Speaker 1: Welcome to Bedtime Astronomy. Explore the wonders of the cosmos
Speaker 1: with our soothing Bedtime Astronomie podcast. Each episode offers a
Speaker 1: gentle journey through the stars, planets, and beyond, perfect for
Speaker 1: unwinding after a long day. Let's travel through the mysteries
Speaker 1: of the universe as you drift off into a peaceful
Speaker 1: slumber under the night sky.
Speaker 2: Researchers at Harvard University have just figured out how to
Speaker 2: use quantum entanglement to detect impossibly weak single photon light
Speaker 2: signals across a one point five to five kilometer fiberlink. Yeah,
Speaker 2: just pause for a second and let the weight of
Speaker 2: that sink in. It sounds like something pulled straight from
Speaker 2: a hard sci fi novel.
Speaker 3: It really does.
Speaker 2: But it is a very real and very profound breakthrough
Speaker 2: that is going to fundamentally change how we see the cosmos.
Speaker 3: I want you to pose a scenario in your mind
Speaker 3: right now, Okay, Imagine you are trying to see the
Speaker 3: sharpest possible image of the deepest, darkest, most ancient parts
Speaker 3: of the universe.
Speaker 2: Like looking at the exact photon ring at the edge
Speaker 2: of a supermassive black hole.
Speaker 3: Right or perhaps you're trying to resolve the atmospheric absorption
Speaker 3: lines of a rocky exoplanet forty light years away. Up
Speaker 3: until now, our optical telescopes have hit a hard, unforgiving
Speaker 3: physical wall in terms of how clearly they could see.
Speaker 2: A literal wall.
Speaker 3: We've been trapped by the literal laws of classical physics,
Speaker 3: specifically the diffraction limits of monolithic mirrors.
Speaker 2: Right Because, no matter how perfectly we polish our beryllium
Speaker 2: or glass, or no matter how clever our active optics
Speaker 2: engineering gets.
Speaker 3: The universe had essentially placed a hard limit on our
Speaker 3: visual acuity exactly.
Speaker 2: But now by harnessing the absolute, strangest, most counterintuitive rules
Speaker 2: of quantum mechanics, we are figuring out how to cheat
Speaker 2: those physical limits entirely.
Speaker 3: What's fascinating here is this year scale of the ambition
Speaker 3: behind this. We are not talking about a marginal improvement
Speaker 3: in telescope technology, right.
Speaker 2: This isn't just an iterative update.
Speaker 3: No, we aren't talking about a new deconvolution algorithm that
Speaker 3: cleans up blurry pixels, or a slightly more reflective meta
Speaker 3: material coding for a mirror. No, this is a foundational,
Speaker 3: paradigm altering shift in optical physics. The research we are
Speaker 3: looking at published recently in the journal Nature by peterion
Speaker 3: Stass and his team.
Speaker 2: At Harvard amazing paper.
Speaker 3: It is the first real stepping stone toward a future
Speaker 3: that astrophysicists have been dreaming about for decades.
Speaker 2: They've successfully paved the way for completely new class of
Speaker 2: optical telescopes.
Speaker 3: Ones that will operate with totally unprecedented, world changing resolution.
Speaker 3: By proving that you can take a delicate, single photon
Speaker 3: of optical light and process its phase information across a
Speaker 3: vast distance using quantum entanglement.
Speaker 2: Which is just wild to think about, they.
Speaker 3: Have essentially provided the blueprint for optical telescope arrays that
Speaker 3: could one day be the size of entire continents.
Speaker 2: Okay, let's unpack this, because it truly appreciates how mind
Speaker 2: blowing this Harvard breakthrough is. We have to contextualize it
Speaker 2: within how astronomers currently push the boundaries of high resolution imaging.
Speaker 3: We have to look at the physical limits of building
Speaker 3: a single monolithic mirror, right.
Speaker 2: You can't just cast a piece of blast the size
Speaker 2: of a city.
Speaker 3: No, it would collapse under its own weight right.
Speaker 2: Away and warp from thermal gradients.
Speaker 3: Exactly, and it would be impossible to steer, which is
Speaker 3: why the field relies heavily on very long baseline.
Speaker 2: Interferometry or VLBI.
Speaker 3: Right. VLBI. Instead of one giant mirror, you build a
Speaker 3: network of spatially separated detectors.
Speaker 2: You point all of these individual observation stations at the
Speaker 2: exact same astrophysical object.
Speaker 3: Yeah, you collect the incoming electromagnetic waves simultaneously and then
Speaker 3: computationally or physically combine those waves.
Speaker 2: But the mechanics of how that combination actually works are
Speaker 2: incredibly demanding.
Speaker 3: Extremely demanding, and it relies heavily on Foura transform mathematics. Right.
Speaker 3: The ultimate genius of interferometry is what happens when you
Speaker 3: combine those separate signals correctly. By perfectly synchronizing the electromagnetic
Speaker 3: waves gathered from all those widely spaced locations, the interferometric
Speaker 3: array effectively creates a single giant virtual synthetic.
Speaker 2: Aperture, a virtual telescope.
Speaker 3: Yes, And the defining characteristic of that synthetic aperture, its
Speaker 3: angular resolution, isn't determined by the size of the individual
Speaker 3: collection dishes.
Speaker 2: It's determined by the distance exactly.
Speaker 3: It's determined by the maximum physical distance between the two
Speaker 3: antennas that are furthest apart in your network. That distance
Speaker 3: is called the baseline.
Speaker 2: So if you have two observation stations separated by ten
Speaker 2: thousand kilometers.
Speaker 3: And you can capture and combine the phase and amplitude
Speaker 3: of the incoming light perfectly.
Speaker 2: You achieve the angular resolution of a single continuous telescope
Speaker 2: mirror that is ten thousand kilometers wide.
Speaker 3: You are leveraging the interference patterns of the incoming waves
Speaker 3: to trick the universe into giving you the visual sharpness
Speaker 3: of a behemoth instrument without actually having to construct it.
Speaker 2: And we have seen the triumph of this specific technique
Speaker 2: in recent history. The prime example that comes to mind
Speaker 2: is the event Horizon telescope collaboration back in twenty nineteen
Speaker 2: oh absolutely, they gave us the first direct image.
Speaker 3: Of a black hole, the supermassive black hole at the
Speaker 3: center of the galaxy MESA eighty.
Speaker 2: Seven, right, that glowing asymmetrical ring of light surrounding the
Speaker 2: dark shadow of the event horizon. To get that image,
Speaker 2: they didn't use a single radio dish.
Speaker 3: No, they used a global network of observatories.
Speaker 2: Spanning from Hawaii to Chile, from Spain to the south
Speaker 2: Pole precisely.
Speaker 3: The MESAA eighty seven milestone is the textbook example of
Speaker 3: VLBI operating at its absolute maximum classical limit. They were
Speaker 3: looking at radio frequencies, specifically two hundred and thirty gigahertz.
Speaker 2: Which is crucial to point out, very crucial.
Speaker 3: To achieve the resolution necessary to see an object roughly
Speaker 3: the size of our solar system from fifty five million
Speaker 3: light years away, they had to effectively turn the entire
Speaker 3: Earth into one singular radio telescope.
Speaker 2: And the challenge there was data synchronization, massive data synchronization.
Speaker 3: They had to record the incoming radio waves at each
Speaker 3: independent station, timestamping every single fluctuation of the electric.
Speaker 2: Field using highly stable hydrogen maser atomic clocks.
Speaker 3: Right they recorded petabytes of this rawway formed data unto physical.
Speaker 2: Hard drives, loaded those hard drives onto airplanes and flew.
Speaker 3: Them to central supercomputing correlators at MIT Haystack and the
Speaker 3: Max Planck Institute.
Speaker 2: Because the files were just too big to send over
Speaker 2: the Internet exactly.
Speaker 3: The correlators then played those recordings back, aligning the atomic
Speaker 3: clock timestamps down to the picosecond and allowed the recorded
Speaker 3: radio waves to computationally interfere with one another.
Speaker 2: And that computationally generated interference pattern is what allowed them
Speaker 2: to extract the image of the black hole. I really
Speaker 2: want you to just sit with the sheer scale of
Speaker 2: that for a moment. Imagine a synthetic aperture that is
Speaker 2: literally as wide as the planet Earth looking out into
Speaker 2: the void.
Speaker 3: It's staggering.
Speaker 2: When we talk about angular resolution and astronomy, it is
Speaker 2: usually buried in units like microarcsect which feels incredibly.
Speaker 3: Abstract, very abstract.
Speaker 2: But when you realize that resolution is directly tied to
Speaker 2: the physical baseline of your instrument, the concept becomes massive
Speaker 2: and concrete.
Speaker 3: It's the difference between trying to resolve a grain of
Speaker 3: sand in New York while standing in Los Angeles versus
Speaker 3: looking through a lens that spans the entire North American continent.
Speaker 2: That is the power of interferometric baselines. So this brings
Speaker 2: up the obvious million dollar question, if we can do
Speaker 2: that with the event horizon telescope, If we.
Speaker 3: Can timestamp radio waves with atomic clocks, load them onto airplanes,
Speaker 3: and turn the Earth into a giant radio dish to
Speaker 3: see a black hole, why.
Speaker 2: Does optical astronomy require quantum mechanics. Why can't we just
Speaker 2: use the exact same VLBI technique to see visible or
Speaker 2: infrared light.
Speaker 3: That is exactly where the classical physics of the universe
Speaker 3: throws a massive roadblock in our path, and it fundamentally
Speaker 3: comes down to the frequency spectrum of the electromagnetic waves.
Speaker 3: We are trying to observe.
Speaker 2: The actual wavelength of the light.
Speaker 3: Yes, radio waves like the two hundred and thirty gigaherd
Speaker 3: signals the Event Horizon telescope is collecting have relatively long
Speaker 3: wavelengths on the order of millimeters because the waves are
Speaker 3: undulating relatively slowly. The electric field is oscillating at a
Speaker 3: rate that our fastest analog to digital converters can actually handle.
Speaker 2: We can physically measure the peats and valleys.
Speaker 3: We can directly measure the amplitude and the phase of
Speaker 3: the radio wave in real time. We can record its
Speaker 3: exact shape onto a hard drive because we can sample
Speaker 3: it fast enough.
Speaker 2: But when you move up the electromagnetic spectrum to visible
Speaker 2: or near infrared light, you are entering an entirely different
Speaker 2: regime of physics. The wavelengths of optical light are on
Speaker 2: the order of hundreds of nanometers right, which.
Speaker 3: Means the frequency is astronomically high. We are talking about
Speaker 3: hundreds of terra.
Speaker 2: Heerts, hundreds of trillions of times.
Speaker 3: Per second, exactly. An optical light wave is oscillating hundreds
Speaker 3: of trillions of times per second. There is no analog
Speaker 3: to digital converter on Earth and likely never will be
Speaker 3: that can sample an electric field at petahertz frequency and
Speaker 3: record its exact wave pattern onto a hard drive. It's
Speaker 3: just too fast, way too fast. You cannot simply timestamp
Speaker 3: a visible photon and save its phase to a disc
Speaker 3: to be correlated later on a supercomputer.
Speaker 2: Because we cannot digitize the electric field of optical light,
Speaker 2: we cannot use computational correlation.
Speaker 3: Instead, to do optical interferometry, we are forced to perform
Speaker 3: what is called direct interference.
Speaker 2: Direct physical interference.
Speaker 3: Yes, we have to physically take the actual delicate photons
Speaker 3: collected by Telescope A and physically overlap them with the
Speaker 3: delicate photons collected by Telescope.
Speaker 2: BA in real time on a physical beam splitter exam.
Speaker 2: So we can't record the light. We literally have to
Speaker 2: pipe it through optical cables to a central mixing room.
Speaker 2: But wait, if we use fiber optic cables to send
Speaker 2: the Internet across oceans without a problem. Why can't we
Speaker 2: just pipe visible starlight through those same cables to a
Speaker 2: central mixing station.
Speaker 3: Because of the massive difference between a robust, classical laser
Speaker 3: pulse used for telecommunications and the fragile single photon thermal
Speaker 3: states arriving from a distant star.
Speaker 2: They behave entirely differently completely.
Speaker 3: When you send Internet data across the Atlantic, you are
Speaker 3: firing billions of photons in a single pulse, and you
Speaker 3: have classical optical amplifiers repeating that signal every few dozen kilometers.
Speaker 3: But in optical astronomy you are dealing with impossibly faint starlight.
Speaker 2: You might be collecting just a handful of photons per second.
Speaker 3: Exactly, And you cannot amplify a quantum state without destroying
Speaker 3: its phase information.
Speaker 2: Oh right, that's prohibited by the note cloning theorem of
Speaker 2: quantum mechanics exactly.
Speaker 3: So you have to send that bare single photon through
Speaker 3: the silica glass of a fiber optic cable. And silica glass,
Speaker 3: no matter how pure, is lossy.
Speaker 2: It absorbs and scatters the light.
Speaker 3: Correct. The attenuation is brutal, even at the highly optimized
Speaker 3: telecom wavelength of one point five to five micrometers, you
Speaker 3: lose about half your photons every fifteen kilometers.
Speaker 2: Wow.
Speaker 3: At visible wavelengths, it's vastly worse. If you try to
Speaker 3: send a single photon from a star through just a
Speaker 3: few kilometers of fiber optic cable, the probability of it
Speaker 3: surviving the journey to that central mixing station drops exponentially.
Speaker 2: And remember, for interferometry to work, the photon from telescope
Speaker 2: A and the photon from telescope B both have to
Speaker 2: survive the journey and arrive at the central beam splitter
Speaker 2: at the exact same pekosecond.
Speaker 3: Because of this massive, unavoidable signal loss, traditional optical interferometer
Speaker 3: networks have been trapped at a very frustrating physical limit.
Speaker 2: They have been restricted to physical baselines of just about
Speaker 2: three hundred meters.
Speaker 3: And that three hundred meters wall is the bane of
Speaker 3: modern optical astronomy.
Speaker 2: You look at a facility like the very large telescope
Speaker 2: in the Atacoma Desert in Chile. They have four main
Speaker 2: telescopes and they can do optical interferometry by physically routing
Speaker 2: the starlight through underground vacuum tunnels to a central combining room.
Speaker 3: But the maximum distance between those telescopes is roughly one
Speaker 3: hundred and thirty meters.
Speaker 2: You simply cannot connect an optical telescope in Chili to
Speaker 2: an optical telescope in Hawaii.
Speaker 3: The stellar photons would scatter and die in the transoceanic
Speaker 3: cables long before they ever reached the central mixing room.
Speaker 2: So we have this agonizing situation where radio astronomers are
Speaker 2: building earth sized synthetic apertures, while optical astronomers are stuck
Speaker 2: with apertures the size of a football field, and.
Speaker 3: That restriction fundamentally throttles our understanding in the universe.
Speaker 2: If we could extend optical baselines from three hundred meters
Speaker 2: to say, one thousand kilometers, the angular resolution wouldn't.
Speaker 3: Just improve, No, it would open up entirely new fields
Speaker 3: of astrophysics. We could directly image the surface features of
Speaker 3: active galactic nuclei.
Speaker 2: Or resolve the kinematic structures of protoplanetary disks with subastronomical
Speaker 2: unit precision.
Speaker 3: But to do that you have to solve the physical
Speaker 3: routing problem. You have to somehow compare the phase of
Speaker 3: a photon. It telscope A with the phase of a
Speaker 3: photode at telescope B without ever sending the photons to
Speaker 3: a central location, which.
Speaker 2: Sounds like a paradox. How do you physically interfere two
Speaker 2: particles of light if you can't physically bring them to
Speaker 2: the same location.
Speaker 3: This is where we have to dive into the theory
Speaker 3: theoretical foundation that made the Harvard experiment.
Speaker 2: Possible, because before there was physical hardware, there was a
Speaker 2: mathematical blueprint to bypass the three hundred met a wall,
Speaker 2: generally referred to in the field as the twenty twelve
Speaker 2: Gotsman Genoine Kresser paper.
Speaker 3: Or what we can loosely call the Gotsman prophecy.
Speaker 2: I love that name.
Speaker 3: Yes. Daniel Gotsman and his colleagues looked at this strict
Speaker 3: optical baseline limit and proposed a mathematically audacious workaround.
Speaker 2: They realized that the fundamental bottleneck was the direct physical
Speaker 2: transportation of the thermal astronomical photon.
Speaker 3: So they asked a question rooted in the deepest, most
Speaker 3: counterintuitive aspects of quantum mechanics. What if you use quantum teleportation?
Speaker 2: What if you use pre shared quantum entanglement to extract
Speaker 2: the phase information of the starlight locally and then teleport
Speaker 2: that quantum state across the baseline. Hold on, let me
Speaker 2: stop you right there. When you say teleport the starlight's information,
Speaker 2: that immediately triggers a red flag for anyone familiar with relativity. Naturally,
Speaker 2: doesn't that imply instantaneous communication? Doesn't teleporting phase information violate
Speaker 2: the speed of light?
Speaker 3: It is a vital distinction to make, and the answer
Speaker 3: is no, it does not violate relativity. Quantum teleportation does
Speaker 3: not move physical matter instantaneously, nor does it allow for
Speaker 3: faster than light communication. What Gotsman proposed is using a resource,
Speaker 3: specifically an entangled pair of quantum states that is distributed
Speaker 3: between the two telescopes before the starlight.
Speaker 2: Even arrives pre shared entangle.
Speaker 3: In yes, if telescope A and telescope B share a
Speaker 3: pair of entangled particles, their quantum states are fundamentally mathematically correlated,
Speaker 3: regardless of the physical distance separating them. When the astronomical
Speaker 3: photon arrives at telescope A, it is forced to interact
Speaker 3: with the local half of that entangled pair through a
Speaker 3: specific process called a Bell state measurement.
Speaker 2: And this is where the phase information gets transferred without
Speaker 2: moving the original photon exactly.
Speaker 3: The Bell state measurement at Telescope A destroys the original
Speaker 3: astronomy photon, it consumes it, but in doing so it
Speaker 3: intrinsically entangles the incoming starlight state with the pre shared
Speaker 3: entanglement resource.
Speaker 2: Because the other half of that entangled resource is sitting
Speaker 2: over at telescope B.
Speaker 3: Right, So, the quantum state of the astronomical photon, its
Speaker 3: exact phase and amplitude at the moment it arrived, is
Speaker 3: effectively transferred to the quantum memory at telescope B.
Speaker 2: But causality is maintained.
Speaker 3: Right, Yes, because the actual physical data regarding the outcome
Speaker 3: of the measurement at Telescope A still has to be
Speaker 3: sent to Telescope B over a standard classical internet connection.
Speaker 2: Which is limited by the speed of light.
Speaker 3: So causality is perfectly preserved. But the crucial breakthrough is
Speaker 3: that the delicate quantum phase information didn't have to survive
Speaker 3: a brutal journey through a lossy optical fiber.
Speaker 2: It bypassed the environment completely.
Speaker 3: Okay, let's unpack this because the implications are staggering. You're
Speaker 3: essentially saying that if we can create an invisible entangled
Speaker 3: bridge between two telescopes. The starlight only has to travel
Speaker 3: from deep space down to the local telescope dish.
Speaker 2: It hits, the dish, interacts with the local entangled particle,
Speaker 2: and its essential quantum signature is instantly mapped onto the
Speaker 2: other side of the network.
Speaker 3: It completely negates the photon loss problem of fiber optic
Speaker 3: cables entirely. But if Gotsman and his team proved the
Speaker 3: math for this continuous variable quantum teleportation back in twenty twelve,
Speaker 3: why did it remain a chalk poor dream for over
Speaker 3: a decade. If the math works, why didn't we build
Speaker 3: it immediately?
Speaker 2: If we connect this to the bigger picture, the mathematical
Speaker 2: elegance of quantum teleportation belies the absolute nightmare of engineering
Speaker 2: it in physical reality.
Speaker 3: The hardware just wasn't there, not even close.
Speaker 2: Gotsman knew that the practical roadblocks were immense. To make
Speaker 2: this work for astronomy, you need a physical system that
Speaker 2: can do three exceedingly difficult things simultaneously.
Speaker 3: Okay, what's the first. First, it must act as an
Speaker 3: optical interface to catch the incredibly weak, randomly arriving thermal
Speaker 3: photons from the star that makes sense. Second, it must
Speaker 3: be able to generate and hold robust quantum entanglement over
Speaker 3: long physical distances.
Speaker 2: Which is incredibly hard.
Speaker 3: And third, it has to store that delicate quantum state
Speaker 3: in a memory long enough for the classical data of
Speaker 3: the measurement to travel across the.
Speaker 2: Network right because of the speed of light limit on
Speaker 2: that classical data channel.
Speaker 3: Exactly in twenty twelve, deterministic entanglement generation rates between distant
Speaker 3: physical nodes were abysmal. The technology simply did not exist
Speaker 3: to maintain a stable, high fidelity quantum memory that could
Speaker 3: interface with visible light at the rates required to do
Speaker 3: actual astrophysics.
Speaker 2: It was a beautiful protocol waiting for the hardware to
Speaker 2: catch up, which perfectly sets the stage for bringing our
Speaker 2: timeline right back to the present day and focusing on
Speaker 2: the physical hardware that Peter Jonstass and his team at Harvard.
Speaker 3: Actually built because they took Gosman's theoretical protocol and dragged
Speaker 3: it kicking and screaming into physical reality.
Speaker 2: To do that, they didn't rely on standard silicon computing chips, no,
Speaker 2: and they certainly weren't using bulk optical mirrors. They had
Speaker 2: to engineer a highly specific quantum memory using what are
Speaker 2: called silicon vacancy centers embedded in diamond nanocavities. And I
Speaker 2: want to get deeply into the solid state physics here.
Speaker 3: It's fascinating physics.
Speaker 2: Why diamond and what exactly is a silicon vacancy center.
Speaker 3: To understand the hardware, we have to look at the crystallography. Okay.
Speaker 3: A pure diamond is a rigid, perfectly repeating lattice of
Speaker 3: carbon atoms bonded in a tetrahedral structure. It has a
Speaker 3: very wide electronic band gap, meaning it is highly transparent,
Speaker 3: and it has an extremely rigid lattice, which means the
Speaker 3: speed of sound inside a diamond is very high, and
Speaker 3: the thermal vibrations the phonons are tightly.
Speaker 2: Constrained, so it's a very quiet material.
Speaker 3: Computationally speaking, This makes diamond an exceptionally quiet environment in
Speaker 3: cryogenic temperatures. But the Harvard researchers don't want a perfect.
Speaker 2: Diamond because a perfect diamond is inert.
Speaker 3: Exactly, it doesn't interact with light in the way we need.
Speaker 3: So they use a process like chemical vapor deposition to
Speaker 3: grow the diamond, and during that process or through targeted
Speaker 3: ion beam implantation, they intentionally introduce a specific microscopic defect.
Speaker 2: They break the perfect lattice.
Speaker 3: They knock out two adjacent carbon atoms from the lattice,
Speaker 3: and they insert a single larger silicon atom right in
Speaker 3: the middle of that empty space.
Speaker 2: So you have a silicon atom sitting suspended between two
Speaker 2: missing carbon spots.
Speaker 3: Precisely. That specific geometric arrangement is the silicon vacancy or
Speaker 3: cieves center, and it has a unique property that is
Speaker 3: absolutely vital for this experiment inversion symmetry. Yes, inversion symmetry.
Speaker 3: Because the silicon atom sits perfectly centered between the two vacancies,
Speaker 3: the defect is highly protected from local chaotic electric field
Speaker 3: fluctuations in the surrounding diamond crystal.
Speaker 2: In quantum mechanics, we call this spectral stability.
Speaker 3: It means that the optical transitions of this defect, the
Speaker 3: exact frequencies of light it will absorb or Emit remain
Speaker 3: incredibly sharp and consistent over time, unlike other defects that
Speaker 3: jitter wildly due to environmental noise.
Speaker 2: And it is inside this incredibly stable microscopic pocket that
Speaker 2: the actual quantum data processing happens. Because the silicon vacancy
Speaker 2: center isn't just a structural flaw. It traps a single
Speaker 2: unpaired electron.
Speaker 3: Yes, and that trapped electron acts as the active optical interface.
Speaker 3: The electron has a quantum property called spin, which you
Speaker 3: can loosely visualize as a microscopic magnetic moment pointing either
Speaker 3: up or down. Okay, When an external magnetic field is applied,
Speaker 3: the energy levels of that spin state split. This is
Speaker 3: known as the Zeman effect. The beauty of the Sieb
Speaker 3: center is that the optical absorption of an incoming photon
Speaker 3: is entirely dependent on the spin state of that electron.
Speaker 2: It acts as a perfect highly responsive catchers mit for
Speaker 2: the incoming light exactly.
Speaker 3: But electrons are flighty. They are even in the pristine
Speaker 3: environment of the diamond lattice. An electron spin will eventually decohere.
Speaker 3: It will interact with stray magnetic fields or leftover THERMAE noise,
Speaker 3: and its quantum state will.
Speaker 2: Scramble its coherence time, The amount of time it can
Speaker 2: faithfully hold on to quantum information, is relatively.
Speaker 3: Short, right, often just microseconds or milliseconds, which is a
Speaker 3: massive problem if you are trying to hold on to
Speaker 3: the phase information of starlight while waiting for the classical
Speaker 3: measurement data to travel across a one point five to
Speaker 3: five kilometer baseline.
Speaker 2: If the electron loses the state before the network can
Speaker 2: confirm the entanglement protocol, the data is gone, forever gone.
Speaker 2: So how do they extend that memory?
Speaker 3: They execute a brilliant transfer of information using the hyperfine interaction.
Speaker 2: Let's break that down.
Speaker 3: Sitting right next to the C center in the diamond lattice,
Speaker 3: there are naturally occurring isotopes of carbon, specifically carbon thirteen.
Speaker 2: Okay.
Speaker 3: Unlike the standard carbon twelve, carbon thirteen has a nuclear
Speaker 3: spin and atomic nucleus is thousands of times heavier than
Speaker 3: an electron, and his magnetic moment is incredibly weak.
Speaker 2: Meaning it doesn't get bumped around by noise nearly as easily.
Speaker 3: This means the nucleus interact very weakly with its surrounding environment.
Speaker 3: It is deeply insulated from the chaotic noise of the
Speaker 3: outside world. Right through highly precise microwave and radio frequency
Speaker 3: control pulses. The researchers can take the delicate quantum state
Speaker 3: residing on the flighty electron spin and perfectly map it
Speaker 3: onto the heavy, stable nuclear spin of the nearby carbon
Speaker 3: thirteen atom.
Speaker 2: It is essentially a quantum vault. You use the electron,
Speaker 2: which interacts strongly with light, to catch the photon's phase information,
Speaker 2: and then you immediately write that information into the nuclear
Speaker 2: spin of the carbon atom, which doesn't interact with light,
Speaker 2: but can hold the quantum state for seconds or even minutes.
Speaker 3: That is exactly the architecture. The CIVA center provides the
Speaker 3: fast optical interface to entangle the nodes, and the carbon
Speaker 3: thirteen nucleus provides the long lived quantum memory to store
Speaker 3: the state.
Speaker 2: And to make this entire interface as efficient as possible,
Speaker 2: the Harvard team doesn't just use a bulk chunk of diamond.
Speaker 2: They sculpt the diamond down to the nanoscale.
Speaker 3: They carve a nanophotonic cavity, essentially a microscopic hall of
Speaker 3: mirrors made of perfectly spaced holes directly around the SIEF center.
Speaker 2: This forces the incoming photons to bounce back and forth
Speaker 2: across the defect thousands of times, massively increasing the probability
Speaker 2: that the weak single photon will actually interact with the
Speaker 2: electron spin. I want to constantly remind you why this
Speaker 2: deeply technical dive into solid state physics matters. This microscopic flaw,
Speaker 2: This single silicon atom deliberately implanted into a carve speck
Speaker 2: of diamond operating at temperatures just a fraction of a
Speaker 2: degree above absolute zero inside a dilution refrigerator. This is
Speaker 2: the physical hardware required to cheat the classical limits of
Speaker 2: optical astronomy.
Speaker 3: It really is profound when you frame it that way.
Speaker 2: We are engineering the smallest, most isolated subatomic spins in
Speaker 2: nature to build an interferometric bridge to the most massive
Speaker 2: objects in the universe.
Speaker 3: The contrast in scales is mind boggling.
Speaker 2: So we have the quantum memory hardware. How did Stats
Speaker 2: and his team actually deploy it to shatter the three
Speaker 2: hundred meters wall. Let's look at the physical set up
Speaker 2: of their one point five to five kilometer demonstration.
Speaker 3: The setup was a master class in quantum network engineering.
Speaker 3: They established two entirely independent experimental stations representing our telescope
Speaker 3: A and telescope B.
Speaker 2: Inside each station was a dilution refrigerator cooling a highly
Speaker 2: tuned diamond sieve quantum memory down to milli kelvin temperatures.
Speaker 3: And crucially, these two stations were connected by a massive
Speaker 3: School of standard telecommunications fiber optic cable exactly one point
Speaker 3: five to five kilometers long.
Speaker 2: Right, there By introducing a one point five to five
Speaker 2: kilometer baseline, they are immediately stepping five times past the
Speaker 2: three hundred meter exponential attenuation limit of standard optical interferometry. Yes,
Speaker 2: so picture these two stations, separated by nearly a mile
Speaker 2: of coiled glass, walk us through the exact sequence of
Speaker 2: events required to successfully capture and interfere a photon across
Speaker 2: that gap.
Speaker 3: The protocol is a complex multi step quantum choreography. Step
Speaker 3: one must occur before any simulated starlight.
Speaker 2: Arise the pre shared entanglement.
Speaker 3: The two stations may to establish high fidelity remote entanglement
Speaker 3: between their respective diamond memories. To do this, both Station
Speaker 3: A and Station B excite their local electron spins with
Speaker 3: a highly specific laser pulse. The physics of the SiGe
Speaker 3: center dictate that if the electron emits a photon in response,
Speaker 3: the polarization or phase of that emitted photon is fundamentally
Speaker 3: entangled with the spin state of the electron left behind.
Speaker 2: So they each generate an entangled photon electron pair locally.
Speaker 3: Yes, then both stations send their newly emitted entangled photons
Speaker 3: down the fiber optic link to a central beam splitter
Speaker 3: station located exactly halfway between them.
Speaker 2: And this is where we hit the absolute core requirement
Speaker 2: of interferometry, the erasure of path information.
Speaker 3: Precisely, the two photons from station A and Station B
Speaker 3: meet at a fifty to fifty optical beam splitter. Now,
Speaker 3: if the quantum states of the photons are completely indistinguishable,
Speaker 3: meaning they have the exact same frequency of the exact
Speaker 3: same polarization and arrive at the exact same picosecond, they
Speaker 3: will undergo a phenomenon known as two foot photon.
Speaker 2: Interference, such as the hung Mandel effect.
Speaker 3: Yes, the crucial aspect of the beam splitter is that
Speaker 3: when a photon exits one of the output ports and
Speaker 3: triggers a detector, there is absolutely no physical way to
Speaker 3: know whether that photon originated from station A or station B.
Speaker 2: The path information is fundamentally erased from reality. It's exactly
Speaker 2: if you try to place a detector on the input
Speaker 2: fiber to see where it came from, you destroy the entanglement.
Speaker 2: The wave function collapses.
Speaker 3: Yes, the indistinguishability is mandatory. When the central detectors register
Speaker 3: a specific coincidence pattern, meaning they detect the photons simultaneously
Speaker 3: at the output ports. It heralds a successful Bell state measurement.
Speaker 2: Because the paths were erase. The measurement projects the remaining
Speaker 2: electron spins back at station A and Station B into
Speaker 2: a highly entangled state with each other.
Speaker 3: The invisible one point five to five kilometer quantum bridge
Speaker 3: is now established. The two diamond memories act as a
Speaker 3: single unified spatially distributed quantum system WOW. Once that bridge
Speaker 3: is verified, the researchers transfer that entangled state from the
Speaker 3: flighty electron spins down into the robust carbon thirteen nuclear
Speaker 3: spins for safekeeping. That's just step one.
Speaker 2: That's just to prep the system.
Speaker 3: The network is now primed and waiting.
Speaker 2: Step two is the arrival of the actual signal. In
Speaker 2: a real observatory, this would be the photone from the exoplanet.
Speaker 2: In this laboratory demonstration, it is a highly attenuated weak
Speaker 2: coherent laser pulse simulating the incoming starlight.
Speaker 3: The weak optical signal arrives independently at the two stations.
Speaker 3: Because the nuclear memories are already entangled, the system can
Speaker 3: perform the local measurements necessary to map the relative phase
Speaker 3: of the incoming starlight directly onto the unified quantum state.
Speaker 2: But earlier, when we discuss the theoretical Gotsman protocol, we
Speaker 2: established that measuring the starlight locally usually destroys it. How
Speaker 2: do they actually extract the phase of this weak incoming
Speaker 2: light without just absorbing it as random noise.
Speaker 3: They use a technique that leverages the optical reflectivity of
Speaker 3: the sieve cavity itself. Okay, when the weak coherent pulse arrives,
Speaker 3: it is reflected off the nanophotonic cavity. The phase of
Speaker 3: the reflected light experiences a shift that depends entirely on
Speaker 3: the state of the electron spin inside the cavity.
Speaker 2: By reflecting the light off both station A and Station
Speaker 2: B simultaneously and then letting those reflected pulses interfere, the
Speaker 2: relative phase of the incoming light is imprinted onto the
Speaker 2: entangled state of the diamond memories.
Speaker 3: But as you noted, there is a massive problem. Astronomical
Speaker 3: signals are incredibly weak, and the ambient noise in any
Speaker 3: physical system is high.
Speaker 2: There are stray photons, thermal fluctuations, and dark counts in
Speaker 2: the detectors.
Speaker 3: Right. Yeah, If you just look at the memory at
Speaker 3: the end of the day, how do you know if
Speaker 3: you actually capture the phase of a valid incoming photon
Speaker 3: or if your system just drifted due to noise.
Speaker 2: You need a highly specific conformation signal exactly. The researchers
Speaker 2: call this non local photon heralding. This sounds like deeply
Speaker 2: impenetrable jargon, but it is actually the lynchpin that makes
Speaker 2: the entire differential phase measurement possible. Explain how this non
Speaker 2: local herald works.
Speaker 3: Let's break down the terminology. Heralding in quantum octics simply
Speaker 3: means generating a measurable signal that announces the successful preparation
Speaker 3: or capture of a quantum state without measuring the state itself.
Speaker 2: It is the bell ringing to tell you the oven
Speaker 2: is done, without you having to open the door and
Speaker 2: let the heat out.
Speaker 3: I love that analogy. Yes. In this experiment, after the
Speaker 3: weak simulated starlight reflects off the cavities and interacts with
Speaker 3: the electron spins, those reflected optical pulses are combined on
Speaker 3: a beam splitter. If a single photon is detected at
Speaker 3: the output of this final beam splitter. It serves as
Speaker 3: the herald. It confirms with high probability that the incoming
Speaker 3: optical phase was successfully imprinted onto the memories.
Speaker 2: And what makes it non local.
Speaker 3: It is non local because the original entanglement between station
Speaker 3: A and station B means that the successful herald detection
Speaker 3: doesn't just confirm that station A saw a photon or
Speaker 3: station B saw a photon. It confirms that the entire
Speaker 3: distributed one point five to five kilometer quantum network successfully
Speaker 3: process the relative phase of the incoming wave without ever
Speaker 3: revealing which specific station contributed.
Speaker 2: What it is a collective network wide confirmation. By only
Speaker 2: looking at the state of the carbon thirteen nuclear memories
Speaker 2: after they receive this non local herald click, the researchers
Speaker 2: can filter out the vast majority of the background noise.
Speaker 3: They only query the vault when they have absolute confirmation
Speaker 3: that the vault contains valid astronomical data.
Speaker 2: And the result of all this brilliant, exhausting, deeply complex
Speaker 2: quantum choreography.
Speaker 3: The researchers triumphantly achieve their goal.
Speaker 2: By querying those nuclear memories after the non local herald,
Speaker 2: they successfully extracted the relative phase of the weak incoming
Speaker 2: light between those two stations.
Speaker 3: They prove that you can extract the exact shape and
Speaker 3: timing of the optical waves, maintaining perfect phase coherent across
Speaker 3: a physical gap of one point five to five kilometers
Speaker 3: entirely bypassing the physical photon loss limits of the fiber
Speaker 3: optic cable.
Speaker 2: They absolutely shadow the three hundred meter baseline wall. It
Speaker 2: is a flawless proof of concept that the twenty twelve
Speaker 2: Gotsman proposal is physically achievable.
Speaker 3: Is a monumental achievement in experimental physics. They demonstrated spin
Speaker 3: photon entanglement, high fidelity quantum memory storage, remote bell state measurements,
Speaker 3: and non local phase heralding, all working synchronously in a
Speaker 3: single unified experiment.
Speaker 2: It's just incredible.
Speaker 3: But this raises an important question and we have to
Speaker 3: be brutally grounded about the current state of the art.
Speaker 2: The reality check.
Speaker 3: Are we ready to roll out into the Atacama Desert tomorrow,
Speaker 3: unspool one thousand kilometers of fiber and start taking ultra
Speaker 3: high resolution quantum images of protoplanetary disks.
Speaker 2: The answer is a resounding, unambiguous no.
Speaker 3: We have to examine the profound reality check embedded in
Speaker 3: this demonstration.
Speaker 2: Right and the biggest, most glaring catch right now, the
Speaker 2: hurdle that will require perhaps another decade of intense material
Speaker 2: science and quantum engineering to overcome is the speed limit.
Speaker 3: Yes, the speed limit is severe.
Speaker 2: When stasa's team was running this brilliant one point five
Speaker 2: five five kilometer experiment successfully storing and extracting the phase
Speaker 2: data of the weak light, they could only collect heralded
Speaker 2: data at a rate of roughly twelve milliher twelve millerhertz.
Speaker 3: To put that in perspective, twelve milihertz is a point
Speaker 3: zero one two events per second, which.
Speaker 2: Equates to roughly one successful data point every eighty three seconds.
Speaker 3: It is an agonizingly glacially slow rate of data acquisition.
Speaker 3: If you are doing optical interferometry to build an image
Speaker 3: of a dynamic astrophysical object, you don't just need one
Speaker 3: data point.
Speaker 2: No, you need to sample the fourty a plane, the
Speaker 2: so called UV plane, millions or billions of times to
Speaker 2: mathematically reconstruct a clear, high fidelity image.
Speaker 3: If it takes you a minute and a half to
Speaker 3: get a single successful coincidence detection, acquiring enough data for
Speaker 3: one image could literally take decades or centuries of continuous observation.
Speaker 2: So what exactly is causing this massive bottleneck? If the
Speaker 2: CIV centers are so efficient and the carbon thirteen memories
Speaker 2: are so stable, why is the data rate pinned at
Speaker 2: twelve milliher.
Speaker 3: The bottleneck is directly tied to the probabilistic nature of
Speaker 3: the entanglement generation itself.
Speaker 2: Remember step one of the protocol.
Speaker 3: Right, The two stations have to emit entangled photons, send
Speaker 3: them down the one point five to five kilometer fiber,
Speaker 3: and have them successfully interfere at the central beam splitter
Speaker 3: to establish the remote entanglement link.
Speaker 2: But because of the inherent photon loss in the fiber
Speaker 2: optic cables and the finite collection efficiency of the nanophotonic cavities,
Speaker 2: most of the photons emitted by the electron spins are lost.
Speaker 3: Furthermore, the two photon interference at the beam splitter is
Speaker 3: fundamentally probabilistic. Even if both photons arrive perfectly, the bell
Speaker 3: state measurement only succeeds a fraction of the time, So.
Speaker 2: The network spends the vast majority of its time just
Speaker 2: trying and failing to establish the invisible bridge.
Speaker 3: Exactly, the system is pulsing lasers at the city centers
Speaker 3: thousands or millions of times per second, desperately trying to
Speaker 3: get a successful herald that the entanglement link is established, and.
Speaker 2: The carbon thirteen memories only have a coherence time of
Speaker 2: maybe a few seconds. If the network takes too long
Speaker 2: to establish the link, the previously stored state to grades
Speaker 2: and they have to start over.
Speaker 3: The end to end efficiency of the entire multi step
Speaker 3: protocol generating entanglement, catching the weak starlight, reflecting it, and
Speaker 3: detecting the non local herald multiplies all of those individual
Speaker 3: inefficiencies together, resulting in that brutal twelve miliheritz overall success rate.
Speaker 2: And when you are dealing with such an excruciatingly slow
Speaker 2: data rate, you run headfirst into a secondary, equally massive.
Speaker 3: Hurdle, the signal to noise ratio.
Speaker 2: Yes, the noise problem is explicitly noted by the Harvard
Speaker 2: team as the primary limitation to scaling. This immediately, when you.
Speaker 3: Are dealing with such incredibly sparse data, any false positive
Speaker 3: becomes highly destructive. The detectors they use, likely superconducting nanowire
Speaker 3: single photon detectors, are incredibly sensitive, but they still have
Speaker 3: a non zero dark count rate.
Speaker 2: A dark count is one that detector registers a photon
Speaker 2: hit due to a random thermal spike or stray electronics noise,
Speaker 2: even though no actual photon arrived.
Speaker 3: If if your true heralded signal is coming in once
Speaker 3: every eighty three seconds and your detector randomly fires a
Speaker 3: dark count once every hundred seconds, your signal to noise
Speaker 3: ratio drops to roughly one to one.
Speaker 2: Half of your hard earned data is completely fake and
Speaker 2: you have no way to distinguish the real astronomical figures
Speaker 2: from the random thermal noise.
Speaker 3: It heavily pollutes the extremely sparse data set and makes
Speaker 3: extracting a clear interference fringe deeply mathematically challenging.
Speaker 2: It sounds incredibly bleak when you lay out the map
Speaker 2: like that, a rate of twelve millerhertz buried in detector
Speaker 2: dark counts. But despite those immense hurdles, despite the agonizing
Speaker 2: speed limit and the spiking noise, the perspective we need
Speaker 2: to maintain here is one of historical precedent. Absolutely, this
Speaker 2: is not a failure of the technology. It is the
Speaker 2: fundamental proof of it. All the core components of entanglement
Speaker 2: assisted continuous variable interferometry actually work together in practice.
Speaker 3: The entanglement generation, the diamond memory storage, the phase mapping,
Speaker 3: the quantum erasure.
Speaker 2: The heralding took the most incredibly fragile puzzle pieces in
Speaker 2: modern physics, forced them to interact over a macroscopic distance
Speaker 2: of one point five to five kilometers, and the underlying
Speaker 2: physical theory proved perfectly sound. The three hundred meter wall
Speaker 2: has a door in it.
Speaker 3: Now, the physics works now, it is just an engineering
Speaker 3: problem of how to walk through that door faster.
Speaker 2: That is exactly the right perspective to borrow and analogy.
Speaker 2: This is the right brothers at Kittyhawk.
Speaker 3: The plane was made of canvas and wood. It only
Speaker 3: flew for twelve seconds. It was wobbly, and it barely
Speaker 3: got off the ground. By any metric of modern aviation,
Speaker 3: it was a terrible, useless flight.
Speaker 2: But it proved irrevocably that heavier than air powered flight
Speaker 2: was a physical reality, not just a mathematical dream or
Speaker 2: a drawing on a chalkboard.
Speaker 3: Stats and his team have proven that quantum assisted optical
Speaker 3: interferometry is a reality. The path forward is clear.
Speaker 2: As material science improves the fabrication of the diamond cavities,
Speaker 2: pushing collection efficiencies closer to one hundred percent.
Speaker 3: As quantum engineering moves from single defects to highly moultiplex
Speaker 3: arrays of sea bulls centers operating in parallel, the rate
Speaker 3: of entanglement generation will scale exponentially.
Speaker 2: It will go from millihertz to hurtz to kill ahertz,
Speaker 2: and as that efficiency scales, this approach will eventually enable
Speaker 2: a totally new class of quantum enhanced imaging arrays.
Speaker 3: We will be able to stretch optical baselines from one
Speaker 3: point five to five kilometers, to fifteen kilometers, and eventually
Speaker 3: to continent spanning scales.
Speaker 2: And the researchers themselves are looking even further ahead because
Speaker 2: the implications of this core technology are not restricted to
Speaker 2: just building bigger telescopes to look at black holes.
Speaker 3: Once you perfect this specific hardware architecture, once you can
Speaker 3: faithfully catch, store, and process the delicate phase of single
Speaker 3: visible photons over vast distances using quantum entanglement, you are
Speaker 3: unlocking the fundamental infrastructure for an entirely different field.
Speaker 2: Indeed, you're unlocking the physical foundation for the future of
Speaker 2: deep space quantum communication.
Speaker 3: Consider the challenges of space exploration over the next century.
Speaker 3: If humanity is going to send autonomous probes to the
Speaker 3: outer Solar System, or eventually launch light sale probes to
Speaker 3: neighboring star systems like Alphacentry. The communication link back to
Speaker 3: Earth will be operating under the exact same extreme constraints
Speaker 3: as optical astronomy.
Speaker 2: A laser pulse sent from Alphacentaury will spread out and
Speaker 2: attenuate so severely over four light years that by the
Speaker 2: time it reaches Earth, we will not be receiving a robust,
Speaker 2: classical beam of light.
Speaker 3: We will be receiving an incredibly weak stream of single
Speaker 3: isolated photons.
Speaker 2: The exact same diamond quantum memories, the exact same non
Speaker 2: local heralding, and the exact same entanglement protocols that will
Speaker 2: let us computationally combine the light of a distant exoplanet
Speaker 2: will be the exact same tools that allow us to
Speaker 2: receive and decrypt a clean, noise free, highly secured data
Speaker 2: stream from a probe billions of miles away.
Speaker 3: It is a dual use technology of the highest order,
Speaker 3: bridging aftrophysics and quantum telecommunications.
Speaker 2: I want to leave you with one final profound thought, Tomlover.
Speaker 2: As you process the sheer density of the physics we
Speaker 2: have discussed. When we look up at the night sky,
Speaker 2: we are traditionally trained to think big. We admire the massive,
Speaker 2: brute force engineering of modern astronomy. We build colossal concrete
Speaker 2: observatories on the peaks of dormant volcanoes. We launch school
Speaker 2: bus sized, multi billion dollar satellites with intricately folded beryllium
Speaker 2: mirrors into orbit. We grind and polish glass optics that
Speaker 2: weigh literal tons, striving to capture just a fraction more light.
Speaker 2: But the reality that this Harvard breakthrough reveals is fundamentally different.
Speaker 2: The grandest most massive structures in the entire universe, the
Speaker 2: violent swirling accretion disks of supermassive black holes, the colliding
Speaker 2: hyperluminous hearts of distant ancient galaxies, the very edges of
Speaker 2: deep space. They will ultimately be brought into sharpest furpos
Speaker 2: not by building increasingly heavier, more gargantuan physical mirrors. They
Speaker 2: will be revealed to us by mastering the absolute smallest,
Speaker 2: most invisible, most ethereal properties of nature. The future of
Speaker 2: understanding the macrocosm entirely depends on our ability to precisely
Speaker 2: control the microscope quirts of a single electron spinning perfectly
Speaker 2: inside a deliberately flawed, microscopic speck of diamond s.