The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Akira Furusawa - One of the best experts on this subject based on the ideXlab platform.
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Low-Latency Digital Feedforward for Universal Continuous-Variable Quantum Computation in Time Domain
2018 Conference on Lasers and Electro-Optics (CLEO), 2018Co-Authors: Atsushi Sakaguchi, Hisashi Ogawa, Masaya Kobayashi, Shigenari Suzuki, Hidehiro Yonezawa, Elanor Huntington, Shuntaro Takeda, Jun-ichi Yoshikawa, Akira FurusawaAbstract:We demonstrate a programmable optical quantum gate with a 25ns-latency digital feedforward. Such a flexible, stable, and fast feedforward enables large-scale universal Continuous-Variable quantum computation in time domain.
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hybrid discrete and Continuous Variable quantum information
Nature Physics, 2015Co-Authors: Ulrik L Andersen, Peter Van Loock, Jonas S Neergaardnielsen, Akira FurusawaAbstract:Research in quantum information processing has followed two different directions: the use of discrete Variables (qubits) and that of high-dimensional, Continuous-Variable Gaussian states (coherent and squeezed states). Recently, these two approaches have been converging in potentially more powerful hybrid protocols. The traditional approaches to quantum information processing using either discrete or Continuous Variables can be combined in hybrid protocols for tasks including quantum teleportation, computation, entanglement distillation or Bell tests.
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Continuous Variable entanglement on a chip
Nature Photonics, 2015Co-Authors: Genta Masada, Kazunori Miyata, Alberto Politi, Toshikazu Hashimoto, Jeremy L Obrien, Akira FurusawaAbstract:The capabilities of Continuous Variable (CV) quantum technology — homodyne detection and characterization of Einstein–Podolsky–Rosen entangled light — are demonstrated by sending CV light at 860 nm to optical circuits on a chip.
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experimental generation of four mode Continuous Variable cluster states
Physical Review A, 2008Co-Authors: Mitsuyoshi Yukawa, Peter Van Loock, Ryuji Ukai, Akira FurusawaAbstract:Continuous-Variable Gaussian cluster states are a potential resource for universal quantum computation. They can be efficiently and unconditionally built from sources of squeezed light using beam splitters. Here we report on the generation of three different kinds of Continuous-Variable four-mode cluster states. In our realization, the resulting cluster-type correlations are such that no corrections other than simple phase-space displacements would be needed when quantum information propagates through these states. At the same time, the inevitable imperfections from the finitely squeezed resource states and from additional thermal noise are minimized, as no antisqueezing components are left in the cluster states.
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detecting genuine multipartite Continuous Variable entanglement
Physical Review A, 2003Co-Authors: Peter Van Loock, Akira FurusawaAbstract:We derive necessary conditions in terms of the variances of position and momentum linear combinations for all kinds of separability of a multiparty multimode Continuous-Variable state. Their violations can be sufficient for genuine multipartite entanglement, provided the combinations contain both conjugate Variables of all modes. Hence, a complete state determination, for example, by detecting the entire correlation matrix of a Gaussian state, is not needed.
T C Ralph - One of the best experts on this subject based on the ideXlab platform.
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on the efficiency definition for reconciliation in Continuous Variable quantum key distribution
arXiv: Quantum Physics, 2016Co-Authors: Sarah J Johnson, Andrew M Lance, Lawrence Ong, T C Ralph, Thomas SymulAbstract:The maximum operation range of Continuous Variable quantum key distribution systems is constrained by the efficiency of the forward error correction post processing step. In this paper, we show that the current definition of this forward error correction efficiency can exceed unity when employing fixed-rate error correction codes operating at high word error rates. For efficiencies greater than unity, we show that it is possible achieve a positive secret key over an entanglement breaking channel, equivalent to an intercept and resend attack, a condition in which no secret key is possible. We subsequently propose a new definition of error correction efficiency and show that this new efficiency is bounded from above by unity. We apply this new efficiency to the secret key rate of a Continuous Variable quantum key distribution system. The net result is a reduction in the operational range of such Continuous Variable quantum key distribution systems.
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high fidelity teleportation of Continuous Variable quantum states using delocalized single photons
Physical Review Letters, 2013Co-Authors: Ulrik L Andersen, T C RalphAbstract:Traditional Continuous-Variable teleportation can only approach unit fidelity in the limit of an infinite (and unphysical) amount of squeezing. We describe a new method for Continuous-Variable teleportation that approaches unit fidelity with finite resources. The protocol is not based on squeezed states as in traditional teleportation but on an ensemble of single photon entangled states. We characterize the teleportation scheme with coherent states, mesoscopic superposition states, and two-mode squeezed states and we find several situations in which near-unity teleportation fidelity can be obtained with modest resources.
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quantum error correction of Continuous Variable states against gaussian noise
Physical Review A, 2011Co-Authors: T C RalphAbstract:We describe a Continuous-Variable error correction protocol that can correct the Gaussian noise induced by linear loss on Gaussian states. The protocol can be implemented using linear optics and photon counting. We explore the theoretical bounds of the protocol as well as the expected performance given current knowledge and technology.
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universal quantum computation with Continuous Variable cluster states
Physical Review Letters, 2006Co-Authors: Nicolas C. Menicucci, Mile Gu, Christian Weedbrook, T C Ralph, Peter Van Loock, Michael A NielsenAbstract:We describe a generalization of the cluster-state model of quantum computation to Continuous-Variable systems, along with a proposal for an optical implementation using squeezed-light sources, linear optics, and homodyne detection. For universal quantum computation, a nonlinear element is required. This can be satisfied by adding to the toolbox any single-mode non-Gaussian measurement, while the initial cluster state itself remains Gaussian. Homodyne detection alone suffices to perform an arbitrary multimode Gaussian transformation via the cluster state. We also propose an experiment to demonstrate cluster-based error reduction when implementing Gaussian operations.
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Continuous Variable quantum cryptography beating the 3 db loss limit
Physical Review Letters, 2002Co-Authors: Christine Silberhorn, T C Ralph, Norbert Lutkenhaus, Gerd LeuchsAbstract:We demonstrate that secure quantum key distribution systems based on Continuous Variable implementations can operate beyond the apparent 3 dB loss limit that is implied by the beam splitting attack. The loss limit was established for standard minimum uncertainty states such as coherent states. We show that, by an appropriate postselection mechanism, we can enter a region where Eve's knowledge on Alice's key falls behind the information shared between Alice and Bob, even in the presence of substantial losses.
Nicolas C. Menicucci - One of the best experts on this subject based on the ideXlab platform.
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temporal mode Continuous Variable cluster states using linear optics
Physical Review A, 2011Co-Authors: Nicolas C. MenicucciAbstract:An extensible experimental design for optical Continuous-Variable cluster states of arbitrary size using four offline (vacuum) squeezers and six beam splitters is presented. This method has all the advantages of a temporal-mode encoding [Phys. Rev. Lett. 104, 250503 (2010)], including finite requirements for coherence and stability even as the computation length increases indefinitely, with none of the difficulty of inline squeezing. The extensibility stems from a construction based on Gaussian projected entangled pair states. The potential for use of this design within a fully fault-tolerant model is discussed.
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Quantum computing with Continuous-Variable clusters
Physical Review A - Atomic Molecular and Optical Physics, 2009Co-Authors: Mile Gu, Nicolas C. Menicucci, Timothy C. Ralph, Christian Weedbrook, Peter Van LoockAbstract:Continuous-Variable cluster states offer a potentially promising method of implementing a quantum computer. This paper extends and further refines theoretical foundations and protocols for experimental implementation. We give a cluster-state implementation of the cubic phase gate through photon detection, which, together with homodyne detection, facilitates universal quantum computation. In addition, we characterize the offline squeezed resources required to generate an arbitrary graph state through passive linear optics. Most significantly, we prove that there are universal states for which the offline squeezing per mode does not increase with the size of the cluster. Simple representations of Continuous-Variable graph states are introduced to analyze graph state transformations under measurement and the existence of universal Continuous-Variable resource states.
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universal quantum computation with Continuous Variable cluster states
Physical Review Letters, 2006Co-Authors: Nicolas C. Menicucci, Mile Gu, Christian Weedbrook, T C Ralph, Peter Van Loock, Michael A NielsenAbstract:We describe a generalization of the cluster-state model of quantum computation to Continuous-Variable systems, along with a proposal for an optical implementation using squeezed-light sources, linear optics, and homodyne detection. For universal quantum computation, a nonlinear element is required. This can be satisfied by adding to the toolbox any single-mode non-Gaussian measurement, while the initial cluster state itself remains Gaussian. Homodyne detection alone suffices to perform an arbitrary multimode Gaussian transformation via the cluster state. We also propose an experiment to demonstrate cluster-based error reduction when implementing Gaussian operations.
Ulrik L Andersen - One of the best experts on this subject based on the ideXlab platform.
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hybrid discrete and Continuous Variable quantum information
Nature Physics, 2015Co-Authors: Ulrik L Andersen, Peter Van Loock, Jonas S Neergaardnielsen, Akira FurusawaAbstract:Research in quantum information processing has followed two different directions: the use of discrete Variables (qubits) and that of high-dimensional, Continuous-Variable Gaussian states (coherent and squeezed states). Recently, these two approaches have been converging in potentially more powerful hybrid protocols. The traditional approaches to quantum information processing using either discrete or Continuous Variables can be combined in hybrid protocols for tasks including quantum teleportation, computation, entanglement distillation or Bell tests.
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high fidelity teleportation of Continuous Variable quantum states using delocalized single photons
Physical Review Letters, 2013Co-Authors: Ulrik L Andersen, T C RalphAbstract:Traditional Continuous-Variable teleportation can only approach unit fidelity in the limit of an infinite (and unphysical) amount of squeezing. We describe a new method for Continuous-Variable teleportation that approaches unit fidelity with finite resources. The protocol is not based on squeezed states as in traditional teleportation but on an ensemble of single photon entangled states. We characterize the teleportation scheme with coherent states, mesoscopic superposition states, and two-mode squeezed states and we find several situations in which near-unity teleportation fidelity can be obtained with modest resources.
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Continuous Variable quantum key distribution with modulated entangled states
Nature Communications, 2012Co-Authors: Lars S Madsen, Mikael Lassen, Vladyslav C Usenko, Radim Filip, Ulrik L AndersenAbstract:Quantum key distribution enables two remote parties to grow a shared key, which they can use for unconditionally secure communication over a certain distance. The maximal distance depends on the loss and the excess noise of the connecting quantum channel. Several quantum key distribution schemes based on coherent states and Continuous Variable measurements are resilient to high loss in the channel, but are strongly affected by small amounts of channel excess noise. Here we propose and experimentally address a Continuous Variable quantum key distribution protocol that uses modulated fragile entangled states of light to greatly enhance the robustness to channel noise. We experimentally demonstrate that the resulting quantum key distribution protocol can tolerate more noise than the benchmark set by the ideal Continuous Variable coherent state protocol. Our scheme represents a very promising avenue for extending the distance for which secure communication is possible.
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Continuous Variable quantum information processing
arXiv: Quantum Physics, 2010Co-Authors: Ulrik L Andersen, Gerd Leuchs, Christine SilberhornAbstract:Observables of quantum systems can posses either a discrete or a Continuous spectrum. For example, upon measurements of the photon number of a light state, discrete outcomes will result whereas measurements of the light's quadrature amplitudes result in Continuous outcomes. If one uses the Continuous degree of freedom of a quantum system either for encoding, processing or detecting information, one enters the field of Continuous Variable (CV) quantum information processing. In this paper we review the basic principles of CV quantum information processing with main focus on recent developments in the field. We will be addressing the three main stages of a quantum informational system; the preparation stage where quantum information is encoded into CVs of coherent states and single photon states, the processing stage where CV information is manipulated to carry out a specified protocol and a detection stage where CV information is measured using homodyne detection or photon counting.
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Continuous Variable quantum information processing
Laser & Photonics Reviews, 2010Co-Authors: Ulrik L Andersen, Gerd Leuchs, Christine SilberhornAbstract:Observables of quantum systems can possess either a discrete or a Continuous spectrum. For example, upon measurements of the photon number of a light state, discrete outcomes will result whereas measurements of the light's quadrature amplitudes result in Continuous outcomes. If one uses the Continuous degree of freedom of a quantum system for encoding, processing or detecting information, one enters the field of Continuous-Variable (CV) quantum information processing. In this paper we review the basic principles of CV quantum information processing with main focus on recent developments in the field. We will be addressing the three main stages of a quantum information system; the preparation stage where quantum information is encoded into CVs of coherent states and single-photon states, the processing stage where CV information is manipulated to carry out a specified protocol and a detection stage where CV information is measured using homodyne detection or photon counting.
Peter Van Loock - One of the best experts on this subject based on the ideXlab platform.
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hybrid discrete and Continuous Variable quantum information
Nature Physics, 2015Co-Authors: Ulrik L Andersen, Peter Van Loock, Jonas S Neergaardnielsen, Akira FurusawaAbstract:Research in quantum information processing has followed two different directions: the use of discrete Variables (qubits) and that of high-dimensional, Continuous-Variable Gaussian states (coherent and squeezed states). Recently, these two approaches have been converging in potentially more powerful hybrid protocols. The traditional approaches to quantum information processing using either discrete or Continuous Variables can be combined in hybrid protocols for tasks including quantum teleportation, computation, entanglement distillation or Bell tests.
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Quantum computing with Continuous-Variable clusters
Physical Review A - Atomic Molecular and Optical Physics, 2009Co-Authors: Mile Gu, Nicolas C. Menicucci, Timothy C. Ralph, Christian Weedbrook, Peter Van LoockAbstract:Continuous-Variable cluster states offer a potentially promising method of implementing a quantum computer. This paper extends and further refines theoretical foundations and protocols for experimental implementation. We give a cluster-state implementation of the cubic phase gate through photon detection, which, together with homodyne detection, facilitates universal quantum computation. In addition, we characterize the offline squeezed resources required to generate an arbitrary graph state through passive linear optics. Most significantly, we prove that there are universal states for which the offline squeezing per mode does not increase with the size of the cluster. Simple representations of Continuous-Variable graph states are introduced to analyze graph state transformations under measurement and the existence of universal Continuous-Variable resource states.
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experimental generation of four mode Continuous Variable cluster states
Physical Review A, 2008Co-Authors: Mitsuyoshi Yukawa, Peter Van Loock, Ryuji Ukai, Akira FurusawaAbstract:Continuous-Variable Gaussian cluster states are a potential resource for universal quantum computation. They can be efficiently and unconditionally built from sources of squeezed light using beam splitters. Here we report on the generation of three different kinds of Continuous-Variable four-mode cluster states. In our realization, the resulting cluster-type correlations are such that no corrections other than simple phase-space displacements would be needed when quantum information propagates through these states. At the same time, the inevitable imperfections from the finitely squeezed resource states and from additional thermal noise are minimized, as no antisqueezing components are left in the cluster states.
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Continuous Variable telecloning with phase conjugate inputs
Physical Review A, 2008Co-Authors: Jing Zhang, Changde Xie, Kunchi Peng, Peter Van LoockAbstract:We propose a scheme for Continuous-Variable telecloning with phase-conjugate inputs (PCI). Two cases of PCI telecloning are considered. The first case is where PCI telecloning produces M clones nonlocally and M anticlones locally, or vice versa. This kind of PCI telecloning requires only one Einstein-Podolsky-Rosen (EPR) entangled, two-mode squeezed state as a resource for building the appropriate multimode, multipartite entangled state via linear optics. The other case is a PCI telecloning protocol in which both clones and anticlones are created nonlocally. Such a scheme requires two EPR entangled states for the generation of a suitable multipartite entangled state. As our schemes are reversible, optimal cloning fidelities are achieved in the limit of infinite squeezing.
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detecting genuine multipartite Continuous Variable entanglement
Physical Review A, 2003Co-Authors: Peter Van Loock, Akira FurusawaAbstract:We derive necessary conditions in terms of the variances of position and momentum linear combinations for all kinds of separability of a multiparty multimode Continuous-Variable state. Their violations can be sufficient for genuine multipartite entanglement, provided the combinations contain both conjugate Variables of all modes. Hence, a complete state determination, for example, by detecting the entire correlation matrix of a Gaussian state, is not needed.
