Speaker 1: Welcome to the quark 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 at the smallest scales.
Speaker 2: I want you to imagine, just for a second, a
Speaker 2: world where teleportation isn't you know, some parlor trick or
Speaker 2: a sci fi movie.
Speaker 3: Trope, right, like something out of Star Trek.
Speaker 2: Exactly. Imagine a reality where ultrafast quantum computing and like
Speaker 2: instant fundamentally unhackable information transfer are just the everyday backbone
Speaker 2: of our technology.
Speaker 3: It's wild to think about it, really is.
Speaker 2: You wake up, you log on, and you use a
Speaker 2: global network that shares data with zero lag and perfect security,
Speaker 2: and all of it relies on the strangest, most mind
Speaker 2: bending rules of the universe.
Speaker 3: Yeah, the rules that defy all classical logic.
Speaker 2: Welcome back to the Deep Dive. If you're new here.
Speaker 2: This is the show where we take a massive stack
Speaker 2: of recent research articles, technical papers and we extract the
Speaker 2: absolute most important insights you need to know.
Speaker 3: And today is a big one.
Speaker 2: It is huge. Today our mission is to break down
Speaker 2: a freshly unveiled twenty twenty six scientific breakthrough from researchers
Speaker 2: at Kyoto University and Hiroshima University in Japan.
Speaker 3: Yeah, they've done something incredible.
Speaker 2: They have finally cracked a twenty five year old quantum puzzle,
Speaker 2: and in doing so, they've basically brought next generation quantum
Speaker 2: networks right to our doorstep.
Speaker 3: Okay, let's unpack this because to really grasp how we
Speaker 3: are making this leap from a theoretical dream into hard,
Speaker 3: functual infrastructure, we need to talk about the raw material
Speaker 3: making it all possible.
Speaker 2: Yeah, it really is a profound paradigm shift, because before
Speaker 2: we can dive into how the these Japanese researchers crack
Speaker 2: the code to actually read these complex quantum systems, we
Speaker 2: have to look at how our relationship with quantum entanglement
Speaker 2: has completely evolved. Right now, we know you listeners follow
Speaker 2: this space, so we aren't gonna bore you with the
Speaker 2: whole Shrewdinger's cat thing or basic particle physics one oh one.
Speaker 2: You already know what entanglement is, right, the.
Speaker 3: Idea that subatomic particles like photons can become so deeply
Speaker 3: linked that their properties just can't be understood individually anymore, exactly.
Speaker 3: Try have to treat the whole system as a unified
Speaker 3: reality exactly. But what's vital to understand here is the
Speaker 3: philosophical shift. In the scientific community. For decades, entanglement was
Speaker 3: viewed mostly as a headache.
Speaker 2: We're really complicated headache.
Speaker 3: Yeah. It famously troubled Albert Einstein. He called it spooky
Speaker 3: action at a distance because it seemed to completely violate
Speaker 3: the classical rules of reality.
Speaker 2: Right, it broke all's rules.
Speaker 3: It was a curiosity, a puzzle to be observed. But
Speaker 3: today it is the actual tangible raw material for a
Speaker 3: new industrial revolution. It is like the clay we're trying
Speaker 3: to mold.
Speaker 2: Which is still incredibly spooky when you think about it.
Speaker 2: I mean, even if we accept it as raw material,
Speaker 2: it defies everyday logic.
Speaker 3: Oh absolutely.
Speaker 2: Imagine you have a pair of magic dice. If you
Speaker 2: roll one of those dice in New York and it
Speaker 2: lands on a six, the entangled die sitting in a
Speaker 2: server room in Tokyo instantly rolls a six, no matter
Speaker 2: the distance between them, instantaneously, right, no wires, no physical signals,
Speaker 2: just an instant link. But wait, if it's just spooky action,
Speaker 2: How do we actually use it to build a computer?
Speaker 2: How do you take that magic trick and turn it
Speaker 2: into a reliable machine.
Speaker 3: This raises an important question because it gets to the
Speaker 3: very heart of the engineering bottleneck. Okay, in a classical computer,
Speaker 3: your infrastructure is built on transistors reading physical states as
Speaker 3: simple ones or.
Speaker 2: Zeros, right, standard binary exactly.
Speaker 3: But in a quantum computer, you are using the entangled
Speaker 3: state itself to perform calculations and route information.
Speaker 2: Wow.
Speaker 3: Okay, yeah. By treating a system of entangled particles as
Speaker 3: a unified whole, any manipulation of the system inherently processes
Speaker 3: vast amounts of data simultaneously.
Speaker 2: So it's exponentially faster.
Speaker 3: Right. So creating the entanglement is step one. But the
Speaker 3: real challenge, the thing that has held up the quantum
Speaker 3: Internet for decades, is step two, which is what figuring
Speaker 3: out how to measure or read that entanglement without destroying
Speaker 3: its usefulness.
Speaker 2: Ah. I see. So if entanglement is our magic clay,
Speaker 2: it's not enough to just mash the clay together. If
Speaker 2: you actually want to process information, you have to be
Speaker 2: able to look at the clay and know exactly what
Speaker 2: shape it to.
Speaker 3: Me precisely creating entangled states in a laboratory is something
Speaker 3: physicists have actually gotten quite good at. Oh really, Yeah,
Speaker 3: but just throwing photons together isn't enough. You have to
Speaker 3: reliably verify what kind of entangled state you have created,
Speaker 3: purely and accurately, right.
Speaker 2: You need to know what you made exactly.
Speaker 3: And for years, the standard method for doing this was
Speaker 3: something called quantum tomography.
Speaker 2: Tomography like a CT scam in a hospital.
Speaker 3: Similar concept, yeah, but infinitely more frustrating. At the quantum level.
Speaker 3: Quantum tomography tries to estimate a quantum state by taking
Speaker 3: thousands upon thousands of measurements of identical copies of that state.
Speaker 2: That sounds exhausting, it is.
Speaker 3: It's basically a statistical guessing game, and it has a
Speaker 3: fatal mathematical flaw. As you add more photons to the system,
Speaker 3: the number of measurements you need to take grows explosively.
Speaker 3: It scales exponentially.
Speaker 2: Wow. So, if I'm trying to build a fast network,
Speaker 2: quantum demography is basically like trying to figure out a
Speaker 2: wedding kick's exact recipe by tasting it one microscopic crumb
Speaker 2: at a time. Yeah, Like, Okay, this crumbhusbandilla, let me
Speaker 2: test the next crumb. It takes forever, and by the
Speaker 2: time you've mapped the whole cake, the data is useless.
Speaker 2: You've completely bogged down the network.
Speaker 3: That is a perfect way to visualize it. You are
Speaker 3: destroying the system crumb by crumb to guess the recipe.
Speaker 2: So what's the alternative.
Speaker 3: The solution to this massive bottleneck is something called an
Speaker 3: entangled measurement.
Speaker 2: Okay.
Speaker 3: Instead of looking at into visual crumbs, an entangled measurement
Speaker 3: allows scientists to identify a specific complex entangled state in
Speaker 3: a single shot. You measure the whole cake at once.
Speaker 2: Which sounds way more efficient.
Speaker 3: It is, and scientists had already proven this single shot
Speaker 3: method was possible for one specific type of entanglement known
Speaker 3: as the GHz state GC. Yeah, named after the physicists Greenberger,
Speaker 3: Horn and Xylander.
Speaker 2: Okay, got it.
Speaker 3: But there is another vastly more important type of multiphoton
Speaker 3: entanglement called the W state, And for twenty five years,
Speaker 3: a single shot measurement for the W state remained entirely
Speaker 3: out of reach, completely impossible.
Speaker 2: Okay, I have to ask why was this WO state
Speaker 2: so uniquely difficult? What makes it different from the GHz state.
Speaker 3: What's fascinating here is the mechanics of how the entanglement
Speaker 3: is distributed. Think of the GHD state like a very
Speaker 3: rigid house of cars. If you measure one photon, it
Speaker 3: immediately determines the state of the others in a very strict,
Speaker 3: predictable way. But because it's so rigid, it's also incredibly fragile.
Speaker 2: Like blowing on a house of cards.
Speaker 3: Exactly, if you lose a single photon to environmental noise,
Speaker 3: the entire entangled system collapses. The W state, though, is
Speaker 3: entirely different. It is characterized by a shared distributed.
Speaker 2: Entanglement distributed how the.
Speaker 3: Quantum information is smeared delicately across all the photons.
Speaker 2: Oh wow, so it's less like a house of cards
Speaker 2: and more like, uh, a safety net.
Speaker 3: Exactly, if you lose a photon in a W state,
Speaker 3: the remaining photons actually stay entangled.
Speaker 2: That's amazing.
Speaker 3: It is incredibly robust against noise and particle loss, which
Speaker 3: is exactly why it is the holy grail for real
Speaker 3: world quantum networks.
Speaker 2: Right because the real world is messy, Right, You.
Speaker 3: Want that durability. If you're sending data under city streets.
Speaker 3: But that very same distributed smeared nature made it agonizingly
Speaker 3: difficult to mathematically design a measurement that could identify it
Speaker 3: in a single shot.
Speaker 2: Here's where it gets really interesting, because Shigeki ta Kuchi
Speaker 2: and the university teams in Japan didn't just try to
Speaker 2: smash these W states with brute force.
Speaker 3: No they didn't.
Speaker 2: According to the research, they found a structural workaround. They
Speaker 2: successfully performed a single shot entangled measurement identifying the W
Speaker 2: state using three photons.
Speaker 3: Yeah, a massively.
Speaker 2: And they did it by looking for something called cyclic
Speaker 2: shift symmetry. Let me try to wrap my head around
Speaker 2: that is cyclic shifts symmetry kind of like a musical chord.
Speaker 3: A musical chord.
Speaker 2: Yeah, Like think of a C major chord on a
Speaker 2: piano c eng If you move the seed to the
Speaker 2: top so it's EGC, it's still fundamentally a C major chord.
Speaker 2: It's an inversion.
Speaker 3: Oh, I see where you're going, right.
Speaker 2: No matter how you cycle or shift those specific notes around,
Speaker 2: the underlying harmony stays perfectly recognizable.
Speaker 3: That is a brilliant analogy. Yes, even as the specific
Speaker 3: configurations of the photons shift within the system. There is
Speaker 3: a fundamental symmetrical property, a underlying harmon that defines the
Speaker 3: entire system as a W state.
Speaker 2: Okay, so how do they actually measure that?
Speaker 3: To actually detect this cord, the Japanese researchers designed a
Speaker 3: highly specialized photonic quantum circuit.
Speaker 2: Built out of light.
Speaker 3: Built out of light, This circuit performs something called a
Speaker 3: quantum fourya transformation, specifically tailored for W states.
Speaker 2: A four EA transform. I know that's used in audio
Speaker 2: engineering to break down complex sound waves into individual frequencies.
Speaker 2: How does a quantum circuit do that to light?
Speaker 3: Well, In a traditional computer, a Fouria transform is a
Speaker 3: really heavy mathematical calculation. But in this photonic circuit, the
Speaker 3: math is done physically by the light itself.
Speaker 2: Wait, physically yeah.
Speaker 3: The circuit uses an intricate web of beam splitters and
Speaker 3: phase shifters. As the entangled photons travel through these paths,
Speaker 3: their light waves naturally interfere with each other.
Speaker 2: Oh wow.
Speaker 3: This physical interference acts as the calculation, taking that hidden
Speaker 3: shifting symmetry of the W state and naturally amplifying it
Speaker 3: into a clear, measurable signal at the output.
Speaker 2: That is wild.
Speaker 3: They literally built an optical machine that naturally filters for
Speaker 3: that specific quantum harmony.
Speaker 2: That is incredible. But you know, the paper also notes
Speaker 2: that they fed three single photons into this device, and
Speaker 2: they were looking at the fidelity of the results, right,
Speaker 2: fidelity fidelity being the probability that the device gives the
Speaker 2: right result when it's fed a pure W state. Does
Speaker 2: this mean the machine still makes mistakes? I mean, if
Speaker 2: we are building an ultra secure Internet of the future,
Speaker 2: we can't have a router that just drops packets or
Speaker 2: misreads data because of probability error.
Speaker 3: Right, it's very valid concern, But in quantum mechanics, fidelity
Speaker 3: doesn't mean the machine is glitching or making a software error.
Speaker 2: Okay, so what does it mean.
Speaker 3: It's a measure of absolute precision against microscopic environmental noise.
Speaker 3: No physical system is ever one hundred percent perfect, but
Speaker 3: achieving a highly elevated fidelity means the fundamental mechanism is
Speaker 3: definitively proven.
Speaker 2: So it works.
Speaker 3: It works, But honestly, the fidelity isn't even the most
Speaker 3: groundbreaking part of the device. The real game changer is
Speaker 3: its stability. This entire optical circuit is passive.
Speaker 2: Wait passive that defies everything I know about quantum labs.
Speaker 2: Usually you see these giant gold, steampunk chandeliers hanging inside
Speaker 2: deep freeze vacuum chambers.
Speaker 3: Oh yeah, the dilution refrigerators, right, and.
Speaker 2: They require a whole team of postdocs constantly tweaking lasers
Speaker 2: just to keep the experiment alive for like a millisecond exactly.
Speaker 3: Traditional quantum setups are agonizingly fragile, but this team built
Speaker 3: a device out of light that ran for an extended
Speaker 3: period without any active real time control or continuous calibration.
Speaker 2: It just ran on its own.
Speaker 3: They remain highly stable on its own. Yeah, And proving
Speaker 3: that we can achieve high fidelity readings on a stable
Speaker 3: passive device is the turning point. It proves we don't
Speaker 3: need a perfectly pristine, constantly adjusted, million dollar laboratory to read.
Speaker 2: These networks, which means we can actually take the technology outside.
Speaker 2: We can out of the lab and start bolting it
Speaker 2: into actual city infrastructure.
Speaker 3: Exactly, we can put it in the real world.
Speaker 2: And that transition into the real world brings us to
Speaker 2: the actual teleportation networks. Just to be absolutely clear for
Speaker 2: everyone listening, we are talking about beaming data instantaneously, not
Speaker 2: beaming humans like on Star Trek, right, right.
Speaker 3: It is vital to be precise with the terminology. Quantum
Speaker 3: teleportation is the transfer of quantum information from one location
Speaker 3: to another without physically moving any matter through the space
Speaker 3: between them.
Speaker 2: So we aren't mailing a photon.
Speaker 3: No, you aren't sending a photon in a microscopic FedEx
Speaker 3: box from point A to point B. You are utilizing
Speaker 3: that entangled link we talked about at the beginning to
Speaker 3: instantly transfer the exact quantum state of a particle in
Speaker 3: location A onto a completely different waiting particle in location B.
Speaker 2: And what blows my mind is the timeline of how
Speaker 2: fast this is moving. The source of show that in
Speaker 2: late twenty twenty five researchers achieved all photonic quantum teleportation
Speaker 2: in a hybrid urban network. Yes, a major milestone, and
Speaker 2: they did it using something called quantum dots. What exactly
Speaker 2: is a quantum dot doing in a city network?
Speaker 3: A quantum dot is essentially a tiny nanoscale semiconductor crystal.
Speaker 3: You can think of them as artificial atoms. Artificial atoms, yeah,
Speaker 3: because of their size, they trap electrons in a way
Speaker 3: that allows them to emit single photons on demand. Very predictably.
Speaker 2: Oh, I see, in a.
Speaker 3: Hybrid urban network, you need a reliable, high quality source
Speaker 3: of single photons to carry the quantum information, and quantum
Speaker 3: dots act as those perfect little photon factories interfacing between
Speaker 3: different types of quantum hardware across the city.
Speaker 2: So they are generating the data carriers. And the pace
Speaker 2: of this is just staggering, because right after that urban
Speaker 2: network test in twenty twenty five, twenty twenty six saw
Speaker 2: another massive leap.
Speaker 3: It really did.
Speaker 2: The reports show a completely different team built an integrated
Speaker 2: photonic chip capable of manipulating and measuring complex multipart entanglement
Speaker 2: all on a single tiny device.
Speaker 3: Incredible miniaturization right.
Speaker 2: And perhaps most impressively, also in twenty twenty six, researchers
Speaker 2: tested a three node quantum network right across existing standard
Speaker 2: fiber optic cables in New York.
Speaker 3: City using standard cables.
Speaker 2: Yeah, they did this using a process called entanglement swapping.
Speaker 2: How exactly do you swap entanglement under the streets of Manhattan.
Speaker 3: Entanglement swapping is essentially a quantum relay race. Imagine you
Speaker 3: have three nodes in the network, Alice, Bob and Charlie Okay,
Speaker 3: Alice and Bob are far apart and have never interacted,
Speaker 3: but they both share an entangled link with Charlie, who
Speaker 3: is sitting in the middle.
Speaker 2: So Charlie is the hub.
Speaker 3: Right, Charlie performs a specific entangled measurement on his particles.
Speaker 3: Because of the rules of quantum mechanics, the very act
Speaker 3: of Charlie taking that measurement instantly causes Alice and Bob's
Speaker 3: particles to become entangled with each other, even though they've
Speaker 3: never met.
Speaker 2: Wait, really that fast.
Speaker 3: Instantly, Charlie just swapped the entanglement to them. This is
Speaker 3: how you route a quantum connection over long distances, bouncing
Speaker 3: it from node to node through the messy temper fluctuating
Speaker 3: fiber cables under New York.
Speaker 2: And if we connect the dots here, the Japanese team's
Speaker 2: W state breakthrough is the ultimate missing piece for that
Speaker 2: relay race. You can have the fiber cables, you can
Speaker 2: use entanglement swapping to rout the signal, and you can
Speaker 2: use quantum dots to generate the photons. But to make
Speaker 2: it work at scale without lagging, you need to be
Speaker 2: able to verify that the robust W state information actually
Speaker 2: arrived correctly yes, you need an ultrafast single shot scanner.
Speaker 2: Without this new Kyoto and Hiroshima circuit, the New York
Speaker 2: network would just get bogged down trying to read the
Speaker 2: cake crumb by chrome.
Speaker 3: If we connect this to the bigger picture, yes, they
Speaker 3: have provided the high speed optical scanner for the future Internet,
Speaker 3: and they were already planning their next moves.
Speaker 2: Oh, what's next.
Speaker 3: The researchers intend to extend this passive method to larger
Speaker 3: multiphoton states, well beyond just three photons, and they're actively
Speaker 3: working to develop on ship photonic circuits to make it
Speaker 3: even small. They want to make the process of reading
Speaker 3: these states faster, smaller, and vastly more practical for mass production.
Speaker 3: They are literally laying the bricks for a fundamentally unhackable Internet.
Speaker 2: Completely unhackable because.
Speaker 3: In a quantum network, information cannot be intercepted or copied
Speaker 3: by a hacker without instantly destroying the state and alerting
Speaker 3: the sender. It represents the absolute pinnacle of data security.
Speaker 2: So what does this all mean. Let's pull all these
Speaker 2: threads together. We started with the basic reality of quantum entanglement,
Speaker 2: a concept so bizarre that it made Einstein's headspin.
Speaker 3: It definitely did.
Speaker 2: For decades. Even as we learned to create that spooky
Speaker 2: action in pristine labs, we were stuck at a massive
Speaker 2: engineering bottleneck. We could make the magic clay, but we
Speaker 2: couldn't read it efficiently because quantum tomography was just too
Speaker 2: slow and destructive, way too slow. Then this massive twenty
Speaker 2: twenty six breakthrough happens. Researchers in Japan finally figure out
Speaker 2: how to instantly read the highly complex durable W state.
Speaker 3: In a single shot, such a huge deal.
Speaker 2: They use cyclic shift symmetry to physically listen for the
Speaker 2: underlying musical cord of the photons using a completely passive
Speaker 2: light based circuit. And this is all happening concurrently with
Speaker 2: massive real world strides miniaturized quantum chips, single photon quantum dots,
Speaker 2: and actual teleportation networks swapping entanglement through the dirty fiber
Speaker 2: optic cables under New York City.
Speaker 3: It's all coming together at once, it really is.
Speaker 2: I really want you the listener, to think about how
Speaker 2: this transforms the reality you interact with every day. We
Speaker 2: are moving away from fragile science experiments and toward actual
Speaker 2: durable chips that will power the communication networks you will
Speaker 2: use in the near future. The quantum Internet isn't one
Speaker 2: hundred years away, It's actively being built right beneath our feet.
Speaker 3: It truly is the dawn of a new era of infrastructure,
Speaker 3: and as we transition from struggling to read just three
Speaker 3: entangled photons to eventually networking billions of them across global
Speaker 3: fiber optics, it forces us to ask a profound question,
Speaker 3: what happens to our traditional concepts of distance, time, and security.
Speaker 3: If massive amounts of information can be shared instantly and
Speaker 3: intrinsically across the globe without ever physically traveling the space
Speaker 3: between two points, are we on the verge of building
Speaker 3: a world where distance simply ceases to exist. Wow, just
Speaker 3: like the teleportation we imagined at the very beginning. We
Speaker 3: might not be beaming humanity through space, but we are
Speaker 3: absolutely beaming reality.