̽��ֱ�� of Cambridge - quantum computing

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.

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Building business partnerships in AI, quantum, cybersecurity and computer architecture

skbf2 — Wed, 18 Sep 2024 14:25:55 +0000

Hear from four of our leading researchers on their work and why partnering with industry is key to their success.

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)

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Quantum leap

skbf2 — Thu, 21 Mar 2024 14:27:14 +0000

Meet the brilliant founder and CEO of Nu Quantum, a Cambridge spinout paving the way for a new era of quantum computing.

Two-dimensional material could store quantum information at room temperature

sc604 — Fri, 11 Feb 2022 11:01:00 +0000

Quantum memory is a major building block to be addressed in the building of a quantum internet, where quantum information is securely stored and sent via photons, or particles of light.

Researchers from the Cavendish Laboratory at the ̽��ֱ�� of Cambridge, in collaboration with colleagues from UT Sydney in Australia, have identified a two-dimensional material, hexagonal boron nitride, that can emit single photons from atomic-scale defects in its structure at room temperature.

̽��ֱ��researchers discovered that the light emitted from these isolated defects gives information about a quantum property that can be used to store quantum information, called spin, meaning the material could be useful for quantum applications. Importantly, the quantum spin can be accessed via light and at room temperature.

̽��ֱ��finding could eventually support scalable quantum networks built from two-dimensional materials that can operate at room temperature. ̽��ֱ��results are reported in the journal Nature Communications.

Future communication networks will use single photons to send messages around the world, which will lead to more secure global communication technologies.

Computers and networks built on the principles of quantum mechanics would be both far more powerful and more secure than current technologies. However, in order to make such networks possible, researchers need to develop reliable methods of generating single, indistinguishable photons as carriers of information across quantum networks.

“We can send information from one place to another using photons, but if we’re going to build real quantum networks, we need to send information, store it and send it somewhere else,” said Dr Hannah Stern from Cambridge’s Cavendish Laboratory, the study’s co-first author, along with Qiushi Gu and Dr John Jarman. “We need materials that can hold onto quantum information for a certain amount of time at room temperature, but most current material platforms we’ve got are challenging to make and only work well at low temperatures.”

Hexagonal boron nitride is a two-dimensional material that is grown by chemical vapour deposition in large reactors. It’s cheap and scalable. Recent efforts have revealed the presence of single photon emitters and the presence of a dense ensemble of optically accessible spins, but not individually isolated spin-photon interfaces operating under ambient conditions.

“Usually, it’s a pretty boring material that’s normally used as an insulator,” said Stern, who is a Junior Research Fellow at Trinity College. “But we found that there are defects in this material that can emit single photons, which means it could be used in quantum systems. If we can get it to store quantum information in spin, then it’s a scalable platform.”

Stern and her colleagues set up a hexagon boron nitride sample near a tiny gold antenna and a magnet of set strength. By firing a laser at the sample at room temperature, they were able to observe lots of different magnetic field-dependent responses on the light being emitted from the material.

̽��ֱ��researchers found that when they shone the laser on the material, they were able to manipulate the spin, or inherent angular momentum, of the defects, and use the defects as a way of storing quantum information.

“Typically, the signal is always the same in these systems, but in this case, the signal changes depending on the particular defect we’re studying, and not all defects show a signal, so there is a lot to still discover,” said co-first author Qiushi Gu. “There’s a lot of variation across the material, like a blanket draped over a moving surface – you see lots of ripples, and they’re all different.”

Professor Mete Atature, who supervised the work, adds “now that we have identified optically accessible isolated spins at room temperature in this material, the next steps will be to understand their photophysics in detail and explore the operation regimes for possible applications including information storage and quantum sensing. There will be a stream of fun physics following this work.”

̽��ֱ��research was supported in part by the European Research Council. Mete Atature is a Fellow of St John's College, Cambridge.

Reference:
Hannah L. Stern, Quishi Gu, John Jarman, et al. ‘Room-temperature optically detected magnetic resonance of single defects in hexagonal boron nitride.’ Nature Communications (2022). DOI: 10.1038/s41467-022-28169-z

Researchers have identified a two-dimensional material that could be used to store quantum information at room temperature.

There are defects in this material that can emit single photons, which means it could be used in quantum systems

Hannah Stern

Qiushi Gu

Artistic rendition of isolated spins on hexagonal boron nitride under an optical microscope

̽��ֱ��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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Giant 'quantum twisters' may form in liquid light

sc604 — Fri, 05 Mar 2021 16:55:21 +0000

Anyone who has drained a bathtub or stirred cream into coffee has seen a vortex, a ubiquitous formation that appears when fluid circulates. But unlike water, fluids governed by the strange rules of quantum mechanics have a special restriction: as was first predicted in 1945 by future Nobel winner Lars Onsager, a vortex in a quantum fluid can only twist by whole-number units.

These rotating structures are predicted to be widely useful for studying everything from quantum systems to black holes. But while the smallest possible quantum vortex, with a single unit of rotation, has been seen in many systems, larger vortices are not stable. While scientists have attempted to force larger vortices to hold themselves together, the results have been mixed: when the vortices have been formed, the severity of the methods used have generally destroyed their usefulness.

Now, Samuel Alperin and Professor Natalia Berloff from the ̽��ֱ�� of Cambridge have discovered a theoretical mechanism through which giant quantum vortices are not only stable but form by themselves in otherwise near-uniform fluids. ̽��ֱ��findings, published in the journal Optica, could pave the way for experiments that might provide insight into the nature of rotating black holes that have similarities with giant quantum vortices.

To do this, the researchers used a quantum hybrid of light and matter, called a polariton. These particles are formed by shining laser light onto specially layered materials. “When the light gets trapped in the layers, the light and the matter become inseparable, and it becomes more practical to look at the resulting substance as something that is distinct from either light or matter, while inheriting properties of both,” said Alperin, a PhD student at Cambridge’s Department of Applied Mathematics and Theoretical Physics.

One of the most significant properties of polaritons comes from the simple fact that light can’t be trapped forever. A fluid of polaritons, which requires a high density of the exotic particles, is constantly expelling light, and needs to be fed with fresh light from the laser to survive. “ ̽��ֱ��result,” said Alperin, “is a fluid which is never allowed to settle, and which doesn’t need to obey what are usually basic restrictions in physics, like the conservation of energy. Here the energy can change as a part of the dynamics of the fluid.”

It was exactly these constant flows of liquid light that the researchers exploited to allow the elusive giant vortex to form. Instead of shining the laser on the polariton fluid itself, the new proposal has the light shaped like a ring, causing a constant inward flow similarly to how water flows to a bathtub drain. According to the theory, this flow is enough to concentrate any rotation into a single giant vortex.

“That the giant vortex really can exist under conditions that are amenable to their study and technical use was quite surprising,” Alperin said, “but really it just goes to show how utterly distinct the hydrodynamics of polaritons are from more well-studied quantum fluids. It’s exciting territory.”

̽��ֱ��researchers say that they are just at the beginning of their work on giant quantum vortices. They were able to simulate the collision of several quantum vortices as they dance around each other with ever increasing speed until they collide to form a single giant vortex analogous to the collision of black holes. They also explained the instabilities that limit the maximum vortex size while exploring intricate physics of the vortex behaviour.

“These structures have some interesting acoustic properties: they have acoustic resonances that depend on their rotation, so they sort of sing information about themselves,” said Alperin. “Mathematically, it’s quite analogous to the way that rotating black holes radiate information about their own properties.”

̽��ֱ��researchers hope that the similarity could lead to new insights into the theory of quantum fluid dynamics, but they also say that polaritons might be a useful tool to study the behaviour of black holes.

Professor Berloff is jointly affiliated with Cambridge and the Skolkovo Institute of Science and Technology in Russia.

Reference:
Samuel N. Alperin and Natalia G. Berloff. ‘Multiply charged vortex states of polariton condensates.’ Optica (2021). DOI: 10.1364/OPTICA.418377

New mechanism found for generating giant vortices in quantum fluids of light.

Stable giant quantum vortices

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Through the looking glass: artificial ‘molecules’ open door to ultrafast devices

sc604 — Wed, 03 Mar 2021 00:00:01 +0000

Polaritons are quantum particles that consist of a photon and an exciton, another quasiparticle, combining light and matter in a curious union that opens up a multitude of possibilities in next-generation devices.

̽��ֱ��researchers have shown that geometrically coupled polariton condensates, which appear in semiconductor devices, are capable of simulating molecules with various properties.

Ordinary molecules are groups of atoms bound together with molecular bonds, and their physical properties differ from those of their constituent atoms quite drastically: consider the water molecule, H₂O, and elemental hydrogen and oxygen.

“In our work, we show that clusters of interacting polaritonic and photonic condensates can form a range of exotic and entirely distinct entities – ‘molecules’ – that can be manipulated artificially,” said first author Alexander Johnston, from Cambridge Department of Applied Mathematics and Theoretical Physics. “These artificial molecules possess new energy states, optical properties, and vibrational modes from those of the condensates comprising them.”

Johnston and his colleagues – Kirill Kalinin from DAMTP and Professor Natalia Berloff, who holds joint positions at Cambridge and Skoltech – were running numerical simulations of two, three, and four interacting polariton condensates, when they noticed some curious asymmetric stationary states in which not all of the condensates have the same density in their ground state.

“Upon further investigation, we found that such states came in a wide variety of different forms, which could be controlled by manipulating certain physical parameters of the system,” said Johnston. “This led us to propose such phenomena as artificial polariton molecules and to investigate their potential uses in quantum information systems.”

In particular, the team focused on an ‘asymmetric dyad’, which consists of two interacting condensates with unequal occupations. When two of those dyads are combined into a tetrad structure, the latter is, in some sense, analogous to a homonuclear molecule – for instance, to molecular hydrogen H₂. Furthermore, artificial polariton molecules can also form more elaborate structures, which could be thought of as artificial polariton compounds.

“There is nothing preventing more complex structures from being created,” said Johnston. “We’ve found that there is a wide range of exotic, asymmetric states possible in tetrad configurations. In some of these, all condensates have different densities, despite all of the couplings being of equal strength, inviting an analogy with chemical compounds.”

In specific tetrad structures, each asymmetric dyad can be viewed as an individual ‘spin,’ defined by the orientation of the density asymmetry. This has interesting consequences for the system’s degrees of freedom, or the independent physical parameters required to define states. ̽��ֱ��spins introduce a separate degree of freedom, in addition to the continuous degrees of freedom given by the condensate phases.

̽��ֱ��relative orientation of each of the dyads can be controlled by varying the coupling strength between them. Since quantum information sem.

“In addition, we have discovered a plethora of exotic asymmetric states in triad and tetrad systems,” said Berloff. “It is possible to seamlessly transition between such states simply by varying the pumping strength used to form the condensates. This property suggests that such states could form the basis of a polaritonic multi-valued logic system, which could enable the development of polaritonic devices that dissipate significantly less power than traditional methods and, potentially, operate orders of magnitude faster.”

Reference:
Alexander Johnston, Kirill P. Kalinin, and Natalia G. Berloff. ‘Artificial polariton molecules.’ Physical Review Letters B (2021). DOI: 10.1103/PhysRevB.103.L060507

Adapted from a Skoltech press release.

Researchers from the ̽��ֱ�� of Cambridge and Skoltech in Russia have shown that polaritons, the quirky particles that may end up running the quantum supercomputers of the future, can form structures that behave like molecules – and these ‘artificial molecules’ can potentially be engineered on demand. Their results are published in the journal Physical Review B Letters.

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Light used to detect quantum information stored in 100,000 nuclear quantum bits

sc604 — Mon, 15 Feb 2021 15:18:20 +0000

̽��ֱ��researchers, from the ̽��ֱ�� of Cambridge, were able to inject a ‘needle’ of highly fragile quantum information in a ‘haystack’ of 100,000 nuclei. Using lasers to control an electron, the researchers could then use that electron to control the behaviour of the haystack, making it easier to find the needle. They were able to detect the ‘needle’ with a precision of 1.9 parts per million: high enough to detect a single quantum bit in this large ensemble.

̽��ֱ��technique makes it possible to send highly fragile quantum information optically to a nuclear system for storage, and to verify its imprint with minimal disturbance, an important step in the development of a quantum internet based on quantum light sources. ̽��ֱ��results are reported in the journal Nature Physics.

̽��ֱ��first quantum computers – which will harness the strange behaviour of subatomic particles to far outperform even the most powerful supercomputers – are on the horizon. However, leveraging their full potential will require a way to network them: a quantum internet. Channels of light that transmit quantum information are promising candidates for a quantum internet, and currently there is no better quantum light source than the semiconductor quantum dot: tiny crystals that are essentially artificial atoms.

However, one thing stands in the way of quantum dots and a quantum internet: the ability to store quantum information temporarily at staging posts along the network.

“ ̽��ֱ��solution to this problem is to store the fragile quantum information by hiding it in the cloud of 100,000 atomic nuclei that each quantum dot contains, like a needle in a haystack,” said Professor Mete Atatüre from Cambridge’s Cavendish Laboratory, who led the research. “But if we try to communicate with these nuclei like we communicate with bits, they tend to ‘flip’ randomly, creating a noisy system.”

̽��ֱ��cloud of quantum bits contained in a quantum dot don’t normally act in a collective state, making it a challenge to get information in or out of them. However, Atatüre and his colleagues showed in 2019 that when cooled to ultra-low temperatures also using light, these nuclei can be made to do ‘quantum dances’ in unison, significantly reducing the amount of noise in the system.

Now, they have shown another fundamental step towards storing and retrieving quantum information in the nuclei. By controlling the collective state of the 100,000 nuclei, they were able to detect the existence of the quantum information as a ‘flipped quantum bit’ at an ultra-high precision of 1.9 parts per million: enough to see a single bit flip in the cloud of nuclei.

“Technically this is extremely demanding,” said Atatüre, who is also a Fellow of St John’s College. “We don’t have a way of ‘talking’ to the cloud and the cloud doesn’t have a way of talking to us. But what we can talk to is an electron: we can communicate with it sort of like a dog that herds sheep.”

Using the light from a laser, the researchers are able to communicate with an electron, which then communicates with the spins, or inherent angular momentum, of the nuclei.

By talking to the electron, the chaotic ensemble of spins starts to cool down and rally around the shepherding electron; out of this more ordered state, the electron can create spin waves in the nuclei.

“If we imagine our cloud of spins as a herd of 100,000 sheep moving randomly, one sheep suddenly changing direction is hard to see,” said Atatüre. “But if the entire herd is moving as a well-defined wave, then a single sheep changing direction becomes highly noticeable.”

In other words, injecting a spin wave made of a single nuclear spin flip into the ensemble makes it easier to detect a single nuclear spin flip among 100,000 nuclear spins.

Using this technique, the researchers are able to send information to the quantum bit and ‘listen in’ on what the spins are saying with minimal disturbance, down to the fundamental limit set by quantum mechanics.

“Having harnessed this control and sensing capability over this large ensemble of nuclei, our next step will be to demonstrate the storage and retrieval of an arbitrary quantum bit from the nuclear spin register,” said co-first author Daniel Jackson, a PhD student at the Cavendish Laboratory.

“This step will complete a quantum memory connected to light – a major building block on the road to realising the quantum internet,” said co-first author Dorian Gangloff, a Research Fellow at St John’s College.

Besides its potential usage for a future quantum internet, the technique could also be useful in the development of solid-state quantum computing.

̽��ֱ��research was supported in part by the European Research Council (ERC), the Engineering and Physical Sciences Research Council (EPSRC) and the Royal Society.

Reference:
D. M. Jackson et al. ‘Quantum sensing of a coherent single spin excitation in a nuclear ensemble.’ Nature Physics (2021). DOI: 10.1038/s41567-020-01161-4

Researchers have found a way to use light and a single electron to communicate with a cloud of quantum bits and sense their behaviour, making it possible to detect a single quantum bit in a dense cloud.

We don’t have a way of ‘talking’ to the cloud and the cloud doesn’t have a way of talking to us. But what we can talk to is an electron: we can communicate with it sort of like a dog that herds sheep

Mete Atatüre

Gerd Altmann from Pixabay

Quantum particles

Yes