Simulating quantum systems is something that classical computers struggle with. Not surprisingly, quantum computers are expected to do a much better job – particularly when a quantum-computer’s architecture is designed to solve a specific type of physics problem.

My guest in this episode of the Physics World Weekly podcast is Ross Jenkinson of the UK’s University of Manchester. He talks about the challenges and rewards of using quantum computers in particle physics – a field where classical supercomputers can struggle to simulate simple systems.

We also explore how quantum information theory is being combined with Einstein’s general theory of relativity to shed light on the nature of space and time.

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As I was strolling through Belfast’s Titanic Quarter last summer, I discovered with delight a road called Bell’s Theorem Crescent. It’s named in honour of the Belfast-born physicist John Bell, best known for his eponymous theorem. Despite not being as embedded in popular culture as Schrödinger’s cat, his theorem will certainly ring a bell (forgive the pun) with most physicists.

The story goes back to 1935 when Albert Einstein, Boris Podolsky and Nathan Rosen (EPR) came up with their now-famous thought experiment, which was designed to show that quantum mechanics was, as a description of nature, incomplete. In the EPR scenario, non-local influences can affect the measurement outcomes performed on spatially separated particles.

Given how odd that seemed, some physicists invoked what are known as “hidden variables” to get rid of these non-local correlations and restore local realism. It was in 1964, while working at the CERN particle-physics lab, that Bell showed that no local hidden-variable theory can be compatible with the predictions of quantum mechanics.

This result – Bell’s theorem – is something I was familiar with but I had paid little attention to where it had originally appeared. As I discovered, it was published in a paper called “On the Einstein Podolsky Rosen paradox” in the journal Physics (3 195) in 1964. Also known as Physics Physique Физика, this little-known publication existed only from 1964 to 1968. In fact, Bell’s theorem is the most important result published in it.

The journal was set up by two physicists at Bell Laboratories in the US – Bernd Matthias and future Nobel laureate Philip Anderson. According to A Mind Over Matter – Andrew Zangwill’s 2021 biography of Anderson – they were not too happy with conventional physics journals. “The referees,” Anderson said, “often did a bad job, the editors took too long to make decisions, and too much wrong physics got published.”

Those are complaints you’ll still hear in coffee breaks at most physics conferences today, and they prompted Matthias to contact the media magnate Robert Maxwell, who’d founded Oxford-based publishing house Pergamon Press. Maxwell had figured out that scientific publishing could be a very lucrative business so he helped the two physicists to set up the journal.

A publishing experiment

In their first editorial, Anderson and Matthias called Physics an “experimental journal”, which they hoped would solve the problem of there being “far more good physics written than any physicist can read”. Their solution was to pick only those papers worth the attention of all physicists, which the editors did by reviewing – then accepting or rejecting – every submission themselves. They even paid authors 10 cents a word if their paper appeared in print.

Anderson and Matthias admitted that many physicists had already written to them, criticizing their proposed selection model. They’d been told that their “judgements will be fallible”, that they might be “overimpressed by showiness”, and that they’d end up rejecting excellent work. In response, the pair promised to try their best, accepting they would make mistakes and that their “criteria will be, not better, but different”.

The journal’s criteria clearly succeeded, in that Anderson and Matthias identified the merits of Bell’s paper, which was far from mainstream

These criteria clearly succeeded, in that they identified the merits of Bell’s paper, which was far from mainstream. Keen to find out more about the events surrounding its publication, I contacted Zangwill, who had interviewed Anderson several times for his book. Zangwill shared the following quote, published here for the first time.

“One day,” Anderson recalled, “a paper came in from a guy neither of us had heard of – John Bell. It was about hidden variables in quantum mechanics. Bernd had no clue, but I accepted it with the hope that its publication would spell the death of Bohmian trajectory quantum mechanics. It’s a very famous paper today.”

In 1967 the quantum physicist John Clauser found Bell’s paper after stumbling upon Physics Physique Физика, attracted by its unusual title. Clauser, who shared the 2022 Nobel Prize in Physics, carried out the first Bell test in 1972 with Stuart Friedmann. Their work triggered a long series of experiments that would deepen our understanding of quantum mechanics and catalyse the development of quantum technologies.

Over its short life, Physics did publish work from other notable physicists including Murray Gell-Mann, Leonard Susskind and Leo Kadanoff. In fact, the journal was ahead of its time, with the model of in-house editorial selection for broad interest returning in the 2000s with the Nature series of journals. The inclusive, multi-language title was also well ahead of its day.

Sadly, Physics Physique Физика was discontinued in 1968 after just three volumes

Sadly, Physics Physique Физика was discontinued in 1968 after just three volumes. According to what Anderson told Zangwill, it stopped “not because it lacked submissions, but because they had promised contributors rapid publication and Maxwell kept increasing the time between the appearances of successive issues”. Maxwell’s aggressive pursuit of profit might also have played a role.

The journal has since been archived by the American Physical Society and is freely accessible online. One can only wonder what might have happened if Anderson and Matthias had picked a different name for their journal.

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Science fiction has long embraced the idea of travelling backward in time, but the advent of Einstein’s general theory of relativity transformed these ideas from fantasies into potential – albeit contested – realities. In particular, solutions to the equations of general relativity known as closed time-like curves (CTCs) seem to allow a system’s trajectory to return to a previous point in time. Although the existence of CTCs has never been proven, their admissibility within general relativity has inspired many physicists to study their implications, which include increases in information processing speeds as well as retrograde time travel.

Inspired by the 2014 film Interstellar, in which a father sends messages to his daughter in the past, Kaiyuan Ji and Mark Wilde of Cornell University, together with Seth Lloyd at the Massachusetts Institute of Technology, have now investigated the potential advantages of a retrograde messaging channel based on a CTC. As well as deriving an exact expression for the information capacity of such a channel, they showed that this capacity exceeds that of regular channels that do not involve backward time travel.

Post-selected CTC models

To model their CTC, the researchers used an approach that Lloyd and his then-collaborators developed 15 years ago. This approach exploits the mathematical equivalence between a CTC and the combined operations of quantum teleportation and post selection, so it is often referred to as a post-selected CTC model. Previous analyses established that this model disallows time-travel paradoxes such as going back in time to kill your grandfather, while still preserving correlations between the system that travels backward in time and the environment.

The latter feature is important, Ji notes, because quantum CTC models without it have a distinct drawback: “If you travel through that closed time-like curve, you end up in the past, but basically you lost all the memory of what has happened before you do time travel,” he explains.

A further advantage of the team’s chosen model is that it does not prohibit causal loops in which correspondents in the past and future influence each other. To return to the Interstellar scenario, Ji explains that while the daughter is influenced by her father’s message, she also influences her father, because he witnessed how she decoded the message and therefore used that information to optimize his encoding protocols.

The existence of causal loops in the model allowed Ji and his colleagues to formulate an expression for the channel’s bit capacity. It also pointed towards the best way of maximizing that capacity. The optimal strategy, Ji explains, would involve the father using his memory from the past when encoding his message to the past, which makes sending messages to the past more efficient (and capable of a higher bit capacity) than sending messages to the future. “The causal loop is essential to the design of the optimal communication protocol in this retro causal communication setting,” he tells Physics World. “It is not possible in standard communication from the past to the future.”

Capacity for messages

The CTC can also be used to form a quantum channel capable of transmitting either regular classical data or quantum data back in time. Using their expression for the channel’s bit capacity, the researchers were able to show that its classical bit capacity is twice that of its quantum counterpart.

Nicole Yunger Halpern, a theoretical physicist at the University of Maryland who has studied some implications of CTCs for metrology but was not involved in the current work, describes the research as “creative and technically impressive”. She points out that while calculating a communication channel’s capacity is a common challenge in the field of information theory, obtaining straightforward answers can be difficult. “The authors combined this workaday task with a highly unusual (retrocausal) setting and, moreover, obtained a simple solution,” Halpern says.

Not everyone is sold on the mathematical format of post-selected CTC models, though. Scott Aaronson, a computer scientist at the University of Texas at Austin, US, who has previously studied the speed advantages of information processing using CTCs, believes that studies with this approach “attempt to model time travel but don’t fully succeed at it”. However, with respect to the question of channel capacity, Aaronson concedes it may be “interesting to prove things”.

While the current model considered the effects of distortion (“noise”) on messages in the channel, Ji suggests it might be interesting to broaden this to include noise in the memory of the process – like the father in Interstellar having a hazy recall of his daughter’s decoding protocol. Ji also notes that the post-selection CTC model has some mathematical equivalence with black hole final state projections, and he says it might be interesting to explore these connections, too.

The research is described in Physical Review Letters.

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Think big, win big. The University of Tennessee at Chattanooga (UTC) is ticking both boxes, it seems, with a programme of strategic investments spanning quantum research, education, workforce development and academic-industry partnerships. By 2030, the hope is that those investments will pay out, putting Chattanooga on the fast-track to becoming the “Quantum Capital of the South” – a destination where researchers, students, entrepreneurs, industry leaders, national laboratories and public-sector partners work together to accelerate quantum discovery and deployment.

“Success will be measured not only through research funding and scholarly output, but also through the strength of the quantum ecosystem and the opportunities it creates throughout the region,” says Mina Sartipi, UTC’s interim vice-chancellor for research. Equally important, early-career faculty and researchers will have the opportunity to make an outsized impact. “They are not entering an environment where every role has already been defined,” she adds. “They are helping to build the future of quantum science and engineering in Tennessee, delivering a long-term vision that extends well beyond the university.”

Quantum excellence

The UTC Quantum Initiative got under way in 2022 and, two years later, was followed by the establishment of UTC Quantum Center. The latter provides the engine-room for UTC’s quantum ambitions, bringing together a cross-disciplinary mix of departments and colleges across the university to support targeted development efforts in research infrastructure, translational R&D and education. “Ultimately, we want UTC Quantum Center to be recognized as a destination for top quantum talent,” says Sartipi. “A virtuous circle that will see us attracting outstanding faculty, students and research partners from across the country and internationally.”

That quantum vision has already yielded significant outcomes at UTC, including Tennessee’s first undergraduate certificate in quantum information science and engineering (with a focus on quantum programming languages); a cross-disciplinary PhD programme in quantum science and technology; as well as eye-catching research collaborations with the likes of EPB (Chattanooga’s municipal energy and communications utility) and Oak Ridge National Laboratory (ORNL) in eastern Tennessee

As the inaugural director of UTC Quantum Center, Rick Mukherjee is tasked with implementing and delivering UTC’s quantum growth plan. “The priority is to put Chattanooga on the map in terms of quantum science and technology innovation,” he notes. “We’re creating a quantum centre-of-excellence at UTC where interdisciplinarity underpins everything we do, engaging associated faculty and research students from core disciplines like physics, mathematics, electrical engineering and computer science.”

Entangled pathways

If that’s the back story, what of the detail? The research effort at UTC Quantum Center is organized around four headline themes: quantum networking; quantum imaging and sensing; quantum information theory; and quantum simulation of many-body phenomena (using one quantum system to emulate another).

The collaboration with EPB is pivotal in each case, with UTC Quantum Center providing one of the nodes on the utility’s metro-area quantum network (the first commercial quantum network of its kind in the US) and, by extension, gaining priority access to EPB’s in-house quantum computer (an IonQ trapped-ion system with 36 physical qubits).

The EPB network, which runs across a pre-installed fibre-optic base, is effectively a proof-of-principle testbed for national and international quantum connectivity. “This is one brick in the wall towards next-generation quantum networking applications – from quantum key distribution and quantum cryptography to distributed quantum computing and the quantum Internet,” notes Mukherjee.

A case in point: one of the first experiments that UTC Quantum Center performed in collaboration with ORNL involved the development of an automatic system that continuously corrects for distortions in fibre-optic cables and, in so doing, allows quantum information to transit reliably across a city-scale network. The system maintained high-quality quantum entanglement for more than 30 hours, demonstrating a key capability for future quantum communication networks.

“Currently, our researchers are transmitting pairs of entangled photons across EPB’s fibre network and characterizing multipartite entangled states,” explains Mukherjee. “This work represents the next step toward realizing the potential of quantum networks for advanced communication, sensing and distributed quantum computing applications.”

Alongside his leadership role, Mukherjee remains an active researcher and oversees a group of research faculty, postdocs and graduate/undergraduate students who specialize in theoretical quantum physics, quantum algorithms and quantum machine-learning applications. Crucially, the team’s algorithms are designed to be hardware-agnostic, allowing them to run across diverse quantum computing architectures – from superconducting and neutral-atom systems to photonic platforms – regardless of the vendor.

By avoiding dependence on any one technology, the research is positioned to adapt versus a rapidly changing quantum landscape. “Whatever modality ultimately wins the race to deliver at-scale quantum computing,” Mukherjee says, “we’ll be ready to deploy our algorithms and unlock quantum advantage on those machines.”

The quantum connector

Alignment with industry is a defining theme at UTC Quantum Center, evidenced by a twin-track approach that aims to engage both technology developers and future end-users. On the one hand, Mukherjee and colleagues are initiating traditional academic-industry partnerships with hardware and software companies at all levels of the quantum supply chain; on the other, they are positioning UTC as a “quantum connector” to help businesses and public-sector organizations de-risk the early-stage adoption of quantum technologies and applications.

“Universities have an important role to play here,” says Mukherjee. As such, he sees UTC Quantum Center as an “honest broker”, providing specialist information in an unbiased manner to help engineering and management teams understand the commercial upsides of quantum technologies across sectors as diverse as finance, healthcare, telecoms and energy.

“We are working with the future adopters of quantum on their early-stage orientation and upskilling,” he explains. “Our professional development programmes – ‘Quantum 101’ if you like – will ensure Tennessee has a ‘quantum-ready’ workforce.”

Proof-of-concept R&D studies represent a natural progression of such partnerships, with UTC researchers addressing real-world problems that could potentially be better solved using quantum methods and applications. Joint projects with utilities like the Tennessee Valley Authority, for example, are developing quantum algorithms for power grid optimization and load management. Elsewhere, UTC Quantum Center recently published work on the gate-assignment problem (another quantum optimization challenge) with Lufthansa Industry Solutions (the research arm of Germany’s Lufthansa Airlines). A similar research collaboration is underway with the consultancy Deloitte.

Network effects

That engagement with industry is matched by UTC Quantum Center’s efforts to build bridges with other academic institutions. Over the past two years, Mukherjee and his team have put in place a network of collaborations with quantum researchers at top-tier universities, among them Harvard, Purdue, Texas A&M and the University of Tennessee at Knoxville in the US as well as the University of Hamburg in Germany.

Meanwhile, a series of joint projects is underway with ORNL in areas like quantum networking, quantum information theory and quantum simulation. UTC Quantum Center will also shortly become an official partner of ORNL’s Quantum Science Center (one of five dedicated National Quantum Information Science Research Centers within the US Department of Energy National Laboratory system).

The recently announced UTC/ORNL Governor’s Chair in Quantum Information Science and Engineering reflects the momentum of these efforts. This senior faculty position will further strengthen ties between UTC and ORNL, with the eventual post-holder overseeing a joint team across both institutions to create new opportunities for collaborative research, student engagement and workforce development.

So what does success look like for UTC Quantum Center in 2030? “Ultimately,” concludes Sartipi, “success means that when people think about the future of quantum technologies in the US, they think of Chattanooga as the Quantum Capital of the South – a place where talent is cultivated, partnerships flourish and discoveries translate out of the laboratory into societal and economic impact.”

• UTC is currently inviting applications for PhD and postdoctoral research positions in quantum information science. Applications are also invited for the Governor’s Chair Professor in Quantum Information Science and Engineering, a joint appointment with ORNL.

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The Glasgow-based quantum hardware manufacturer Quantcore has been awarded the 2026 qBIG prize from the Institute of Physics (IOP). The annual prize, awarded by the IOP’s member-led quantum Business Innovation and Growth (qBIG) group, is given to a small or medium-sized company in the UK or Ireland for breakthroughs in the commercialization of quantum technologies.

Quantcore is a spin-out from the University of Glasgow and is based at the university’s Advanced Research Centre.

Quantcore builds the superconducting processors, resonators and sensors used in quantum computers and certain sensing systems. The firm uses niobium-based components, which can operate at higher temperatures than materials currently used in quantum computers. The firm recently received £2.5m in seed funding from several backers.

The qBIG award, now in its fourth year, is sponsored by the UK-based venture capital firm Quantum Exponential and includes a £10,000 cash prize as well as mentoring from Quantum Exponential and business support from the IOP.  The award was presented yesterday in London at the Economist Commercialising Quantum 2026 event.

Accepting the prize on behalf of the company, Quantcore chief executive officer Jack Brennan says he is “delighted” to win the award.

“The previous winners are a great example of up-and-coming quantum companies, and it’s a privilege to be part of that list,” he says. “A huge thanks to the qBIG group for choosing Quantcore, and a huge thanks to my fantastic team for working so hard to build the company.”

Two runners up were commended by the IOP. One is Mater-AI, which develops thermoelectric materials for energy conversion and cooling. The other is Skydiamond, which produces lab-grown diamonds  that can be used in quantum computing as a material for creating qubits.

“The UK quantum industry is going from strength to strength – and is becoming a major growth engine,” says Louis Barson, IOP’s director of science, business & education. “The qBIG prize is all about celebrating the strong pipeline of new physics-powered quantum innovators like Quantcore coming through – and giving them a platform to help accelerate that growth.”

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“There are two types of people when it comes to quantum,” joked Howard Dawber, deputy mayor of London for business and growth at a meeting at the Institute of Physics last night to celebrate the first anniversary of the London Quantum Cluster.

“There are those who understand quantum mechanics. There are those who don’t. And there are those who are in superposition of understanding and not understanding until they are observed.”

It was a light-hearted remark that matched the mood of what was essentially an evening of boosterism for quantum technology in London ahead of London Tech Week next week.

As chair of London and Partners – the growth agency for London – Dawber told the gathering of more than 100 “quantum influencers” that the organization was “100% behind the London Quantum Cluster”.

Founded in 2025 by University College London, King’s College London and Imperial College London, with support from the Mayor of London and the UK government, the cluster seeks to establish the capital as a powerhouse of quantum tech.

Georgia Siora from Warwick Economics and Development presented data to show that London is already doing well in the sector, being home to more than 160 quantum companies, with seven of the top 10 UK quantum firms based in the city. Small- and medium-sized quantum firms in the capital, she added, contribute an estimated £153m annually to the economy.

“Quantum and deep tech are at the heart of the capital’s 10-year growth plan,” added Janet Coyle, managing director of London and Partners.

Geraint Rees, vice-provost for research, innovation and global engagement at UCL, said his aim was “to make London the best place on the planet for serious quantum companies”. He pointed to UCL spin-out Quantum Motion, which has just won $160m of venture-capital funding, as an example of the kind of firm making a name in the city.

The evening ended with a panel debate chaired by Jess Wade from Imperial College London, featuring Maria Maragkou from Nu Quantum as well as Richard Murray, founder of ORCA Computing, who drew a distinction between universities being all about expanding the frontiers of knowledge, whereas for start-ups “the aim is to win”.

Also on the panel was physicist Alejandro Montblanch – head of quantum communication and networking at banking group HSBC – who made it clear that what he wanted to know was: “How can your quantum company help HSBC make more money?”

A welcome note of caution came from London-based venture-capital investor Eloisa Angeles, who pointed out that while the UK has a good track record of government-funded research, the UK  is weak at “follow through”, with the government not focused on procurement and not having the end customer of the research in sight.

• For more about the commercial impact of quantum economy, check out this feature by Philip Ball.

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