In the past three decades astronomers have discovered more than 6000 exoplanets – planets that orbit stars other than the Sun. Many of these exoplanets are very unlike the eight planets of the solar system, making it clear that the cosmos contains a rich and varied array of alien worlds.

Weird and wonderful planets are also firmly entrenched in the world of science fiction, and the interplay between imagined and real planets is explored in the new book Amazing Worlds of Science Fiction and Science Fact. Its author Keith Cooper is my guest in this episode of the Physics World Weekly podcast and our conversation ranges from the amazing science of “hot Jupiter” exoplanets to how the plot of a popular Star Trek episode could inform our understanding of how life could exist on distant exoplanets.

• Keith Cooper has written a three-part feature article about the nature of dark matter for Physics World. The first instalment is “Cosmic combat: delving into the battle between dark matter and modified gravity“

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It is Peer Review Week and the theme for 2025 is “Rethinking Peer Review in the AI Era”. This is not surprising given the rapid rise in the use and capabilities of artificial intelligence. However, views on AI are deeply polarized for reasons that span its legality, efficacy and even its morality.

A recent survey done by IOP Publishing – the scientific publisher that brings you Physics World – reveals that physicists who do peer review are polarized regarding whether AI should be used in the process.

IOPP’s Laura Feetham-Walker is lead author of AI and Peer Review 2025, which describes the survey and analyses its results. She joins me in this episode of the Physics World Weekly podcast in a conversation that explores reviewers’ perceptions of AI and their views of how it should, or shouldn’t, be used in peer review.

The post Peer review in the age of artificial intelligence appeared first on Physics World.

“Imagine the day the aliens arrive.” So begins Do Aliens Speak Physics? by the US particle physicist Daniel Whiteson and the cartoonist and author Andy Warner. From that starting point, if you believe the plots of many works of science fiction, it wouldn’t be long before we’re communicating with emissaries of an extraterrestrial civilization. Quickly, we’d be marvelling at their advanced science and technology.

But is this a reasonable assumption? Would we really be able to communicate with aliens? Even if we could, would their way of doing science have any meaning to us? What if an advanced alien civilization had no science at all? These are some of the questions tackled by Whiteson and Warner in their entertaining and thought-provoking book.

While Do Aliens Speak Physics? focuses on the possible differences between human and alien science, it made me think about what science means to humans – and the role of science in our civilization. Indeed, when I spoke to Whiteson for a future episode of the Physics World Weekly podcast, he told me that his original plan for the book was to examine if physics is universal or shaped by human perspective.

But when he pitched the idea to his teenage son, Whiteson realized that approach was a bit boring and decided to spice things up using an alien landing. At the heart of the book is a new equation for estimating the number of alien civilizations that scientists could potentially communicate with – ideally, when the aliens arrive on Earth.

The authors aren’t the first people to do such a calculation. In 1961 the US astrophysicist Frank Drake famously did so by estimating how many habitable planets might exist and whether they could harbour life that’s evolved so far that it could communicate with us. Whiteson and Warner’s “extended Drake equation” adds four extra terms related to alien science.

The first is the probability that a civilization has developed science. The second is the likelihood that we would be able to communicate with the civilization, with the third being the probability that an alien civilization would ask scientific questions that are meaningful to us. The final term is whether human science would benefit from the answers to those questions.

One of Whiteson and Warner’s more interesting ideas is that aliens could perceive science and technology in very different ways to us. After all, an alien civilization could be completely focused on developing technology and not be at all interested in the underlying science. Technology without science might seem deeply foreign to us today, but for most of history humans have focused on how things work – not why.

Blacksmiths of the past, for example, developed impressive swords and other metal implements without any understanding of how the materials they worked with behaved at a microscopic level. So perhaps our alien visitors will come from a planet of blacksmiths rather than materials scientists.

Mind you, communicating with alien scientists could be a massive challenge given that we do so mainly using sound and visual symbols, whereas an alien might use smells or subatomic particles to get their point across. As the authors point out, it’s difficult even translating the Danish/Norwegian word hygge into English, despite the concept’s apparent popularity in the English-speaking world. Imagine how much harder things would be if we used a different form of communication altogether.

But could physics function as a kind of Rosetta Stone, offering a universal way of translating one language into another? We could then get the aliens to explain various physical processes – such as how a mass falls under the influence of gravity – and compare their reasoning to our understanding of the same phenomena.

Of course, an alien scientist’s questions might depend on how they perceive the universe. In a chapter titled “Can aliens taste electrons?”, the authors explore what might happen if aliens were so small that they experience quantum effects such as entanglement in their daily lives. What if an organism were so big that it feels the gravitational tug of dark matter? Or what if an intelligent alien could exist in an ultracold environment where everything moves so slowly that their perception of physics is completely different to ours?

The final term in the authors’ extended Drake equation looks at whether the answers to the questions of alien physics would be meaningful to humans. We naturally assume there are deep truths about nature that can be explored using experimental and mathematical tools. But what if there are no deep truths out there – and what if our alien friends are already aware of that fact?

When Drake proposed his equation, humans did not know of any planets beyond the solar system. Today, however, we have discovered nearly 6000 such exoplanets, and it is possible that there are billions of habitable, Earth-like exoplanets in the Milky Way. So it does not seem at all fanciful that we could soon be communicating with an alien civilization.

But when I asked Whiteson if he’s worried that visiting aliens could be hostile towards humans, he said he hoped for a “peaceful” visit. In fact, Whiteson is unable to think of a good reason why an advanced civilization would be hostile to Earth – pointing out that there is probably nothing of material value here for them. Fingers crossed, any visit will be driven by curiosity, peace and goodwill.

• 4 November 2025 WW Norton & Company 272pp £23.00 hb; £21.84 ebook

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The concept of cause and effect plays an important role in both our everyday lives, and in physics. If you set a ball down in front of a window and kick it hard, a split-second later the ball will hit the window and smash it. What we don’t observe is a world where the window smashes on its own, thereby causing the ball to be kicked – that would seem rather nonsensical. In other words, kick before smash, and smash before kick, are two different physical processes each having a unique and definite causal order.

But, does definite causal order also reign supreme in the quantum world, where concepts like position and time can be fuzzy?  Most physicists are happy to accept the paradox of Schrödinger’s cat – a thought experiment in which a cat hidden in a box is simultaneously dead and alive at the same time, until you open the box to check. Schrödinger’s cat illustrates the quantum concept of “superposition”, whereby a system can be in two or more states at the same time. It is only when a measurement is made (by opening the box), does the system collapse into one of its possible states.

But could two (or more) causally distinct processes occur at the same time in the quantum world? The answer, perhaps shockingly, is yes and this paradoxical phenomenon is called indefinite causal order (ICO).

Stellar superpositions and the order of time

It turns out that different causal processes can also exist in a superposition. One example is a thought experiment called the “gravitational quantum switch”, which was proposed in 2019 by Magdalena Zych of the University of Queensland and colleagues (Nat. Comms 10 3772). This features our favourite quantum observers Alice and Bob, who are in the vicinity of a very large mass, such as a star. Alice and Bob both have initially synchronized clocks and in the quantum world, these clocks would continue to run at identical rates. However, Einstein’s general theory of relativity dictates that the flow of time is influenced by the distribution of matter in the vicinity of Alice and Bob. This means that if Alice is closer to the star than Bob, then her clock will run slower than Bob’s, and vice versa.

Like with Schrödinger’s cat, quantum mechanics allows the star to be in a superposition of spatial states; meaning that in one state Alice is closer to the star than Bob, and in the other Bob is closer to the star than Alice. In other words, this is a superposition of a state in which Alice’s clock runs slower than Bob’s, and a state in which Bob’s clock runs slower than Alice’s.

Alice and Bob are both told they will receive a message at a specific time (say noon) and that they would then pass that message on to the their counterpart. If Alice’s clock is running faster than Bob’s then she will receive the message first, and then pass it on to Bob, and vice versa. This superposition of Alice to Bob with Bob to Alice is an example of indefinite causal order.

Now, you might be thinking “so what” because this seems to be a trivial example. But it becomes more interesting if you replace the message with a quantum particle like a photon; and have Alice and Bob perform different operations on that photon. If the two operations do not commute – such as rotations of the photon polarization in the X and Z planes – then the order in which the operations are done will affect the outcome.

As a result, this “gravitational quantum switch” is a superposition of two different causal processes with two different outcomes. This means that Alice and Bob could do more exotic operations on the photon, such as “measure-and-reprepare” operations (where a quantum system is first measured, and then, based on the measurement outcome, a new quantum state is prepared). In this case Alice measures the quantum state of the received photon and prepares a photon that she sends to Bob (or vice versa).

Much like Schrödinger’s cat, a gravitational quantum switch cannot currently be realized in the lab. But, never say never. Physicists have been able to create experimental analogues of some thought experiments, so who knows what the future will bring. Indeed, a gravitational quantum switch could provide important information regarding a quantum description of gravity – something that has eluded physicists ever since quantum mechanics and general relativity were being developed in the early 20^th century.

Switches and superpositions

Moving on to more practical ICO experiments, physicists have already built and tested light-based quantum switches in the lab. Instead of having the position of the star determining whether Alice or Bob go first, the causal order is determined by a two-level quantum state – which can have a value of 0 or 1. If this control state is 0, then Alice goes first and if the control state is 1, then Bob goes first. Crucially, when the control state is in a superposition of 0 and 1 the system shows indefinite causal order (see figure 1).

The first such quantum switch was created by in 2015 by Lorenzo Procopio (now at Germany’s University of Paderborn) and colleagues at the Vienna Center for Quantum Science and Technology (Nat. Comms 6, 7913). Their quantum switch involves firing a photon at a beam splitter, which puts the photon into a superposition of a photon that has travelled straight through the splitter (state 0) and a photon that has been deflected by 90 degrees (state 1). This spatial superposition is the control state of the quantum switch, playing the role of the star in the gravitational quantum switch.

State 0 photons first travel to an Alice apparatus where a polarization rotation is done in a specific direction (say X). Then the photons are sent to a Bob apparatus where a non-commuting rotation (say Z) is done. Conversely, the photons that travel along the state 1 path encounter Bob before Alice.

Finally, the state 0 and state 1 paths are recombined at a second beamsplitter, which is monitored by two photon-detectors. Because Alice-then-Bob has a different effect on a photon than does Bob-then-Alice, interference can occur between recombined photons. This interference is studied by systematically changing certain aspects of the experiment. For example, by changing Alice’s direction of rotation or the polarization of the incoming photons.

In 2017 quantum-information researcher Giulia Rubino, then at the Vienna Center for Quantum Science and Technology, teamed up with Procopia and colleagues to verify ICO in their quantum switch using a “causal witness” (Sci. Adv. 3 e1602589). This involves doing a specific set of experiments on the quantum switch and calculating a mathematical entity (the causal witness) that reveals whether a system has definite or indefinite causal order. Sure enough, this test revealed that their system does indeed have ICO. Since then, physicists working in several independent labs have successfully created their own quantum switches.

Computational speed up?

While this effect might still seem somewhat obscure, in 2019, an international team led by the renowned Chinese physicist Jian-Wei Pan showed that a quantum switch can be very useful for doing computations that are distributed between two parties (Phys. Rev. Lett. 122 120504). In such a scenario a string of data is received and then processed by Alice, who then passes the results on to Bob for further processing. In an experiment using photons, they showed that ICO delivers an exponential speed-up of the rate at which longer strings are processed – compared to a system with no ICO.

Physicists are also exploring if ICO could be used to enhance quantum metrology. Indeed, recent calculations by Oxford University’s Giulio Chiribella and colleagues suggest that it could lead to a significant increase in precision when compared to techniques that involve states with definite causal order (Phys. Rev. Lett. 124 190503).

While other applications could be possible, it is often difficult to work out whether ICO offers the best solution to a specific problem. For example, physicists had thought a quantum switch offered an advantage when it comes to communicating along a noisy channel, but it turns out that some configurations of Alice and Bob with definite causal order were just as good as an ICO.

Beyond the quantum switch, there are other types of circuits that would display ICO. These include “quantum circuits with quantum control of causal order”, which have yet to be implemented in the lab because of their complexity.

But despite the challenges in creating ICO systems and proving that they outperform other solutions, it looks like ICO is set to join ranks of other weird phenomena such as superposition and entanglement that have found practical applications in quantum technologies.

The post Indefinite causal order: how quantum physics is challenging our understanding of cause and effect appeared first on Physics World.

Can artificial intelligence predict future research directions in quantum science? Listen to this episode of the Physics World Weekly podcast to discover what is already possible.

My guests are Mario Krenn – who heads the Artificial Scientist Lab at Germany’s Max Planck Institute for the Science of Light – and Felix Frohnert, who is doing a PhD on the intersection of quantum physics and machine learning at Leiden University in the Netherlands.

Frohnert, Krenn and colleagues published a paper earlier this year called “Discovering emergent connections in quantum physics research via dynamic word embeddings” in which they analysed more than 66,000 abstracts from the quantum-research literature to see if they could predict future trends in the field. They were particularly interested in the emergence of connections between previously isolated subfields of quantum science.

We chat about what motivated the duo to use machine learning to study quantum science; how their prediction system works; and I ask them whether they have been able to predict current trends in quantum science using historical data.

Their paper appears in the journal Machine Learning Science and Technology. It is published by IOP Publishing – which also brings you Physics World.  Krenn is on the editorial board of the journal and in the podcast he explains why it is important to have a platform to publish research at the intersection of physics and machine learning.

 

The post Artificial intelligence predicts future directions in quantum science appeared first on Physics World.

My guest in this episode of the Physics World Weekly podcast is the journalist Jason Palmer, who co-hosts “The Intelligence” podcast at The Economist.

Palmer did a PhD in chemical physics at Imperial College London before turning his hand to science writing with stints at the BBC and New Scientist.

He explains how he made the transition from the laboratory to the newsroom and offers tips for scientists planning to make the same career journey. We also chat about how artificial intelligence is changing how journalists work.

The post From a laser lab to <em>The Economist</em>: physicist Jason Palmer on his move to journalism appeared first on Physics World.

Science and technology go hand in hand but it’s not always true that basic research leads to applications. Many early advances in thermodynamics, for example, followed the opposite path, emerging from experiments with equipment developed by James Watt, who was trying to improve the efficiency of steam engines. In a similar way, much progress in optics and photonics only arose after the invention of the laser.

The same is true in quantum physics, where many of the most exciting advances are occurring in companies building quantum computers, developing powerful sensors, or finding ways to send information with complete security. The cutting-edge techniques and equipment developed to make those advances then, in turn, let us understand the basic scientific and philosophical questions of quantum physics.

Quantum entanglement, for example, is no longer an academic curiosity, but a tangible resource that can be exploited in quantum technology. But because businesses are now applying this resource to real-world problems, it’s becoming possible to make progress on basic questions about what entanglement is. It’s a case of technological applications leading to fundamental answers, not the other way round.

In a recent panel event in our Physics World Live series, Elise Crull (a philosopher), Artur Ekert (an academic) and Stephanie Simmons (an industrialist) came together to discuss the complex interplay between quantum technology and quantum foundations. Elise Crull, who trained in physics, is now associate professor of philosophy at the City University of New York. Artur Ekert is a quantum physicist and cryptographer at the University of Oxford, UK, and founding director of the Center for Quantum Technologies in Singapore. Stephanie Simmons is chief quantum officer at Photonic, co-chair of Canada’s Quantum Advisory Council, and associate professor of physics at Simon Fraser University in Vancouver.

Presented here is an edited extract of their discussion, which you can watch in full online.

Can you describe the interplay between applications of quantum physics and its fundamental scientific and philosophical questions?

Stephanie Simmons: Over the last 20 years, research funding for quantum technology has risen sharply as people have become aware of the exponential speed-ups that lie in store for some applications. That commercial potential has brought a lot more people into the field and made quantum physics much more visible. But in turn, applications have also let us learn more about the fundamental side of the subject.

We’re learning so much at a fundamental level because of technological advances

Stephanie Simmons

They have, for example, forced us to think about what quantum information really means, how it can be treated as a resource, and what constitutes intelligence versus consciousness. We’re learning so much at a fundamental level because of those technological advances. Similarly, understanding those foundational aspects lets us develop technology in a more innovative way.

If you think about conventional, classical supercomputers, we use them in a distributed fashion, with lots of different nodes all linked up. But how can we achieve that kind of “horizontal scalability” for quantum computing? One way to get distributed quantum technology is to use entanglement, which isn’t some kind of afterthought but the core capability.

How do you manage entanglement, create it, distribute it and distil it? Entanglement is central to next-generation quantum technology but, to make progress, you need to break free from previous thinking. Rather than thinking along classical lines with gates, say, an “entanglement-first” perspective will change the game entirely.

Artur Ekert: As someone more interested in the foundations of quantum mechanics, especially the nature of randomness, technology has never really been my concern. However, every single time I’ve tried to do pure research, I’ve failed because I’ve discovered it has interesting links to technology. There’s always someone saying: “You know, it can be applied to this and that.”

Think about some of the classic articles on the foundations of quantum physics, such as the 1935 Einstein–Podolsky–Rosen (EPR) paper suggesting that quantum mechanics is incomplete. If you look at them from the perspective of data security, you realize that some concepts – such as the ability to learn about a physical property without disturbing it – are relevant to cryptography. After all, it offers a way into perfect eavesdropping.

So while I enjoy the applications and working with colleagues on the corporate side, I have something of a love–hate relationship with the technological world.

Elise Crull: These days physicists can test things that they couldn’t before – maybe not the really weird stuff like indefinite causal ordering but certainly quantum metrology and the location of the quantum-classical boundary. These are really fascinating areas to think about and I’ve had great fun interacting with physicists, trying to fathom what they mean by fundamental terms like causality.

Was Schrödinger right to say that it’s entanglement that forces our entire departure from classical lines of thought? What counts as non-classical physics and where is the boundary with the quantum world? What kind of behaviour is – and is not – a signature of quantum phenomena? These questions make it a great time to be a philosopher.

Do you have a favourite quantum experiment or quantum technology that’s been developed over the last few decades?

Artur Ekert: I would say the experiments of Alain Aspect in Orsay in the early 1980s, who built on the earlier work of John Clauser, to see if there is a way to violate Bell inequalities. When I was a graduate student in Oxford, I found the experiment absolutely fascinating, and I was surprised it didn’t get as much attention at the time as I thought it should. It was absolutely mind-blowing that nature is inherently random and refutes the notion of local “hidden variables”.

There are, of course, many other beautiful experiments in quantum physics. There are cavity quantum electrodynamic and ion-trap experiments that let physicists go from controlling a bunch of atoms to individual atoms or ions. But to me the Aspect experiment was different because it didn’t confirm something that we’d already experienced. As a student I remember thinking: “I don’t understand this; it just doesn’t make sense. It’s mind-boggling.”

Elise Crull: The Bell-type experiments are how I got interested in the philosophy of quantum mechanics. I wasn’t around when Aspect did his first experiments, but at the recent Helgoland conference marking the centenary of quantum mechanics, he was on stage with Anton Zeilinger debating the meaning of Bell violations. So, it’s an experiment that’s still unsettled almost 50 years later and we have different stories involving causality to explain it.

The game is to go from a single qubit or small quantum systems to many-body quantum systems and to look at the emergent phenomena there

Elise Crull

I’m also interested in how physicists are finding clever ways to shield systems from decoherence, which is letting us see quantum phenomena at higher and higher levels. It seems the game is to go from a single qubit or small quantum systems to many-body quantum systems and to look at the emergent phenomena there. I’m looking forward to seeing further results.

Stephanie Simmons: I’m particularly interested in large quantum systems, which will let us do wonderful things like error correction and offer exponential speed-ups on algorithms and entanglement distribution for large distances. Having those capabilities will unlock new technology and let us probe the measurement problem, which is the core of so many of the unanswered questions in quantum physics.

Figuring out how to get reliable quantum systems out of noisy quantum systems was not at all obvious. It took a good decade for various teams around the world to do that. You’re pushing the edges of performance but it’s a really fast-moving space and I would say quantum-error correction is the technology that I think is most underappreciated.

How large could a quantum object or system be? And if we ever built it, what new fundamental information about quantum mechanics would it tell us?

Artur Ekert: Technology has driven progress in our understanding of the quantum world. We’ve gone from being able to control zillions of atoms in an ensemble to just one but the challenge is now to control more of them – two, three or four. It might seem paradoxical to have gone from many to one and back to many but the difference is that we can now control those quantum states. We can engineer those interactions and look at emerging phenomena. I don’t believe there will be a magic number where quantum will stop working – but who knows? Maybe when we get to 42 atoms the world will be different.

Elise Crull: It depends what you’re looking for. To detect gravitational waves, LIGO already uses Weber bars, which are big aluminium rods – weighing about a tonne – that vibrate like quantum oscillators. So we already have macroscopic systems that need to be treated quantum mechanically. The question is whether you can sustain entanglement longer and over greater distance.

What are the barriers to scaling up quantum devices so they can be commercially successful?

Stephanie Simmons: To unleash exponential speed-ups in chemistry or cybersecurity, we will need quantum computers with 400 to 2000 application-grade logical qubits. They will need to perform to a certain degree of precision, which means you need error correction. The overheads will be high but we’ve raised a lot of money on the assumption that it all pans out, though there’s no reason to think there’s a limit.

I don’t feel like there’s anything that would bar us from hitting that kind of commercial success. But when you’re building things that have never been built before, there are always “unknown unknowns”, which is kind of fun. There’s always the possibility of seeing some kind of interesting emergent phenomenon when we build very large quantum systems that don’t exist in nature.

Artur Ekert: To build a quantum computer, we have to create enough logical qubits and make them interact, which requires an amazing level of precision and degree of control. There’s no reason why we shouldn’t be able to do that, but what would be fascinating is if – in the process of doing so – we discovered there is a fundamental limit.

While I support all efforts to build quantum computers, I’d almost like them to fail because we might then discover something that refutes quantum physics

Artur Ekert

So while I support all efforts to build quantum computers, I’d almost like them to fail because we might then discover something that refutes quantum physics. After all, building a quantum computer is probably the most complicated and sophisticated experiment in quantum physics. It’s more complex than the whole of the Apollo project that sent astronauts to the Moon: the degree of precision of every single component that is required is amazing.

If quantum physics breaks down at some point, chances are it’ll be in this kind of experiment. Of course, I wish all my colleagues investing in quantum computing get a good return for their money, but I have this hidden agenda. Failing to build a quantum computer would be a success for science: it would let us learn something new. In fact, we might even end up with an even more powerful “post-quantum” computer.

Surely the failure of quantum mechanics, driven by those applications, would be a bombshell if it ever happened?

Artur Ekert: People seeking to falsify quantum prediction are generally looking at connections between quantum and gravity so how would you be able to refute quantum physics with a quantum computer? Would it involve observing no speed-up where a speed-up should be seen, or would it be failure of some other sort?

My gut feeling is make this quantum experiment as complex and as sophisticated as you want, scale it up to the limits, and see what happens. If it works as we currently understand it should work, that’s fine, we’ll have quantum computers that will be useful for something.  But if it doesn’t work for some fundamental reason, it’s also great – it’s a win–win game.

Are we close to the failure of quantum mechanics?

Elise Crull: I think Arthur has a very interesting point. But we have lots of orders of magnitude to go before we have a real quantum computer. In the meantime, many people working on quantum gravity – whether string theory or canonical quantum gravity – are driven by their deep commitment to the universality of quantization.

There are, for example, experiments being designed by some to disprove classical general relativity by entangling space–time geometries. The idea is to kick out certain other theories or find upper and lower bounds on a certain theoretical space. I think we will make a lot of progress by not by trying to defeat quantum mechanics but to look at the “classicality” of other field theories and try to test those.

How will quantum technology benefit areas other than, say, communication and cryptography?

Stephanie Simmons: History suggests that every time we commercialize a branch of physics, we aren’t great at predicting where that platform will go. When people invented the first transistor, they didn’t anticipate the billions that you could put onto a chip. So for the new generation of people who are “quantum native”, they’ll have access to tools and concepts with which they’ll quickly become familiar.

You have to remember that people think of quantum mechanics as counterintuitive. But it’s actually the most self-consistent set of physics principles. Imagine if you’re a character in a video game and you jump in midair; that’s not reality, but it’s totally self-consistent. Quantum is exactly the same. It’s weird, but self-consistent. Once you get used to the rules, you can play by them.

I think that there’s a real opportunity to think about chemistry in a much more computational sense. Quantum computing is going to change the way people talk about chemistry. We have the opportunity to rethink the way chemistry is put together, whether it’s catalysts or heavy elements. Chemicals are quantum-mechanical objects – if you had 30 or 50 atoms, with a classical computer it would just take more bits than there are atoms in the universe to work out their electronic structure.

Has industry become more important than academia when it comes to developing new technologies?

Stephanie Simmons: The grand challenge in the quantum world is to build a scaled-up, fault-tolerant, exponentially sped-up quantum system that could simultaneously deliver the repeaters we need to do all the entanglement distribution technologies. And all of that work, or at least a good chunk of it, is in companies. The focus of that development has left academia.

Industry is the most fast-moving place to be in quantum at the moment, and things will emerge that will surprise people

Stephanie Simmons

Sure, there are still contributions from academia, but there is at least 10 times as much going on in industry tackling these ultra-complicated, really complex system engineering challenges. In fact, tackling all those unknown unknowns, you actually become a better “quantum engineer”. Industry is the most fast-moving place to be in quantum at the moment, and things will emerge that will surprise people.

Artur Ekert: We can learn a lot from colleagues who work in the commercial sector because they ask different kinds of questions. My own first contact was with John Rarity and Paul Tabster at the UK Defence Evaluation and Research Agency, which became QinetiQ after privatization. Those guys were absolutely amazing and much more optimistic than I was about the future of quantum technologies. Paul in particular is an unsung hero of quantum tech. He showed me how you can think not in terms of equations, but devices – blocks you can put together, like quantum LEGO.

Over time, I saw more and more of my colleagues, students and postdocs going into the commercial world. Some even set up their own companies and I have a huge respect for my colleagues who’ve done that. I myself am involved with Speqtral in Singapore, which does satellite quantum communication, and I’m advising a few other firms too.

Most efforts to build quantum devices are now outside academia. In fact, it has to be that way because universities are not designed to build quantum computers, which requires skills and people not found in a typical university. The only way to work out what quantum is good for is through start-up companies. Some will fail; but some will survive – and the survivors will be those that bet on the right applications of quantum theory.

What technological or theoretical breakthrough do you most hope to see that make the biggest difference?

Elise Crull: I would love someone to design an experiment to entangle space–time geometries, which would be crazy but would definitely kick general relativity off the table. It’s a dream that I’d love to see happen.

Stephanie Simmons: I’m really keen to see distributed logical qubits that are horizontally scalable.

Artur Ekert: On the practical side, I’d like to see real progress in quantum-error-correcting codes and fault-tolerant computing. On the fundamental side, I’d love experiments that provide a better understanding of the nature of randomness and its links with special relativity.

The post Why quantum technology is driving quantum fundamentals appeared first on Physics World.

This episode features a wide-ranging interview with the astrochemist Ewine van Dishoeck, who is professor emeritus of molecular astrophysics at Leiden Observatory in the Netherlands. In 2018 she was awarded The Kavli Prize in Astrophysics and in this podcast she talks about her passion for astrochemistry and how her research combines astronomy, astrophysics, theoretical chemistry and laboratory experiments.

Van Dishoeck talks about some of the key unanswered questions in astrochemistry, including how complex molecules form on the tiny specks of dust in interstellar space. We chat about the recent growth in our understanding of exoplanets and protoplanetary discs and the prospect of observing signs of life on distant planets or moons.

The Atacama Large Millimetre Array radio telescope and the James Webb Space Telescope are two of the major facilities that Van Dishoeck has been involved with. She talks about the challenges of getting the astronomy community to agree on the parameters of a new observatory and explains the how collaborative nature of these projects ensures that instruments meet the needs of multiple research communities.

Van Dishoeck looks to the future of astrochemistry and what new observatories could bring to the field. The interview ends with a call for the next generation of scientists to pursue careers in astrochemistry.

This podcast is sponsored by The Kavli Prize.

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What is the mission of the Quantum Science Center?

The Quantum Science Center is one of five of the DoE’s National Quantum Information Science Research Centers.  The Quantum Science Center is a partnership led by Oak Ridge and it includes more than 20 other institutions including universities and companies.

ORNL and the other national laboratories play a crucial role in research and development within the United States. And partnerships play a crucial role in that activity. Some partnerships are with universities, especially individual investigators who require access to the powerful instruments that we develop and maintain. The labs are funded by the DOE, and users can apply to use the instruments or collaborate with our resident scientists to develop research ideas and follow through to publication.

In addition to providing cutting edge facilities to the nation’s scientists, national labs also play an important role in creating a scientific workforce that is educated in how to develop and use a range of scientific infrastructure and instrumentation. These personnel will ensure that scientific breakthroughs will continue to be made and that scientists will continue to have access to the best research facilities.

ORNL is home to several facilities for material characterization, including the Spallation Neutron Source (SNS). How is the lab using these facilities to develop new materials for quantum technologies?

ORNL has many unique facilities, including the SNS, which is a user facility of the DOE. It is one of the brightest sources of neutrons in the world, which makes it an incredibly powerful tool for characterizing novel materials.

We are using the SNS to look at some remarkable materials that have useful quantum properties such as topological order and entanglement. These strongly correlated systems have useful electronic or magnetic properties. What makes them so interesting is that under the right conditions they have unique phases in which their electrons or spins are entangled quantum mechanically.

We probe these materials using a range of instruments on the SNS and infer whether or not the materials are entangled. This allows us to identify materials that will be useful for developing new quantum technologies.

What other instruments are used to develop new quantum materials at ORNL?

The SNS is certainly one of our biggest and boldest instruments that we have for characterizing these types of systems, but in no way is it the only one. ORNL is also home to the Center for Nanophase Materials Sciences (CNMS). This is one of the DOE’s Office of Science Nanoscale Science Research Centers and it’s a remarkable facility co-located with the SNS at ORNL. The CNMS enables the synthesis and characterization of new quantum materials with the ultimate goal of gaining control over their useful properties.

Can you give an example of that work?

We are very interested in a type of material called a spin liquid. It’s a magnetic system where the quantum spins within the material can become entangled with each other and have correlations over very large distances – relative to the size of individual atoms. Using SNS we have detected a signature of entanglement in these materials. That material is ruthenium trichloride and it is one type of quantum magnet that we are studying at ORNL.

The next step is to take materials that have been certified as quantum or entangled and translate them into new types of devices. This is what the CNMS excels and involves fabricating a quantum material into unique geometries; and connecting it to electrodes and other types of control systems that then provide a path to demonstrating novel physics and other types of unique behaviours.

In the case of quantum spin liquids, for example, we believe that they can be translated into a new qubit (quantum bit) technology that can store and process quantum information. We haven’t got there yet, but the tools and capabilities that we have here at Oak Ridge are incredibly empowering for that type of technology development.

ORNL is also famous for its supercomputing capabilities and is home to Frontier, which is one of the world’s most powerful supercomputers. How does the lab’s high-performance computing expertise support the use of its instrumentation for the development of new quantum materials?

High-performance computing (HPC) has been a remarkable and disruptive tool because it allows us to explain and understand the physics of complex systems and how these systems can be controlled and ultimately exploited to create new technologies. One of the most remarkable developments in the last several years has been the application of HPC to machine learning and artificial intelligence.

This benefits material science, chemistry, biology, and the study of other complex physical systems, where modelling and simulation play a huge role in our scientific discovery process. And supercomputers are also used in the design and optimization of products that are based on those complex physical systems. In fact, many people would say that next to theory and experiment, computation is a third pillar of the R&D ecosystem.

In my view HPC is just as powerful a research tool as the SNS or the CNMS when it comes to understanding and exploring these complex physical systems.

Why is it important to have the SNS, CNMS, Frontier and other facilities co-located at ORNL?

This integration allows our researchers to very quickly compare computer simulations to experimental data from neutron scattering and other experiments. This results in a very tight and coordinated cycle of development that ensures that we get to the best results the fastest way possible. This way of working also highlights the multidisciplinary nature of how we operate – something we call “team science”.

This requires good coordination between all parties, you have to have clarity in your communication, and you have to have a very clear vision about the goals that you’re trying to accomplish. This ensures that everyone has a common understanding of the mission of ORNL and the DOE.

How do you ensure that collaboration across different instruments and disciplines is done efficiently?

In my experience, the ability of team members to communicate efficiently, to understand each other’s concepts and reasoning, and to translate back and forth across these disciplinary boundaries is probably one of the central and most important parts of this type of scientific development. This is crucial to ensuring that people using a common infrastructure gain powerful scientific results.

For example, when we talk about qubits in quantum science and technology, people working in different subdisciplines have slightly different definitions of that word. For computer scientists, a qubit is a logical representation of information that we manipulate through quantum algorithms. In contrast, material scientists think of a qubit as a two-level quantum system that is embedded in some electronic or magnetic degree of freedom. They will often see qubits as being independent of the logical and computational connections that are necessary to create quantum computers. Bridging such differences is an important aspect of multidisciplinary research and amplifies success at our facilities.

I would say that the facilities and the ecosystem that we’ve created within the laboratory support interchange and collaboration across disciplines. The instruments enable new fundamental discoveries and the science is then developed and translated into new technologies.

That is a multi-step process and can only succeed when you have a team of  people working together on large-scale problems – and that team is always multidisciplinary.

Can you talk about your partnerships with industry

In the last decade quantum science and technology has emerged as a national priority in terms of science, industry and national security. This interest is driven by concerns for national security as well as the economic advantage – in terms of new products and services – that quantum brings. Innovation in the energy sector is an important example of how quantum has important implications for both security and the economy.

As a result, US national laboratories are partnering very closely with industry to provide access to instruments at the SNS, the CNMS and other facilities. At the same time, our researchers get access to technologies developed by industry – especially commercial quantum computing platforms.

I think that one of the most exciting things for us at ORNL today is gaining insights into these new quantum products and services and adapting this knowledge into our own scientific discovery workflows.

• You can listen to the full interview with Travis Humble in the Physics World Weekly podcast

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In this episode of the Physics World Weekly podcast I am in conversation two physicists who are leading lights in the quantum science and technology community in the US state of Illinois. They are Preeti Chalsani who is chief quantum officer at Intersect Illinois, and David Awschalom who is director of Q-NEXT.

As well as being home to Chicago, the third largest urban area in the US, the state also hosts two national labs (Fermilab and Argonne) and several top universities. In this episode, Awschalom and Chalsani explain how the state is establishing itself as a burgeoning hub for quantum innovation – along with neighbouring regions in Wisconsin and Indiana.

Chalsani talks about the Illinois Quantum and Microelectronics Park, a 128-acre technology campus that being developed on the site of a former steel mill just south of Chicago. The park has already attracted its first major tenant, PsiQuantum, which will build a utility-scale, fault-tolerant quantum computer at the park.

Q-NEXT is led by Argonne National Laboratory, and Awschalom explains how academia, national labs, industry, and government are working together to make the region a quantum powerhouse.

• Related podcasts include interviews with Celia Merzbacher of the US’s Quantum Economic Development Consortium; Nadya Mason of the Pritzker School of Molecular Engineering at the University of Chicago; and Travis Humble of the Quantum Science Center at Oak Ridge National Laboratory

The post Building a quantum powerhouse in the US Midwest appeared first on Physics World.

This episode of the Physics World Weekly podcast features an interview with Kirsty McGhee, who is a scientific writer at the quantum-software company Qruise. It is the second episode in our two-part miniseries on careers for physicists.

While she was doing a PhD in condensed matter physics, McGhee joined Physics World’s Student Contributors Network. This involved writing articles about peer-reviewed research and also proof reading articles written by other contributors.

McGhee explains how the network broadened her knowledge of physics and improved her communication skills. She also says that potential employers looked favourably on her writing experience.

At Qruise, McGhee has a range of responsibilities that include writing documentation, marketing, website design, and attending conference exhibitions. She explains how her background in physics prepared her for these tasks, and what new skills she is learning.

• The first episode of this miniseries looks at what physicists can look forward to in retirement: “Third age careers for physicists: writing and the arts beckon“

The post Building a career from a passion for science communication appeared first on Physics World.

An experiment that scattered high-energy electrons from helium-3 and tritium nuclei has provided the first evidence for three-nucleon short-range correlations. The data were taken in 2018 at Jefferson Lab in the US and further studies of these correlations could improve our understanding of both atomic nuclei and neutron stars.

Atomic nuclei contain nucleons (protons and neutrons) that are bound together by the strong force. These nucleons are not static and they can move rapidly about the nucleus. While nucleons can move independently, they can also move as correlated pairs, trios and larger groupings. Studying this correlated motion can provide important insights into interactions between nucleons – interactions that define the structures of tiny nuclei and huge neutron stars.

The momenta of nucleons can be measured by scattering a beam of high-energy electrons from nuclei. This is because the de Broglie wavelength of these electrons is smaller that the size of the nucleons – allowing individual nucleons to be isolated. During the scattering process, momentum is exchanged between a nucleon and an electron, and how this occurs provides important insights into the correlations between nucleons.

Electron scattering has already revealed that most of the momentum in nuclei is associated with single nucleons, with some also assigned to correlated pairs. These experiments also suggested that nuclei have additional momenta that had not been accounted for.

Small but important

“We know that the three-nucleon interaction is important in the description of nuclear properties, even though it’s a very small contribution,” explains John Arrington at the Lawrence Berkeley National Laboratory in the US. “Until now, there’s never really been any indication that we’d observed them at all. This work provides a first glimpse at them.”

In 2018, Arrington and others did a series of electron-scattering experiments at Jefferson Lab with helium-3 and tritium targets. Now Arrington and an international team of physicists has scoured this scattering data for evidence of short-range, three-nucleon correlations.

Studying these correlations in nuclei with just three nucleons is advantageous because there are no correlations between four or more nucleons. These correlations would make it more difficult to isolate three-nucleon effects in the scattering data.

A further benefit of looking at tritium and helium-3 is that they are “mirror nuclei”. Tritium comprises one proton and two neutrons, while helium-3 comprises two protons and a neutron. The strong force that binds nucleons together acts equally on protons and neutrons. However, there are subtle differences in how protons and neutrons interact with each other – and these differences can be studied by comparing tritium and helium-3 electron scattering experiments.

A clean picture

“We’re trying to show that it’s possible to study three-nucleon correlations at Jefferson Lab even though we can’t get the energies necessary to do these studies in heavy nuclei,” says principle investigator Shujie Li, at Lawrence Berkeley. “These light systems give us a clean picture — that’s the reason we put in the effort of getting a radioactive target material.”

Both helium-3 and tritium are rare isotopes of their respective elements. Helium-3 is produced from the radioactive decay of tritium, which itself is produced in nuclear reactors. Tritium is a difficult isotope to work with because it is used to make nuclear weapons; has a half–life of about 12 years; and is toxic when ingested or inhaled. To succeed, the team had to create a special cryogenic chamber to contain their target of tritium gas.

Analysis of the scattering experiments revealed tantalizing hints of three-nucleon short-range correlations. Further investigation is need to determine exactly how the correlations occur. Three nucleons could become correlated simultaneously, for example, or an existing correlated pair could become correlated to a third nucleon.

Three-nucleon interactions are believed to play an important role in the properties of neutron stars, so further investigation into some of the smallest of nuclei could shed light on the inner workings of much more massive objects. “It’s much easier to study a three-nucleon correlation in the lab than in a neutron star,” says Arrington.

The research is described in Physics Letters B.

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