A5031549578- Quantum Information and Cryptography
- Quantum Mechanics and Applications
- Quantum Computing Algorithms and Architecture
- Quantum optics and atomic interactions
- Quantum and electron transport phenomena
- Orbital Angular Momentum in Optics
- Neural Networks and Reservoir Computing
- Molecular Communication and Nanonetworks
- Spectroscopy and Quantum Chemical Studies
- Space Science and Extraterrestrial Life
- Cold Atom Physics and Bose-Einstein Condensates
- Optical Network Technologies
- Atomic and Subatomic Physics Research
- Advanced Frequency and Time Standards
- Distributed systems and fault tolerance
- Spacecraft Design and Technology
- Spacecraft Dynamics and Control
- Sparse and Compressive Sensing Techniques
- Space Satellite Systems and Control
- Quantum-Dot Cellular Automata
- Satellite Communication Systems
- Atmospheric Ozone and Climate
- CCD and CMOS Imaging Sensors
- Quantum Electrodynamics and Casimir Effect
- Random lasers and scattering media
University of Strathclyde
2014-2025
South East Technological University
2023-2024
Scottish Universities Physics Alliance
2024
Leibniz University Hannover
2024
King's College London
2024
National University of Singapore
2009-2022
Tech-X Corporation (United States)
2022
Centre for Quantum Technologies
2009-2022
University of Glasgow
2018
University of Cambridge
2003-2007
We provide a physical prescription based on interferometry for introducing the total phase of mixed state undergoing unitary evolution, which has been an elusive concept in past. define parallel transport condition that provides connection form obtaining geometric states. The expression reduces to well known formulas pure case when system undergoes noncyclic and quantum evolution.
We present a simple quantum network, based on the controlled-SWAP gate, that can extract certain properties of states without recourse to tomography. It be used as basic building block for direct estimations both linear and nonlinear functionals any density operator. The network has many potential applications ranging from purity tests eigenvalue characterization some channels. Experimental realizations proposed are within reach technology is currently being developed.
We describe in detail a general strategy for implementing conditional geometric phase between two spins. Combined with single-spin operations, this simple operation is universal gate quantum computation, that any unitary transformation can be implemented arbitrary precision using only operations and shifts. Thus geometrical phases form the basis of computation. Moreover, as induced depends on geometry paths executed by spins it resilient to certain types errors offers potential naturally...
Global quantum networks for secure communication can be realized using large fleets of satellites distributing entangled photon pairs between ground-based nodes. Because the cost a satellite depends on its size, smallest will most cost-effective. This Letter describes miniaturized, polarization entangled, photon-pair source operating board nano-satellite. The violates Bell’s inequality with Clauser–Horne–Shimony–Holt parameter <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"...
Global scale quantum communication links will form the backbone of internet. However, exponential loss in optical fibres precludes any realistic application beyond few hundred kilometres. Quantum repeaters and space-based systems offer to overcome this limitation. Here, we analyse use memory (QM)-equipped satellites for focussing on global range Measurement-Device-Independent (MDI) QKD. We demonstrate that equipped with QMs provide three orders magnitude faster entanglement distribution...
Advances in quantum technologies are giving rise to a revolution the way fundamental physics questions explored at empirical level. At same time, they seeds for future disruptive technological applications of physics. Remarkably, space-based environment may open many new avenues exploring and employing technologies. Recently, space missions or applied studies have been proposed implemented with stunning results. The combination its application is focus this review: we cover both scientific...
Abstract Global quantum communications will enable long-distance secure data transfer, networked distributed information processing, and other entanglement-enabled technologies. Satellite communication overcomes optical fibre range limitations, with the first realisations of satellite key distribution (SatQKD) being rapidly developed. However, limited transmission times between ground station severely constrains amount secret due to finite-block size effects. Here, we analyse these effects...
Quantum key distribution with solid-state single-photon emitters is gaining traction due to their rapidly improving performance and compatibility future quantum networks. Here we emulate a scheme quantum-dot-generated single photons frequency-converted 1550 nm, achieving count rates of 1.6 MHz [Formula: see text] asymptotic positive over 175 km telecom fibre. We show that the commonly used finite-key analysis for non-decoy state QKD drastically overestimates secure acquisition times overly...
Quantum key distribution (QKD) has matured in recent years from laboratory proof-of-principle demonstrations to commercially available systems. One of the major bottlenecks is limited communication distance fiber networks due exponential signal damping. To bridge intercontinental distances, low Earth orbit satellites transmitting quantum signals over atmosphere can be used. These free-space links, however, only operate during night, as sunlight otherwise saturates detectors used measure...
Global-scale quantum networking faces significant technical and scientific obstacles. Quantum repeaters (QRs) have been proposed to overcome the inherent direct transmission range limit through optical fiber. However, QRs are typically limited a total distance of few thousand kilometers and/or require extensive hardware overhead. Recent proposals suggest that strings space-borne with on-board memories (QMs) able provide global coverage. Here, we propose an alternative such repeater...
Examples of geometric phases abound in many areas physics. They offer both fundamental insights into physical phenomena and lead to interesting practical implementations. One them, as indicated recently, might be an inherently fault-tolerant quantum computation. This, however, requires one deal with the presence noise interactions between different subsystems. Despite wealth literature on subject very little is known about this important case. Here we report first experimental study for...
Progress in quantum computers, and their threat to conventional public-key infrastructure, drives new forms of encryption, including key distribution using entangled photons. Beaming photons Earth from orbit could provide secure communication over long distances. The authors transform a large, delicate quantum-optics setup into robust payload for shoebox-sized CubeSat satellite. Their gear survives the trip space, correlated are produced detected aboard satellite, validating design---a...
Quantum key distribution (QKD) offers future proof security based on fundamental laws of physics. Long-distance QKD spanning regions such as the United Kingdom (UK) may employ a constellation satellites. Small satellites, CubeSats in particular, low Earth orbit are relatively low-cost alternative to traditional, large platforms. They allow deployment number spacecrafts, ensuring greater coverage and mitigating some risk associated with availability due cloud cover. We present our mission...
Abstract Satellite-based platforms are currently the only feasible way of achieving intercontinental range for quantum communication, enabling thus future global internet. Recent demonstrations by Chinese spacecraft Micius have spurred an international space race and enormous interest in development both scientific commercial systems. Research efforts so far concentrated upon in-orbit involving a single satellite one or two ground stations. Ultimately key distribution should enable secure...
We introduce a model of quantum computation intermediate between the gate-based and measurement-based models. A register is manipulated remotely with help single ancilla that ``drives'' evolution register. The fully controlled qubit coupled to computational only via fixed unitary two-qubit interaction then measured in suitable bases, driving both single- operations on Arbitrary single-qubit directly qubits are not needed. characterize all interactions $E$ induce unitary, stepwise...
Quantum communication is a prime space technology application and offers near-term possibilities for long-distance quantum key distribution (QKD) experimental tests of entanglement. However, there exists considerable developmental risks subsequent costs time required to raise the technological readiness level terrestrial technologies adapt them operations. The small-space revolution promising route by which synergistic advances in miniaturization both satellite systems can be combined...
We present a programme for establishing the space worthiness of highly-miniaturised, polarisation-entangled, photon pair sources using CubeSat nanosatellites. Once demonstrated, can be deployed on more advanced satellites that are equipped with optical links to establish global space-based quantum key distribution network. In doing so, this work will also bring experimental tests overlap between and relativistic regimes closer realisation.
Concerted efforts are underway to establish an infrastructure for a global quantum internet realise spectrum of technologies. This will enable more precise sensors, secure communications, and faster data processing. Quantum communications front-runner with networks already implemented in several metropolitan areas. A number recent proposals have modelled the use space segments overcome range limitations purely terrestrial networks. Rapid progress design devices enabled their deployment...
Abstract Global-scale quantum communication networks will require efficient long-distance distribution of signals. While optical fibre communications are range-limited due to exponential losses in the absence memories and repeaters, satellites enable intercontinental communications. However, design satellite key (SatQKD) systems has unique challenges over terrestrial networks. The typical approach modelling SatQKD been estimate performances with a fully optimised protocol parameter space few...
We generalize the notion of relative phase to completely positive (CP) maps with known unitary representation, based on interferometry. Parallel transport conditions that define geometric for such are introduced. The interference effect is embodied in a set patterns defined by flipping environment state one two paths. show qubit this structure gives rise interesting additional information about geometry evolution CP map.
Precision control of a quantum system requires accurate determination the effective Hamiltonian. We develop method for estimating Hamiltonian parameters some unknown two-state and providing uncertainty bounds on these parameters. This only one measurement basis ability to initialize in arbitrary state which is not an eigenstate question. The scaling studied large numbers measurements found be proportional reciprocal square root number measurements.
Observation of coherent single-electron dynamics is severely limited by experimental bandwidth. We present a method to overcome this using moving quantum dots defined surface acoustic waves. Each dot holds single electron, and travels through static potential landscape. When the passes abruptly between regions different confinement, electron excited into superposition states, oscillates unitarily from side side. detect these oscillations weak, repeated measurement current across tunnel...
Generalized quantum measurements (positive operator valued measures or probability measures) are important for optimally extracting information communication and computation. The standard realization via the Neumark extension requires extensive resources in form of operations an extended Hilbert space. For arbitrary measurement, we show how to construct a binary search tree with depth logarithmic number possible outcomes. This could be implemented experimentally by coupling measured system...
We propose an experiment to test the effects of gravity and acceleration on quantum entanglement in space-based setups. show that between excitations two Bose–Einstein condensates is degraded after one them undergoes a change gravitational field strength. This prediction can be tested if are initially entangled separate satellites while being same orbit then moves different orbit. effect observable typical orbital manoeuvre nanosatellites like CanX4 CanX5.