̽��ֱ�� of Cambridge - quantum

Researchers demonstrate the UK’s first long-distance ultra-secure communication over a quantum network

sc604 — Mon, 07 Apr 2025 23:38:58 +0000

̽��ֱ��team, from the Universities of Bristol and Cambridge, created the network, which uses standard fibreoptic infrastructure, but relies on a variety of quantum phenomena to enable ultra-secure data transfer.

̽��ֱ��network uses two types of quantum key distribution (QKD) schemes: ‘unhackable’ encryption keys hidden inside particles of light; and distributed entanglement: a phenomenon that causes quantum particles to be intrinsically linked.

̽��ֱ��researchers demonstrated the capabilities of the network via a live, quantum-secure video conference link, the transfer of encrypted medical data, and secure remote access to a distributed data centre. ̽��ֱ��data was successfully transmitted between Bristol and Cambridge – a fibre distance of over 410 kilometres.

This is the first time that a long-distance network, encompassing different quantum-secure technologies such as entanglement distribution, has been successfully demonstrated. ̽��ֱ��researchers presented their results at the 2025 Optical Fiber Communications Conference (OFC) in San Francisco.

Quantum communications offer unparalleled security advantages compared to classical telecommunications solutions. These technologies are immune against future cyber-attacks, even with quantum computers, which – once fully developed – will have the potential to break through even the strongest cryptographic methods currently in use.

In the past few years, researchers have been working to build and use quantum communication networks. China recently set up a massive network that covers 4,600 kilometres by connecting five cities using both fibreoptics and satellites. In Madrid, researchers created a smaller network with nine connection points that use different types of QKD to securely share information.

In 2019, researchers at Cambridge and Toshiba demonstrated a metro-scale quantum network operating at record key rates of millions of key bits per second. And in 2020, researchers in Bristol built a network that could share entanglement between multiple users. Similar quantum network trials have been demonstrated in Singapore, Italy and the USA.

Despite this progress, no one has built a large, long-distance network that can handle both types of QKD, entanglement distribution, and regular data transmission all at once, until now.

̽��ֱ��experiment demonstrates the potential of quantum networks to accommodate different quantum-secure approaches simultaneously with classical communications infrastructure. It was carried out using the UK’s Quantum Network (UKQN), established over the last decade by the same team, supported by funding from the Engineering and Physical Sciences Research Council (EPSRC), and as part of the Quantum Communications Hub project.

“This is a crucial step toward building a quantum-secured future for our communities and society,” said co-author Dr Rui Wang, Lecturer for Future Optical Networks in the Smart Internet Lab's High Performance Network Research Group at the ̽��ֱ�� of Bristol. “More importantly, it lays the foundation for a large-scale quantum internet—connecting quantum nodes and devices through entanglement and teleportation on a global scale.”

“This marks the culmination of more than ten years of work to design and build the UK Quantum Network,” said co-author Adrian Wonfor from Cambridge’s Department of Engineering. “Not only does it demonstrate the use of multiple quantum communications technologies, but also the secure key management systems required to allow seamless end-to-end encryption between us.”

“This is a significant step in delivering quantum security for the communications we all rely upon in our daily lives at a national scale,” said co-author Professor Richard Penty, also from Cambridge and who headed the Quantum Networks work package in the Quantum Communications Hub. “It would not have been possible without the close collaboration of the two teams at Cambridge and Bristol, the support of our industrial partners Toshiba, BT, Adtran and Cisco, and our funders at UKRI.”

“This is an extraordinary achievement which highlights the UK’s world-class strengths in quantum networking technology,” said Gerald Buller, Director of the IQN Hub, based at Heriot-Watt ̽��ֱ��. “This exciting demonstration is precisely the kind of work the Integrated Quantum Networks Hub will support over the coming years, developing the technologies, protocols and standards which will establish a resilient, future-proof, national quantum communications infrastructure.”

̽��ֱ��current UKQN covers two metropolitan quantum networks around Bristol and Cambridge, which are connected via a ‘backbone’ of four long-distance optical fibre links spanning 410 kilometres with three intermediate nodes.

̽��ֱ��network uses single-mode fibre over the EPSRC National Dark Fibre Facility (which provides dedicated fibre for research purposes), and low-loss optical switches allowing network reconfiguration of both classical and quantum signal traffic.

̽��ֱ��team will pursue this work further through a newly funded EPSRC project, the Integrated Quantum Networks Hub, whose vision is to establish quantum networks at all distance scales, from local networking of quantum processors to national-scale entanglement networks for quantum-safe communication, distributed computing and sensing, all the way to intercontinental networking via low-earth orbit satellites.

Reference:
R. Yang et al. ‘A UK Nationwide Heterogeneous Quantum Network.’ Paper presented at the 2025 Optical Fiber Communications Conference and Exhibition (OFC): https://www.ofcconference.org/en-us/home/schedule/

Researchers have successfully demonstrated the UK’s first long-distance ultra-secure transfer of data over a quantum communications network, including the UK’s first long-distance quantum-secured video call.

MR.Cole_Photographer via Getty Images

Abstract background

̽��ֱ��text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

Yes

A peek inside the box that could help solve a quantum mystery

sc604 — Tue, 19 Nov 2024 15:22:24 +0000

Appearing as ‘bumps’ in the data from high-energy experiments, these signals came to be known as short-lived ‘XYZ states.’ They defy the standard picture of particle behaviour and are a problem in contemporary physics, sparking several attempts to understand their mysterious nature.

But theorists at the U.S. Department of Energy’s Thomas Jefferson National Accelerator Facility in Virginia, with colleagues from the ̽��ֱ�� of Cambridge, suggest the experimental data could be explained with fewer XYZ states, also called resonances, than currently claimed.

̽��ֱ��team used a branch of quantum physics to compute the energy levels, or mass, of particles containing a specific ‘flavour’ of the subatomic building blocks known as quarks. Quarks, along with gluons, a force-carrying particle, make up the Strong Force, one of the four fundamental forces of nature.

̽��ֱ��researchers found that multiple particle states sharing the same degree of spin – or angular momentum – are coupled, meaning only a single resonance exists at each spin channel. This new interpretation is contrary to several other theoretical and experimental studies.

̽��ֱ��researchers have presented their results in a pair of companion papers published for the international Hadron Spectrum Collaboration (HadSpec) in Physical Review Letters and Physical Review D. ̽��ֱ��work could also provide clues about an enigmatic particle: X(3872).

̽��ֱ��charm quark, one of six quark ‘flavours’, was first observed experimentally in 1974. It was discovered alongside its antimatter counterpart, the anticharm, and particles paired this way are part of an energy region called ‘charmonium.’

In 2003, Japanese researchers discovered a new charmonium candidate dubbed X(3872): a short-lived particle state that appears to defy the present quark model.

“X(3872) is now more than 20 years old, and we still haven’t obtained a clear, simple explanation that everyone can get behind,” said lead author Dr David Wilson from Cambridge’s Department of Applied Mathematics and Theoretical Physics (DAMTP).

Thanks to the power of modern particle accelerators, scientists have detected a hodgepodge of exotic charmonium candidate states over the past two decades.

“High-energy experiments started seeing bumps, interpreted as new particles, almost everywhere they looked,” said co-author Professor Jozef Dudek from William & Mary. “And very few of these states agreed with the model that came before.”

But now, by creating a tiny virtual ‘box’ to simulate quark behaviour, the researchers discovered that several supposed XYZ particles might actually be just one particle seen in different ways. This could help simplify the confusing jumble of data scientists have collected over the years.

Despite the tiny volumes they were working with, the team required enormous computing power to simulate all the possible behaviours and masses of quarks.

̽��ֱ��researchers used supercomputers at Cambridge and the Jefferson Lab to infer all the possible ways in which mesons – made of a quark and its antimatter counterpart – could decay. To do this, they had to relate the results from their tiny virtual box to what would happen in a nearly infinite volume – that is, the size of the universe.

“In our calculations, unlike experiment, you can't just fire in two particles and measure two particles coming out,” said Wilson. “You have to simultaneously calculate all possible final states, because quantum mechanics will find those for you.”

̽��ֱ��results can be understood in terms of just a single short-lived particle whose appearance could differ depending upon which possible decay state it is observed in.

“We're trying to simplify the picture as much as possible, using fundamental theory with the best methods available,” said Wilson. “Our goal is to disentangle what has been seen in experiments.”

Now that the team has proved this type of calculation is feasible, they are ready to apply it to the mysterious particle X(3872).

“ ̽��ֱ��origin of X(3872) is an open question,” said Wilson. “It appears very close to a threshold, which could be accidental or a key part of the story. This is one thing we will look at very soon."

Professor Christopher Thomas, also from DAMTP, is a member of the Hadron Spectrum Collaboration, and is a co-author on the current studies. Wilson’s contribution was made possible in part by an eight-year fellowship with the Royal Society. ̽��ֱ��research was also supported in part by the Science and Technology Facilities Council (STFC), part of UK Research and Innovation (UKRI). Many of the calculations for this study were carried out with the support of the Cambridge Centre for Data Driven Discovery (CSD3) and DiRAC high-performance computing facilities in Cambridge, managed by Cambridge’s Research Computing Services division.

Reference:
David J. Wilson et al. ‘Scalar and Tensor Charmonium Resonances in Coupled-Channel Scattering from Lattice QCD.’ Physical Review Letters (2024). DOI: 10.1103/PhysRevLett.132.241901

David J. Wilson et al. ‘Charmonium xc0 and xc2 resonances in coupled-channel scattering from lattice QCD.’ Physical Review D (2024). DOI: 10.1103/PhysRevD.109.114503

Adapted from a Jefferson Lab story.

An elusive particle that first formed in the hot, dense early universe has puzzled physicists for decades. Following its discovery in 2003, scientists began observing a slew of other strange objects tied to the millionths of a second after the Big Bang.

gremlin via Getty Images

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Yes

Five hubs launched to ensure UK benefits from quantum future

sc604 — Fri, 26 Jul 2024 06:30:07 +0000

̽��ֱ��hub, called Q-BIOMED, is one of 5 quantum research hubs announced on 26 July by Peter Kyle MP, the Secretary of State for Science, Innovation and Technology, supported by £160 million in funding.

̽��ֱ��hub will exploit advances in quantum sensors capable of detecting cells and molecules, potentially orders of magnitude more sensitively than traditional diagnostic tests.

This includes developing quantum-enhanced blood tests to diagnose infectious diseases and cancer quickly and cheaply using portable instruments, and sensors measuring tiny changes to the magnetic fields in the brain that have the potential to detect early markers of Alzheimer’s disease before symptoms occur.

Other research will include quantum-enhanced MRI scans, heart scanners and surgical and treatment interventions for early-stage and hard-to-treat cancers.

“Quantum technologies harness quantum physics to achieve a functionality or a performance which is otherwise unattainable, deriving from science which cannot be explained by classical physics,” said Hub Co-Director Professor Mete Atatüre, Head of Cambridge’s Cavendish Laboratory. “Q-BIOMED will be delivered by an outstanding team of researchers from academia, the NHS, charities, government and industry to exploit quantum-enhanced advances for human health and societal good.”

“Our hub aims to grow a new quantum for health innovation ecosystem in the UK, and has already shaped the UK's new Quantum Mission for Health,” said Hub Co-Director Professor Rachel McKendry, from the London Centre for Nanotechnology and Division of Medicine at UCL. “Our long-term vision is to accelerate the entire innovation pipeline from discovery research, to translation, adoption and implementation within the NHS and global health systems, for the benefit of patients and societal good.”

“Quantum sensing allows us to gather information at cellular and molecular levels with unprecedented sensitivity to electric and magnetic fields," said Dr Ljiljana Fruk from the Department of Chemical Engineering and Biotechnology, a member of the Q-BIOMED team. "I look forward to learning from colleagues and engaging in challenging discussions to develop more sensitive, affordable tools for doctors and patients, advancing the future of healthcare.”

Cambridge researchers are also involved in three of the other newly-announced hubs:

̽��ֱ��UK Hub for Quantum Enabled Position, Navigation and Timing (QEPNT), led by the ̽��ֱ�� of Glasgow, will develop quantum technologies which will be key for national security and critical infrastructure and sectors such as aerospace, connected and autonomous vehicles (CAVs), finance, maritime and agriculture. Luca Sapienza (Engineering), Louise Hirst (Materials Science and Metallurgy/Cavendish Laboratory) and Dave Ellis (Cavendish Laboratory) are part of the QEPNT team.
QCI3: Hub for Quantum Computing via Integrated and Interconnected Implementations, led by the ̽��ֱ�� of Oxford, aims to develop the technologies needed for the UK to play a key role in the development of quantum computers, a market estimated to be worth $1.3 trillion by 2030. Ulrich Schneider (Cavendish Laboratory), Helena Knowles (Cavendish Laboratory), and Chander Velu (Institute for Manufacturing) are part of the QCI3 team.
̽��ֱ��Integrated Quantum Networks (IQN) Quantum Technology Research Hub, led by Heriot-Watt ̽��ֱ��, will undertake research towards the ultimate goal of a ‘quantum internet’, globally interlinked quantum networks connecting multiple quantum computers to produce enormous computational power. Richard Penty, Adrian Wonfor and Qixiang Cheng (Engineering), Atatüre and Dorian Gangloff (Cavendish Laboratory) are part of the IQN team.

̽��ֱ��fifth hub, UK Quantum Technology Hub in Sensing, Imaging and Timing (QuSIT), is led by the ̽��ֱ�� of Birmingham.

̽��ֱ��five hubs are delivered by the UKRI Engineering and Physical Sciences Research Council (EPSRC), with a £106 million investment from EPSRC, the UKRI Biotechnology and Biological Research Council, UKRI Medical Research Council, and the National Institute for Health and Care Research. Added to this are contributions from industry and other partners worth more than £54 million.

Peter Kyle, Secretary of State for Science, Innovation and Technology, said: “We want to see a future where cutting-edge science improves everyday lives. That is the vision behind our investment in these new quantum technology hubs, by supporting the deployment of technology that will mean faster diagnoses for diseases, critical infrastructure safe from hostile threats and cleaner energy for us all.

“This isn’t just about research; it’s about putting that research to work. These hubs will bridge the gap between brilliant ideas and practical solutions. They will not only transform sectors like healthcare and security, but also create a culture of accelerated innovation that helps to grow our economy.”

EPSRC Executive Chair Professor Charlotte Deane said: “Technologies harnessing quantum properties will provide unparalleled power and capacity for analysis at a molecular level, with truly revolutionary possibilities across everything from healthcare to infrastructure and computing.

“ ̽��ֱ��5 Quantum Technology Hubs announced today will harness the UK’s expertise to foster innovation, support growth and ensure that we capitalise on the profound opportunities of this transformative technology.”

A major new research hub led by the ̽��ֱ�� of Cambridge and UCL aims to harness quantum technology to improve early diagnosis and treatment of disease.

James Tye/UCL

L-R: Professor John Morton (UCL), Professor Rachel McKendry (UCL), Professor Mete Atatüre (Cambridge), Professor Eleni Nastouli (UCL)

Yes

£11m semiconductor research centre could be key player in UK’s net zero mission

sc604 — Tue, 13 Feb 2024 13:24:00 +0000

Semiconductors, also known as microchips, are a key component in nearly every electrical device from mobile phones and medical equipment to electric vehicles.

They are increasingly being recognised as an area of global strategic significance due to the integral role they play in net zero, AI and quantum technology.

Co-created and delivered with industry, the REWIRE IKC is led by the ̽��ֱ�� of Bristol, in partnership with Cambridge and Warwick Universities.

̽��ֱ��IKC will accelerate the UK’s ambition for net zero by transforming the next generation of high-voltage electronic devices using wide/ultra-wide bandgap (WBG/UWBG) compound semiconductors.

̽��ֱ��project is being led by Professor Martin Kuball and his team at the ̽��ֱ�� of Bristol. Cambridge members of the IKC team include Professors Rachel Oliver, Florin Udrea and Teng Long.

̽��ֱ��centre will advance the next generation of semiconductor power device technologies and enhance the security of the UK’s semiconductor supply chain.

Compound semiconductor WBG/UWBG devices have been recognised in the UK National Semiconductor Strategy as key elements to support the net zero economy through the development of high voltage and low energy-loss power electronic technology.

They are essential building blocks for developing all-electric trains, ships and heavy goods electric vehicles, better charging infrastructure, renewable energy and High Voltage Direct Current grid connections, as well as intelligent power distribution and energy supplies to telecommunication networks and data centres.

“Power devices are at the centre of all power electronic systems and pave the way for more efficient and compact power electronic systems, reducing energy loss,” said Kuball. “ ̽��ֱ��REWIRE IKC will focus on power conversion of wind energy, electric vehicles, smart grids, high-temperature applications, device and packaging, and improving the efficiency of semiconductor device manufacture.”

Our home electrical supply is at 240 Volts, but to handle the power from offshore wind turbines, devices will have to operate at thousands of Volts. These very high voltages can easily damage the materials normally used in power electronics.

“Newly emerging ultra-wide bandgap materials have properties which enable them to handle very large voltages more easily,” said Oliver, Director of the Cambridge Centre for Gallium Nitride. “ ̽��ֱ��devices based on these materials will waste less energy and be smaller, lighter and cheaper. ̽��ֱ��same materials can also withstand high temperatures and doses of radiation, which means they can be used to enable other new electricity generation technologies, such as fusion energy.”

“ ̽��ֱ��REWIRE IKC will play a prominent role within the UK’s semiconductor strategy, in cementing the UK’s place as a leader in compound semiconductor research and development, developing IP to be exploited here in the UK, rebuilding the UK semiconductor supply chain, and training the next generation of semiconductor materials scientists and engineers,” said Professor Peter Gammon from the ̽��ֱ�� of Warwick.

Industry partners in the REWIRE IKC include Ampaire, BMW, Bosch, Cambridge GaN Devices (CGD), Element-Six Technologies, General Electric, Hitachi Energy, IQE, Oxford Instruments, Siemens, ST Microelectronics and Toshiba.

REWIRE is one of two new IKCs announced being funded by the Engineering and Physical Sciences Research Council (EPSRC) and Innovate UK, both part of UK Research and Innovation. ̽��ֱ��second IKC at the ̽��ֱ�� of Southampton will improve development and commercialisation of silicon photonics technologies in the UK.

“This investment marks a crucial step in advancing our ambitions for the semiconductor industry, with these centres helping bring new technologies to market in areas like net zero and AI, rooting them right here in the UK,” said Minister for Tech and the Digital Economy Saqib Bhatti. “Just nine months into delivering on the National Semiconductor Strategy, we’re already making rapid progress towards our goals. This isn’t just about fostering growth and creating high-skilled jobs, it's about positioning the UK as a hub of global innovation, setting the stage for breakthroughs that have worldwide impact.”

Adapted from a ̽��ֱ�� of Bristol media release.

For more information on energy-related research in Cambridge, please visit the Energy IRC, which brings together Cambridge’s research knowledge and expertise, in collaboration with global partners, to create solutions for a sustainable and resilient energy landscape for generations to come.

̽��ֱ�� ̽��ֱ�� of Cambridge is a partner in the new £11m Innovation and Knowledge Centre (IKC) REWIRE, set to deliver pioneering semiconductor technologies and new electronic devices.

Yuichiro Chino via Getty Images

Robot arms and semiconductor wafer

Yes

Diamonds and rust help unveil ‘impossible’ quasi-particles

sc604 — Tue, 05 Dec 2023 10:02:43 +0000

Researchers led by the ̽��ֱ�� of Cambridge used a technique known as diamond quantum sensing to observe swirling textures and faint magnetic signals on the surface of hematite, a type of iron oxide.

̽��ֱ��researchers observed that magnetic monopoles in hematite emerge through the collective behaviour of many spins (the angular momentum of a particle). These monopoles glide across the swirling textures on the surface of the hematite, like tiny hockey pucks of magnetic charge. This is the first time that naturally occurring emergent monopoles have been observed experimentally.

̽��ֱ��research has also shown the direct connection between the previously hidden swirling textures and the magnetic charges of materials like hematite, as if there is a secret code linking them together. ̽��ֱ��results, which could be useful in enabling next-generation logic and memory applications, are reported in the journal Nature Materials.

According to the equations of James Clerk Maxwell, a giant of Cambridge physics, magnetic objects, whether a fridge magnet or the Earth itself, must always exist as a pair of magnetic poles that cannot be isolated.

“ ̽��ֱ��magnets we use every day have two poles: north and south,” said Professor Mete Atatüre, who led the research. “In the 19th century, it was hypothesised that monopoles could exist. But in one of his foundational equations for the study of electromagnetism, James Clerk Maxwell disagreed.”

Atatüre is Head of Cambridge’s Cavendish Laboratory, a position once held by Maxwell himself. “If monopoles did exist, and we were able to isolate them, it would be like finding a missing puzzle piece that was assumed to be lost,” he said.

About 15 years ago, scientists suggested how monopoles could exist in a magnetic material. This theoretical result relied on the extreme separation of north and south poles so that locally each pole appeared isolated in an exotic material called spin ice.

However, there is an alternative strategy to find monopoles, involving the concept of emergence. ̽��ֱ��idea of emergence is the combination of many physical entities can give rise to properties that are either more than or different to the sum of their parts.

Working with colleagues from the ̽��ֱ�� of Oxford and the National ̽��ֱ�� of Singapore, the Cambridge researchers used emergence to uncover monopoles spread over two-dimensional space, gliding across the swirling textures on the surface of a magnetic material.

̽��ֱ��swirling topological textures are found in two main types of materials: ferromagnets and antiferromagnets. Of the two, antiferromagnets are more stable than ferromagnets, but they are more difficult to study, as they don’t have a strong magnetic signature.

To study the behaviour of antiferromagnets, Atatüre and his colleagues use an imaging technique known as diamond quantum magnetometry. This technique uses a single spin – the inherent angular momentum of an electron – in a diamond needle to precisely measure the magnetic field on the surface of a material, without affecting its behaviour.

For the current study, the researchers used the technique to look at hematite, an antiferromagnetic iron oxide material. To their surprise, they found hidden patterns of magnetic charges within hematite, including monopoles, dipoles and quadrupoles.

“Monopoles had been predicted theoretically, but this is the first time we’ve actually seen a two-dimensional monopole in a naturally occurring magnet,” said co-author Professor Paolo Radaelli, from the ̽��ֱ�� of Oxford.

“These monopoles are a collective state of many spins that twirl around a singularity rather than a single fixed particle, so they emerge through many-body interactions. ̽��ֱ��result is a tiny, localised stable particle with diverging magnetic field coming out of it,” said co-first author Dr Hariom Jani, from the ̽��ֱ�� of Oxford.

“We’ve shown how diamond quantum magnetometry could be used to unravel the mysterious behaviour of magnetism in two-dimensional quantum materials, which could open up new fields of study in this area,” said co-first author Dr Anthony Tan, from the Cavendish Laboratory. “ ̽��ֱ��challenge has always been direct imaging of these textures in antiferromagnets due to their weaker magnetic pull, but now we’re able to do so, with a nice combination of diamonds and rust.”

̽��ֱ��study not only highlights the potential of diamond quantum magnetometry but also underscores its capacity to uncover and investigate hidden magnetic phenomena in quantum materials. If controlled, these swirling textures dressed in magnetic charges could power super-fast and energy-efficient computer memory logic.

̽��ֱ��research was supported in part by the Royal Society, the Sir Henry Royce Institute, the European Union, and the Engineering and Physical Sciences Research Council (EPSRC), part of UK Research and Innovation (UKRI).

Reference:
K C Tan, Hariom Jani, Michael Högen et al. ‘Revealing Emergent Magnetic Charge in an Antiferromagnet with Diamond Quantum Magnetometry.’ Nature Materials (2023). DOI: 10.1038/s41563-023-01737-4.

Researchers have discovered magnetic monopoles – isolated magnetic charges – in a material closely related to rust, a result that could be used to power greener and faster computing technologies.

If monopoles did exist, and we were able to isolate them, it would be like finding a missing puzzle piece that was assumed to be lost

Mete Atatüre

Anthony Tan and Michael Hoegen

Magnetic monopoles in hematite

̽��ֱ��text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

Yes

Simulations of ‘backwards time travel’ can improve scientific experiments

vb425 — Thu, 12 Oct 2023 15:00:00 +0000

If gamblers, investors and quantum experimentalists could bend the arrow of time, their advantage would be significantly higher, leading to significantly better outcomes.

Researchers at the ̽��ֱ�� of Cambridge have shown that by manipulating entanglement – a feature of quantum theory that causes particles to be intrinsically linked – they can simulate what could happen if one could travel backwards in time. So that gamblers, investors and quantum experimentalists could, in some cases, retroactively change their past actions and improve their outcomes in the present.

Whether particles can travel backwards in time is a controversial topic among physicists, even though scientists have previously simulated models of how such spacetime loops could behave if they did exist. By connecting their new theory to quantum metrology, which uses quantum theory to make highly sensitive measurements, the Cambridge team has shown that entanglement can solve problems that otherwise seem impossible. The study appears in the journal Physical Review Letters.

“Imagine that you want to send a gift to someone: you need to send it on day one to make sure it arrives on day three,” said lead author David Arvidsson-Shukur, from the Hitachi Cambridge Laboratory. “However, you only receive that person’s wish list on day two. So, in this chronology-respecting scenario, it’s impossible for you to know in advance what they will want as a gift and to make sure you send the right one.

“Now imagine you can change what you send on day one with the information from the wish list received on day two. Our simulation uses quantum entanglement manipulation to show how you could retroactively change your previous actions to ensure the final outcome is the one you want.”

̽��ֱ��simulation is based on quantum entanglement, which consists of strong correlations that quantum particles can share and classical particles—those governed by everyday physics—cannot.

̽��ֱ��particularity of quantum physics is that if two particles are close enough to each other to interact, they can stay connected even when separated. This is the basis of quantum computing – the harnessing of connected particles to perform computations too complex for classical computers.

“In our proposal, an experimentalist entangles two particles,” said co-author Nicole Yunger Halpern, researcher at the National Institute of Standards and Technology (NIST) and the ̽��ֱ�� of Maryland. “ ̽��ֱ��first particle is then sent to be used in an experiment. Upon gaining new information, the experimentalist manipulates the second particle to effectively alter the first particle’s past state, changing the outcome of the experiment.”

“ ̽��ֱ��effect is remarkable, but it happens only one time out of four!” said Arvidsson-Shukur. “In other words, the simulation has a 75% chance of failure. But the good news is that you know if you have failed. If we stay with our gift analogy, one out of four times, the gift will be the desired one (for example a pair of trousers), another time it will be a pair of trousers but in the wrong size, or the wrong colour, or it will be a jacket.”

To give their model relevance to technologies, the theorists connected it to quantum metrology. In a common quantum metrology experiment, photons—small particles of light—are shone onto a sample of interest and then registered with a special type of camera. If this experiment is to be efficient, the photons must be prepared in a certain way before they reach the sample. ̽��ֱ��researchers have shown that even if they learn how to best prepare the photons only after the photons have reached the sample, they can use simulations of time travel to retroactively change the original photons.

To counteract the high chance of failure, the theorists propose to send a huge number of entangled photons, knowing that some will eventually carry the correct, updated information. Then they would use a filter to ensure that the right photons pass to the camera, while the filter rejects the rest of the ‘bad’ photons.

“Consider our earlier analogy about gifts,” said co-author Aidan McConnell, who carried out this research during his master’s degree at the Cavendish Laboratory in Cambridge, and is now a PhD student at ETH, Zürich. “Let’s say sending gifts is inexpensive and we can send numerous parcels on day one. On day two we know which gift we should have sent. By the time the parcels arrive on day three, one out of every four gifts will be correct, and we select these by telling the recipient which deliveries to throw away.”

“That we need to use a filter to make our experiment work is actually pretty reassuring,” said Arvidsson-Shukur. “ ̽��ֱ��world would be very strange if our time-travel simulation worked every time. Relativity and all the theories that we are building our understanding of our universe on would be out of the window.

“We are not proposing a time travel machine, but rather a deep dive into the fundamentals of quantum mechanics. These simulations do not allow you to go back and alter your past, but they do allow you to create a better tomorrow by fixing yesterday’s problems today.”

This work was supported by the Sweden-America Foundation, the Lars Hierta Memorial Foundation, Girton College, and the Engineering and Physical Sciences Research Council (EPSRC), part of UK Research and Innovation (UKRI).

Reference:
David R M Arvidsson-Shukur, Aidan G McConnell, and Nicole Yunger Halpern, ‘Nonclassical advantage in metrology established via quantum simulations of hypothetical closed timelike curves’, Phys. Rev. Lett. 2023. DOI: 10.1103/PhysRevLett.131.150202

Physicists have shown that simulating models of hypothetical time travel can solve experimental problems that appear impossible to solve using standard physics.

We are not proposing a time travel machine, but rather a deep dive into the fundamentals of quantum mechanics

David Arvidsson-Shukur

Yaroslav Kushta via Getty Images

Digital generated image of abstract glowing tech data tunnel

̽��ֱ��text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

Yes

Switching ‘spin’ on and off (and up and down) in quantum materials at room temperature

sc604 — Wed, 16 Aug 2023 15:00:00 +0000

Spin is the term for the intrinsic angular momentum of electrons, which is referred to as up or down. Using the up/down spin states of electrons instead of the 0 and 1 in conventional computer logic could transform the way in which computers process information. And sensors based on quantum principles could vastly improve our abilities to measure and study the world around us.

An international team of researchers, led by the ̽��ֱ�� of Cambridge, has found a way to use particles of light as a ‘switch’ that can connect and control the spin of electrons, making them behave like tiny magnets that could be used for quantum applications.

̽��ֱ��researchers designed modular molecular units connected by tiny ‘bridges’. Shining a light on these bridges allowed electrons on opposite ends of the structure to connect to each other by aligning their spin states. Even after the bridge was removed, the electrons stayed connected through their aligned spins.

This level of control over quantum properties can normally only be achieved at ultra-low temperatures. However, the Cambridge-led team has been able to control the quantum behaviour of these materials at room temperature, which opens up a new world of potential quantum applications by reliably coupling spins to photons. ̽��ֱ��results are reported in the journal Nature.

Almost all types of quantum technology – based on the strange behaviour of particles at the subatomic level – involve spin. As they move, electrons usually form stable pairs, with one electron spin up and one spin down. However, it is possible to make molecules with unpaired electrons, called radicals. Most radicals are very reactive, but with careful design of the molecule, they can be made chemically stable.

“These unpaired spins change the rules for what happens when a photon is absorbed and electrons are moved up to a higher energy level,” said first author Sebastian Gorgon, from Cambridge’s Cavendish Laboratory. “We’ve been working with systems where there is one net spin, which makes them good for light emission and making LEDs.”

Gorgon is a member of Professor Sir Richard Friend’s research group, where they have been studying radicals in organic semiconductors for light generation, and identified a stable and bright family of materials a few years ago. These materials can beat the best conventional OLEDs for red light generation.

“Using tricks developed by different fields was important,” said Dr Emrys Evans from Swansea ̽��ֱ��, who co-led the research. “ ̽��ֱ��team has significant expertise from a number of areas in physics and chemistry, such as the spin properties of electrons and how to make organic semiconductors work in LEDs. This was critical for knowing how to prepare and study these molecules in the solid state, enabling our demonstration of quantum effects at room temperature.”

Organic semiconductors are the current state-of-the-art for lighting and commercial displays, and they could be a more sustainable alternative to silicon for solar cells. However, they have not yet been widely studied for quantum applications, such as quantum computing or quantum sensing.

“We’ve now taken the next big step and linked the optical and magnetic properties of radicals in an organic semiconductor,” said Gorgon. “These new materials hold great promise for completely new applications, since we’ve been able to remove the need for ultra-cold temperatures.”

“Knowing what electron spins are doing, let alone controlling them, is not straightforward, especially at room temperature,” said Friend, who co-led the research. “But if we can control the spins, we can build some interesting and useful quantum objects.”

̽��ֱ��researchers designed a new family of materials by first determining how they wanted the electron spins to behave. Using this bottom-up approach, they were able to control the properties of the end material by using a building block method and changing the ‘bridges’ between different modules of the molecule. These bridges were made of anthracene, a type of hydrocarbon.

For their ‘mix-and-match’ molecules, the researchers attached a bright light-emitting radical to an anthracene molecule. After a photon of light is absorbed by the radical, the excitation spreads out onto the neighbouring anthracene, causing three electrons to start spinning in the same way. When a further radical group is attached to the other side of the anthracene molecules, its electron is also coupled, bringing four electrons to spin in the same direction.

“In this example, we can switch on the interaction between two electrons on opposite ends of the molecule by aligning electron spins on the bridge absorbing a photon of light,” said Gorgon. “After relaxing back, the distant electrons remember they were together even after the bridge is gone.

“In these materials we’ve designed, absorbing a photon is like turning a switch on. ̽��ֱ��fact that we can start to control these quantum objects by reliably coupling spins at room temperature could open up far more flexibility in the world of quantum technologies. There’s a huge potential here to go in lots of new directions.”

“People have spent years trying to get spins to reliably talk to each other, but by starting instead with what we want the spins to do and then the chemists can design a molecule around that, we’ve been able to get the spins to align,” said Friend. “It’s like we’ve hit the Goldilocks zone where we can tune the spin coupling between the building blocks of extended molecules.”

̽��ֱ��advance was made possible through a large international collaboration – the materials were made in China, experiments were done in Cambridge, Oxford and Germany, and theory work was done in Belgium and Spain.

̽��ֱ��research was supported in part by the European Research Council, the European Union, the Engineering and Physical Sciences Research Council (EPSRC), part of UK Research and Innovation (UKRI), and the Royal Society. Richard Friend is a Fellow of St John’s College, Cambridge.

Reference:
Sebastian Gorgon et al. ‘Reversible spin-optical interface in luminescent organic radicals.’ Nature (2023). DOI: 10.1038/s41586-023-06222-1

Researchers have found a way to control the interaction of light and quantum ‘spin’ in organic semiconductors, that works even at room temperature.

These new materials hold great promise for completely new applications, since we’ve been able to remove the need for ultra-cold temperatures

Sebastian Gorgon

Artist's impression of aligned spins in an organic semiconductor

̽��ֱ��text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

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Smart lighting system based on quantum dots more accurately reproduces daylight

sc604 — Wed, 03 Aug 2022 09:00:00 +0000

̽��ֱ��researchers, from the ̽��ֱ�� of Cambridge, designed the next-generation smart lighting system using a combination of nanotechnology, colour science, advanced computational methods, electronics and a unique fabrication process.

̽��ֱ��team found that by using more than the three primary lighting colours used in typical LEDs, they were able to reproduce daylight more accurately. Early tests of the new design showed excellent colour rendering, a wider operating range than current smart lighting technology, and wider spectrum of white light customisation. ̽��ֱ��results are reported in the journal Nature Communications.

As the availability and characteristics of ambient light are connected with wellbeing, the widespread availability of smart lighting systems can have a positive effect on human health since these systems can respond to individual mood. Smart lighting can also respond to circadian rhythms, which regulate the daily sleep-wake cycle, so that light is reddish-white in the morning and evening, and bluish-white during the day.

When a room has sufficient natural or artificial light, good glare control, and views of the outdoors, it is said to have good levels of visual comfort. In indoor environments under artificial light, visual comfort depends on how accurately colours are rendered. Since the colour of objects is determined by illumination, smart white lighting needs to be able to accurately express the colour of surrounding objects. Current technology achieves this by using three different colours of light simultaneously.

Quantum dots have been studied and developed as light sources since the 1990s, due to their high colour tunability and colour purity. Due their unique optoelectronic properties, they show excellent colour performance in both wide colour controllability and high colour rendering capability.

̽��ֱ��Cambridge researchers developed an architecture for quantum-dot light-emitting diodes (QD-LED) based next-generation smart white lighting. They combined system-level colour optimisation, device-level optoelectronic simulation, and material-level parameter extraction.

̽��ֱ��researchers produced a computational design framework from a colour optimisation algorithm used for neural networks in machine learning, together with a new method for charge transport and light emission modelling.

̽��ֱ��QD-LED system uses multiple primary colours – beyond the commonly used red, green and blue – to more accurately mimic white light. By choosing quantum dots of a specific size – between three and 30 nanometres in diameter – the researchers were able to overcome some of the practical limitations of LEDs and achieve the emission wavelengths they needed to test their predictions.

̽��ֱ��team then validated their design by creating a new device architecture of QD-LED based white lighting. ̽��ֱ��test showed excellent colour rendering, a wider operating range than current technology, and a wide spectrum of white light shade customisation.

̽��ֱ��Cambridge-developed QD-LED system showed a correlated colour temperature (CCT) range from 2243K (reddish) to 9207K (bright midday sun), compared with current LED-based smart lights which have a CCT between 2200K and 6500K. ̽��ֱ��colour rendering index (CRI) – a measure of colours illuminated by the light in comparison to daylight (CRI=100) – of the QD-LED system was 97, compared to current smart bulb ranges, which are between 80 and 91.

̽��ֱ��design could pave the way to more efficient, more accurate smart lighting. In an LED smart bulb, the three LEDs must be controlled individually to achieve a given colour. In the QD-LED system, all the quantum dots are driven by a single common control voltage to achieve the full colour temperature range.

“This is a world-first: a fully optimised, high-performance quantum-dot-based smart white lighting system,” said Professor Jong Min Kim from Cambridge’s Department of Engineering, who co-led the research. “This is the first milestone toward the full exploitation of quantum-dot-based smart white lighting for daily applications.”

“ ̽��ֱ��ability to better reproduce daylight through its varying colour spectrum dynamically in a single light is what we aimed for,” said Professor Gehan Amaratunga, who co-led the research. “We achieved it in a new way through using quantum dots. This research opens the way for a wide variety of new human responsive lighting environments.”

̽��ֱ��structure of the QD-LED white lighting developed by the Cambridge team is scalable to large area lighting surfaces, as it is made with a printing process and its control and drive is similar to that in a display. With standard point source LEDs requiring individual control this is a more complex task.

̽��ֱ��research was supported in part by the European Union and the Engineering and Physical Sciences Research Council (EPSRC), part of UK Research and Innovation (UKRI).

Reference:
Chatura Samarakoon et al. ‘Optoelectronic System and Device Integration for Quantum-Dot Light-Emitting Diode White Lighting with Computational Design Framework.’ Nature Communications (2022). DOI: 10.1038/s41467-022-31853-9

Researchers have designed smart, colour-controllable white light devices from quantum dots – tiny semiconductors just a few billionths of a metre in size – which are more efficient and have better colour saturation than standard LEDs, and can dynamically reproduce daylight conditions in a single light.

This research opens the way for a wide variety of new human-responsive lighting environments

Gehan Amaratunga

Yaorusheng via Getty Images

Long exposure light painting

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

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