Speaker 1: Welcome to the quarre Side. Quantum Physics podcast, an exploration
Speaker 1: of the fundamental structure of reality where quantum laws govern matter, energy,
Speaker 1: and information. Here, uncertainty is a feature, not a flaw,
Speaker 1: and understanding begins of the smallest scales.
Speaker 2: Imagine you're holding like the single most powerful piece of technology.
Speaker 3: In human history, always a fun thought experiment, right, Like.
Speaker 2: A machine that's capable of simulating the molecular structure of
Speaker 2: complex life saving drugs, or cracking cryptographic codes that would
Speaker 2: take classical computer's millennia to break.
Speaker 3: Basically modeling the very fabric of the universe exactly.
Speaker 2: So you power it up, you input the variables, you
Speaker 2: get ready to change the world, and then you discover
Speaker 2: your multimillion dollar machine has the memory of a old fish.
Speaker 3: Yeah, that is a That's the great paradox of modern
Speaker 3: physics right there. I mean, we spend billions developing machines
Speaker 3: with almost unimaginable computational promise, but their current hardware instability
Speaker 3: is just it's the absolute bottleneck.
Speaker 2: Because they literally forget what they're doing.
Speaker 3: Right If the processor literally forgets the math problem halfway
Speaker 3: through solving it, the theoretical power just doesn't matter.
Speaker 2: So today we're going to explore this Achilles heel of
Speaker 2: quantum computers. We're getting into the unpredictable fluctuation of quantum memory, and.
Speaker 3: More importantly, unpacking a massive new breakthrough that has accelerated
Speaker 3: our ability to measure this information loss by more than
Speaker 3: one hundred times.
Speaker 2: Which is just a staggering leap. I mean, the conversation
Speaker 2: around quantum computing usually gets bogged down in theory.
Speaker 3: Right, oh, constantly right, But the reality of engineering these
Speaker 3: devices requires confronting some incredibly harsh microscopic physics. To build
Speaker 3: a reliable machine, you have to measure its unreliability first.
Speaker 3: Makes sense, and for a long time our measurement tools
Speaker 3: were just well, they were simply too slow to see
Speaker 3: the actual problems.
Speaker 2: So let's get right into the hardware of that unreliability.
Speaker 2: For the audience listening, we all know what equib it is,
Speaker 2: and we know they operate in delicate stakes of superposition.
Speaker 2: But let's look at the physical architecture.
Speaker 3: Yeah, specifically, we're talking about superconducting quibits.
Speaker 2: Here, right. These are microscopic electrical circuits, usually made of
Speaker 2: metals like aluminium or niobium, printed on a silicon or
Speaker 2: sapphire chip, and they are cooled down to fractions of
Speaker 2: a degree above absolute zero, Yes.
Speaker 3: Around fifteen millik Elvin's to be exact, which is colder
Speaker 3: than the vacuum of deep space. That's crazy, it is, Yeah,
Speaker 3: And we do that so the electrons can pair up
Speaker 3: into what are called Cooper pairs. They flow without any
Speaker 3: electrical resistance.
Speaker 2: And that frictionless flow is what allows the quantum state
Speaker 2: to survive exactly. But clearly it doesn't survive for very long.
Speaker 2: There's this constant thread of relaxation or decoherence.
Speaker 3: Right, decoherence to the enemy.
Speaker 2: Let me flow an analogy here. If maintaining a classical
Speaker 2: bit is like laying a heavy coin flat on the table, Okay,
Speaker 2: like it takes a lot of force to flip it over,
Speaker 2: But a quibit in superposition is more like a spinning coin.
Speaker 3: I like that.
Speaker 2: Yeah, it holds both heads and tails dynamically, but eventually
Speaker 2: microscopic friction from the air or the table, you know,
Speaker 2: it SAPs its momentum and it clatters flat. It completely
Speaker 2: loses its quantum state.
Speaker 3: That captures the physics beautifully actually, and that friction causing
Speaker 3: the coin to clatter flat is what we call environmental noise.
Speaker 2: Even in a freezer that's colder than space.
Speaker 3: Even there inside a dilution refrigerator at fifteen milik Ellen's
Speaker 3: the environment is not perfectly silent. You've got stray photons
Speaker 3: wandering through the chamber, you have cosmic rays striking the
Speaker 3: outer casing. But mostly you have microscopic defects within the
Speaker 3: silicon or sapphire substrate itself. Wait really, yeah, tiny atomic
Speaker 3: imperfections called two level system defects.
Speaker 2: So the noise isn't just coming from the outside. The
Speaker 2: ship itself is inherently flawed at the atomic level.
Speaker 3: That is the insidious part of the problem. As the
Speaker 3: temperature shift slightly or electric fields fluctuate, these atomic defects
Speaker 3: within the chip actually absorb energy from the quibit. Oh wow,
Speaker 3: they act like microscopic sponges. They just suck the quantum
Speaker 3: information right out of the circuit. That's brutal, it really is.
Speaker 3: When that happens, the quibit drops out of its excited
Speaker 3: state back to its ground state. The information is gone,
Speaker 3: and in physics we measure the life stan of that
Speaker 3: memory using a metric called T one. The relaxation time,
Speaker 3: right the relaxation time.
Speaker 2: And according to Jiro and Danen, who's a professor at
Speaker 2: NTNU involved in this research, the problem isn't just that
Speaker 2: T one is short. It's that T one is wildly unpredictable.
Speaker 3: And that is the core engineering nightmare right there. I mean,
Speaker 3: if the relaxation time was uniformly short, say every quibit
Speaker 3: perfectly held its memory for exactly fifty micros, you could
Speaker 3: just work around it exactly. You could meticulously schedule your
Speaker 3: calculations to execute and finish in forty nine microseconds.
Speaker 2: But it's not a static timer, not at all. Like
Speaker 2: the life span of the memory fluctuates randomly over time.
Speaker 2: One minute, the quibbit might hold information for one hundred microseconds,
Speaker 2: and the next minute it forgets everything after like ten microseconds.
Speaker 3: Because those microscopic atomic defects in the chip, they're constantly shifting,
Speaker 3: they're coupling and decoupling with equibit. It's just a highly
Speaker 3: dynamic environment.
Speaker 2: It sounds chaotic, it is.
Speaker 3: You're basically trying to build a perplectly synchronized orchestra out
Speaker 3: of instruments that randomly change their tuning every few seconds.
Speaker 2: Okay, So if I'm an engineer trying to fix this,
Speaker 2: my very first instinct is, well, I need to observe
Speaker 2: the machine while it's running. I need to find out
Speaker 2: exactly when and why the tuning changes and fix that
Speaker 2: specific defect naturally. But this brings us to the massive
Speaker 2: roadblock that this new research published in Physical Review X
Speaker 2: finally solved, because historically scientists were essentially flying blind.
Speaker 3: They were because you know, measuring a quantum system is
Speaker 3: fundamentally different from measuring a classical system. It used to
Speaker 3: take researchers roughly a full second to measure that T
Speaker 3: one relaxation time.
Speaker 2: Now, let me push back on that a bit, because
Speaker 2: I think a lot of people might hear one second
Speaker 2: and think, well, a second is incredibly fast. Like if
Speaker 2: my laptop diagnosed a hardware error in one second, I'd
Speaker 2: be thrilled. Why is a one second measurement lag such
Speaker 2: a catastrophic bottleneck When we're measuring quantum computers, you really have.
Speaker 3: To scale your perception of time down to the microscopic
Speaker 3: round here. A single second in a quantum processor isn't
Speaker 3: a quick diagnostic check. It is an absolute eternity, and
Speaker 3: eternity Yeah, the environment around that superconducting circuit is shifting,
Speaker 3: it's vibrating, and it's changing state millions of times per second.
Speaker 2: So a one second measurement means you are just entirely
Speaker 2: missing millions of microscopic events.
Speaker 3: Yes, you're just completely missing them. But to understand why
Speaker 3: it took a full second, we have to look at
Speaker 3: the mechanics of quantum op Okay, you can't just point
Speaker 3: a continuous sensor at equibit and watch its energy fade
Speaker 3: over time. It's not like watching a battery icon drain
Speaker 3: on your phone.
Speaker 2: Right because of the observer effect. Exactly, if you look
Speaker 2: at the spinning coin, you force it to clatter flat immediately.
Speaker 2: You force it to choose a definitive state of zero
Speaker 2: or one, which destroys that delicate superposition you were trying
Speaker 2: to measure in the first place.
Speaker 3: Spot On the act of measuring the quibbot destroys the memory.
Speaker 3: So how do you find out how long the memory
Speaker 3: lasts if looking at it actually kills it.
Speaker 2: That sounds impossible.
Speaker 3: It's tricky. You have to use a statistical approach called
Speaker 3: inversion recovery.
Speaker 2: Okay, walk me through that. How does inversion recovery actually work.
Speaker 3: So you send a microwave pulse to excite the quibbit.
Speaker 3: Basically you spin the.
Speaker 2: Coin okay, coin of spinning.
Speaker 3: Then you purposefully wait for a specific duration, let's say
Speaker 3: ten microseconds. Right after exactly ten microseconds, you hit it
Speaker 3: with a measurement pulse to see if it is still
Speaker 3: spinning or if it fell flat.
Speaker 2: But that only tells you the result for that single trial.
Speaker 2: It doesn't give you the average lifespan.
Speaker 3: Correct. So you have to reset the quibit and do
Speaker 3: that exact same ten microsecond waight time thousands of times
Speaker 3: just to build a reliable probability thousands of times thousands
Speaker 3: And then you have to increase the weight time to
Speaker 3: say fifteen microseconds, and run another thousand trials. Oh my god,
Speaker 3: then twenty microseconds, another thousand trials. You painstakingly sweep through
Speaker 3: all these different weight times, plotting the probabilities until you
Speaker 3: build this beautiful, smooth, exponential decay curve, and.
Speaker 2: The slope of that curve tells you the t one
Speaker 2: relaxation time. Wow, Okay, I see the problem.
Speaker 3: Now.
Speaker 2: It's not that a single measurement takes a second. It's
Speaker 2: that you have to run tens of thousands of individual
Speaker 2: excite weight measure reset cycles just to plot a single curve.
Speaker 2: And that entire ensemble process is what takes a full second.
Speaker 3: And here is where the physics really bite you. During
Speaker 3: that one second you spent gathering all those thousands of
Speaker 3: data points, the atomic defects in the chip were actively shifting.
Speaker 2: The environment was fluctuating, right, which means the curve you
Speaker 2: just claweded is basically a.
Speaker 3: Lie, or at least a massive blur.
Speaker 1: Yeah.
Speaker 2: It's like trying to take a photograph of a chaotic
Speaker 2: mosh pit, but you leave the camera shutter open for
Speaker 2: a full minute.
Speaker 3: Oh, that's a great way to put it.
Speaker 2: You wouldn't see any of the individual collisions or the
Speaker 2: dynamic movement. You just get the smeared, useless blob of
Speaker 2: average motion.
Speaker 3: That is a phenomenal conceptualization. Over that one second integration time,
Speaker 3: the quibot's actual relaxation rate might have spiked and plummeted
Speaker 3: one hundred times. Wow, But your one second ensemble measurement
Speaker 3: just spits out a single smeared average. You know the
Speaker 3: memory fluctuates, but you have no idea what specific microscopic
Speaker 3: event triggered the loss in that exact fraction of a millisecond, And.
Speaker 2: If you can't see the details of the noise, you
Speaker 2: obviously can't engineer a defense against it. You just can't,
Speaker 2: which brings us to the breakthrough the t at the
Speaker 2: niels Bore Institute in Copenhagen, led by Fabrizio Barita, alongside
Speaker 2: Jero and Dan and the NTNU researchers, they basically decided
Speaker 2: that staring at a smeared mosh pit wasn't going to
Speaker 2: scale quantum computing.
Speaker 3: No, it certainly wasn't.
Speaker 2: They needed a high speed camera and they achieved something
Speaker 2: called real time adaptive tracking. They took that agonizing one
Speaker 2: second measurement window and slashed it down to roughly ten milliseconds.
Speaker 3: Which is a speed increase of more than one hundred times.
Speaker 2: That's insane. So how do you actually do that If
Speaker 2: the rules of quantum mechanics dictate that looking at the
Speaker 2: quivot destroys the state and you're forced to run thousands
Speaker 2: of trials to build that decay curve, how do you
Speaker 2: suddenly do it one hundred times faster? Do they just
Speaker 2: like buy a faster microwave pulse generator to cycle, the
Speaker 2: resets quicker.
Speaker 3: No. No, the hardware pulsing speed is already pretty much
Speaker 3: near its physical limit. The breakthrough wasn't about pulsing faster,
Speaker 3: It was about measuring smarter. Okay. They completely threw out
Speaker 3: the traditional brute force method of sweeping through all the
Speaker 3: wait times from scratch every single time. Instead, they integrated
Speaker 3: an active machine learning inspired feedback loop.
Speaker 2: Okay, break that down for me. What does the algorithm
Speaker 2: actually do differently?
Speaker 3: Think about the traditional method. You're blindly testing weight times
Speaker 3: of one microsecond, two microseconds, three microseconds, all the way
Speaker 3: up right. But if you already know from the last
Speaker 3: measurement that the Quivitt generally survives for fifty microseconds, testing
Speaker 3: a one microsecond wait time is a complete waste of
Speaker 3: physical time.
Speaker 2: Because you already know it's going to survive that long.
Speaker 3: You already know the probability is going to be near
Speaker 3: one hundred percent.
Speaker 2: Ah, So the algorithm stopped searching the entire haystack. It
Speaker 2: remembers where the needle was a millisecond ago, and only
Speaker 2: searches in that immediate vicinity.
Speaker 3: Precisely, they optimize the tracking by using what we can
Speaker 3: call a hot and cold approach. The software dynamically calculates
Speaker 3: this deepest part of the exponential decay curve, the absolute
Speaker 3: most sensitive weight time, where the probability is roughly fifty
Speaker 3: to fifty okay, and it focuses its measurement pulses almost
Speaker 3: entirely right there on that sensitive edge.
Speaker 2: I love that. It's like trying to monitor the edge
Speaker 2: of a cliff in the dark. Yes, instead of mapping
Speaker 2: the entire mountain from the base to the peak over
Speaker 2: and over again, you find the cliff edge once. Then
Speaker 2: you just take tiny steps back and forth exactly. If
Speaker 2: your foot hits air, you know the edge eroded inward.
Speaker 2: If you hit rock, you know it shifted outward. You're
Speaker 2: only probing the exact boundary of the change.
Speaker 3: And because they're only probing the boundary, they don't need
Speaker 3: thousands of data points to find the new curve. They
Speaker 3: only need a handful.
Speaker 2: That is so smart.
Speaker 3: They programmed a field programmable gate array, an ultra fast
Speaker 3: FPGA processor to capture the readout data, run a Bayesian
Speaker 3: estimation algorithm to calculate the new t one time, and
Speaker 3: instantly adjust the weight time for the very next pulse. Wow,
Speaker 3: all of that computation and physical adjustment happens entirely on
Speaker 3: the fly.
Speaker 2: Real time adaptive tracking. So instead of a one second
Speaker 2: long exposure photograph, you're taking razor sharp snapshots every ten milliseconds. Yep,
Speaker 2: you're watching the quantum system live in high definition as
Speaker 2: it breeds and fluctuates.
Speaker 3: It really represents a fundamental paradigm shift in quantum observation.
Speaker 3: For the first time, researchers can watch the relaxation rate dynamically.
Speaker 3: They can observe the peaks and valleys of the quibbet
Speaker 3: stability almost perfectly syncd with the actual environmental changes happening
Speaker 3: inside the chip, and that leads.
Speaker 2: To the ultimate So what of this whole conversation, Now
Speaker 2: that we have this ten millisecond high speed camera, how
Speaker 2: does this actually help us build a better quantum computer. No,
Speaker 2: because observing a problem is great, but it doesn't automatically
Speaker 2: fix the fact that the house of cards is falling.
Speaker 3: No, it doesn't fix it automatically, but it makes fixing
Speaker 3: it physically possible. Observation in physics is the absolute prerequisite
Speaker 3: for diagnosis. When your measurement took a full second, all
Speaker 3: the different microscopic causes of decoherence blended together. But at
Speaker 3: ten milliseconds, you can finally start correlating the rapid drops
Speaker 3: in memory stability with SPECIFCI simultaneous physical events.
Speaker 2: Oh, I see, it's about matching the time stamp of
Speaker 2: the crime to.
Speaker 3: The suspect exactly. If the T one relaxation rate suddenly
Speaker 3: plummets at exactly millisecond forty, and your other sensors detect
Speaker 3: a tiny burst of background radiation hitting the substrate at
Speaker 3: exactly millisecond forty, you have a direct correlation.
Speaker 2: Have caught them red handed?
Speaker 3: You have? You can say definitively, this specific type of
Speaker 3: cosmic ray interaction creates a phone on vibration that breaks
Speaker 3: the Cooper pairs and kills our kubit memory.
Speaker 2: And once you know exactly what is killing the memory,
Speaker 2: you can start writing the ultimate hardware path.
Speaker 3: You can engineer targeted solutions. You can design novel shielding
Speaker 3: materials that specifically absorb that exact frequency of radiation. You
Speaker 3: can design microcircuit topographies that isolate the superconducting loops from
Speaker 3: the atomic defects in the silicon. You can even write
Speaker 3: more efficient error correcting codes.
Speaker 2: Because the software will actually know the precise frequency and
Speaker 2: nature of the errors it's trying to.
Speaker 3: Correct precisely makes quantum engineering out of the dark ages
Speaker 3: of trial and error and brings it into an era
Speaker 3: of precision diagnostics.
Speaker 2: It's incredible to think about the journey here. We went
Speaker 2: from superconducting quibits that just randomly hemorrhage their memory while
Speaker 2: scientists stared helplessly through a one second.
Speaker 3: Blur, a very frustrating blur, to.
Speaker 2: The teams at NTNU and the Neils Bohr Institute leveraging
Speaker 2: active feedback loops and smart algorithms to slice that window
Speaker 2: down to ten milliseconds. They didn't just build a better sensor,
Speaker 2: they completely reimagine how to ask the quantum system a question.
Speaker 3: It's a profound reminder that in deep tech, a measurement
Speaker 3: breakthrough is often the match that lights the fuse for
Speaker 3: an engineering revolution. Absolutely without stable memory, quantum computing just
Speaker 3: remains a fascinating lab experiment. By giving engineers the ability
Speaker 3: to track and diagnose instability in real time, this breakthrough
Speaker 3: brings us significantly closer to reality altering computational.
Speaker 2: Power, and that leaves us with a truly mind expanding
Speaker 2: concept upon As we wrap up today.
Speaker 3: Okay, let's hear it.
Speaker 2: We've talked entirely about humans using this ten millisecond tracking
Speaker 2: to engineer better hardware. But what if we integrate this
Speaker 2: algorithm directly into the quantum processor's own operating system?
Speaker 3: Oh wow? Right?
Speaker 2: If a machine can now track its own memory de
Speaker 2: ka in ten milliseconds, how long will it be before
Speaker 2: it uses that real time data to predict its own
Speaker 2: information loss?
Speaker 3: That is fascinating.
Speaker 2: Could a future quantum computer sense a microscopic disturbance coming,
Speaker 2: realize its t one is plummeting, and actively course correct
Speaker 2: or reroute the calculation before the memory even disappears.
Speaker 3: Self correcting on the fly.
Speaker 2: Exactly are we looking at the dawn of self healing
Speaker 2: quantum computers?
Speaker 3: That is the frontier we are racing toward. The microscopic
Speaker 3: world is full of chaotic noise, but as we learn
Speaker 3: to see it clearly, we can learn to master it.
Speaker 3: I encourage everyone listening to keep questioning the invisible mechanisms
Speaker 3: that power our reality.
Speaker 2: Thank you so much for exploring the quantum realm with
Speaker 2: us today. Keep wondering, keep asking those hard questions, and
Speaker 2: we will see you next time.