, and crucially,
<v Speaker 3>it measures its spin.
<v Speaker 2>Okay, energy and spin makes sense for what we've been
<v Speaker 2>talking about. But why the angle? Why does it matter
<v Speaker 2>which direction the electron flies offen.
<v Speaker 3>That's a fantastic question, and it's key to the precision
<v Speaker 3>of the experiment. The angle tells you about the electron's
<v Speaker 3>momentum while it was still inside the crystal. In a material,
<v Speaker 3>electrons don't just buzz around randomly. Like a swarm of bees.
<v Speaker 3>They exist in specific energy bands and travel along specific
<v Speaker 3>pathways or highways defined by the crystal structure.
<v Speaker 2>So the exit direction tells you which highway it came from.
<v Speaker 3>Precisely by measuring the angle, you can trace its trajectory
<v Speaker 3>back and say, ah, this electron came from this specific
<v Speaker 3>orbital with this specific momentum. It's the difference between hearing
<v Speaker 3>the roar of a crowd and being able to pick
<v Speaker 3>out a single person's voice and what they were saying.
<v Speaker 3>It gives them incredible specificity.
<v Speaker 2>So SARPs is this amazing machine that basically acts like
<v Speaker 2>a quantum forensics lab. It catches the escaped electrons and
<v Speaker 2>it figures out how fast they're going, where they came from,
<v Speaker 2>and it reads their internal clock.
<v Speaker 3>That's a perfect summary. It's forensic physics. And with those
<v Speaker 3>three pieces of data, energy, angle, and spin, they can
<v Speaker 3>reconstruct the entire story of that quantum transition.
<v Speaker 2>Amazing. Okay, so we have the method, we have the machine.
<v Speaker 2>Now the experiment itself. They didn't just want to prove
<v Speaker 2>they could measure the time. They wanted to test a hypothesis.
<v Speaker 3>This is where it gets really profound. We now have
<v Speaker 3>a stopwatch. The next question is does the racetrack itself
<v Speaker 3>affect the lab time? Does the geometry of the material
<v Speaker 3>the stage affect the performance of the actor.
<v Speaker 2>And to do that, they chose materials with very different
<v Speaker 2>atomic sheapes.
<v Speaker 3>Yes, they very cleverly pick three classes of materials to
<v Speaker 3>represent different dimensionalities, different kinds of symmetry. First up, the
<v Speaker 3>use just plain old copper, the.
<v Speaker 2>Stuff in our pipes and wires exactly, And the reason
<v Speaker 2>they chose it is because copper has a very standard,
<v Speaker 2>fully three dimensional crystal structure.
<v Speaker 3>It's highly symmetric. The atoms are arranged in a repeating
<v Speaker 3>cube like pattern. You can imagine it as a perfectly
<v Speaker 3>built jungle gym that extends forever in all three directions up, down, left, right, forward, back.
<v Speaker 2>So every atom has neighbors on all sides. It's a
<v Speaker 2>very connected three D world for an electron.
<v Speaker 3>Right, that's our three D baseline, the jungle gym. Next,
<v Speaker 3>they look at two materials, titanium disalinde are tis and
<v Speaker 3>titanium detelluride tight.
<v Speaker 2>Definitely more exotic.
<v Speaker 3>These are what we call layered or two dimensional materials.
<v Speaker 3>Think of a perfect stack of infinitely thin sheets of
<v Speaker 3>paper or a deck of cards. Within each sheet, the
<v Speaker 3>atoms are very strongly bonded together, but the connection between
<v Speaker 3>the sheets is very weak.
<v Speaker 2>So an electron can zip around on one sheet really easily,
<v Speaker 2>but it's hard for it to jump to the sheet
<v Speaker 2>above or below it.
<v Speaker 3>Precisely, for all intents and purposes, the electrons are living
<v Speaker 3>in a two D world. They've gone from a three
<v Speaker 3>D jungle gym to a two D stack of pancakes.
<v Speaker 3>The symmetry has been broken in one of the three dimensions.
<v Speaker 2>Okay, I see the progression three D then two D.
<v Speaker 3>What's next next is a material called copper telluride or cute,
<v Speaker 3>and this one has a chain.
<v Speaker 2>Like structure, so like beads on a string.
<v Speaker 3>A perfect analogy, the atoms are arranged in long linear chains,
<v Speaker 3>so an electron is basically confined to moving forward or
<v Speaker 3>backward along that one dimensional line. That's a one D world.
<v Speaker 2>So we have the three D jungle gym, the two
<v Speaker 2>D pancakes, and the one D string of beads. The
<v Speaker 2>only major variable between them is the geometry the symmetry
<v Speaker 2>of the environment the electron lives in.
<v Speaker 3>And that was a whole point. The hypothesis was does
<v Speaker 3>the shape of the room affect how long it takes
<v Speaker 3>the electron to find the exit door.
<v Speaker 2>I really love this experimental design. It's so elegant. It's
<v Speaker 2>like you're setting up a race with three identical run
<v Speaker 2>but one is running across a wide, open ballroom, the
<v Speaker 2>second is running down a narrow hallway, and the third
<v Speaker 2>is running on a tightrope, and you want to see
<v Speaker 2>who gets out the fastest.
<v Speaker 3>And the results were not just clear, they were I
<v Speaker 3>think quite surprising.
<v Speaker 2>Okay, let's get into the results, because this is where
<v Speaker 2>my normal, everyday intuition starts to break down. If I'm
<v Speaker 2>one of those runners, I might think the tight rope,
<v Speaker 2>the one D chain would be the fastest. It's the
<v Speaker 2>most direct path, no distractions, no side to side movement,
<v Speaker 2>just go straight.
<v Speaker 3>That would be a perfectly logical assumption in our classical world,
<v Speaker 3>but the quantum world, it doesn't play by our rules.
<v Speaker 3>The results showed a very clear and opposite pattern. The
<v Speaker 3>less symmetry the structure had, the more time the transition took.
<v Speaker 3>The simpler the geometry, the slower the event.
<v Speaker 2>Wait, really, the simplest structure is the slowest. That feels
<v Speaker 2>completely backwards.
<v Speaker 3>It's profoundly counterintuitive, but the data is unambiguous. Let's just
<v Speaker 3>go through the numbers. The fastest transition by far was
<v Speaker 3>in the three D copper, the jungle.
<v Speaker 2>Okay, what was the time?
<v Speaker 3>The time for that electron transition was measured to be
<v Speaker 3>approximately twenty six out of seconds.
<v Speaker 2>Twenty six okay, that's our baseline, blistringly fast.
<v Speaker 3>Right. Now, Let's go to the two D layered materials,
<v Speaker 3>the stack of pancakes, tier on tier. The transition time
<v Speaker 3>jumped way up. It was in the range of one
<v Speaker 3>hundred and forty to one hundred and seventy five auto seconds.
<v Speaker 2>Well, hang on, from twenty six to let's say one
<v Speaker 2>hundred and fifty that's what five almost six times slower,
<v Speaker 2>just from taking away one dimension of movement.
<v Speaker 3>Yes, just by confining the electrons to flat sheets. The
<v Speaker 3>whole process slowed down dramatically. And then the real shocker,
<v Speaker 3>the one D material, the chain like copper. Tell your ride,
<v Speaker 3>the tightrope walker.
<v Speaker 2>What was its time?
<v Speaker 3>It was the slowest of all. The transition time stretched
<v Speaker 3>to over two hundred out of seconds.
<v Speaker 2>So the tightrope was the slowest. We go from about
<v Speaker 2>twenty six and three D to about one hundred and
<v Speaker 2>fifty and two D and over two hundred and one D.
<v Speaker 2>That is a clear trend. But why why does being
<v Speaker 2>stuck in a simple chain make the electron so much
<v Speaker 2>more slow huggish than when it's in the complex three
<v Speaker 2>D world of copper. You'd think the jungle gym would
<v Speaker 2>be full of obstacles.
<v Speaker 3>It all comes back to those quantum roots we talked
<v Speaker 3>about the wave function and interference. In the highly symmetric
<v Speaker 3>three D copper, the electron has a huge number of
<v Speaker 3>possible paths that can take simultaneously. There's a rich network
<v Speaker 3>of connections.
<v Speaker 2>So it's like a city with a perfect grid system,
<v Speaker 2>lots of options to get from A to B exactly.
<v Speaker 3>And because there are so many available routes, there are
<v Speaker 3>more opportunities for the different parts of the wave function
<v Speaker 3>to interfere constructively to build up the necessary oof to
<v Speaker 3>complete the transition quickly. The high symmetry facilitates a very efficient,
<v Speaker 3>very rapid evolution of the wave function.
<v Speaker 2>The crowd can move quickly because there are doors and
<v Speaker 2>windows open in every direction.
<v Speaker 3>There are no bottlenecks, A great way to put it. Now,
<v Speaker 3>contrast that with the one D chain, the electron is
<v Speaker 3>stuck on a single track. Its neighbors are only in
<v Speaker 3>front of it and behind it. This severe confinement drastically
<v Speaker 3>limits the number of quantum pathways available. The interference patterning
<v Speaker 3>can create is much simpler, much more restricted.
<v Speaker 2>So because it has fewer options, it takes longer to
<v Speaker 2>build up the right conditions to make the jump.
<v Speaker 3>That's the essence of it. Yes, the constraint itself introduces
<v Speaker 3>a delay. The accumulated phase, which is our internal clock,
<v Speaker 3>It just builds up differently, more slowly. The wave function
<v Speaker 3>has to sort of wait longer for the quantum mechanics
<v Speaker 3>to align and just the right way for the transition
<v Speaker 3>to finalize.
<v Speaker 2>That is so fascinating. We think of complexity creating bureaucracy
<v Speaker 2>and slowing things down, but here the quantum complexity of
<v Speaker 2>the three D structure is what makes it so efficient
<v Speaker 2>and fast.
<v Speaker 3>It's the shape of the world the electron lives in.
<v Speaker 3>That's what dictates its temporal behavior. The less freedom it
<v Speaker 3>has geometrically, the longer it takes to act. Lower symmetry
<v Speaker 3>means longer transition times.
<v Speaker 2>This really brings that phrase geometry meets time to life.
<v Speaker 2>We are literally seeing the physical architecture of a material
<v Speaker 2>warping the local flow of time.
<v Speaker 3>For a quantum particle, it is, for all practical purposes,
<v Speaker 3>a localized time dilation, not caused by gravity like in
<v Speaker 3>relative tivity, but by quantum geometry.
<v Speaker 2>Okay, we've established this incredible counterintuitive result. Three D is fast,
<v Speaker 2>one D is slow. We've clocked the unclockable. Now let's
<v Speaker 2>get to the big So what I can hear people
<v Speaker 2>listening and thinking, Okay, that's neat physics. But twenty six
<v Speaker 2>auto seconds versus two hundred auto seconds, it's all literally
<v Speaker 2>faster than the blink of an eye. Why should I care?
<v Speaker 3>And it's a completely fair question. For our human senses,
<v Speaker 3>the difference is zero. But for fundamental physics and for
<v Speaker 3>the future of our technology, the difference is absolutely monumental.
<v Speaker 2>Let's start with the big picture, the theoretical side. Professor
<v Speaker 2>Dill is quoted as saying this work could help us
<v Speaker 2>finally understand the role of time in quantum mechanics. That's
<v Speaker 2>a huge claim.
<v Speaker 3>It's a massive claim, and I think it's justified. For
<v Speaker 3>the better part of a century, there's been this nagging
<v Speaker 3>debate are quantum jumps truly instantaneous. The early models, the
<v Speaker 3>Bore model of the atom, they depicted them as these
<v Speaker 3>magical instant leaps an electron teleports from orbit A to
<v Speaker 3>orbit B. This research provides of the strongest evidence yet
<v Speaker 3>that they are not instantaneous.
<v Speaker 2>It puts a number on it. It kills the instant myth.
<v Speaker 3>It does, and it does something more. It tells us
<v Speaker 3>that the duration that time is not some fixed universal constant.
<v Speaker 3>It's interactive. It depends on the material, on the geometry.
<v Speaker 3>This hints at a much much deeper connection between the
<v Speaker 3>fabric of space, the geometry, and the flow of time.
<v Speaker 3>At the most fundamental level.
<v Speaker 2>It almost sounds like it's echoing general relativity. You know
<v Speaker 2>where massive objects curve space time, and that curvature is
<v Speaker 2>what we feel is gravity, and it also affects time
<v Speaker 2>clocks tick slower in near black hole.
<v Speaker 3>That's a very sharp insight. It feels like a quantum
<v Speaker 3>mechanical parallel to that relativity tells us that mass and
<v Speaker 3>energy curve space time and thus bend the flow of time.
<v Speaker 3>This is telling us that quantum geometry, the arrangement of atoms,
<v Speaker 3>also bends the flow of time. For quantum processes. It
<v Speaker 3>might be a crucial clue in the search for a
<v Speaker 3>unified theory that can connect the world of gravity with
<v Speaker 3>the world of quantum mechanics.
<v Speaker 2>Okay, so philosophically it's a game changer. What about the
<v Speaker 2>practical side, the engineering, the gadgets. How does knowing this
<v Speaker 2>let us build better things?
<v Speaker 3>This is where it gets really exciting. Think about where
<v Speaker 3>all of our advanced technology is heading. We're moving deeper
<v Speaker 3>into the quantum realm. Quantum computing, quantum sensors, quantum cryptography.
<v Speaker 3>All of these technologies depend on one thing, the precise
<v Speaker 3>control of quantum.
<v Speaker 2>States, controlling quibbits, getting electrons to do exactly what you
<v Speaker 2>want them.
<v Speaker 3>To do exactly. Now, if you're building a quantum processor,
<v Speaker 3>you are essentially switching these states on and off, or
<v Speaker 3>moving an electron from one place to another to represent
<v Speaker 3>a piece of information. The speed of that switch, the
<v Speaker 3>duration of that transition, becomes a critical design parameter.
<v Speaker 2>And if you've been assuming that switch is instantaneous, but
<v Speaker 2>it actually takes two hundred out of seconds because you
<v Speaker 2>built your device out of a one D chain like material,
<v Speaker 2>your whole calculation could be off.
<v Speaker 3>Your timing could be completely off. You could get what
<v Speaker 3>you called quantum lag in the field. It could lead
<v Speaker 3>to decoherence where the delicate quantum state just falls apart
<v Speaker 3>because you didn't account for that delay. The system gets
<v Speaker 3>out of sync with itself.
<v Speaker 2>But now now we know that geometry controls timing, so
<v Speaker 2>we can use that. We can design materials to have
<v Speaker 2>specific clock speaks.
<v Speaker 3>That is the key takeaway. It gives us a brand
<v Speaker 3>new knob to turn in material science. It's a design tool.
<v Speaker 3>If I need to build a quantum switch that has
<v Speaker 3>to operate incredibly fast, I should probably build it using
<v Speaker 3>a material with high three D like symmetry.
<v Speaker 2>And if I need a process to be a little slower,
<v Speaker 2>maybe I need an electron to stay in an excited
<v Speaker 2>state for a bit longer to act as a memory
<v Speaker 2>buffer to sync up with a slower signal.
<v Speaker 3>Then you might intentionally design your material with a one
<v Speaker 3>D chain like structure to deliberately stretch out that transition time.
<v Speaker 3>You can engineer the timing by engineering the atomic architecture.
<v Speaker 3>It's an incredible level of control that we just didn't
<v Speaker 3>know we had.
<v Speaker 2>We can build materials that are fast or slow on
<v Speaker 2>a quantum level by.
<v Speaker 3>Design also gives us a new way to investigate materials
<v Speaker 3>we don't understand yet. Suppose we discovered some new exotic superconductor.
<v Speaker 3>We can hit it with this SARPs technique and measure
<v Speaker 3>the internal timing of its electrons. That timing profile could
<v Speaker 3>reveal all sorts of hidden symmetries or strange geometric properties
<v Speaker 3>that we couldn't see with any other tool.
<v Speaker 2>It's a diagnostic tool. You can listen to the material's
<v Speaker 2>quantum heartbeat to figure out what's going.
<v Speaker 3>On inside a very very fast heartbeat.
<v Speaker 2>But yes, okay, so let's try and wrap this all up.
<v Speaker 2>We started with this image of a melting quantum clock.
<v Speaker 2>We went down to the attosecond scale, a world where
<v Speaker 2>light can't even cross a virus.
<v Speaker 3>An almost unimaginable world.
<v Speaker 2>And we learned that you can't time an event there
<v Speaker 2>with an external stopwatch, because your stopwatch will break the
<v Speaker 2>very thing you're trying to measure, the hot thermometer problem.
<v Speaker 3>If you have to be clever, you have to find
<v Speaker 3>the clock that's already there.
<v Speaker 2>Which turned out to be the electron's own spin it's
<v Speaker 2>internal compass needle that records the wear and tear of
<v Speaker 2>its journey, hiker shoes, hikershoes. And then we looked at
<v Speaker 2>the big race, the three D jungle gym of copper
<v Speaker 2>versus the two D pancakes of titanium disalinide versus the
<v Speaker 2>one D tightrope of copper telluride.
<v Speaker 3>And the result was completely counterintuitive.
<v Speaker 2>The simplest path, the one D tightrope, was by far
<v Speaker 2>the slowest. The complex, highly connected three D world was
<v Speaker 2>the fastest. More complexity and at more speed, more simplicity
<v Speaker 2>em at more delay.
<v Speaker 3>It's an incredible conclusion. The big lesson here is that
<v Speaker 3>time at this fundamental level is not an absolute, universal river.
<v Speaker 3>It's a local phenomenon. Its flow is shaped and dictated
<v Speaker 3>by the immediate environment of the particle.
<v Speaker 2>It makes you look at a simple copper wire completely differently.
<v Speaker 2>You realize that for the trillions of electrons zipping around
<v Speaker 2>inside it, their experience of time, the very rhythm of
<v Speaker 2>their existence, is different from the electrons inside the graphite
<v Speaker 2>and your pencil.
<v Speaker 3>It just reminds us that our human scale perception of
<v Speaker 3>a steady ticking clock is just a massive statistical average.
<v Speaker 3>Underneath it, all the universe is a symphony of incredibly
<v Speaker 3>complex rhythms speeding up and slowing down based on the
<v Speaker 3>local geometry.
<v Speaker 2>Before we sign off, I just want to leave our
<v Speaker 2>listeners with one final, bigger thought to chew on. We've
<v Speaker 2>spent this whole conversation talking about how the geometry of
<v Speaker 2>matter dictates the speed of time at the quantum level. Right,
<v Speaker 2>so let's just zoom out, way out. If the shape
<v Speaker 2>of a crystal changes the flow of time for an electron.
<v Speaker 2>What if time, as we experience it is nothing more
<v Speaker 2>than an emergent property, a side effect of the overall
<v Speaker 2>shape of our universe.
<v Speaker 3>That is the ultimate provocative question, isn't it.
<v Speaker 2>I mean, think about it. We see time as this
<v Speaker 2>unstoppable force that carries everything along with it. But this
<v Speaker 2>research shows that if you change the geometry, you change
<v Speaker 2>the time. What if we could somehow change the geometry
<v Speaker 2>of our own environment, not just a crystal, but the
<v Speaker 2>shape of space around us. Could we change the flow
<v Speaker 2>of time for ourselves?
<v Speaker 3>General relativity already tells us that a massive object like
<v Speaker 3>a black hole does exactly that. It warps geometry so
<v Speaker 3>much that time slows to a crawl. But this research
<v Speaker 3>hints that maybe you don't need a black hole Maybe
<v Speaker 3>it's a more fundamental principle. Geometry is temporal destiny. If
<v Speaker 3>we could ever learn to manipulate the geometry of space itself,
<v Speaker 3>who knows.
<v Speaker 2>Maybe the key to time travel isn't a machine that
<v Speaker 2>moves through time. Maybe it's a machine that just reshapes
<v Speaker 2>the room you're standing in. And on that note, I
<v Speaker 2>think we'll leave it there. Thank you so much for
<v Speaker 2>joining us.
<v Speaker 3>Thank you it's a pleasure. Keep asking questions
<v Speaker 2>Until next time.