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Timing the Quantum World: How Spin Reveals the Speed of Atomic Events · The Quark Side - Quantum Physics Podcast

• 0:01
  Speaker 1: Welcome to the quark Side Quantum Physics Podcast, an exploration
• 0:05
  Speaker 1: of the fundamental structure of reality, where quantum laws govern matter, energy,
• 0:11
  Speaker 1: and information. Here, uncertainty is a feature, not a flaw,
• 0:16
  Speaker 1: and understanding begins at the smallest scales.
• 0:27
  Speaker 2: Hello and welcome. It is February sixth, twenty twenty six.
• 0:31
  Speaker 2: I want to start today with the little thought experiment.
• 0:34
  Speaker 2: Just you know, humor me for a second. I want
• 0:36
  Speaker 2: you to imagine a clock, a simple analog clock on
• 0:39
  Speaker 2: a wall.
• 0:40
  Speaker 3: Okay, got it.
• 0:41
  Speaker 2: Now, imagine that clock starts to melt. The numbers are
• 0:44
  Speaker 2: dripping down the wall like something out of a surrealist painting.
• 0:47
  Speaker 2: Or maybe the gears inside start spinning so fast they liquefy,
• 0:51
  Speaker 2: or they start going backwards, or somehow exist in two places.
• 0:54
  Speaker 3: At the same time, a quantum clock.
• 0:56
  Speaker 2: Exactly, because we are starting today's conversation with a question
• 1:00
  Speaker 2: has I mean, it's kept philosophers up at night for
• 1:03
  Speaker 2: centuries and has pushed physicists to the absolute edge. What
• 1:07
  Speaker 2: is time?
• 1:08
  Speaker 3: It's the big one, isn't it. It is the one
• 1:10
  Speaker 3: constant we all experience, but the one thing nobody can
• 1:13
  Speaker 3: really define. I think Augustin had that famous quote about it.
• 1:16
  Speaker 2: Oh right, what was that?
• 1:18
  Speaker 3: It was something like, what then is time? If no
• 1:19
  Speaker 3: one asks me? I know, if I wish to explain
• 1:21
  Speaker 3: it to one who asks, I know not. It's just it.
• 1:24
  Speaker 3: It's the water we're swimming in, but we can't grab
• 1:26
  Speaker 3: a handful of it.
• 1:27
  Speaker 2: It feels so absolute to us, you know, day in
• 1:30
  Speaker 2: day out, But we know from physics, from relativity, that
• 1:33
  Speaker 2: it isn't. It's flexible. And when you go small, really
• 1:37
  Speaker 2: really small, it gets even stranger.
• 1:40
  Speaker 3: It really does. It stops being this sort of universal
• 1:42
  Speaker 3: metronomes background beat for reality, and it becomes a property
• 1:46
  Speaker 3: of the system itself.
• 1:47
  Speaker 2: It becomes a variable, and that is exactly where we're
• 1:49
  Speaker 2: headed today. We're looking at a pretty incredible breakthrough coming
• 1:53
  Speaker 2: out of EPFL, the Equal Polytechnique federalde Lausanne over in Switzerland.
• 1:59
  Speaker 3: A fantastic to constitution.
• 2:01
  Speaker 2: They've managed to do something that honestly sounds impossible. They
• 2:05
  Speaker 2: figured out a way to measure time on the smallest
• 2:07
  Speaker 2: possible scale. But and this is the part that really
• 2:10
  Speaker 2: got me, they discovered that the speed of time actually
• 2:13
  Speaker 2: changes it depends on the shape of the matter it's.
• 2:15
  Speaker 3: In, which is a huge deal because Normally, when you
• 2:17
  Speaker 3: bring quantum mechanics into the discussion about time, the problem
• 2:21
  Speaker 3: gets harder, not easier. Time is notoriously slippery in the
• 2:25
  Speaker 3: quantum world.
• 2:26
  Speaker 2: Right, because we tend to think of quantum events, these
• 2:28
  Speaker 2: little jumps and electron makes as being instant Right, it's
• 2:33
  Speaker 2: in one place, one energy level, and then poof, it's
• 2:35
  Speaker 2: in another.
• 2:36
  Speaker 3: Exactly like a teleport. We often treat them as instantaneous,
• 2:39
  Speaker 3: partly because the math is a lot cleaner that way,
• 2:42
  Speaker 3: but also because honestly, measuring any duration has been next
• 2:45
  Speaker 3: to impossible.
• 2:46
  Speaker 2: It's just too fast to see.
• 2:47
  Speaker 3: But this new research it basically pulls back that curtain.
• 2:51
  Speaker 3: It says, no, it's not a magic trick, it's not instantaneous.
• 2:55
  Speaker 3: There is a duration. It's a process. And what's really
• 2:58
  Speaker 3: amazing is that the length of that process is controlled
• 3:01
  Speaker 3: by geometry.
• 3:02
  Speaker 2: So that's our mission for today. We're going to unpack
• 3:05
  Speaker 2: this whole thing. We're going to figure out how on
• 3:07
  Speaker 2: Earth you can clock a quantum event without an actual clock,
• 3:11
  Speaker 2: because using one apparently messes up the whole experiment. And
• 3:14
  Speaker 2: then we're going to get into this really mind bending
• 3:16
  Speaker 2: finding that the symmetry of a material it's actual atomic
• 3:20
  Speaker 2: architecture can warp how fast time passes for the electrons
• 3:24
  Speaker 2: living inside it.
• 3:25
  Speaker 3: It's this beautiful place where geometry, quantum theory, and the
• 3:29
  Speaker 3: very philosophy of time all intersect. Reallyically makes you question
• 3:33
  Speaker 3: if time is this fundamental thing flowing everywhere, or if
• 3:36
  Speaker 3: it's more of a local effect generated by the environment itself.
• 3:39
  Speaker 2: Okay, so let's get into it Part one, the scale
• 3:42
  Speaker 2: and the struggle. Before we talk about timing something, we
• 3:45
  Speaker 2: need to be really clear on what it is. When
• 3:47
  Speaker 2: you say a quantum event, what were the researchers actually measuring?
• 3:52
  Speaker 3: So they were looking at one of the most fundamental
• 3:54
  Speaker 3: processes in quantum mechanics. It's called a quantum transition. The
• 3:58
  Speaker 3: classic example is the photoelectric effect, which Einstein won his
• 4:02
  Speaker 3: no Bell for.
• 4:03
  Speaker 2: That's where light hits a metal and knocks an electron out.
• 4:06
  Speaker 3: Precisely, a photon, which is a particle of light, comes
• 4:10
  Speaker 3: in and smacks into an electron that's bound inside a material.
• 4:13
  Speaker 3: The electron absorbs the energy from that photon, gets super
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  Speaker 3: excited and uses that energy to well make a run
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  Speaker 3: for it. It escapes the material entirely. It's a prison break,
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  Speaker 3: a quantum prison break. Yes, it's transitioning from being bound
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  Speaker 3: to the material to being a free particle. And the
• 4:31
  Speaker 3: huge question has always been how long does that take?
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  Speaker 3: Is the escape instant, the moment the photon hits, is
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  Speaker 3: the electron out or is there a delay a kind
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  Speaker 3: of reaction time?
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  Speaker 2: And I'm guessing we're not talking about seconds here or
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  Speaker 2: even nanosecond Oh, not even close.
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  Speaker 3: We are operating in the realm of the attosecond.
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  Speaker 2: The attosecond, it's one of those words that sounds fast
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  Speaker 2: just saying it. But help us, you know, get a
• 4:55
  Speaker 2: handle on this. The number ten to the minus eighteen
• 4:59
  Speaker 2: seconds is just us. It's an abstraction, a decimal point
• 5:03
  Speaker 2: seventeen zeros than a one. How do we even begin
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  Speaker 2: to visualize that?
• 5:06
  Speaker 3: It is almost impossible to wrap your head around. You're right.
• 5:08
  Speaker 3: The analogy the researchers from epfl use is probably the
• 5:11
  Speaker 3: best one I've heard.
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  Speaker 2: Okay, lay it on us, all right.
• 5:13
  Speaker 3: Think about light, The fastest thing there is. It travels
• 5:16
  Speaker 3: in about three hundred thousand kilometers per second. It can
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  Speaker 3: zip around the entire Earth more than seven times in
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  Speaker 3: a single second.
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  Speaker 2: The ultimate speed limit.
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  Speaker 3: Right now, imagine a very very small virus, and at
• 5:27
  Speaker 3: a second is so short that in that amount of time,
• 5:29
  Speaker 3: a beam of light can't even make it across the
• 5:32
  Speaker 3: width of that single tiny virus.
• 5:34
  Speaker 2: Wait, hold on, say that again, light the cosmic speed
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  Speaker 2: limit cannot cross a virus in one atto second.
• 5:41
  Speaker 3: That's correct. Let's break it down even more. A small
• 5:43
  Speaker 3: virus might be say twenty nanometers across. A nanometer is
• 5:47
  Speaker 3: a billionth of a meter, So already that's incredibly.
• 5:49
  Speaker 2: Small, invisible to us completely.
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  Speaker 3: But for a photon, which is a particle of light
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  Speaker 3: traveling at its breakneck speed, it still takes a measurable
• 5:57
  Speaker 3: amount of time to cross that twenty nanometers discs and
• 6:00
  Speaker 3: that time is roughly sixty to seventy auto seconds.
• 6:04
  Speaker 2: Okay, so the time it takes light to cross a
• 6:06
  Speaker 2: germ is about seventy out a second roughly.
• 6:08
  Speaker 3: Yes. Now consider the events they measured in this experiment.
• 6:11
  Speaker 3: For material like copper, the quantum transition we're talking about
• 6:14
  Speaker 3: the electrons escape took about twenty six autoseconds.
• 6:17
  Speaker 2: So the entire process of the electron getting hit, getting excited,
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  Speaker 2: and completing its transition happens in less than half the
• 6:23
  Speaker 2: time it takes light to cross a single virus exactly.
• 6:27
  Speaker 3: It's not that the electrons moving faster than light, of course,
• 6:29
  Speaker 3: nothing does that. But the duration of the event, the
• 6:33
  Speaker 3: time it takes for its entire quantum state, its wave
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  Speaker 3: function to evolve from stuck to free, is shorter than
• 6:40
  Speaker 3: that light crossing time.
• 6:42
  Speaker 2: That's just absurd. It feels like trying to measure the
• 6:45
  Speaker 2: duration of a single thought, but then scaling that down
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  Speaker 2: by a factor of a billion.
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  Speaker 3: It gives you a sense of the fundamental clock speed
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  Speaker 3: of reality. If you could stretch a single second to
• 6:55
  Speaker 3: be as long as the entire age of the universe
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  Speaker 3: about thirteen point eight billion year, an attosecond would be
• 7:02
  Speaker 3: just a few seconds in comparison.
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  Speaker 2: Wow. Okay, So that brings us to the next obvious
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  Speaker 2: and I imagine, very difficult question. If it's happening that fast,
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  Speaker 2: how on earth do you measure it? You can't just
• 7:11
  Speaker 2: you know, click a stopwatch.
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  Speaker 3: You absolutely cannot. And this gets us right to the
• 7:15
  Speaker 3: heart of the problem in this field, what we can
• 7:17
  Speaker 3: call the external clock issue. It's a massive challenge in
• 7:20
  Speaker 3: quantum physics, the measurement problem, yes, a version of it.
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  Speaker 3: Professor Hugo. Dill, who is The lead on this study
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  Speaker 3: is very clear about this. If you try to bring
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  Speaker 3: in any kind of external tool to time the event,
• 7:33
  Speaker 3: say an ultra fast laser pulse that acts like a
• 7:36
  Speaker 3: flash on a camera, that tool itself is going to
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  Speaker 3: interact with the electron you're trying to measure.
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  Speaker 2: It's the classic observer effect. Right by looking at something
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  Speaker 2: quantum you change it.
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  Speaker 3: It's exactly that, but in a very physical, very direct way.
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  Speaker 3: It's more than just looking. I think the best analogy
• 7:53
  Speaker 3: is when they hint at in the paper. Imagine you
• 7:55
  Speaker 3: have a tiny thimble full of water and you want
• 7:58
  Speaker 3: to measure its temperature with perfect accuracy. Okay, but the
• 8:01
  Speaker 3: only thermometer you have is a giant industrial one fresh
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  Speaker 3: out of a furnace, glowing red hot.
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  Speaker 2: Right, if I stick that enormous hot poker into my
• 8:09
  Speaker 2: tiny thimble of water, I'm just going to boil the
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  Speaker 2: water away.
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  Speaker 3: Precisely, you're not measuring the water's original temperature. You're measuring
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  Speaker 3: the temperature of water that you just flash boiled with
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  Speaker 3: your tool. The very act of measuring has completely disported
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  Speaker 3: the reality you wanted to observe.
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  Speaker 2: Your measurement created a new reality.
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  Speaker 3: It induced artifacts that's the technical term for it.
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  Speaker 2: Can you explain what an artifact is in this physics context,
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  Speaker 2: because it makes me think of finding old pottery, not data.
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  Speaker 3: It is a great question. In experimental science. An artifact
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  Speaker 3: is any signal in your data that looks like it's
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  Speaker 3: a real phenomenon, but it was actually created by your
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  Speaker 3: measurement process or your equipment.
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  Speaker 2: So it's a ghost in the machine.
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  Speaker 3: A ghost in the machine. Perfect. Yeah. Imagine you're taking
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  Speaker 3: a photo of a sprinter at the finish line, but
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  Speaker 3: your camera has a really slow shutter and you use
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  Speaker 3: a brake flash when you look at the photo, so
• 9:00
  Speaker 3: the sprinter might look blurry, or maybe they look like
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  Speaker 3: they have two heads because they moved while the shutter
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  Speaker 3: was still open.
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  Speaker 2: And if I didn't know anything about photography, I might
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  Speaker 2: publish a paper saying, incredible discovery, humans grow a second
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  Speaker 2: head when they run at high speed.
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  Speaker 3: Exactly, you'd be misinterpreting an artifact at the camera as
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  Speaker 3: a real biological event. In the quantum world, when you
• 9:21
  Speaker 3: use these intense laser pulses as an external clock, the
• 9:25
  Speaker 3: laser's own electric field starts yanking the electron around it pushes,
• 9:29
  Speaker 3: I pulls on.
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  Speaker 2: It, So it's not just a passive observer, it's actively interfering.
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  Speaker 3: Actively. You might measure a certain wobble in the electron's
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  Speaker 3: path and say, ah, huh, I've discovered the natural wobble
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  Speaker 3: of an escaping electron. But you haven't. You've discovered the
• 9:43
  Speaker 3: wobble caused by your laser. It's an artifact and Professor
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  Speaker 3: Dill's whole point is that any external reference, any outside clock,
• 9:50
  Speaker 3: carries this huge risk of distortion.
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  Speaker 2: And this is even with the amazing technology that won
• 9:55
  Speaker 2: the twenty twenty three Nobel Prize in Physics, which was
• 9:58
  Speaker 2: for generating these out of second laser pulses. So even
• 10:02
  Speaker 2: those tools are too clumsy, too loud for this kind
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  Speaker 2: of work.
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  Speaker 3: They are brilliant for creating the at asecond scale light.
• 10:08
  Speaker 3: They give us access to that world, but for this
• 10:11
  Speaker 3: specific task measuring the intrinsic time it takes for an
• 10:14
  Speaker 3: electron to evolve on its own, using them as the
• 10:17
  Speaker 3: stopwatch is like using a sledgehammer to perform brain surgery.
• 10:20
  Speaker 3: You need something more subtle.
• 10:21
  Speaker 2: We needed a stealth mode.
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  Speaker 3: We needed a way to ask the electron how long
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  Speaker 3: its journey took without it knowing we were even there.
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  Speaker 2: Okay, so that sets up the conflict perfectly. We need
• 10:30
  Speaker 2: to time a race that's over in the time it
• 10:33
  Speaker 2: takes light to not even cross a virus. But we
• 10:35
  Speaker 2: can't be at the finish line with a stopwatch because
• 10:37
  Speaker 2: just our presence there completely screws up the race. So
• 10:40
  Speaker 2: what do they do.
• 10:41
  Speaker 3: Well, if you can't bring a clock to the electron.
• 10:44
  Speaker 2: You use a clock that's already there.
• 10:46
  Speaker 3: You use the clock that's already there. This is the
• 10:48
  Speaker 3: core of their breakthrough. The team led by Hugo Dill
• 10:52
  Speaker 3: and the first author Fagwo, They figured out how to
• 10:55
  Speaker 3: use a fundamental property of the electron itself as the
• 10:58
  Speaker 3: internal timing mechanism, and that property is its spin.
• 11:02
  Speaker 2: Okay, spin, This is one of those quantum terms that
• 11:04
  Speaker 2: we hear all the time, but it's really slippery. Is
• 11:07
  Speaker 2: the electron actually spinning like a tiny basketball on its axis?
• 11:11
  Speaker 3: It's a great question, and the honest answer is not. Really.
• 11:14
  Speaker 3: It's not a classical spinning ball, but it has a
• 11:17
  Speaker 3: property that is mathematically identical to angular momentum. It has
• 11:23
  Speaker 3: a magnetic orientation of sort of north and south pole.
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  Speaker 3: For our purposes, the crucial thing is that this spin
• 11:28
  Speaker 3: state can hold information.
• 11:30
  Speaker 2: It's like a tiny compass needle built into the electron.
• 11:32
  Speaker 3: That's a very good way to think of it. And
• 11:34
  Speaker 3: when that electron absorbs a photon and starts its prison
• 11:39
  Speaker 3: break out of the material that compass needle it moves.
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  Speaker 3: The spin state evolves during the journey.
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  Speaker 2: So the spin is like the electrons black box recorder.
• 11:50
  Speaker 2: It's flight data recorder. It's logging the trip.
• 11:52
  Speaker 3: That is a fantastic analogy. Yes, Fay Guo, the lead author, says,
• 11:56
  Speaker 3: their experiments yield the timescale required for a wave function
• 12:00
  Speaker 3: of the electron to evolve the final direction of that
• 12:03
  Speaker 3: compass needle. The spin state, when it comes out, tells
• 12:06
  Speaker 3: you exactly what happened during the trip.
• 12:08
  Speaker 2: You mentioned wave function, Just to refresh, that's the mathematical
• 12:11
  Speaker 2: cloud of probabilities that describes the electron, right, It's not
• 12:14
  Speaker 2: a point, it's a field of possibilities.
• 12:17
  Speaker 3: It is, and this is where it gets really really
• 12:19
  Speaker 3: weird and interesting. When the photon hits the electron, the
• 12:22
  Speaker 3: electron doesn't just pick one exit door and run through it.
• 12:25
  Speaker 3: This is quantum mechanics.
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  Speaker 2: It does everything at once.
• 12:27
  Speaker 3: It takes all the doors at once. It follows several
• 12:30
  Speaker 3: different quantum roots simultaneously. It's in a superposition of all
• 12:34
  Speaker 3: possible paths out of the atom.
• 12:36
  Speaker 2: That's like something out of a science fiction movie. It
• 12:38
  Speaker 2: takes the highway and the side streets and tunnels under
• 12:42
  Speaker 2: the city all at the same time.
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  Speaker 3: In essence, yes, and each of those different paths has
• 12:48
  Speaker 3: something called a phase. You can think of the phase
• 12:50
  Speaker 3: as the ticking hand on a tiny clock that each
• 12:53
  Speaker 3: version of the electron is carrying. As an electron wave
• 12:56
  Speaker 3: travels along a path, its little clockhand rotates. If it
• 13:00
  Speaker 3: takes a very short direct path, the hand might only
• 13:03
  Speaker 3: rotate a little bit. It takes a longer, more convoluted path,
• 13:06
  Speaker 3: the hand rotates a lot more.
• 13:08
  Speaker 2: And all these different versions of the electron, with their
• 13:11
  Speaker 2: clocks all pointing in different directions, they all meet up
• 13:15
  Speaker 2: at the exit.
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  Speaker 3: They do, and they interfere with each other. This is
• 13:18
  Speaker 3: just like ripples in a pond. If you throw two
• 13:20
  Speaker 3: stones in, the waves spread out and overlap. Where two
• 13:24
  Speaker 3: crests meet, you get a bigger wave. That's constructive interference.
• 13:27
  Speaker 3: Where crest meets a trough that cancel out and you
• 13:29
  Speaker 3: get flat water. That's destructive interference.
• 13:32
  Speaker 2: Okay, I'm with you.
• 13:33
  Speaker 3: The electrons different paths do the same thing. They all
• 13:36
  Speaker 3: converge and their phases add up or cancel out, and
• 13:39
  Speaker 3: this final complex interference pattern gets imprinted directly onto the
• 13:43
  Speaker 3: electron spin. The final direction of that compass needle is
• 13:47
  Speaker 3: the sum of all those spinning clock hands.
• 13:49
  Speaker 2: Okay, let me try to put this into an analogy
• 13:51
  Speaker 2: and make sure I've got it. It's like I'm a
• 13:53
  Speaker 2: detective trying to figure out how long a hiker spent
• 13:56
  Speaker 2: in a dense, foggy forest. I can't fall of them
• 14:00
  Speaker 2: because my presence would change their.
• 14:02
  Speaker 3: Path, right, you'd scare off the wildlife. They'd take a
• 14:04
  Speaker 3: different route exactly.
• 14:05
  Speaker 2: So instead I wait for them to come out the
• 14:07
  Speaker 2: other side, and instead of looking at a watch, I
• 14:10
  Speaker 2: look at their shoes. By examining the unique pattern of
• 14:14
  Speaker 2: mud scuffs and worn down tread the interference pattern from
• 14:18
  Speaker 2: all the little paths they took inside, I can work
• 14:21
  Speaker 2: backwards and calculate exactly how long they must have been walking.
• 14:24
  Speaker 3: That is an excellent, excellent analogy. The wear and tear
• 14:27
  Speaker 3: on the shoes is the final spin state, and by
• 14:30
  Speaker 3: reading that you can deduce the duration of the journey.
• 14:33
  Speaker 3: The hiker brings their own clock printed on their.
• 14:35
  Speaker 2: Shoes, and as Fegwo said, the method does not require
• 14:39
  Speaker 2: an external reference. There's no outside clock. It's all internal.
• 14:43
  Speaker 3: It completely removes the risk of those artifacts of the
• 14:46
  Speaker 3: hot thermometer problem. We aren't imposing a clock on the system.
• 14:50
  Speaker 3: We're learning to read the diary the system road itself.
• 14:53
  Speaker 2: That's brilliant. Okay, So they have the theory the spin
• 14:56
  Speaker 2: is the clock. But now you need a machine, a
• 14:59
  Speaker 2: device that can act actually catch these electrons as they
• 15:01
  Speaker 2: fly out and read that incredibly subtle spin state. The
• 15:06
  Speaker 2: source mentioned in acronym SARPs.
• 15:08
  Speaker 3: It does sound a bit like a congbook villain, doesn't
• 15:10
  Speaker 3: it kneel before SARPs?
• 15:12
  Speaker 2: It really does, but it sounds for something much more complicated.
• 15:14
  Speaker 3: It does. It's spin an angle resolved photo emission spectroscopy.
• 15:18
  Speaker 2: WHOA, Okay, that is a mouthful. Let's break that down
• 15:21
  Speaker 2: piece by piece. Photo emission spectroscopy. That's the part where
• 15:24
  Speaker 2: you use light photons to knock electrons out.
• 15:27
  Speaker 3: Right, correct, that's the core of the technique. Let's just
• 15:29
  Speaker 3: walk through it first. You need an incredibly powerful and
• 15:33
  Speaker 3: precise light source for this. They go to a synchrotron facility.
• 15:37
  Speaker 2: These are those huge circular particle accelerators building sized machines exactly.
• 15:42
  Speaker 3: They generate extremely intense beams of light. So step one,
• 15:47
  Speaker 3: you fire this intense synchrotron light at your material sample.
• 15:51
  Speaker 2: Step two, the photons hit the electrons, giving them that
• 15:55
  Speaker 2: energy boost for the prison.
• 15:56
  Speaker 3: Break, right, They get excited to a higher energy state. Three.
• 16:00
  Speaker 3: With enough energy, they are forced to completely leave the material.
• 16:03
  Speaker 3: They get ejected out into a high vacuum chamber.
• 16:06
  Speaker 2: And this is where SARPs the machine is waiting for them.
• 16:09
  Speaker 3: Yes, and this is the resolved part of the name.
• 16:12
  Speaker 3: As the electrons fly out, the detector measures three key
• 16:15
  Speaker 3: things about each one simultaneously, it measures its final energy,
• 16:19
  Speaker 3: it measures its direction of travel or its angle, and crucially,
• 16:23
  Speaker 3: it measures its spin.
• 16:24
  Speaker 2: Okay, energy and spin makes sense for what we've been
• 16:27
  Speaker 2: talking about. But why the angle? Why does it matter
• 16:29
  Speaker 2: which direction the electron flies offen.
• 16:31
  Speaker 3: That's a fantastic question, and it's key to the precision
• 16:34
  Speaker 3: of the experiment. The angle tells you about the electron's
• 16:37
  Speaker 3: momentum while it was still inside the crystal. In a material,
• 16:42
  Speaker 3: electrons don't just buzz around randomly. Like a swarm of bees.
• 16:45
  Speaker 3: They exist in specific energy bands and travel along specific
• 16:49
  Speaker 3: pathways or highways defined by the crystal structure.
• 16:52
  Speaker 2: So the exit direction tells you which highway it came from.
• 16:55
  Speaker 3: Precisely by measuring the angle, you can trace its trajectory
• 16:58
  Speaker 3: back and say, ah, this electron came from this specific
• 17:01
  Speaker 3: orbital with this specific momentum. It's the difference between hearing
• 17:06
  Speaker 3: the roar of a crowd and being able to pick
• 17:07
  Speaker 3: out a single person's voice and what they were saying.
• 17:10
  Speaker 3: It gives them incredible specificity.
• 17:12
  Speaker 2: So SARPs is this amazing machine that basically acts like
• 17:15
  Speaker 2: a quantum forensics lab. It catches the escaped electrons and
• 17:19
  Speaker 2: it figures out how fast they're going, where they came from,
• 17:22
  Speaker 2: and it reads their internal clock.
• 17:23
  Speaker 3: That's a perfect summary. It's forensic physics. And with those
• 17:27
  Speaker 3: three pieces of data, energy, angle, and spin, they can
• 17:30
  Speaker 3: reconstruct the entire story of that quantum transition.
• 17:34
  Speaker 2: Amazing. Okay, so we have the method, we have the machine.
• 17:36
  Speaker 2: Now the experiment itself. They didn't just want to prove
• 17:40
  Speaker 2: they could measure the time. They wanted to test a hypothesis.
• 17:43
  Speaker 3: This is where it gets really profound. We now have
• 17:45
  Speaker 3: a stopwatch. The next question is does the racetrack itself
• 17:50
  Speaker 3: affect the lab time? Does the geometry of the material
• 17:53
  Speaker 3: the stage affect the performance of the actor.
• 17:56
  Speaker 2: And to do that, they chose materials with very different
• 18:00
  Speaker 2: atomic sheapes.
• 18:01
  Speaker 3: Yes, they very cleverly pick three classes of materials to
• 18:04
  Speaker 3: represent different dimensionalities, different kinds of symmetry. First up, the
• 18:08
  Speaker 3: use just plain old copper, the.
• 18:09
  Speaker 2: Stuff in our pipes and wires exactly, And the reason
• 18:12
  Speaker 2: they chose it is because copper has a very standard,
• 18:16
  Speaker 2: fully three dimensional crystal structure.
• 18:18
  Speaker 3: It's highly symmetric. The atoms are arranged in a repeating
• 18:21
  Speaker 3: cube like pattern. You can imagine it as a perfectly
• 18:24
  Speaker 3: built jungle gym that extends forever in all three directions up, down, left, right, forward, back.
• 18:30
  Speaker 2: So every atom has neighbors on all sides. It's a
• 18:32
  Speaker 2: very connected three D world for an electron.
• 18:35
  Speaker 3: Right, that's our three D baseline, the jungle gym. Next,
• 18:38
  Speaker 3: they look at two materials, titanium disalinde are tis and
• 18:42
  Speaker 3: titanium detelluride tight.
• 18:44
  Speaker 2: Definitely more exotic.
• 18:45
  Speaker 3: These are what we call layered or two dimensional materials.
• 18:49
  Speaker 3: Think of a perfect stack of infinitely thin sheets of
• 18:51
  Speaker 3: paper or a deck of cards. Within each sheet, the
• 18:54
  Speaker 3: atoms are very strongly bonded together, but the connection between
• 18:58
  Speaker 3: the sheets is very weak.
• 19:00
  Speaker 2: So an electron can zip around on one sheet really easily,
• 19:02
  Speaker 2: but it's hard for it to jump to the sheet
• 19:04
  Speaker 2: above or below it.
• 19:05
  Speaker 3: Precisely, for all intents and purposes, the electrons are living
• 19:08
  Speaker 3: in a two D world. They've gone from a three
• 19:11
  Speaker 3: D jungle gym to a two D stack of pancakes.
• 19:14
  Speaker 3: The symmetry has been broken in one of the three dimensions.
• 19:16
  Speaker 2: Okay, I see the progression three D then two D.
• 19:18
  Speaker 3: What's next next is a material called copper telluride or cute,
• 19:22
  Speaker 3: and this one has a chain.
• 19:24
  Speaker 2: Like structure, so like beads on a string.
• 19:26
  Speaker 3: A perfect analogy, the atoms are arranged in long linear chains,
• 19:30
  Speaker 3: so an electron is basically confined to moving forward or
• 19:32
  Speaker 3: backward along that one dimensional line. That's a one D world.
• 19:36
  Speaker 2: So we have the three D jungle gym, the two
• 19:38
  Speaker 2: D pancakes, and the one D string of beads. The
• 19:42
  Speaker 2: only major variable between them is the geometry the symmetry
• 19:45
  Speaker 2: of the environment the electron lives in.
• 19:47
  Speaker 3: And that was a whole point. The hypothesis was does
• 19:50
  Speaker 3: the shape of the room affect how long it takes
• 19:52
  Speaker 3: the electron to find the exit door.
• 19:54
  Speaker 2: I really love this experimental design. It's so elegant. It's
• 19:57
  Speaker 2: like you're setting up a race with three identical run
• 20:00
  Speaker 2: but one is running across a wide, open ballroom, the
• 20:03
  Speaker 2: second is running down a narrow hallway, and the third
• 20:06
  Speaker 2: is running on a tightrope, and you want to see
• 20:08
  Speaker 2: who gets out the fastest.
• 20:10
  Speaker 3: And the results were not just clear, they were I
• 20:12
  Speaker 3: think quite surprising.
• 20:14
  Speaker 2: Okay, let's get into the results, because this is where
• 20:16
  Speaker 2: my normal, everyday intuition starts to break down. If I'm
• 20:19
  Speaker 2: one of those runners, I might think the tight rope,
• 20:22
  Speaker 2: the one D chain would be the fastest. It's the
• 20:24
  Speaker 2: most direct path, no distractions, no side to side movement,
• 20:27
  Speaker 2: just go straight.
• 20:28
  Speaker 3: That would be a perfectly logical assumption in our classical world,
• 20:32
  Speaker 3: but the quantum world, it doesn't play by our rules.
• 20:36
  Speaker 3: The results showed a very clear and opposite pattern. The
• 20:40
  Speaker 3: less symmetry the structure had, the more time the transition took.
• 20:43
  Speaker 3: The simpler the geometry, the slower the event.
• 20:46
  Speaker 2: Wait, really, the simplest structure is the slowest. That feels
• 20:49
  Speaker 2: completely backwards.
• 20:50
  Speaker 3: It's profoundly counterintuitive, but the data is unambiguous. Let's just
• 20:55
  Speaker 3: go through the numbers. The fastest transition by far was
• 20:58
  Speaker 3: in the three D copper, the jungle.
• 21:00
  Speaker 2: Okay, what was the time?
• 21:01
  Speaker 3: The time for that electron transition was measured to be
• 21:03
  Speaker 3: approximately twenty six out of seconds.
• 21:05
  Speaker 2: Twenty six okay, that's our baseline, blistringly fast.
• 21:08
  Speaker 3: Right. Now, Let's go to the two D layered materials,
• 21:10
  Speaker 3: the stack of pancakes, tier on tier. The transition time
• 21:14
  Speaker 3: jumped way up. It was in the range of one
• 21:16
  Speaker 3: hundred and forty to one hundred and seventy five auto seconds.
• 21:18
  Speaker 2: Well, hang on, from twenty six to let's say one
• 21:20
  Speaker 2: hundred and fifty that's what five almost six times slower,
• 21:24
  Speaker 2: just from taking away one dimension of movement.
• 21:26
  Speaker 3: Yes, just by confining the electrons to flat sheets. The
• 21:29
  Speaker 3: whole process slowed down dramatically. And then the real shocker,
• 21:34
  Speaker 3: the one D material, the chain like copper. Tell your ride,
• 21:38
  Speaker 3: the tightrope walker.
• 21:39
  Speaker 2: What was its time?
• 21:40
  Speaker 3: It was the slowest of all. The transition time stretched
• 21:44
  Speaker 3: to over two hundred out of seconds.
• 21:46
  Speaker 2: So the tightrope was the slowest. We go from about
• 21:48
  Speaker 2: twenty six and three D to about one hundred and
• 21:50
  Speaker 2: fifty and two D and over two hundred and one D.
• 21:52
  Speaker 2: That is a clear trend. But why why does being
• 21:56
  Speaker 2: stuck in a simple chain make the electron so much
• 21:59
  Speaker 2: more slow huggish than when it's in the complex three
• 22:01
  Speaker 2: D world of copper. You'd think the jungle gym would
• 22:04
  Speaker 2: be full of obstacles.
• 22:05
  Speaker 3: It all comes back to those quantum roots we talked
• 22:07
  Speaker 3: about the wave function and interference. In the highly symmetric
• 22:10
  Speaker 3: three D copper, the electron has a huge number of
• 22:13
  Speaker 3: possible paths that can take simultaneously. There's a rich network
• 22:16
  Speaker 3: of connections.
• 22:17
  Speaker 2: So it's like a city with a perfect grid system,
• 22:19
  Speaker 2: lots of options to get from A to B exactly.
• 22:22
  Speaker 3: And because there are so many available routes, there are
• 22:25
  Speaker 3: more opportunities for the different parts of the wave function
• 22:28
  Speaker 3: to interfere constructively to build up the necessary oof to
• 22:33
  Speaker 3: complete the transition quickly. The high symmetry facilitates a very efficient,
• 22:38
  Speaker 3: very rapid evolution of the wave function.
• 22:40
  Speaker 2: The crowd can move quickly because there are doors and
• 22:42
  Speaker 2: windows open in every direction.
• 22:44
  Speaker 3: There are no bottlenecks, A great way to put it. Now,
• 22:47
  Speaker 3: contrast that with the one D chain, the electron is
• 22:49
  Speaker 3: stuck on a single track. Its neighbors are only in
• 22:52
  Speaker 3: front of it and behind it. This severe confinement drastically
• 22:56
  Speaker 3: limits the number of quantum pathways available. The interference patterning
• 23:00
  Speaker 3: can create is much simpler, much more restricted.
• 23:02
  Speaker 2: So because it has fewer options, it takes longer to
• 23:04
  Speaker 2: build up the right conditions to make the jump.
• 23:07
  Speaker 3: That's the essence of it. Yes, the constraint itself introduces
• 23:11
  Speaker 3: a delay. The accumulated phase, which is our internal clock,
• 23:14
  Speaker 3: It just builds up differently, more slowly. The wave function
• 23:17
  Speaker 3: has to sort of wait longer for the quantum mechanics
• 23:19
  Speaker 3: to align and just the right way for the transition
• 23:21
  Speaker 3: to finalize.
• 23:22
  Speaker 2: That is so fascinating. We think of complexity creating bureaucracy
• 23:25
  Speaker 2: and slowing things down, but here the quantum complexity of
• 23:29
  Speaker 2: the three D structure is what makes it so efficient
• 23:32
  Speaker 2: and fast.
• 23:32
  Speaker 3: It's the shape of the world the electron lives in.
• 23:35
  Speaker 3: That's what dictates its temporal behavior. The less freedom it
• 23:38
  Speaker 3: has geometrically, the longer it takes to act. Lower symmetry
• 23:42
  Speaker 3: means longer transition times.
• 23:44
  Speaker 2: This really brings that phrase geometry meets time to life.
• 23:48
  Speaker 2: We are literally seeing the physical architecture of a material
• 23:51
  Speaker 2: warping the local flow of time.
• 23:53
  Speaker 3: For a quantum particle, it is, for all practical purposes,
• 23:56
  Speaker 3: a localized time dilation, not caused by gravity like in
• 23:59
  Speaker 3: relative tivity, but by quantum geometry.
• 24:01
  Speaker 2: Okay, we've established this incredible counterintuitive result. Three D is fast,
• 24:06
  Speaker 2: one D is slow. We've clocked the unclockable. Now let's
• 24:10
  Speaker 2: get to the big So what I can hear people
• 24:12
  Speaker 2: listening and thinking, Okay, that's neat physics. But twenty six
• 24:14
  Speaker 2: auto seconds versus two hundred auto seconds, it's all literally
• 24:18
  Speaker 2: faster than the blink of an eye. Why should I care?
• 24:20
  Speaker 3: And it's a completely fair question. For our human senses,
• 24:23
  Speaker 3: the difference is zero. But for fundamental physics and for
• 24:27
  Speaker 3: the future of our technology, the difference is absolutely monumental.
• 24:31
  Speaker 2: Let's start with the big picture, the theoretical side. Professor
• 24:34
  Speaker 2: Dill is quoted as saying this work could help us
• 24:36
  Speaker 2: finally understand the role of time in quantum mechanics. That's
• 24:40
  Speaker 2: a huge claim.
• 24:41
  Speaker 3: It's a massive claim, and I think it's justified. For
• 24:44
  Speaker 3: the better part of a century, there's been this nagging
• 24:46
  Speaker 3: debate are quantum jumps truly instantaneous. The early models, the
• 24:51
  Speaker 3: Bore model of the atom, they depicted them as these
• 24:54
  Speaker 3: magical instant leaps an electron teleports from orbit A to
• 24:57
  Speaker 3: orbit B. This research provides of the strongest evidence yet
• 25:01
  Speaker 3: that they are not instantaneous.
• 25:02
  Speaker 2: It puts a number on it. It kills the instant myth.
• 25:05
  Speaker 3: It does, and it does something more. It tells us
• 25:08
  Speaker 3: that the duration that time is not some fixed universal constant.
• 25:12
  Speaker 3: It's interactive. It depends on the material, on the geometry.
• 25:16
  Speaker 3: This hints at a much much deeper connection between the
• 25:19
  Speaker 3: fabric of space, the geometry, and the flow of time.
• 25:22
  Speaker 3: At the most fundamental level.
• 25:23
  Speaker 2: It almost sounds like it's echoing general relativity. You know
• 25:26
  Speaker 2: where massive objects curve space time, and that curvature is
• 25:31
  Speaker 2: what we feel is gravity, and it also affects time
• 25:34
  Speaker 2: clocks tick slower in near black hole.
• 25:36
  Speaker 3: That's a very sharp insight. It feels like a quantum
• 25:39
  Speaker 3: mechanical parallel to that relativity tells us that mass and
• 25:42
  Speaker 3: energy curve space time and thus bend the flow of time.
• 25:46
  Speaker 3: This is telling us that quantum geometry, the arrangement of atoms,
• 25:50
  Speaker 3: also bends the flow of time. For quantum processes. It
• 25:53
  Speaker 3: might be a crucial clue in the search for a
• 25:56
  Speaker 3: unified theory that can connect the world of gravity with
• 25:59
  Speaker 3: the world of quantum mechanics.
• 26:00
  Speaker 2: Okay, so philosophically it's a game changer. What about the
• 26:03
  Speaker 2: practical side, the engineering, the gadgets. How does knowing this
• 26:07
  Speaker 2: let us build better things?
• 26:09
  Speaker 3: This is where it gets really exciting. Think about where
• 26:11
  Speaker 3: all of our advanced technology is heading. We're moving deeper
• 26:14
  Speaker 3: into the quantum realm. Quantum computing, quantum sensors, quantum cryptography.
• 26:19
  Speaker 3: All of these technologies depend on one thing, the precise
• 26:22
  Speaker 3: control of quantum.
• 26:24
  Speaker 2: States, controlling quibbits, getting electrons to do exactly what you
• 26:28
  Speaker 2: want them.
• 26:28
  Speaker 3: To do exactly. Now, if you're building a quantum processor,
• 26:32
  Speaker 3: you are essentially switching these states on and off, or
• 26:35
  Speaker 3: moving an electron from one place to another to represent
• 26:38
  Speaker 3: a piece of information. The speed of that switch, the
• 26:41
  Speaker 3: duration of that transition, becomes a critical design parameter.
• 26:45
  Speaker 2: And if you've been assuming that switch is instantaneous, but
• 26:48
  Speaker 2: it actually takes two hundred out of seconds because you
• 26:51
  Speaker 2: built your device out of a one D chain like material,
• 26:55
  Speaker 2: your whole calculation could be off.
• 26:57
  Speaker 3: Your timing could be completely off. You could get what
• 26:59
  Speaker 3: you called quantum lag in the field. It could lead
• 27:03
  Speaker 3: to decoherence where the delicate quantum state just falls apart
• 27:06
  Speaker 3: because you didn't account for that delay. The system gets
• 27:08
  Speaker 3: out of sync with itself.
• 27:09
  Speaker 2: But now now we know that geometry controls timing, so
• 27:12
  Speaker 2: we can use that. We can design materials to have
• 27:15
  Speaker 2: specific clock speaks.
• 27:16
  Speaker 3: That is the key takeaway. It gives us a brand
• 27:18
  Speaker 3: new knob to turn in material science. It's a design tool.
• 27:22
  Speaker 3: If I need to build a quantum switch that has
• 27:23
  Speaker 3: to operate incredibly fast, I should probably build it using
• 27:26
  Speaker 3: a material with high three D like symmetry.
• 27:29
  Speaker 2: And if I need a process to be a little slower,
• 27:33
  Speaker 2: maybe I need an electron to stay in an excited
• 27:35
  Speaker 2: state for a bit longer to act as a memory
• 27:38
  Speaker 2: buffer to sync up with a slower signal.
• 27:41
  Speaker 3: Then you might intentionally design your material with a one
• 27:44
  Speaker 3: D chain like structure to deliberately stretch out that transition time.
• 27:49
  Speaker 3: You can engineer the timing by engineering the atomic architecture.
• 27:53
  Speaker 3: It's an incredible level of control that we just didn't
• 27:55
  Speaker 3: know we had.
• 27:55
  Speaker 2: We can build materials that are fast or slow on
• 27:57
  Speaker 2: a quantum level by.
• 27:59
  Speaker 3: Design also gives us a new way to investigate materials
• 28:02
  Speaker 3: we don't understand yet. Suppose we discovered some new exotic superconductor.
• 28:07
  Speaker 3: We can hit it with this SARPs technique and measure
• 28:09
  Speaker 3: the internal timing of its electrons. That timing profile could
• 28:13
  Speaker 3: reveal all sorts of hidden symmetries or strange geometric properties
• 28:17
  Speaker 3: that we couldn't see with any other tool.
• 28:18
  Speaker 2: It's a diagnostic tool. You can listen to the material's
• 28:21
  Speaker 2: quantum heartbeat to figure out what's going.
• 28:23
  Speaker 3: On inside a very very fast heartbeat.
• 28:25
  Speaker 2: But yes, okay, so let's try and wrap this all up.
• 28:27
  Speaker 2: We started with this image of a melting quantum clock.
• 28:31
  Speaker 2: We went down to the attosecond scale, a world where
• 28:34
  Speaker 2: light can't even cross a virus.
• 28:36
  Speaker 3: An almost unimaginable world.
• 28:38
  Speaker 2: And we learned that you can't time an event there
• 28:40
  Speaker 2: with an external stopwatch, because your stopwatch will break the
• 28:44
  Speaker 2: very thing you're trying to measure, the hot thermometer problem.
• 28:47
  Speaker 3: If you have to be clever, you have to find
• 28:49
  Speaker 3: the clock that's already there.
• 28:50
  Speaker 2: Which turned out to be the electron's own spin it's
• 28:53
  Speaker 2: internal compass needle that records the wear and tear of
• 28:56
  Speaker 2: its journey, hiker shoes, hikershoes. And then we looked at
• 28:59
  Speaker 2: the big race, the three D jungle gym of copper
• 29:02
  Speaker 2: versus the two D pancakes of titanium disalinide versus the
• 29:06
  Speaker 2: one D tightrope of copper telluride.
• 29:08
  Speaker 3: And the result was completely counterintuitive.
• 29:11
  Speaker 2: The simplest path, the one D tightrope, was by far
• 29:14
  Speaker 2: the slowest. The complex, highly connected three D world was
• 29:17
  Speaker 2: the fastest. More complexity and at more speed, more simplicity
• 29:21
  Speaker 2: em at more delay.
• 29:23
  Speaker 3: It's an incredible conclusion. The big lesson here is that
• 29:26
  Speaker 3: time at this fundamental level is not an absolute, universal river.
• 29:31
  Speaker 3: It's a local phenomenon. Its flow is shaped and dictated
• 29:35
  Speaker 3: by the immediate environment of the particle.
• 29:37
  Speaker 2: It makes you look at a simple copper wire completely differently.
• 29:40
  Speaker 2: You realize that for the trillions of electrons zipping around
• 29:43
  Speaker 2: inside it, their experience of time, the very rhythm of
• 29:45
  Speaker 2: their existence, is different from the electrons inside the graphite
• 29:49
  Speaker 2: and your pencil.
• 29:51
  Speaker 3: It just reminds us that our human scale perception of
• 29:53
  Speaker 3: a steady ticking clock is just a massive statistical average.
• 29:57
  Speaker 3: Underneath it, all the universe is a symphony of incredibly
• 30:01
  Speaker 3: complex rhythms speeding up and slowing down based on the
• 30:05
  Speaker 3: local geometry.
• 30:06
  Speaker 2: Before we sign off, I just want to leave our
• 30:08
  Speaker 2: listeners with one final, bigger thought to chew on. We've
• 30:11
  Speaker 2: spent this whole conversation talking about how the geometry of
• 30:13
  Speaker 2: matter dictates the speed of time at the quantum level. Right,
• 30:17
  Speaker 2: so let's just zoom out, way out. If the shape
• 30:20
  Speaker 2: of a crystal changes the flow of time for an electron.
• 30:23
  Speaker 2: What if time, as we experience it is nothing more
• 30:26
  Speaker 2: than an emergent property, a side effect of the overall
• 30:30
  Speaker 2: shape of our universe.
• 30:31
  Speaker 3: That is the ultimate provocative question, isn't it.
• 30:34
  Speaker 2: I mean, think about it. We see time as this
• 30:36
  Speaker 2: unstoppable force that carries everything along with it. But this
• 30:40
  Speaker 2: research shows that if you change the geometry, you change
• 30:43
  Speaker 2: the time. What if we could somehow change the geometry
• 30:47
  Speaker 2: of our own environment, not just a crystal, but the
• 30:50
  Speaker 2: shape of space around us. Could we change the flow
• 30:53
  Speaker 2: of time for ourselves?
• 30:55
  Speaker 3: General relativity already tells us that a massive object like
• 30:58
  Speaker 3: a black hole does exactly that. It warps geometry so
• 31:02
  Speaker 3: much that time slows to a crawl. But this research
• 31:05
  Speaker 3: hints that maybe you don't need a black hole Maybe
• 31:08
  Speaker 3: it's a more fundamental principle. Geometry is temporal destiny. If
• 31:12
  Speaker 3: we could ever learn to manipulate the geometry of space itself,
• 31:15
  Speaker 3: who knows.
• 31:15
  Speaker 2: Maybe the key to time travel isn't a machine that
• 31:17
  Speaker 2: moves through time. Maybe it's a machine that just reshapes
• 31:20
  Speaker 2: the room you're standing in. And on that note, I
• 31:23
  Speaker 2: think we'll leave it there. Thank you so much for
• 31:24
  Speaker 2: joining us.
• 31:24
  Speaker 3: Thank you it's a pleasure. Keep asking questions
• 31:27
  Speaker 2: Until next time.