# International Year of Quantum Science and Technology: our celebrations begin with a look at quantum networks and sensors

An episode of [Physics World Weekly Podcast](https://invisiblenetwork.ai/podcast/1400686733), 2 Jan 2025, 37 min.

Audio: https://media.blubrry.com/physicsworldweeklypodcast/content.blubrry.com/physicsworldweeklypodcast/PWWeekly2January2025MeteAtature.mp3

This podcast features quantum physicist Mete Atatüre of the University of Cambridge

## Transcript

[0:07] Hello, and welcome to the 1st Physics World
[0:11] weekly podcast of 2025.
[0:14] I'm Hamish Johnston.
[0:16] The United Nations has proclaimed
[0:18] that 2025
[0:20] is the international year of Quantum Science and
[0:24] Technology,
[0:25] or IYQ
[0:26] for short.
[0:28] This year was chosen because it marks the
[0:31] centenary
[0:32] of the initial development
[0:33] of quantum mechanics
[0:35] by Werner Heisenberg.
[0:38] In the early days, the quantum world perplexed
[0:41] the physics community
[0:43] with its numerous
[0:44] paradoxes.
[0:46] A century later, and physicists are much more
[0:49] comfortable
[0:50] in the quantum world.
[0:52] And it's not just physicists.
[0:54] Over the past decade or so, a burgeoning
[0:58] quantum technology
[0:59] business sector has emerged,
[1:02] and engineers,
[1:04] financiers,
[1:05] and others
[1:06] are entering the quantum realm.
[1:09] To kick off IYQ,
[1:12] this podcast features the Turkish physicist
[1:15] Mete
[1:16] Atatore,
[1:17] who is at the UK's
[1:19] University of Cambridge.
[1:21] In a wide ranging conversation
[1:23] with Physics World's Katherine Skipper,
[1:26] Atatore talks about Quantour,
[1:29] I y q's
[1:31] equivalent to the Olympic torch,
[1:34] and he also talks about his research
[1:36] into quantum sensors
[1:38] and quantum networks.
[1:47] Hello. Welcome to the Physics World Podcast. I'm
[1:49] Katherine Schipper.
[1:51] So last summer was the Paris Olympics, which
[1:54] was
[1:55] marked by the ceremonial relay of the Olympic
[1:57] torch. Now we have to wait another 4
[1:59] years for the next Olympics, but 2025
[2:03] is the international year of quantum. And that
[2:05] too will be marked by
[2:06] the relay of,
[2:08] of a of a light source. But because
[2:10] it's the International Year of Quantum, it's going
[2:12] to be a very, very, very small
[2:15] light source. It's going to be a single
[2:16] photon,
[2:18] emitter.
[2:19] It's called, Contour,
[2:22] and it is
[2:23] touring 12 quantum labs around Europe over the
[2:27] course of 12 months.
[2:29] And I am in Cambridge today,
[2:31] visiting Contour, the quantum light source, on its
[2:34] stopover in England.
[2:36] And I'm joined today in Cambridge by, Mette
[2:38] Asasier,
[2:40] who is,
[2:42] responsible for the light source while it's in
[2:43] England. He's the head of the Cavendish Laboratory
[2:46] in Cambridge
[2:48] and also the head of the
[2:50] quantum optical materials and systems group. He's also
[2:53] the one of the founders of the quantum
[2:56] networking startup, NuQuantum.
[2:57] So, Messi, thank you so much for joining
[2:59] me today. Thank you very much for hitting
[3:01] me.
[3:02] So first question, can you
[3:04] explain
[3:05] what Contour is about and why it's something
[3:06] you wanted to be involved with here in
[3:08] Cambridge?
[3:09] I like to start with the,
[3:12] the the Paris Olympics and the the Olympic
[3:13] torch. It is in a sense the quantum
[3:16] torch that's going around, Europe. We wanted to
[3:18] be part of it because,
[3:20] we are part of the European,
[3:23] endeavor
[3:24] to achieve,
[3:25] useful operational quantum technologies.
[3:28] And one way or another light,
[3:31] appears in most of these,
[3:34] strands of research that we're pursuing.
[3:36] So it was important that that that we
[3:38] bring that forward. They,
[3:41] we did have a year of light a
[3:43] few years back. We're going into a year
[3:45] of quantum. So it is natural that we
[3:47] have this this essential part, the optics, the
[3:50] photonics, but in the quantum realm, to be
[3:52] showcased across the Europe,
[3:54] for two reasons. 1, to bring forward, of
[3:56] course, its importance, but also to show that
[3:59] we do interact.
[4:00] We do form a scientific network,
[4:03] around the concept of quantum light,
[4:06] and how it can impact the various technologies
[4:08] that might come in the future. Yeah. So
[4:10] talking about the technologies, I think the International
[4:12] Year of Quantum
[4:13] and Quantar, I guess, is quite a nice
[4:16] opportunity
[4:16] to
[4:17] showcase
[4:19] to people who don't have, you know, a
[4:21] specialism in physics what quantum science and quantum
[4:24] technology is about. Do you think that, I
[4:26] guess, the general public and
[4:29] politicians who are making decisions about, you know,
[4:32] quantum technologies and quantum policy
[4:34] know enough about what quantum is and how
[4:37] it could impact them?
[4:39] It's very difficult to know enough of quantum
[4:41] given how
[4:43] counterintuitive
[4:44] it is.
[4:45] And I think partly we are also to
[4:47] blame as we start most of our descriptions
[4:50] of our work, quantum related work with spooky
[4:53] action at a distance or mind boggling or
[4:55] hard to grasp, hard to understand,
[4:58] completely outside our,
[5:00] conceptions of what world is and reality is.
[5:03] That doesn't particularly help in the direction of,
[5:07] making people aware of what it can do
[5:09] for you as a technology as opposed to
[5:11] very interesting science that you might want to,
[5:14] to study or understand.
[5:16] So I think what we need to do,
[5:17] especially in the year of quantum, is to
[5:19] have a a change of word, a change
[5:21] of style so that we focus less on
[5:24] the weirdness of quantum, but focus on what
[5:27] it can actually bring us. And this is
[5:28] how you can grab the attention of public,
[5:32] policy makers,
[5:33] and, and more most importantly, the young minds
[5:36] who, might go into this field with an
[5:38] intention to actually do something useful
[5:41] to tackling,
[5:42] challenges that, we might be facing going forward.
[5:45] Okay. So can you talk a bit about
[5:47] how that relates to your research? What are
[5:49] the
[5:50] quantum
[5:51] technologies that you're looking at? Mhmm. So within
[5:54] my research group,
[5:55] we have a very vibrant team,
[5:58] tackling multiple directions at the same time, that
[6:01] keeps me entertained. Of course, there's not just
[6:03] a one topic that I'm working with. I
[6:05] get to work with, small groups of of,
[6:09] brilliant scientists,
[6:10] on different directions. One of them is quantum
[6:13] sensing and the other one is quantum networks.
[6:15] So sensing and networks are 22 strands, let's
[6:18] say that,
[6:19] that our work tends to focus on.
[6:21] On the sensing side, we're trying to see
[6:24] if quantum properties
[6:26] of light matter interfaces,
[6:29] objects, small net of nanoscale objects,
[6:32] a single electron in some cases or a
[6:34] single nuclear spin buried inside a material in
[6:37] other cases. Could that and its interaction with
[6:40] light
[6:40] be useful
[6:42] to understand,
[6:44] how materials behave or how different phenomena in
[6:47] physics and sciences in general can emerge?
[6:51] And having that view at the, at the
[6:53] nanoscale, at the at the ultimate limits or
[6:55] ranges, operational ranges that we don't have access
[6:58] to at the moment. So that's one direction
[7:00] they're pursuing. As very interestingly, as science takes
[7:03] you,
[7:04] to unexpected places, we are also working with
[7:07] quantum sensors
[7:08] in life sciences. So we have we're looking
[7:10] into how we can incorporate quantum sensors, diamond
[7:13] based quantum sensors in particular,
[7:15] into,
[7:17] into cells, live cells to understand their operations
[7:20] or in larger
[7:22] living organisms like c elegans, for example,
[7:25] to see if we can learn more about
[7:27] their physical properties as they go through a
[7:29] life cycle. So
[7:31] as long as there's it's it's about the
[7:33] development of a technology
[7:35] with very, very well grounded,
[7:37] physics and quantum physics aspect of it is
[7:40] is what highlights the,
[7:41] the quantum sensing aspect of our work. The
[7:43] second strand of our research is on quantum
[7:46] networks.
[7:47] We're exploring
[7:49] all the way from basic science part of
[7:51] it, the understanding materials, novel materials that could
[7:54] be quite relevant for quantum networks going forward.
[7:57] They may not, the future technologies may not
[7:59] necessarily rely on silicon. So we're looking at
[8:01] other,
[8:02] platforms to see if there's any advantage if
[8:05] we look at the,
[8:06] these materials from their,
[8:08] devices that leverage their quantum properties.
[8:12] And we actually push this towards technology a
[8:14] bit more, and we're actually building
[8:16] a small scale networks, very primitive,
[8:18] 2 node, maybe if possible 3 node networks
[8:21] where we like to distribute not just information,
[8:24] but quantum information
[8:25] between these nodes. And we have the ability
[8:27] to actually store it at different nodes
[8:29] and use it when we need to use
[8:31] it. So in a way, you can think
[8:32] of it as quantum networks is there is
[8:34] a communication,
[8:36] concept,
[8:37] but it feeds very closely with, with quantum
[8:40] computing in a in a distributed quantum computing
[8:43] sense. So is the idea with quantum networks
[8:45] that it could one day replace,
[8:48] like, the fiber optic networks that we have
[8:50] now? It would actually not replace it. It
[8:52] would leverage the fiber optic networks. And that's
[8:54] the there's again the spirit of Contour.
[8:56] Ultimately, whether you work with,
[8:59] with intense lasers or light pulses or you
[9:01] operate at a single photon level, the medium
[9:04] that you'll transport your light, your, your information
[9:07] is going to be the same. It's going
[9:09] to be the fiber optic network. So that's
[9:10] why we think that it is actually feasible
[9:12] to implement quantum networks because we don't have
[9:15] to replace
[9:16] existing,
[9:17] infrastructure that we can almost leverage the existing
[9:19] infrastructure.
[9:20] Okay. So you're you're sending it across, again,
[9:22] across the fiber optic network, but
[9:25] you're looking at single photons. Right? So what's
[9:28] the challenge
[9:29] of taking,
[9:31] you know, taking the existing technology and
[9:34] adapting it so that we're looking at single
[9:36] coding information in single photons?
[9:39] The advantage that we have today on classical,
[9:42] communication is that,
[9:44] as photons are lost in an otherwise intense
[9:47] pulse, that carries some information, a bit 0
[9:50] or 1,
[9:52] is is the the the light intensity is
[9:54] diminished,
[9:55] throughout the propagation down a optical fiber,
[9:58] you can,
[9:59] at a different let's say, periodically, you can
[10:02] amplify that that signal and continue. The ones,
[10:05] the message, the information one stays 1, 0
[10:08] stays 0, and you proceed. And you go
[10:10] through a little amplification process,
[10:12] optical amplification.
[10:13] Now when it come down to a single
[10:15] photon, the photon is either there or it's
[10:17] lost. And then when it's lost, the old
[10:19] information is gone. So there's no there's no
[10:22] gradual decline of the, of the quality of
[10:24] the past that carries information. It's a discrete
[10:26] yes, no. We have the information travelling or
[10:29] we don't have it anymore. So, so then
[10:31] you might want to do,
[10:33] you you might want to do an amplification,
[10:37] that looks at takes care of this. And
[10:39] it turns out that quantum mechanically, we cannot
[10:41] do amplification of information. So
[10:44] what what we're able to do classically, we're
[10:46] actually unable to do quantum mechanically. And that
[10:49] is exactly the reason why single photon level
[10:52] quantum communication is fundamentally secure, that you cannot
[10:55] simply amplify and then tap into it by
[10:57] some, by another means.
[10:59] That that photon is the only thing that
[11:01] could carry that information.
[11:03] So,
[11:04] so this puts a limit to how far
[11:06] these networks can be distributed. So that's why
[11:08] you need to bring a node instead of
[11:10] an amplifier unit.
[11:12] You need to bring a quantum node, that
[11:14] is shortened or let's say,
[11:16] approximate enough that without significant photon loss, you
[11:20] can trust,
[11:21] transmit information from a to b. And then
[11:23] in the node, you store that information in
[11:26] something else. Something else that is not prone
[11:28] to loss like photons, but maybe the internal
[11:31] degrees of freedom of an ion, a trapped
[11:33] ion, or or a single atom, or, some
[11:36] defect in a material, for example, hexagon boron
[11:38] nitride or diamond.
[11:40] Okay. So that's something else you're looking at
[11:41] as well, isn't it? How to store
[11:43] information in in different materials.
[11:46] What
[11:47] are the requirements
[11:48] on a material or a system that makes
[11:51] it good at storing quantum information for,
[11:55] reasonable periods of time? That's a great question.
[11:57] I think this is the question we've been
[11:58] banging our heads,
[12:00] on for a long time now.
[12:03] There it it comes with the,
[12:05] dichotomy, actually. It should be isolated enough that
[12:08] it does not interact with the rest of
[12:10] the universe
[12:11] on its own, but it should be integrated
[12:13] enough
[12:14] to our universe so that I can have
[12:16] direct access to it readily and availability. Right?
[12:18] And and that's that's a contradiction almost. Right?
[12:21] Either something is well isolated from everything or
[12:24] it isn't.
[12:25] If it is not well isolated, it decoheres
[12:27] very quickly because
[12:29] as as much as I get to talk
[12:31] to this quantum defect, the qubit,
[12:33] the rest of the universe also continues to
[12:35] talk to, the qubit.
[12:38] So creating an environment
[12:40] where the the the qubit is isolated
[12:43] for most parts, except when we are actually
[12:46] interacting with this with this cubit. I think
[12:47] that will be the,
[12:49] the the
[12:51] the material of choice, the actual physical system
[12:53] of choice. And we do have this available
[12:55] actually. So hence, there is no,
[12:58] winning materials yet. There's no winning material platform.
[13:01] That's why we need to pursue multiple platforms.
[13:04] But the nice thing is that the community,
[13:07] being diverse in terms of which material platform
[13:10] they're they're studying or investigating,
[13:12] we do have a common language. So we
[13:14] do address a a variety of materials and
[13:17] devices and systems
[13:18] with common similar language, which helps build coherence
[13:21] across the community.
[13:23] Okay. So, actually, what's the the quantum quantum
[13:25] light source? What's that what's that made of?
[13:27] Sure. It's, semiconductor
[13:29] quantum dots. So these are small islands of
[13:31] semiconductors
[13:32] buried inside another semiconductor. Their band gap is
[13:35] different of the 2 materials,
[13:37] types. So it's a material based confinement
[13:39] of, these pairs of, excitons and electron and
[13:43] a whole pair, that we can store inside
[13:45] these little islands.
[13:47] And then the electron and hole, they act
[13:49] like almost like a little atom on their
[13:51] own. Like the hydrogen atom is a nucleus,
[13:53] a proton and electron around it. You can
[13:56] think, it's it's kind of the same. You
[13:58] have an electron and a positively charged hole,
[14:01] and the 2 basically go around each other.
[14:03] That's one exciton is our quasi particle, and
[14:06] this has certain finite lifetime,
[14:08] usually on a 4 nanosecond
[14:10] or something, so extremely fast. But when they,
[14:13] recombine the electron and the hole combine, the
[14:15] total charge is 0. Something happens. The total
[14:18] energy goes somewhere and that somewhere is into
[14:21] light. So a single photon is generated per
[14:23] exciton that was stored inside a quantum dot.
[14:26] So what we do is periodically we create
[14:28] an exciton, 1 and only one exciton inside
[14:31] one of these quantum dots.
[14:32] And then they combine, recombine, and then emit
[14:35] a photon, but one and only one photon.
[14:38] And that's why it's a high purity single
[14:40] photon source.
[14:41] And the photon then instead of being emitted
[14:44] in all random directions, it is funnelled by
[14:46] a
[14:47] a a nanophotonic structure,
[14:49] called the bull's eye structures we call it.
[14:51] It funnels it into efficiently into a a
[14:54] a a basically a fiber optic channel, and
[14:56] then we use the single photon stream,
[14:59] to do communication by encoding information off to
[15:01] the photons. Okay. And so
[15:04] you you spoke about, you know, re you're
[15:06] reusing
[15:07] fiber optic,
[15:09] like, infrastructure that we already have, and then
[15:11] you're using materials that have very well defined
[15:15] band
[15:16] band caps.
[15:17] And so and and emit photons at very
[15:21] well defined wavelengths. And I know that in
[15:23] fiber optics, there are
[15:25] certain
[15:26] frequencies that are that are used. So it's
[15:28] 15
[15:30] 1500 and 1550 nanometers, right, is the, like,
[15:33] the the standard wavelength
[15:35] of those optics.
[15:36] And so how do you go about
[15:39] bridging that
[15:41] that, I guess,
[15:43] divide between the materials that you have to
[15:45] use because they have great quantum properties and
[15:47] the wavelengths that you want to use to
[15:49] reuse fiber optic networks?
[15:51] Fantastic question. This is,
[15:53] it's it's always a challenge because that's why
[15:56] there is no winning materials platform yet. If
[15:58] you're focusing on 1550, there are a couple
[16:00] of,
[16:01] platforms we could use,
[16:03] but they bring their own challenges as to
[16:05] why they're not necessarily the obvious,
[16:09] winners.
[16:10] And then we work with other systems like
[16:12] these, semiconductor quantum dots. They're more mature technology.
[16:15] They've been around for a few decades now.
[16:17] So we've really learned how to make them
[16:19] pristine and good quality. We learn how to
[16:21] mold the light that comes out of them.
[16:23] So they are very advantageous on the performance
[16:26] of the photon side, but you're right. They
[16:28] don't match the exactly the wavelength of, 1550
[16:31] of the preferred, emission. So there are 2
[16:33] ways you can cheat. Right? 1, you, look
[16:35] for the next material and that's part of,
[16:38] scientific research that we do. We, we we
[16:40] don't limit ourselves to a very particular class
[16:43] of material platforms.
[16:44] We go bold. We go, out there and
[16:46] look for the craziest,
[16:48] materials you can think of, including diamond, including
[16:50] let single monolayer of of, some, semiconductor,
[16:55] 2 d material.
[16:57] And we're we're finding these. Right? So that's,
[16:59] that's one direction,
[17:01] to pursue.
[17:02] That's the exploratory,
[17:04] part. The second,
[17:05] cheating, of course, is I call this cheating,
[17:07] but these are scientific progress, let's call it,
[17:10] is, is frequency conversion. So we have this
[17:12] fantastic tool in our hands called nonlinear optics.
[17:15] That is where if you have the right
[17:17] medium, a particular, again, material platform
[17:20] that brings not linear optics, but opportunity for
[17:23] nonlinear optics, opportunities for nonlinearities
[17:26] between photons so they can interact and exchange
[17:28] their frequency. Then you can take a 900
[17:31] nanometer,
[17:32] wavelength light and convert that to 1550
[17:35] with the help of another,
[17:37] light source. So that appear for what we
[17:39] call a three way mixing or a four
[17:41] way mixing,
[17:42] geometry. So you can almost, you can cook
[17:44] up the wavelength you want provided you get
[17:47] the photons
[17:48] that normally don't interact with anything to actually
[17:50] directly and strongly interact inside a very special
[17:53] material called chi 3 or chi 2 materials
[17:56] or nonlinear materials. So,
[17:58] this has been demonstrated. So in in a
[18:00] sense, while we lose a bit the efficiency,
[18:03] because not necessarily a 100% efficient,
[18:05] you do have a chance to take anything
[18:07] you want out there that works really well
[18:09] and convert that to the common frequency
[18:11] of a metropolitan network.
[18:14] Okay. And when when you're actually thinking about
[18:16] building
[18:18] these these systems so you spoke about diamond,
[18:20] and you spoke about hexagonal boron nitride,
[18:23] where you're actually you're using cubits that like,
[18:26] lattice defects. So, like, almost like like, holes
[18:28] almost or defects in these crystals.
[18:32] And then you also can use, as you
[18:35] spoke about, semiconductor quantum dots.
[18:38] How
[18:39] much control how how much control do you
[18:42] have when you're actually fabricating these systems over
[18:45] where the cubits are? Mhmm. It's,
[18:49] if if you're down to a single atom
[18:50] level, you have to have that precision to
[18:53] actually say,
[18:54] you, atom, move away and then you, atom,
[18:56] go back in there. So that's very difficult.
[18:59] And we don't have that technology except in
[19:01] a very rare case of,
[19:03] of of scanning tunneling microscope,
[19:06] approaches
[19:07] to constructing
[19:08] a particular device at the atomic level.
[19:13] Professor Simmons in Australia is doing fantastic work
[19:15] on this.
[19:16] She's literally putting atom by atom,
[19:19] construction or engineering of a quantum device,
[19:22] that is that small. It's only a few
[19:24] atoms,
[19:25] wide. But of course,
[19:27] from one side is a big achievement. From
[19:29] another side, this would be quite challenging to
[19:31] scale up, to make larger devices or bigger
[19:34] devices.
[19:36] What we are doing with the defect based
[19:38] systems is,
[19:40] that we rely on the fact that optically
[19:42] active defects,
[19:43] they'll relevant footprint is actually not the size
[19:46] of a single atom, but the size of
[19:47] your wavelength.
[19:48] Because the the atoms have 2 different length
[19:50] scales. 1 is their physical length scale within
[19:53] a crystal, within a lattice.
[19:55] That's like
[19:56] of the order of 1 lattice site.
[19:58] But if they're optically active,
[20:00] then their optical cross section is what we
[20:02] call is their physical size that really matters.
[20:05] And that's off order micron or half a
[20:06] micron. So that means
[20:09] it gives us a chance to not be
[20:10] precise exactly which of the lattice sites our
[20:13] defects sits that optically engages with, with the
[20:16] rest of the world. So that gives us
[20:18] a chance to realize everything we want without
[20:20] having to worry at that length scale of
[20:22] of, a nanometer or or sub nanometer.
[20:25] That's one thing. The advantage for coming back
[20:28] to Contour,
[20:29] it's our this, it's quant quantum torch.
[20:33] The advantage there is that it's actually bulky.
[20:35] It's not a single atomic,
[20:37] system. It's not a single defect based system.
[20:40] It actually is each of these quantum dots,
[20:42] despite the name dot,
[20:44] is actually about 50 to a 100000 atoms
[20:48] cluster.
[20:49] So if you go back, 2 years, the
[20:51] Nobel Prize in chemistry was for colloidal
[20:54] quantum dots. And these were small,
[20:56] balls of atoms combined into,
[20:59] to form a particular material with discrete energy
[21:01] levels, hence the same concept of,
[21:04] clear single photons. In the same spirit, these
[21:07] are only they're they're embedded inside another semiconductor,
[21:10] but otherwise, they are large bulky systems, and
[21:12] we know where to put them. So we
[21:14] can actually say,
[21:16] by by pre processing of the of the,
[21:19] surface that we're going to grow the quantum
[21:21] dots, we can actually tell them where to
[21:23] be with very high precision of of order
[21:25] nanometer,
[21:26] few nanometer
[21:27] precision for these rather,
[21:29] large systems. So it does give us this
[21:31] chance to say,
[21:32] to distribute a large scale,
[21:35] let's say, architecture of where these,
[21:38] special, systems will sit. Okay. And now I
[21:41] wanna talk a little bit about quantum as
[21:42] a
[21:43] technology and as a a commercial,
[21:46] you know, opportunity.
[21:48] I think that's
[21:50] I mean, it the if the International Year
[21:52] of Quantum in 2025,
[21:54] because it's a 100 years since
[21:57] when Heisenberg
[21:58] went to Helgeland to cure his hay fever
[22:01] and wrote down the matrix formalism of of
[22:03] quantum mechanics. But
[22:06] I think it's also been been chosen
[22:09] because quantum has kind of gone mainstream over
[22:11] the last couple of years. And I'm interested
[22:13] to know from your perspective, how long has
[22:15] it felt like this is a
[22:19] a part of physics that people are really
[22:21] seriously trying to turn into
[22:23] technology and commercialize?
[22:26] I think the the change of language is
[22:28] a good indicator for this as as,
[22:31] we discussed before.
[22:32] We were focusing on how weird it is.
[22:35] And we're we we thought experiments,
[22:38] real experiments in the lab were
[22:40] mainly to see if quantum mechanics concepts, the
[22:43] philosophy of quantum mechanics, the foundations of quantum
[22:45] mechanics is in in
[22:47] fact, is it valid or not. Right? So
[22:49] that was the starting point for all these.
[22:51] Now if you go back even further, the
[22:53] starting point for quantum physics was, of course,
[22:56] we'll never measure a single electron. Of course,
[22:58] we'll never be able to see this effect.
[23:00] But if we did, how would the experimental
[23:02] result look like? So it was all like
[23:04] get Duncan experiment, thought experiment. So if so
[23:07] they were in a stage 3 now. The
[23:09] get Duncan experiment has moved into real lab
[23:11] experiments of demonstrating
[23:13] foundations of quantum physics. And now we're in
[23:15] the era of actually turn them into real
[23:18] life feasible operations. Now there's as with most
[23:21] exciting emerging, technologies or potentially emerging technologies, there
[23:25] will always be hype around. And you'll see
[23:27] you'll see, news pieces where they'll say,
[23:30] headline will say something like quantum of quantum
[23:33] computing will cure cancer.
[23:35] And maybe one day it will, but, but
[23:37] we're not at this stage yet, and that's
[23:38] not the main reason why we put it
[23:40] all together. I think the what sets quantum
[23:42] technologies unique is that our one leg is
[23:45] still parked firmly at basic sciences and development
[23:48] of that interface of new concepts, new phenomenon,
[23:53] and new material systems
[23:55] that brings together computer scientists,
[23:57] physicists, and material scientists, chemist in some cases,
[24:01] so that we can all inter this in
[24:02] an interdisciplinary way, look at what beneficial
[24:06] directions we can push when it comes to,
[24:08] technology transfer.
[24:10] Okay. Thinking about quantum
[24:12] network
[24:13] speakers, I know that's one of that's the
[24:15] thing that new quantum
[24:17] is about right about quantum networking. What are
[24:19] the big challenges,
[24:21] outstanding
[24:23] experimental and theoretical challenges to actually
[24:25] bringing that technology
[24:27] to
[24:28] scaling it up and
[24:31] rolling it out on a large scale.
[24:33] Given that the the whole field,
[24:37] emerged, the experimental side of it, the practical
[24:38] side of it emerged
[24:40] in,
[24:41] physics based research labs
[24:43] with focus on the the the singular unit,
[24:45] the isolated
[24:46] quantum bit.
[24:48] We have a we know our quantum bits
[24:51] really well. We know how to control it.
[24:53] We've improved our techniques,
[24:55] including our material quality.
[24:57] What hasn't been developing so far? What is
[25:00] what is the what what's the what's the
[25:02] challenge that we're facing right now is the
[25:04] interconnects.
[25:05] It's connecting them together. And that's the scalability
[25:07] that you refer to as well. How to
[25:09] make 1,000 of these? Actually, it is fairly
[25:11] easy to make 1,000 of the same good
[25:12] qubit.
[25:13] It's not the number that stops us. It
[25:15] is linking them so that you benefit. You
[25:17] don't end up with 1,000 independent qubits, but
[25:20] rather a 1,000 qubit system.
[25:22] And that
[25:24] system, requires their their interaction exchange of,
[25:27] interaction and information,
[25:29] some sort of a network you need to
[25:31] put together regardless of whether it's a quantum
[25:33] computing, monolithic quantum computing you're after, or a
[25:36] a distributed
[25:38] metropolitan size quantum network that you're after, or
[25:41] quantum sensors where we need to make sure
[25:43] that we have direct links to them. Ultimately,
[25:45] the
[25:46] interconnect is going to be the name of
[25:48] the game. So you're talking about entangling?
[25:50] That's right. So how to sustain quantumness
[25:54] distributed over multiple cubits, multiple nodes,
[25:58] and and ensuring that that is operational, that
[26:00] we can do something with it. And that's
[26:02] that's going to be the challenge. The biggest,
[26:05] challenge in front of us across different platforms,
[26:07] across different approaches, and even technologies that we're
[26:10] aiming for is how to get that,
[26:13] link
[26:14] preferably with light, how to get get that
[26:16] link to be efficient and quantum preserving, let's
[26:19] say.
[26:20] Okay. And what sort of avenues are you
[26:22] looking at to try and to try and
[26:24] get there? It's very interesting. We're looking at
[26:26] classical avenues. We're looking at ways to make
[26:28] sure that we are not overlooking anything that
[26:31] has been developed on the classical conventional side
[26:34] of photonics and materials,
[26:36] and engineering and systems packaging. All of those
[26:39] which physicists
[26:40] arguably are not necessarily most accustomed to. All
[26:43] of that is now coming together to say,
[26:45] is there a better way that we could
[26:47] do this
[26:48] rather than a physicist hat, but rather an
[26:50] engineer hat or or a systems hat? Yeah.
[26:52] I think I've been I was sort of
[26:54] surprised to
[26:55] learn more about us and find that there's
[26:57] a big
[26:58] need for
[27:00] radio frequency engineers because it's still, you know
[27:03] even though we're using the the quantum physics,
[27:05] you're still using, you know, that that radio
[27:07] frequency technology to interface with the quantum system.
[27:10] Absolutely. It's it's a fantastic field to be
[27:12] in because you can be operating,
[27:15] at the far end of the technology delivery
[27:17] where you're building some architecture of quantum computers
[27:20] with multi qubit systems. You're doing some operations,
[27:22] and you identify
[27:24] what limits you. And you you realize that
[27:26] what limits you is a material property, and
[27:26] it goes all the way back to the,
[27:26] blackboard, the the drawing board. And then
[27:27] and it goes all the way back to
[27:29] the, blackboard, the the drawing board. And then
[27:32] you start, changing the material that you're using
[27:34] in your devices to build up that whole
[27:36] architecture, and you find out things have improved.
[27:38] So if you don't have that link, if
[27:40] you don't have that conversation, the,
[27:43] you know, bumping shoulders in the hallway with
[27:45] a material scientist and a physicist and a
[27:47] computer scientist, that communication,
[27:50] you're not going to be able to create
[27:51] this, the cycling loop of improvement. So let's
[27:54] think of it as a it's not really
[27:56] a cycle loop. It's more like a spiral
[27:58] upwards that as we tap different aspects, we
[28:01] solve a challenge that's relevant, to certain expertise,
[28:04] and then we go forward with it. Okay.
[28:07] And
[28:08] I was interested to hear the way you
[28:10] spoke about the the quantum weirdness and how
[28:12] that has shifted. Because
[28:15] I think
[28:16] if we are thinking about it being the
[28:18] international quantum and looking back a 100 years
[28:21] to the early days of quantum mechanics,
[28:23] I think it is
[28:25] easy to, if you're not an expert, look
[28:27] at all the stuff that's been done or
[28:29] been that is being done with quantum technologies
[28:31] and think that those fundamental questions that were
[28:34] being asked a 100 years ago have been
[28:35] resolved, and we're just trying to work at
[28:37] how to,
[28:38] you know, commercialize,
[28:40] you know, the the theory, basically. But, actually,
[28:42] all of the questions about, you know, what
[28:45] quantum mechanics means and how it should interpret
[28:47] it and what it means for understanding of
[28:49] reality, a lot of that is I mean,
[28:51] all of that really is still up in
[28:53] the air, and it's still being debated.
[28:56] You know, the the fact that or the
[28:58] the mainstream interpretation of quantum mechanics that,
[29:02] you know, the state of
[29:05] an object is is not in a definite
[29:07] state until you measure it. Is that
[29:10] something that you that sort of
[29:12] uncomfortable weirdness? Because because it is. It sort
[29:15] of defies it defies human comprehension, I think,
[29:18] in a way, when you really think about
[29:19] it. Is that something that you think about
[29:20] in your work and see yourself as
[29:23] looking into?
[29:24] Absolutely. It it it is again what sets,
[29:27] this area,
[29:29] is is a bit unique. We're more used
[29:32] to the production line concept. Right? They you
[29:34] start from the very beginning, the concept, and
[29:36] then you you make a prototype, you you
[29:38] you develop it and it continues. So it's
[29:40] almost like, if if I talk in TRL
[29:42] language, you start from TRL 1 and go
[29:44] on to the the final product and you
[29:46] and and it's it's now in the system.
[29:49] Quantum mechanics is not like that. Quantum mechanics
[29:51] delivers
[29:52] advantages in certain areas, and we're pushing that
[29:54] forward as a technology. And at the same
[29:56] time, it doesn't include as a theory, gravity.
[29:59] So I don't know what to do. Right?
[30:00] At the same time, I'm fundamentally
[30:02] limited with what I have, and I know
[30:04] that it's not complete.
[30:06] But
[30:07] in in in in the phase space that
[30:08] quantum physics covers, there are safe areas that
[30:11] we can tap into to convert them into
[30:13] technology without necessarily understanding its full scope and
[30:17] how it will have to be transformed in
[30:18] the future to be an overarching theory beyond
[30:22] everything else that that, harbors all phenomena that
[30:24] we see today. But, yeah, it's,
[30:27] even today, the technological
[30:29] push, say for example, space. Right? Space is
[30:31] the next frontier for us.
[30:33] We're talking about secure communications in space.
[30:37] One reason, of course, you could say is
[30:38] purely technological and applications. But another reason is
[30:41] to say,
[30:42] does the the concept of entanglement,
[30:45] long distance entanglement, and the the scoop spooky
[30:47] action in the distance,
[30:49] idea of,
[30:50] mention of, Einstein,
[30:52] does that hold over long distances? That's a
[30:54] question to ask because on short distance is
[30:57] fine, but long enough distances where relativity kicks
[30:59] in, special or general relativity kicks in, do
[31:02] we actually see an effect of this? Does
[31:04] gravity actually take part in determining what happens
[31:07] to the entanglement that was distributed?
[31:09] Quantum theory
[31:11] says that there's no mention of the distance
[31:13] d between 2 objects.
[31:15] Reality
[31:16] needs to be checked. So,
[31:18] some people are designing this very technologically advanced
[31:21] experiments
[31:22] to actually test entanglement over very long distances,
[31:26] you know, space,
[31:28] space like distance. So, again, it goes both
[31:30] ways.
[31:31] We will develop the theory more, hopefully,
[31:34] and it it there is room to go,
[31:36] but it shouldn't necessarily stop us using the
[31:39] parts we know are working well. Okay. Yeah.
[31:41] It is pretty amazing that a lot of
[31:43] the
[31:44] a lot of this quantum technology is based
[31:47] on theory that when it was first sort
[31:49] of conceived,
[31:51] the the the the understanding was, well, this
[31:53] is this is cool, but we'll never ever
[31:54] be able to measure it or test it.
[31:56] You know, we can't we can't get enough
[31:57] control over,
[31:59] you know, over quantum objects. And now we
[32:01] kind of we can just do it. I
[32:02] mean, I've, you know, been downstairs, and I've
[32:04] seen the lab where, you know, you're just
[32:06] you're just doing that as your everyday job.
[32:07] It's really cool.
[32:10] So just to sort of round off,
[32:12] we've talked about sort of the the present
[32:14] of of quantum
[32:16] technologies and the past of quantum theory. What
[32:18] are your hopes for the next couple of
[32:20] years of quantum and quantum technologies?
[32:24] I think next couple of years 2 years
[32:26] is is is a short time time frame,
[32:28] of course.
[32:29] The the 2 years is within a PhD.
[32:31] So this would be difficult to
[32:34] to expect big leaps within 2 years. But,
[32:36] of course, leaps come in effectively instantaneously,
[32:39] having leveraged the years years decades in some
[32:42] cases of research. And then you get the
[32:43] big leap. So I expect,
[32:46] clear progress in
[32:47] scaling, when it comes to, quantum computing activities.
[32:51] I expect the first,
[32:53] well, we do have a a 3 node
[32:54] quantum network in Europe, and it's diamond based,
[32:57] interestingly.
[32:58] It's located in the Netherlands. I do expect,
[33:02] similar quantum networks to actually be commissioned and
[33:05] operational,
[33:06] in many other places. So this is around
[33:08] this this time. And it seems like in
[33:10] almost all of these attempts at the moment,
[33:13] diamond seems to be a material of choice,
[33:15] which we wouldn't have guessed,
[33:17] 20 years ago, for example.
[33:19] So I can see again, we'll be more
[33:21] in the in line of translation towards bit
[33:24] more operationally
[33:26] sensible, operationally interesting,
[33:28] modes of what we have, already. But of
[33:30] course breakthroughs happen because,
[33:33] an idea comes when you're at the unexpected
[33:36] talk at the, you know,
[33:39] annual conference, for example. And,
[33:42] the the progress is so fast now, as
[33:44] opposed to many, many decades ago, that translation
[33:47] of an idea, a new concept that comes
[33:49] in to realizing it as proof of principle
[33:52] is actually can be quite fast given all
[33:55] the all the experience that we managed to
[33:57] put together in this interdisciplinary,
[33:59] community that we built over the years. Okay.
[34:01] So it sounds like you're open to surprises
[34:03] in the next couple of weeks. Okay. Well,
[34:05] thank you so much for for joining me
[34:08] today. That was Messe Assessure.
[34:11] And, yeah, thank you very much for for
[34:12] speaking with me. It was great to talk.
[34:14] It was a great pleasure. Thank you for,
[34:15] having me.
[34:23] That was the University of Cambridge's
[34:25] Mettetatore
[34:27] in conversation
[34:28] with Physics World's Katherine Schipper.
[34:31] Stay tuned to the Physics World website
[34:34] for lots more quantum science and technology
[34:38] coverage this year.
[34:40] A good place to start is Bob Kreese's
[34:42] feature article that looks back on the summer
[34:45] of 1925,
[34:48] when the allergy prone
[34:50] Werner Heisenberg
[34:52] traveled to the tiny
[34:54] North Sea island of Helgoland
[34:57] for a pollen free holiday.
[35:00] It was there that the 23 year old
[35:03] formulated
[35:04] matrix mechanics,
[35:06] which was the first consistent
[35:08] mathematical
[35:09] formulation
[35:10] of quantum physics.
[35:12] The article sets the scene on the windswept
[35:15] island
[35:16] and ponders what was going through Heisinsberg's
[35:20] mind as he had his quantum revelation.
[35:24] And it also explains how his ideas have
[35:27] changed
[35:28] physics forever.
[35:30] Helgoland
[35:31] will be hosting a workshop
[35:33] in June of this year to celebrate the
[35:35] birth of quantum physics.
[35:38] And Kries also profiles
[35:40] some of the high profile
[35:42] scientists
[35:43] who will be there.
[35:45] You can find that article on the Physics
[35:47] World website.
[35:49] Just look for the headline
[35:51] return to Helgoland
[35:53] celebrating
[35:54] 100 years of quantum mechanics.
[35:58] I'm afraid that's all the time we have
[36:00] for this week's podcast.
[36:01] Thanks to Mette Atatore
[36:04] and Katherine Skipper for a fascinating
[36:07] conversation.
[36:08] And thanks to our producer Fred Iles.
[36:11] This podcast returns next week, but until then,
[36:14] we wish you a happy
[36:17] international year of quantum science and technology.

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