A5073125796- Quantum Information and Cryptography
- Quantum Mechanics and Applications
- Quantum optics and atomic interactions
- Quantum Computing Algorithms and Architecture
- Cold Atom Physics and Bose-Einstein Condensates
- Laser-Matter Interactions and Applications
- Optical Network Technologies
- Photonic and Optical Devices
- Mechanical and Optical Resonators
- Semiconductor Lasers and Optical Devices
- Advanced Measurement and Metrology Techniques
- Spectroscopy and Quantum Chemical Studies
- Neural Networks and Reservoir Computing
- Chaos-based Image/Signal Encryption
- Advanced Fiber Laser Technologies
- Quantum and electron transport phenomena
- Cryptographic Implementations and Security
- Atomic and Subatomic Physics Research
- Coding theory and cryptography
- Intelligence, Security, War Strategy
- Force Microscopy Techniques and Applications
- Solid State Laser Technologies
- Orbital Angular Momentum in Optics
- Spectroscopy and Laser Applications
- Quantum-Dot Cellular Automata
Laboratoire Charles Fabry
2013-2024
Centre National de la Recherche Scientifique
2005-2022
Université Paris-Saclay
2016-2022
Institut d’Optique Graduate School
2006-2022
Institut Universitaire de France
2012-2016
Université Paris-Sud
2007-2014
École Normale Supérieure Paris-Saclay
2012
In this paper, we present the quantum key distribution (QKD) network designed and implemented by European project SEcure COmmunication based on Quantum Cryptography (SECOQC) (2004–2008), unifying efforts of 41 research industrial organizations. The paper summarizes SECOQC approach to QKD networks with a focus trusted repeater paradigm. It discusses architecture functionality prototype, which has been put into operation in Vienna 2008 publicly demonstrated framework conference held from...
We present a detailed experimental analysis of free-propagating light pulse prepared in "Schrödinger kitten" state, which is defined as quantum superposition "classical" coherent states with small amplitudes. This kitten state generated by subtracting one photon from squeezed vacuum beam, and it clearly presents negative Wigner function. The predicted influence the parameters excellent agreement results. amplitude can be amplified to transform our kittens" into bigger Schrödinger cats,...
We report on the implementation of a reverse-reconciliated coherent-state continuous-variable quantum key distribution system, with which we generated secret keys at rate more than $2\phantom{\rule{0.3em}{0ex}}\mathrm{kb}∕\mathrm{s}$ over $25\phantom{\rule{0.3em}{0ex}}\mathrm{km}$ optical fiber. Time multiplexing is used to transmit both signal and phase reference in same Our system includes all experimental aspects required for field setup. Real-time reverse reconciliation achieved by using...
We describe the observation of a "degaussification" protocol that maps individual pulses squeezed light onto non-Gaussian states. This effect is obtained by sending small fraction vacuum beam an avalanche photodiode, and conditioning single-shot homodyne detection remaining state upon photon-counting events. The experimental data provide clear evidence phase-dependent statistics. closely related to first step entanglement distillation procedure for continuous variables.
We experimentally demonstrate that the entanglement between Gaussian entangled states can be increased by non-Gaussian operations. Coherent subtraction of single photons from quadrature-entangled light pulses, created a nondegenerate parametric amplifier, produces delocalized with negative Wigner functions and complex structures more than initial in terms negativity. The experimental results are very good agreement theoretical predictions.
We propose a feasible optical setup allowing for loophole-free Bell test with efficient homodyne detection. A non-Gaussian entangled state is generated from two-mode squeezed vacuum by subtracting single photon each mode, using beam splitters and standard low-efficiency single-photon detectors. violation exceeding 1% achievable 6 dB light efficiency around 95%. detailed feasibility analysis, based upon the recent experimental generation of single-mode states, suggests that this method opens...
We discuss quantum key distribution protocols using continuous variables. show that such can be made secure against individual gaussian attacks regardless the transmission of optical line between Alice and Bob. %while other ones require is larger than 50%. This achieved by reversing reconciliation procedure subsequent to transmission, is, Bob's instead Alice's data build key. Although squeezing or entanglement may helpful improve resistance noise, they are not required for remain with high...
We present a continuous-variable experimental analysis of two-photon Fock state free-propagating light. This is obtained from pulsed nondegenerate parametric amplifier, which produces two intensity-correlated twin beams. Counting photons in one beam projects the other desired state, analyzed by using homodyne detection. The Wigner function measured clearly negative. developed detailed analytic model allows fast and efficient results.
Quantum mechanics imposes that any amplifier works independently on the phase of input signal has to introduce some excess noise. The impossibility such a noiseless is rooted in unitarity and linearity quantum evolution. A possible way circumvent this limitation interrupt evolution via measurement, providing random outcome able herald successful-and noiseless-amplification event. Here we show successful realization an approach; perform full characterization amplified coherent state using...
We have designed and realized a prototype that implements continuous-variable quantum key distribution (QKD) protocol based on coherent states reverse reconciliation. The system uses time polarization multiplexing for optimal transmission detection of the signal phase reference, employs sophisticated error-correction codes security is guaranteed against general eavesdropping attacks. performance was tested over preinstalled optical fibres as part cryptography network combining different QKD...
Continuous-variable quantum key distribution protocols, based on Gaussian modulation of the quadratures coherent states, have been implemented in recent experiments. A present limitation such systems is finite efficiency detectors, which can principle be compensated for by use classical optical preamplifiers. Here we study this possibility detail, deriving modified secret generation rates when an parametric amplifier placed at output channel. After presenting a general set security proofs,...
We observe and measure dispersive optical non-linearities in an ensemble of cold Rydberg atoms placed inside cavity. The experimental results are agreement with a simple model where the due to progressive appearance blockaded volume within medium. measurements allow direct estimation "blockaded fraction" atomic ensemble.
We show that the maximum transmission distance of continuous-variable quantum key distribution in presence a Gaussian noisy lossy channel can be arbitrarily increased using heralded noiseless linear amplifier. explicitly consider protocol amplitude- and phase-modulated coherent states with reverse reconciliation. Assuming secret rate drops to zero for line transmittance ${T}_{\mathrm{lim}}$, we find amplifier amplitude gain $g$ improve this value ${T}_{\mathrm{lim}}/{g}^{2}$, corresponding...
We report on the design and performance of a point-to-point classical symmetric encryption link with fast key renewal provided by Continuous Variable Quantum Key Distribution (CVQKD) system. Our system was operational able to encrypt communications during more than six months, from end July 2010 until beginning February 2011. This field test first demonstration reliability CVQKD over long period time in server room environment. strengthens potential for information technology security...
We present what is, to our knowledge, the first implementation of a "cat breeding" operation, which allows an iterative growth cat states. thus report experimental generation squeezed state from two single photon Fock states, can be seen as states with zero amplitude. These are mixed on symmetrical beam splitter, and is heralded by homodyne measurement in one output arms. The has fidelity 61% even amplitude α=1.63. This hybrid operation opens up new prospects quantum optics, protocol...
We propose a whole family of physical states that yield violation the Bell CHSH inequality arbitrarily close to its maximum value, when using quadrature phase homodyne detection. This result is based on new binning process called root binning, used transform continuous variables measurements into binary results needed for tests quantum mechanics versus local realistic theories. A in order produce such also suggested. The use high-efficiency spacelike separated detections with these and this...
Entangled coherent states can be prepared remotely by subtracting non-locally a single photon from two quantum superpositions of states, the so-called "Schroedinger's cat" state. Such entanglement further distributed over longer distances successive swapping operations using linear optics and photon-number resolving detectors. The aim this paper is to evaluate performance approach repeaters for long distance communications. Despite many attractive features at first sight, we show that, when...
Non Gaussian states and processes are useful resources in quantum information with continuous variables. An experimentally accessible criterion has been proposed to measure the degree of non Gaussianity states, based on conditional entropy state a reference. Here we adopt such characterise an important class classical single-photon added coherent states. Our studies demonstrate reliability sensitivity this measure, use it quantify how detrimental is role experimental imperfections our realisation.
We describe a continuous-variable coherent-states quantum-key distribution system working at $1550\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$, and entirely made of standard fiber optics telecommunications components, such as integrated-optics modulators, couplers fast InGaAs photodiodes. The setup is composed an emitter randomly modulating coherent state in the complex plane with doubly Gaussian distribution, receiver based on shot-noise limited time-resolved homodyne detector. By using reverse...
We address the experimental estimation of Gaussian quantum discord for two-mode squeezed thermal state, and demonstrate a measurement scheme based on pair homodyne detectors assisted by Bayesian analysis which provides nearly optimal small value discord. Besides, though detection is not discord, noise ratio to ultimate limit, as dictacted Cramer-Rao bound, limited about 10 dB.
Linear amplifiers are necessarily affected by a minimal amount of noise, which is needed in order to preserve the linearity and unitarity prescribed quantum mechanics. Such limitation might be partially overcome if process realized conditioning its operation on trigger event, for instance, result measurement. Here we present detailed analysis noiseless amplifier, implemented using linear optics, down-conversion-based single-photon source, detection. Our results demonstrate an amplification...
Quantum memories are a crucial element toward efficient quantum protocols. In the continuous variables domain, such need to provide high fidelity with an efficiency set one. Moreover, one needs store complex states exhibiting negative Wigner functions after storage. We report storage of single- and two-photon Fock in all-optical memory. The these show negativity time several hundred nanoseconds. This is, our knowledge, first demonstration optical domain non-Gaussian more than photon,...
We demonstrate that different kinds of mesoscopic quantum states light can be efficiently generated from a simple iterative scheme. These exhibit strong non-classical features, and could great interest for many applications such as error-correcting codes or fundamental testings. Based on these states, we further propose protocol allowing large loophole-free violation Clauser–Horne–Shimony–Holt (CHSH)-type Bell's inequality with significant losses, thus showing the properties some remarkable...