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Quantum technology for the 21st century

Discussion meeting

Location

The Royal Society, London, 6-9 Carlton House Terrace, London, SW1Y 5AG

Overview

Scientific discussion meeting organised by Professor Sir Peter Knight FRS, Professor Ian Walmsley FRS, Professor Gerard Milburn, Dr Jonathan Pritchard, Dr Stephen Till.

Quantum technology

The meeting included academic and industry leaders in quantum physics and engineering to identify the next generation of quantum technologies for translational development. These include: simulators for chemistry and materials, imaging systems, enhanced sensors, ultra-precise atomic clocks, secure communications networks and quantum co-processors, such as certified random number generators and small-scale computing engines.

Speaker biographies, abstracts, and recorded audio of the presentations are available below.

This meeting was followed by a related, two-day satellite meeting, Quantum technology challenges for the 21st century, at the Royal Society at Chicheley Hall, home of the Kavli Royal Society Centre.

Enquiries: contact the events team.

Schedule of talks

09 May

Session 1 09:00-10:30

Fundamentals 1

2 talks Show detail Hide detail

Chairs

Sir Peter Knight FRS, Imperial College London, UK

09:00-09:30 Atom interferometry for navigation

Professor Ed Hinds FRS, Imperial College London, UK

Abstract

In the laboratory environment, atom interferometry provides a way to measure rotations and accelerations with spectacular accuracy. Very low noise figures are possible, but also extremely stable bias (zero offset) and calibration. This opens the possibility of inertial navigation over long periods without needing recourse to the global navigation satellite system.

I will outline the basic idea of atom interferometry and explain why it is so accurate. I will also discuss the challenges that arise when trying to incorporate this new technology into a practical inertial navigation system.

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09:30-10:00 Quantum computing in silicon with donor electron spins

Professor Michelle Simmons, University of New South Wales, Australia

Abstract

Extremely long electron and nuclear spin coherence times have recently been demonstrated in isotopically pure Si-28 making silicon one of the most promising semiconductor materials for spin based quantum information. The two level spin state of single electrons bound to shallow phosphorus donors in silicon in particular provide well defined, reproducible qubits and represent a promising system for a scalable quantum computer in silicon. An important challenge in these systems is the realisation of an architecture, where we can position donors within a crystalline environment with approx. 20-50nm separation, individually address each donor, manipulate the electron spins using ESR techniques and read-out their spin states.

We have developed a unique fabrication strategy for a scalable quantum computer in silicon using scanning tunneling microscope hydrogen lithography to precisely position individual P donors in a Si crystal aligned with nanoscale precision to local control gates necessary to initialize, manipulate, and read-out the spin states. During this talk I will focus on demonstrating spin transport and single-shot spin read-out of precisely-positioned P donors in Si. I will also describe our approaches to scale up using rf reflectometry and the investigation of 3D architectures for implementation of the surface code.

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Session 2 11:00-12:30

Fundamentals 2

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Chairs

Professor Ian Walmsley FRS, University of Oxford, UK

11:00-11:30 Suppression and revival of weak localisation of ultra-cold atoms by manipulation of time-reversal symmetry

Professor Alain Aspect ForMemRS, Institut d'Optique, Palaiseau

Abstract

In the early 1980's, observation of a magneto-resistance anomaly in metallic thin films was attributed to the phenomenon of weak localisation of electrons and to time-reversal symmetry breaking due to a magnetic field acting upon charged particles.

In the context of our quantum simulation program, we have directly observed weak localisation of ultra-cold atoms in a 2D configuration, placed in a disordered potential created by a laser speckle. In order to manipulate time-reversal symmetry with our neutral atoms, we take advantage of the slow evolution of our system, and we observe the suppression and revival of weak localisation when time reversal symmetry is cancelled and re-established.

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11:30-12:00 Large scale photonics quantum networks

Professor Ian Walmsley FRS, University of Oxford, UK

Abstract


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Session 3 13:30-15:00

Quantum imaging

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Chairs

Professor John Rarity FRS, University of Bristol, UK

13:30-14:00 Single pixel imaging

Professor Miles Padgett FRS, University of Glasgow, UK

Abstract

Cameras are often marketed in terms of the number of pixels they possess – but do more pixels mean a ‘better’ camera?  Rather than increasing the number of pixels we ask the question 'how can a camera work with a single pixel?'. This talk will link the field of computational ghost imaging to that of single-pixel cameras explaining how spatial structuring of either the illumination or imaging system means that image and video reconstruction can be achieved using just a small number of photodiodes.

Such approaches are particularly useful for imaging at wavelengths where detector arrays are either very expensive or unobtainable. Within QuantIC we are using this technology to make low-cost cameras for imaging the short-wave Infra red, allowing the visualisation of leaking gas.

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14:00-14:30 The promise of quantum imaging

Professor Robert Boyd, University of Ottawa, Canada

Abstract

Quantum imaging strives to develop methods for improved image formation based the use of quantum phenomena. These quantum images can be superior to those created by conventional methods in terms of sharpness, signal-to-noise ratios, ability to work at low light levels, etc. Aims of research in this area include both the development of increased understanding of quantum protocols for superior imaging and the implementation of these protocols. In this presentation we describe several such protocols under recent investigation. One protocol entails ghost imaging, in which coincidence measurements are used to obtain spatial information about an object even though only a non-imaging (“bucket”) detector is used to collect photons that have interacted with the object. This protocol can prove especially useful when the two photons detected in coincidence have very different wavelengths. Another protocol involves the use of Mandel’s induced coherence without induced emission. It has recently been shown that this process can lead to the formation of images carried by photons that are actually never detected. A third example is the development of imaging procedures for use with extremely weak thermal light fields (such as nighttime illumination by star light). The protocol entails subtracting exactly one photon from such a thermal field. This photon-subtracted state displays strong quantum features such as sub-Poissonian noise properties.

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Session 4 15:30-17:00

Quantum information processing 1

3 talks Show detail Hide detail

Chairs

Dr Elham Kashefi, University of Edinburgh, UK; LTCI, CNRS, France

15:30-16:00 Quantum communication with coherent states of light

Professor Gerd Leuchs, Max Planck Institute for the Science of Light, Germany

Abstract

Quantum communication offers long-term security especially relevant for government and industry users. On a very fundamental level the security of quantum key distribution relies on the non-orthogonality of the quantum states used. So even coherent states are well suited for this task, the quantum states that describe the light generated by laser systems. Continuous variable quantum key distribution with coherent states uses a technology that is very similar to the one employed in classical coherent communication systems, the backbone of today's internet connections. Here we review recent developments in this field in two regimes: (1) improving QKD equipment by implementing front-end telecom devices and (2) research into satellite QKD for bridging long distances by building upon existing optical satellite links.

In optical fibre systems continuous variable quantum cryptography reaches GHz speed and offers efficient integration with commercially available telecommunication techniques, especially in short links within an inner-city or a data centre. Compact and efficient sending and receiving devices can be made of integrated optical components including quantum random number generators.

Optical free space communication is a reliable means to transmit classical and quantum information. Free space links offer ad-hoc deployment in intra-city communication, air-to-ground or satellite-to-ground scenarios. In quantum communication the experimental effort has so far been devoted mostly to discrete variables such as the polarisation state of single photons. We present experiments investigating free space transmission of quantum continuous variable states using homodyne measurement, rendering the quantum states immune to stray light and enabling daylight operation. Quantum communication with satellites offers a viable solution to bridge long distances. We will discuss our current joint project with Tesat Spacecom / Airbus in the development of quantum key distribution with coherent optical communication in satellite systems.

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16:00-16:30 Noise: the fundamental obstacle for scalable quantum information systems

Professor Kae Nemoto, Japan National Institute for Informatics, Japan

Abstract

One of the fundamental challenges in the development of quantum technologies is to control noise in these quantum systems.  A quantum system always suffers from noise due to unwanted interactions with the environment and imperfect controls. The noise effects on each component of our quantum system tend to accumulate, and it is impossible without noise control for the system to maintain its quantum coherence required for quantum information processing.  The control of noise is hence essential for one to realise scalable quantum information systems.  In this presentation, we show how we can overcome noise to create a scalable quantum information system both in terms of its size and running time. To achieve this, we consider an approach in which both of the basic device and system architecture are designed together. Such a device can be realised using a single NV centre embedded within an optical cavity. We show how this device as a fundamental module can be used to construct a scalable quantum information system.

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16:30-17:00 Quantum communications in telecom networks

Dr Andrew Shields FREng, Toshiba Cambridge, UK

Abstract

Secure communications based on quantum cryptography is already employed to transmit highly sensitive medical or financial data. Expanding the range of applications to more widespread use will require a dramatic reduction in the cost of deploying the technology.  Central to this challenge is the requirement to avoid expensive dedicated dark fibre for the quantum channel and rather to send the qubits in the ordinary data-carrying network.

Here I review progress on integrating quantum communications into conventional telecom infrastructures. Recent work demonstrates it is possible to send qubits along optical fibres which are simultaneously carrying the high data bandwidths found in modern communication systems. This allows a high bandwidth quantum encryption system to be realised, in which multiple 100 Gb/s data channels are secured by quantum keys transmitted along the same fibre.

Deployment costs can be greatly reduced in conventional fibre optic communications using point to multi-point links to connect many customers to a common point in the network through shared fibre. This concept can also be applied to quantum communications, allowing multiple users to share the fibre and equipment costs. Indeed recent studies show that quantum key distribution can be combined with data transmission in GPON access networks able to connect up to 128 users.

Finally, I will discuss plans to implement these technologies in a large-scale quantum network in the UK.

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10 May

Session 5 09:00-10:30

Quantum enhanced sensors

2 talks Show detail Hide detail

Chairs

Professor Myungshik Kim, Imperial College London, UK

09:00-09:30 Progress in the UK National Quantum Technology Hub in Sensors and Metrology

Professor Kai Bongs, University of Birmingham, UK

Abstract

We are at the verge of a technology revolution, which harnesses deep quantum effects, often termed Quantum 2.0. Quantum Technologies have been identified internationally as a strategic innovation area based on a global research investment surpassing £2bn. The UK has moved to the forefront of innovation in this area, with a £300M investment in technology translation from science into applications and installed four national quantum technology hubs to cover different areas of future technology. This talk will provide an overview of the activities and recent progress within the UK National Quantum Technology Hub in Sensors and Metrology. It will also discuss case studies of where applications of quantum sensors promises to bring a benefit to society and the economy.

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09:30-10:00 Quantum entanglement for precision sensing

Professor Mark Kasevich, Stanford University, USA

Abstract

Engineered quantum entanglement is thought to offer great promise for applications in computation, metrology and communication, and has been the subject of vigorous study in recent years. We will describe quantum metrology implementations in which clusters of as many as 1000 entangled atoms are used to measure phase shifts in a cold atom clock system at levels of sensitivity unavailable with any competing method. We show how to exploit the metrological benefits of entangled states for precision sensing without employing very low noise detectors, thereby easing the engineering requirements for deployed sensors. We expect the demonstrated methods to become a foundation for future atomic sensors, including clocks and gyroscopes.

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Session 6 11:00-12:30

Quantum clocks and networks

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Chairs

Professor Patrick Gill MBE, National Physical Laboratory, UK

11:00-11:30 Frequency conversion of photons from trapped Ba+ ions for quantum networking

Dr James Siverns, University of Maryland, USA

Abstract

One platform for quantum networking includes entanglement between remotely situated quantum memories. Trapped ion systems have features amenable for quantum networking including long-lived memories, flying qubits and on-site processing capabilities. For a two-node quantum network, entanglement and even teleportation have been demonstrated. Despite these desirable features, there remain challenges. Trapped ions, such as Yb+, have excellent, long-lived quantum memories but emit flying qubits in the UV range that have limited propagation range either in free space or optical fibers. However, other ions, such as Ba+, have modest qubit lifetimes but emit flying qubits in the visible range. In this case, using quantum frequency conversion, we can convert the flying qubit into another optical wavelength, either for hybrid quantum networking or for long-haul communication. Remarkably, a single quanta can be frequency converted using periodically poled lithium niobate (PPLN) waveguides. Co-trapping a long-lived memory qubit, Yb+, alongside the Ba+ ion, for a hybrid quantum system, combines long-lived microwave clock-states entangled with telecom photons. The vision is for an intra-city quantum network linking remote situated quantum memories. We will discuss our approach and practical challenges.

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11:30-12:00 Lasers and atoms for time and position

Professor Leo Hollberg, Stanford University, USA

Abstract

With the development of precision laser spectroscopy, laser-cooling and –trapping of atoms, and femtosecond optical frequency combs, we now have the science and technology to measure Time and Space with unprecedented precision. Due to various constraints and bottlenecks, the capabilities of the high performance optical-atomic systems have not yet found their way into real-world applications. In contrast, Laser Atomic Molecular Optical (L-AMO) science is making a significant impact at relatively low performance levels with Chip Scale Atomic Devices. Questions arise as to how we can optimally leverage quantum systems for fundamental science and applications. One limitation of the highest performance atomic clocks is in transferring 'Time' from one location to another. We are exploring the prospects for doing time and frequency transfer using free-space laser links, with the goal of operating links between ground and space. These capabilities would support and enable future scientific missions such as cold-atom clocks in space, tests of General Relativity, high accuracy comparison of ground clocks around the world, and searches for physics beyond the Standard Model. In addition, they could enhance the performance of existing GNSS navigation systems as well as providing precision measurements in earth sciences such as geodesy and sea level determinations. 

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Session 7 13:30-15:00

Quantum information processing 2

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Chairs

Professor Timothy Spiller, University of York, UK

13:30-14:00 Photonic quantum computing

Professor Jeremy O'Brien, University of Bristol, UK

Abstract

Of the various approaches to quantum computing, photons are appealing for their low-noise properties and ease of manipulation at the single qubit level; while the challenge of entangling interactions between photons can be met via measurement induced non-linearities. However, the real excitement with this architecture is the promise of ultimate manufacturability: all of the components-including sources, detectors, filters, switches, delay lines-have been implemented on chip, and increasingly sophisticated integration of these components is being achieved. We will discuss the opportunities and challenges of a fully integrated photonic quantum computer.

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14:00-14:30 Quantum photonic network and physical layer security

Dr Masahide Sasaki, National Institute for Information and Communications Technology, Japan

Abstract

Quantum photonic network is an emerging platform to realise information theoretically secure communications in a resource-efficient way, approaching the optimal rate in secure bits/s/Hz/photon. The core concept is to integrate QKD for the highest security, quantum communication for power-minimum maximum-capacity communications, and a new scheme of physical layer cryptography which merges the merits of these two to realise the secrecy rate with information theoretic security into a network, so that the whole network can provide best solutions for various kinds of use cases. The basic theory behind this platform is simple, namely coding theorem for a wiretap channel scenario. It is to establish physical layer security at the maximum rate. QKD can be regarded as one extreme of branches of this concept. We present our latest results on the two core building blocks, updated Tokyo QKD Network and Tokyo Free Space Optical Testbed. Many interesting questions in theory and basic architecture remain open, and implementations have just started. We then discuss our next challenges and future perspectives.

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Session 8 15:30-17:00

Quantum information processing 3

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Chairs

Professor Timothy Spiller, University of York, UK

15:30-16:00 Quantum information processing with photon temporal modes

Professor Christine Silberhorn, University of Paderborn, Germany

Abstract

Photon temporal modes are defined by sets of field orthogonal superposition states, which are composed of a continuum of monochromatic waves. They describe naturally pulsed quantum light with different spectral-temporal mode shapes, and span intrinsically a high-dimensional Hilbert space. Because they occupy only one single spatial mode, they also lend themselves to integration into current single-mode fibre communication networks.

Using pulsed parametric downconversion processes much effort has been devoted in recent years to engineer sources with uncorrelated spectra, which emit single temporal mode pulsed photon pairs with no intrinsic structure. Contrariwise, we can explore the multi-mode temporal states for multi-dimensional quantum information encoding. Here we show that we can obtain complete control over the three main ingredients for quantum applications, namely the efficient generation of different types of resource states with tailored entanglement properties, the targeted manipulation and processing of temporal modes, as well as their detection. We demonstrate experimentally highly efficient devices based on non-linear waveguide structures for the preparation of temporal single and multi-mode states as well as for their manipulation by means of our new quantum pulse gate setup. By performing quantum state tomography of a four-dimensional temporal mode space we pave the way for harnessing temporal modes for future quantum communication networks.

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16:00-17:00 Closing remarks

Professor Artur Ekert, University of Oxford, UK

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Quantum technology for the 21st century The Royal Society, London 6-9 Carlton House Terrace London SW1Y 5AG UK