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Laha P, Moore DW, Filip R. Entanglement Growth via Splitting of a Few Thermal Quanta. PHYSICAL REVIEW LETTERS 2024; 132:210201. [PMID: 38856241 DOI: 10.1103/physrevlett.132.210201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2022] [Revised: 02/20/2024] [Accepted: 04/08/2024] [Indexed: 06/11/2024]
Abstract
Quanta splitting is an essential generator of Gaussian entanglement, exemplified by Einstein-Podolsky-Rosen states and apparently the most commonly occurring form of entanglement. In general, it results from the strong pumping of a nonlinear process with a highly coherent and low-noise external drive. In contrast, recent experiments involving efficient trilinear processes in trapped ions and superconducting circuits have opened the complementary possibility to test the splitting of a few thermal quanta. Stimulated by such small thermal energy, a strong degenerate trilinear coupling generates large amounts of nonclassicality, detectable by more than 3 dB of distillable quadrature squeezing. Substantial entanglement can be generated via frequent passive linear coupling to a third mode present in parallel with the trilinear coupling. This new form of entanglement, outside any Gaussian approximation, surprisingly grows with the mean number of split thermal quanta; a quality absent from Gaussian entanglement. Using distillable squeezing we shed light on this new entanglement mechanism for nonlinear bosonic systems.
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Affiliation(s)
- Pradip Laha
- Department of Optics, Palacký University, 17. listopadu 1192/12, 771 46 Olomouc, Czech Republic
| | - Darren W Moore
- Department of Optics, Palacký University, 17. listopadu 1192/12, 771 46 Olomouc, Czech Republic
| | - Radim Filip
- Department of Optics, Palacký University, 17. listopadu 1192/12, 771 46 Olomouc, Czech Republic
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2
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Kalaga JK, Kowalewska-Kudłaszyk A, Leoński W, Peřina J. Legget-Garg inequality for a two-mode entangled bosonic system. OPTICS EXPRESS 2024; 32:9946-9957. [PMID: 38571218 DOI: 10.1364/oe.513855] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2023] [Accepted: 02/08/2024] [Indexed: 04/05/2024]
Abstract
We discuss a model of two nonlinear quantum oscillators mutually coupled by linear interaction and continuously driven by external coherent excitation. For such a system, we analyze temporal correlations. We examine the violation of the Leggett-Garg inequality analysing various scenarios of measurements. These scenarios are based on the projection onto different Bell states. We show that the possibility of violation of the Leggett-Garg inequalities is associated with the use of different projectors.
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Naik LP, Das RM, Panigrahi PK. Stronger EPR-steering criterion based on inferred Schrödinger-Robertson uncertainty relation. Sci Rep 2024; 14:420. [PMID: 38172164 PMCID: PMC10764898 DOI: 10.1038/s41598-023-50029-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Accepted: 12/14/2023] [Indexed: 01/05/2024] Open
Abstract
Steering is one of the three in-equivalent forms of nonlocal correlations intermediate between Bell nonlocality and entanglement. Schrödinger-Robertson uncertainty relation (SRUR), has been widely used to detect entanglement and steering. However, the steering criterion in earlier works, based on SRUR, did not involve complete inferred-variance uncertainty relation. In this paper, by considering the local hidden state model and Reid's formalism, we derive a complete inferred-variance EPR-steering criterion based on SRUR in the bipartite scenario. Furthermore, we check the effectiveness of our steering criterion with discrete variable bipartite two-qubit and two-qutrit isotropic states.
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Affiliation(s)
- Laxmi Prasad Naik
- Indian Institute of Science Education And Research Kolkata, Mohanpur, Nadia, West Bengal, 741 246, India
- Indian Institute of Technology Delhi, Hauz Khas, New Delhi, 1100016, India
| | - Rakesh Mohan Das
- Department of Physics, School of Applied Sciences, Kalinga Institute of Industrial Technology, Patia, Bhubaneswar, Odisha, 751024, India
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4
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Fulton J, Thenabadu M, Teh RY, Reid MD. Weak versus Deterministic Macroscopic Realism, and Einstein-Podolsky-Rosen's Elements of Reality. ENTROPY (BASEL, SWITZERLAND) 2023; 26:11. [PMID: 38275490 PMCID: PMC11154650 DOI: 10.3390/e26010011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2023] [Revised: 10/25/2023] [Accepted: 11/13/2023] [Indexed: 01/27/2024]
Abstract
The violation of a Leggett-Garg inequality confirms the incompatibility between quantum mechanics and the combined premises (called macro-realism) of macroscopic realism (MR) and noninvasive measurability (NIM). Arguments can be given that the incompatibility arises because MR fails for systems in a superposition of macroscopically distinct states-or else, that NIM fails. In this paper, we consider a strong negation of macro-realism, involving superpositions of coherent states, where the NIM premise is replaced by Bell's locality premise. We follow recent work and propose the validity of a subset of Einstein-Podolsky-Rosen (EPR) and Leggett-Garg premises, referred to as weak macroscopic realism (wMR). In finding consistency with wMR, we identify that the Leggett-Garg inequalities are violated because of failure of both MR and NIM, but also that both are valid in a weaker (less restrictive) sense. Weak MR is distinguished from deterministic macroscopic realism (dMR) by recognizing that a measurement involves a reversible unitary interaction that establishes the measurement setting. Weak MR posits that a predetermined value for the outcome of a measurement can be attributed to the system after the interaction, when the measurement setting is experimentally specified. An extended definition of wMR considers the "element of reality" defined by EPR for system A, where one can predict with certainty the outcome of a measurement on A by performing a measurement on system B. Weak MR posits that this element of reality exists once the unitary interaction determining the measurement setting at B has occurred. We demonstrate compatibility of systems violating Leggett-Garg inequalities with wMR but point out that dMR has been shown to be falsifiable. Other tests of wMR are proposed, the predictions of wMR agreeing with quantum mechanics. Finally, we compare wMR with macro-realism models discussed elsewhere. An argument in favour of wMR is presented: wMR resolves a potential contradiction pointed out by Leggett and Garg between failure of macro-realism and assumptions intrinsic to quantum measurement theory.
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Affiliation(s)
| | | | | | - Margaret D. Reid
- Centre for Quantum Science and Technology Theory, Swinburne University of Technology, Melbourne 3122, Australia; (J.F.); (M.T.); (R.Y.T.)
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Luo YX, Cong LJ, Zheng ZG, Liu HY, Ming Y, Yang RC. Entanglement enhancement and EPR steering based on a PT-symmetric-like cavity-opto-magnomechanical hybrid system. OPTICS EXPRESS 2023; 31:34764-34778. [PMID: 37859225 DOI: 10.1364/oe.500854] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Accepted: 09/19/2023] [Indexed: 10/21/2023]
Abstract
We investigate the enhancement of entanglement and EPR steering in a parity-time(PT-) symmetric-like cavity-opto-magnomechanical system. The system consists of an optical cavity, a magnon mode in a ferromagnetic crystal, a phonon mode, and a microwave cavity. Our findings demonstrate that microwave-cavity gain significantly boosts distant quantum entanglement and greatly improves the robustness of bipartite entanglement against environment temperature. Additionally, we observe an enhancement of tripartite entanglement within the system and uncover the phenomenon of entanglement transfer. Notably, we also achieve one-way steering and two-way asymmetric steering in the system. This study offers insights into the integration of traditional optomechanics and cavity magnomechanics, presenting a novel approach to manipulate asymmetric quantum steering between two distant macroscopic objects. The implications of our research extend to the fields of quantum state preparation and quantum information.
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6
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Luo S, Shen K, Wang F. Dephasing-assisted preparation of asymmetric steering in coupled quantum wells. OPTICS EXPRESS 2023; 31:30767-30782. [PMID: 37710613 DOI: 10.1364/oe.499410] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Accepted: 08/19/2023] [Indexed: 09/16/2023]
Abstract
It is shown that the dephasing rates are usually harmful for quantum correlations in various systems. Nevertheless, we explore that the dephasing rates in the coupled quantum wells (QWs), as a major contribution of the decay processes, can assist to generate one-way Einstein-Podolsky-Rosen (EPR) steering. By applying two strong fields to drive two dipole-allowed transitions while the other transitions are coupled with two quantized modes, the asymmetric EPR steering is possible to obtain at steady state through a single-pathway dissipation in the three-well system. According to dressed-state and Bogoliubov mode transformation, we find that the dephasing rates play a role in modifying the dressed-state populations and the dissipation rate through multiple quantum interference mechanisms. The positive effect of the dephasing rates from a nanostructure on quantum correlation is expected to find potential applications in quantum information processing.
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Junker J, Wilken D, Steinmeyer D, Heurs M. Reconstructing Gaussian bipartite states with a single polarization-sensitive homodyne detector. OPTICS EXPRESS 2022; 30:33860-33868. [PMID: 36242412 DOI: 10.1364/oe.465186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Accepted: 07/27/2022] [Indexed: 06/16/2023]
Abstract
We present a novel method to fully estimate Gaussian bipartite polarization states using only a single homodyne detector. Our approach is based on [Phys. Rev. Lett.102, 020502 (2009)10.1103/PhysRevLett.102.020502], but circumvents additional optics, and thereby losses, in the signal path. We provide an intuitive explanation of our scheme without needing to define auxiliary modes. With six independent measurements, we fully reconstruct the state's covariance matrix. We validate our method by comparing it to a conventional dual-homodyne measurement scheme.
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Brasil TB, Novikov V, Kerdoncuff H, Lassen M, Polzik ES. Two-colour high-purity Einstein-Podolsky-Rosen photonic state. Nat Commun 2022; 13:4815. [PMID: 35974049 PMCID: PMC9381510 DOI: 10.1038/s41467-022-32495-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2022] [Accepted: 08/01/2022] [Indexed: 11/12/2022] Open
Abstract
We report a high-purity Einstein-Podolsky-Rosen (EPR) state between light modes with the wavelengths separated by more than 200 nm. We demonstrate highly efficient EPR-steering between the modes with the product of conditional variances \documentclass[12pt]{minimal}
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\begin{document}$${{{{{{{{\mathcal{E}}}}}}}}}^{2}=0.11\pm 0.01\ll 1$$\end{document}E2=0.11±0.01≪1. The modes display − 7.7 ± 0.5 dB of two-mode squeezing and an overall state purity of 0.63 ± 0.16. EPR-steering is observed over five octaves of sideband frequencies from RF down to audio-band. The demonstrated combination of high state purity, strong quantum correlations, and extended frequency range enables new matter-light quantum protocols. Engineering quantum correlations between light modes at different frequency would open new avenues for quantum networks and sensing. Here, the authors propose and demonstrate a way for obtaining high-purity strongly entangled continuous variable states with more than 200 nm difference in wavelength.
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Affiliation(s)
| | - Valeriy Novikov
- Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark.,Russian Quantum Center, Skolkovo, Moscow, Russia
| | | | | | - Eugene S Polzik
- Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark.
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9
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Wang F, Wang C, Shen K, Hu X. Stable entanglement and one-way steering via engineering of a single-atom reservoir. OPTICS EXPRESS 2022; 30:15830-15845. [PMID: 36221440 DOI: 10.1364/oe.452974] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2022] [Accepted: 04/02/2022] [Indexed: 06/16/2023]
Abstract
In this paper, we reexamine the quantum correlations in a four-state single-atom system in the weak coupling regime, aiming at the realization of stable entanglement and one-way steering via dissipation rather than coherent evolution process. Under the near-resonant conditions, we find out that a single atom can act as a reservoir and behave like a two-level system with a single dissipation channel, through which the composite Bogoliubov mode will evolve into a vacuum state, resulting in the appearance of stationary entanglement between two original modes. In addition, the one-way steering is generated when the symmetry is broken by choosing asymmetrical coupling constants. The present scheme may provide convenience for experimental implement and find applications in quantum information processing.
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10
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Quantum Steering in Two- and Three-Mode ??-Symmetric Systems. Symmetry (Basel) 2021. [DOI: 10.3390/sym13112201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
We consider two PT-symmetric models, consisting of two or three single-mode cavities. In both models, the cavities are coupled to each other by linear interactions, forming a linear chain. Additionally, the first and last of such cavities interact with an environment. Since the models are PT-symmetric, they are described by non-Hermitian Hamiltonians that, for a specific range of system parameters, possess real eigenvalues. We show that in the models considered in the article, the steering generation process strongly depends on the coupling strengths and rates of the gains/losses in energy. Moreover, we find the values of parameters describing the system for which the steering appears.
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11
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Sun FX, Zheng SS, Xiao Y, Gong Q, He Q, Xia K. Remote Generation of Magnon Schrödinger Cat State via Magnon-Photon Entanglement. PHYSICAL REVIEW LETTERS 2021; 127:087203. [PMID: 34477416 DOI: 10.1103/physrevlett.127.087203] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Revised: 06/30/2021] [Accepted: 07/23/2021] [Indexed: 06/13/2023]
Abstract
The magnon cat state represents a macroscopic quantum superposition of collective magnetic excitations of large number spins that not only provides fundamental tests of macroscopic quantum effects but also finds applications in quantum metrology and quantum computation. In particular, remote generation and manipulation of Schrödinger cat states are particularly interesting for the development of long-distance and large-scale quantum information processing. Here, we propose an approach to remotely prepare magnon even or odd cat states by performing local non-Gaussian operations on the optical mode that is entangled with the magnon mode through pulsed optomagnonic interaction. By evaluating key properties of the resulting cat states, we show that for experimentally feasible parameters, they are generated with both high fidelity and nonclassicality, as well as with a size large enough to be useful for quantum technologies. Furthermore, the effects of experimental imperfections such as the error of projective measurements and dark count when performing single-photon operations have been discussed, where the lifetime of the created magnon cat states is expected to be t∼1 μs.
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Affiliation(s)
- Feng-Xiao Sun
- State Key Laboratory for Mesoscopic Physics, School of Physics, Frontiers Science Center for Nano-Optoelectronics, and Collaborative Innovation Center of Quantum Matter, Peking University, Beijing 100871, China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006, China
| | - Sha-Sha Zheng
- State Key Laboratory for Mesoscopic Physics, School of Physics, Frontiers Science Center for Nano-Optoelectronics, and Collaborative Innovation Center of Quantum Matter, Peking University, Beijing 100871, China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006, China
| | - Yang Xiao
- Department of Applied Physics, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
| | - Qihuang Gong
- State Key Laboratory for Mesoscopic Physics, School of Physics, Frontiers Science Center for Nano-Optoelectronics, and Collaborative Innovation Center of Quantum Matter, Peking University, Beijing 100871, China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006, China
- Yangtze Delta Institute of Optoelectronics, Peking University, Nantong 226010, Jiangsu, China
| | - Qiongyi He
- State Key Laboratory for Mesoscopic Physics, School of Physics, Frontiers Science Center for Nano-Optoelectronics, and Collaborative Innovation Center of Quantum Matter, Peking University, Beijing 100871, China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006, China
- Yangtze Delta Institute of Optoelectronics, Peking University, Nantong 226010, Jiangsu, China
| | - Ke Xia
- Beijing Computational Science Research Center, Beijing 100193, China
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12
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Yadin B, Fadel M, Gessner M. Metrological complementarity reveals the Einstein-Podolsky-Rosen paradox. Nat Commun 2021; 12:2410. [PMID: 33893281 PMCID: PMC8065158 DOI: 10.1038/s41467-021-22353-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Accepted: 03/11/2021] [Indexed: 02/02/2023] Open
Abstract
The Einstein-Podolsky-Rosen (EPR) paradox plays a fundamental role in our understanding of quantum mechanics, and is associated with the possibility of predicting the results of non-commuting measurements with a precision that seems to violate the uncertainty principle. This apparent contradiction to complementarity is made possible by nonclassical correlations stronger than entanglement, called steering. Quantum information recognises steering as an essential resource for a number of tasks but, contrary to entanglement, its role for metrology has so far remained unclear. Here, we formulate the EPR paradox in the framework of quantum metrology, showing that it enables the precise estimation of a local phase shift and of its generating observable. Employing a stricter formulation of quantum complementarity, we derive a criterion based on the quantum Fisher information that detects steering in a larger class of states than well-known uncertainty-based criteria. Our result identifies useful steering for quantum-enhanced precision measurements and allows one to uncover steering of non-Gaussian states in state-of-the-art experiments.
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Affiliation(s)
- Benjamin Yadin
- grid.4563.40000 0004 1936 8868School of Mathematical Sciences and Centre for the Mathematics and Theoretical Physics of Quantum Non-Equilibrium Systems, University of Nottingham, Nottingham, UK ,grid.4991.50000 0004 1936 8948Wolfson College, University of Oxford, Oxford, UK
| | - Matteo Fadel
- grid.6612.30000 0004 1937 0642Department of Physics, University of Basel, Basel, Switzerland
| | - Manuel Gessner
- grid.462844.80000 0001 2308 1657Laboratoire Kastler Brossel, ENS-Université PSL, CNRS, Sorbonne Université, Collège de France, Paris, France
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13
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Walschaers M, Treps N. Remote Generation of Wigner Negativity through Einstein-Podolsky-Rosen Steering. PHYSICAL REVIEW LETTERS 2020; 124:150501. [PMID: 32357026 DOI: 10.1103/physrevlett.124.150501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Accepted: 03/25/2020] [Indexed: 06/11/2023]
Abstract
Negativity of the Wigner function is seen as a crucial resource for reaching a quantum computational advantage with continuous variable systems. However, these systems, while they allow for the deterministic generation of large entangled states, require an extra element such as photon subtraction to obtain such negativity. Photon subtraction is known to affect modes beyond the one where the photon is subtracted, an effect which is governed by the correlations of the state. In this Letter, we build upon this effect to remotely prepare states with Wigner negativity. More specifically, we show that photon subtraction can induce Wigner negativity in a correlated mode if and only if that correlated mode can perform Einstein-Podolsky-Rosen steering in the mode of subtraction.
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Affiliation(s)
- Mattia Walschaers
- Laboratoire Kastler Brossel, Sorbonne Université, CNRS, ENS-PSL Research University, Collège de France; 4 place Jussieu, F-75252 Paris, France
| | - Nicolas Treps
- Laboratoire Kastler Brossel, Sorbonne Université, CNRS, ENS-PSL Research University, Collège de France; 4 place Jussieu, F-75252 Paris, France
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Südbeck J, Steinlechner S, Korobko M, Schnabel R. Demonstration of interferometer enhancement through EPR entanglement. NATURE PHOTONICS 2020; 14:240-244. [PMID: 32231708 PMCID: PMC7104361 DOI: 10.1038/s41566-019-0583-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Accepted: 12/22/2019] [Indexed: 06/10/2023]
Abstract
The recent series of gravitational-wave (GW) detections by the Advanced LIGO and Advanced Virgo observatories launched the new field of GW astronomy. As the sensitivity of GW detectors is limited by quantum noise of light, concepts from quantum metrology have been adapted to increase the observational range. Since 2010, squeezed light with reduced quantum noise has been used for improved sensitivity at signal frequencies above 100 Hz. However, 100 m long optical filter resonators would be required to also improve the sensitivity at lower frequencies, adding significant cost and complexity. Here we report on a proof-of-principle setup of an alternative concept that achieves the broadband noise reduction by using Einstein-Podolsky-Rosen (EPR) entangled states instead. We show that the desired sensitivity improvement can then be obtained with the signal-recycling resonator that is already part of current observatories, providing the viable alternative to high-cost filter cavities.
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Affiliation(s)
- Jan Südbeck
- Institut für Laserphysik und Zentrum für Optische Quantentechnologien der Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - Sebastian Steinlechner
- Institut für Laserphysik und Zentrum für Optische Quantentechnologien der Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - Mikhail Korobko
- Institut für Laserphysik und Zentrum für Optische Quantentechnologien der Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - Roman Schnabel
- Institut für Laserphysik und Zentrum für Optische Quantentechnologien der Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
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15
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Experimental demonstration of Einstein-Podolsky-Rosen entanglement in rotating coordinate space. Sci Bull (Beijing) 2020; 65:280-285. [PMID: 36659092 DOI: 10.1016/j.scib.2019.11.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Revised: 10/22/2019] [Accepted: 10/31/2019] [Indexed: 01/21/2023]
Abstract
Einstein-Podolsky-Rosen (EPR) entanglement involving a pair of particles entangled in their positions and momenta is of special interest in the field of quantum information. Previously, EPR entanglement has been studied in different physical systems but in fixed coordinate spaces. Here, we demonstrate an experiment of ghost imaging and ghost interference in rotated position-momentum spaces by using position-momentum entangled photons generated from a hot atomic ensemble. By using different image objects, the measured position-momentum correlations exhibit intriguing dynamics, including gradual decrease and axis-independent EPR entanglement. The reported results on manipulating the EPR entanglement in rotating coordinate spaces hold promise in quantum communication and distant quantum image processing.
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16
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Quantum Correlations and Quantum Non-Locality: A Review and a Few New Ideas. APPLIED SCIENCES-BASEL 2019. [DOI: 10.3390/app9245406] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In this paper we make an extensive description of quantum non-locality, one of the most intriguing and fascinating facets of quantum mechanics. After a general presentation of several studies on this subject dealing with different but connected facets of quantum non-locality, we consider if this, and the friction it carries with special relativity, can eventually find a “solution” by considering higher dimensional spaces.
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17
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Liu Y, Cai Y, Xiang Y, Li F, Zhang Y, He Q. Tripartite Einstein-Podolsky-Rosen steering with linear and nonlinear beamsplitters in four-wave mixing of Rubidium atoms. OPTICS EXPRESS 2019; 27:33070-33079. [PMID: 31878381 DOI: 10.1364/oe.27.033070] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Accepted: 10/13/2019] [Indexed: 06/10/2023]
Abstract
Multipartite Einstein-Podolsky-Rosen (EPR) steering is an essential resource for secure one-sided device-independent quantum secret sharing. Here, we analyze the EPR steering properties exhibited in three-mode Gaussian states created by four-wave mixing (FWM) in Rubidium atoms combined with a linear beamsplitter and a nonlinear beamsplitter (second FWM), respectively. By quantifying Gaussian steerability based on a measure determined by the covariance matrix of the produced states, we compare the performance of two schemes to achieve one-way, collective, and genuine tripartite steering, as well as the monogamy constraints for distributing steering among three parties. We show that the scheme with nonlinear beamsplitter is feasible to create stronger bipartite steering and genuine tripartite steering and has more flexibility to manipulate the monogamy relation through the cooperation of the two cascaded FWM processes.
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18
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Beckey JL, Ma Y, Boyer V, Miao H. Broadband quantum noise reduction in future long baseline gravitational-wave detectors via EPR entanglement. Int J Clin Exp Med 2019. [DOI: 10.1103/physrevd.100.083011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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19
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Reid MD, He QY. Quantifying the Mesoscopic Nature of Einstein-Podolsky-Rosen Nonlocality. PHYSICAL REVIEW LETTERS 2019; 123:120402. [PMID: 31633988 DOI: 10.1103/physrevlett.123.120402] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Revised: 05/21/2019] [Indexed: 06/10/2023]
Abstract
Evidence for Bell's nonlocality is so far mainly restricted to microscopic systems, where the elements of reality that are negated predetermine results of measurements to within one spin unit. Any observed nonlocal effect (or lack of classical predetermination) is then limited to no more than the difference of a single photon or electron being detected or not (at a given detector). In this paper, we analyze experiments that report the Einstein-Podolsky-Rosen (EPR) steering form of nonlocality for mesoscopic photonic or Bose-Einstein condensate systems. Using an EPR steering parameter, we show how the EPR nonlocalities involved can be quantified for four-mode states, to give evidence of EPR-nonlocal effects corresponding to a two-mode number difference of 10^{5} photons, or of several tens of atoms (at a given site). Applying to experiments, we also show how the variance criterion of Duan, Giedke, Cirac and Zoller for EPR entanglement can be used to determine a lower bound on the number of particles in a pure two-mode EPR-entangled or steerable state.
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Affiliation(s)
- M D Reid
- Centre for Quantum and Optical Science, Swinburne University of Technology, Melbourne, Victoria 3122, Australia
- Institute of Theoretical Atomic, Molecular and Optical Physics (ITAMP), Harvard University, Cambridge, Massachusetts 02138, USA
| | - Q Y He
- State Key Laboratory of Mesoscopic Physics, School of Physics, Peking University, Collaborative Innovation Center of Quantum Matter, Beijing 100871, China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
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Liang YC, Yeh YH, Mendonça PEMF, Teh RY, Reid MD, Drummond PD. Quantum fidelity measures for mixed states. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2019; 82:076001. [PMID: 31022705 DOI: 10.1088/1361-6633/ab1ca4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Applications of quantum technology often require fidelities to quantify performance. These provide a fundamental yardstick for the comparison of two quantum states. While this is straightforward in the case of pure states, it is much more subtle for the more general case of mixed quantum states often found in practice. A large number of different proposals exist. In this review, we summarize the required properties of a quantum fidelity measure, and compare them, to determine which properties each of the different measures has. We show that there are large classes of measures that satisfy all the required properties of a fidelity measure, just as there are many norms of Hilbert space operators, and many measures of entropy. We compare these fidelities, with detailed proofs of their properties. We also summarize briefly the applications of these measures in teleportation, quantum memories and quantum computers, quantum communications, and quantum phase-space simulations.
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Affiliation(s)
- Yeong-Cherng Liang
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan. Center for Quantum Frontiers of Research & Technology (QFort), National Cheng Kung University, Tainan 701, Taiwan
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Zhang C, Cheng S, Li L, Liang QY, Liu BH, Huang YF, Li CF, Guo GC, Hall MJW, Wiseman HM, Pryde GJ. Experimental Validation of Quantum Steering Ellipsoids and Tests of Volume Monogamy Relations. PHYSICAL REVIEW LETTERS 2019; 122:070402. [PMID: 30848627 DOI: 10.1103/physrevlett.122.070402] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Revised: 01/29/2019] [Indexed: 06/09/2023]
Abstract
The set of all qubit states that can be steered to by measurements on a correlated qubit is predicted to form an ellipsoid-called the quantum steering ellipsoid-in the Bloch ball. This ellipsoid provides a simple visual characterization of the initial two-qubit state, and various aspects of entanglement are reflected in its geometric properties. We experimentally verify these properties via measurements on many different polarization-entangled photonic qubit states. Moreover, for pure three-qubit states, the volumes of the two quantum steering ellipsoids generated by measurements on the first qubit are predicted to satisfy a tight monogamy relation, which is strictly stronger than the well-known monogamy of entanglement for concurrence. We experimentally verify these predictions, using polarization and path entanglement. We also show experimentally that this monogamy relation can be violated by a mixed entangled state, which nevertheless satisfies a weaker monogamy relation.
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Affiliation(s)
- Chao Zhang
- Key Laboratory of Quantum Information, University of Science and Technology of China, CAS, Hefei 230026, People's Republic of China
- CAS Center For Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, People's Republic of China
| | - Shuming Cheng
- Centre for Quantum Computation and Communication Technology (Australian Research Council), Centre for Quantum Dynamics, Griffith University, Brisbane QLD 4111, Australia
| | - Li Li
- Centre for Quantum Computation and Communication Technology (Australian Research Council), Centre for Quantum Dynamics, Griffith University, Brisbane QLD 4111, Australia
| | - Qiu-Yue Liang
- Key Laboratory of Quantum Information, University of Science and Technology of China, CAS, Hefei 230026, People's Republic of China
- CAS Center For Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, People's Republic of China
| | - Bi-Heng Liu
- Key Laboratory of Quantum Information, University of Science and Technology of China, CAS, Hefei 230026, People's Republic of China
- CAS Center For Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, People's Republic of China
| | - Yun-Feng Huang
- Key Laboratory of Quantum Information, University of Science and Technology of China, CAS, Hefei 230026, People's Republic of China
- CAS Center For Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, People's Republic of China
| | - Chuan-Feng Li
- Key Laboratory of Quantum Information, University of Science and Technology of China, CAS, Hefei 230026, People's Republic of China
- CAS Center For Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, People's Republic of China
| | - Guang-Can Guo
- Key Laboratory of Quantum Information, University of Science and Technology of China, CAS, Hefei 230026, People's Republic of China
- CAS Center For Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, People's Republic of China
| | - Michael J W Hall
- Centre for Quantum Computation and Communication Technology (Australian Research Council), Centre for Quantum Dynamics, Griffith University, Brisbane QLD 4111, Australia
| | - Howard M Wiseman
- Centre for Quantum Computation and Communication Technology (Australian Research Council), Centre for Quantum Dynamics, Griffith University, Brisbane QLD 4111, Australia
| | - Geoff J Pryde
- Centre for Quantum Computation and Communication Technology (Australian Research Council), Centre for Quantum Dynamics, Griffith University, Brisbane QLD 4111, Australia
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Zhou Y, Yu J, Yan Z, Jia X, Zhang J, Xie C, Peng K. Quantum Secret Sharing Among Four Players Using Multipartite Bound Entanglement of an Optical Field. PHYSICAL REVIEW LETTERS 2018; 121:150502. [PMID: 30362796 DOI: 10.1103/physrevlett.121.150502] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Indexed: 06/08/2023]
Abstract
Secret sharing is a conventional technique for realizing secure communications in information networks, where a dealer distributes to n players a secret, which can only be decoded through the cooperation of k (n/2<k≤n) players. In recent years, quantum resources have been employed to enhance security of secret sharing, which has been named quantum secret sharing (QSS). A multipartite bound entanglement (BE) state of an optical field, due to its special entanglement features, can be used in quantum networks to improve security and flexibility of communication. We design and experimentally demonstrate a QSS protocol, where the dealer modulates a secret on a four-partite BE state and then distributes the submodes of the BE state to four spatially separated players. The presented QSS scheme has the capability to protect secrets from eavesdropping and dishonest players, because a nonlocal and deterministic BE state is shared among four authorized players.
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Affiliation(s)
- Yaoyao Zhou
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan 030006, China and Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
| | - Juan Yu
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan 030006, China and Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
| | - Zhihui Yan
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan 030006, China and Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
| | - Xiaojun Jia
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan 030006, China and Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
| | - Jing Zhang
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan 030006, China and Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
| | - Changde Xie
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan 030006, China and Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
| | - Kunchi Peng
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan 030006, China and Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
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Yang Y, Cao H. Einstein-Podolsky-Rosen Steering Inequalities and Applications. ENTROPY 2018; 20:e20090683. [PMID: 33265772 PMCID: PMC7513208 DOI: 10.3390/e20090683] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Revised: 09/01/2018] [Accepted: 09/05/2018] [Indexed: 11/25/2022]
Abstract
Einstein-Podolsky-Rosen (EPR) steering is very important quantum correlation of a composite quantum system. It is an intermediate type of nonlocal correlation between entanglement and Bell nonlocality. In this paper, based on introducing definitions and characterizations of EPR steering, some EPR steering inequalities are derived. With these inequalities, the steerability of the maximally entangled state is checked and some conditions for the steerability of the X-states are obtained.
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Affiliation(s)
- Ying Yang
- School of Mathematics and Information Science, Shaanxi Normal University, Xi’an 710062, China
- School of Mathematics and Information Technology, Yuncheng University, Yuncheng 044000, China
| | - Huaixin Cao
- School of Mathematics and Information Science, Shaanxi Normal University, Xi’an 710062, China
- Correspondence:
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24
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Hordell J, Benedicto-Orenes D, Petrov PG, Kowalczyk AU, Barontini G, Boyer V. Transport of spatial squeezing through an optical waveguide. OPTICS EXPRESS 2018; 26:22783-22792. [PMID: 30184933 DOI: 10.1364/oe.26.022783] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Accepted: 07/03/2018] [Indexed: 06/08/2023]
Abstract
Multi-core optical fibers are readily used in endoscopic devices to transmit classical images. As an extension to the quantum domain, we study the transmission of the spatial quantum fluctuations of light through a conduit made of the ordered packing of thousands of fibers. Starting from twin beams that are correlated in their local intensity fluctuations, we show that, in the limit of a high density of constituent fiber cores, the intensity-difference squeezing present in arbitrary matching regions of the beams is preserved when one of the beams is sent through the conduit. The capability of using fiber bundles to transport quantum information encoded in the spatial degrees of freedom could bring guided-light technology to the emergent field of quantum imaging.
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25
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Toscano F, Tasca DS, Rudnicki Ł, Walborn SP. Uncertainty Relations for Coarse-Grained Measurements: An Overview. ENTROPY (BASEL, SWITZERLAND) 2018; 20:E454. [PMID: 33265544 PMCID: PMC7512973 DOI: 10.3390/e20060454] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Revised: 06/02/2018] [Accepted: 06/06/2018] [Indexed: 12/04/2022]
Abstract
Uncertainty relations involving incompatible observables are one of the cornerstones of quantum mechanics. Aside from their fundamental significance, they play an important role in practical applications, such as detection of quantum correlations and security requirements in quantum cryptography. In continuous variable systems, the spectra of the relevant observables form a continuum and this necessitates the coarse graining of measurements. However, these coarse-grained observables do not necessarily obey the same uncertainty relations as the original ones, a fact that can lead to false results when considering applications. That is, one cannot naively replace the original observables in the uncertainty relation for the coarse-grained observables and expect consistent results. As such, several uncertainty relations that are specifically designed for coarse-grained observables have been developed. In recognition of the 90th anniversary of the seminal Heisenberg uncertainty relation, celebrated last year, and all the subsequent work since then, here we give a review of the state of the art of coarse-grained uncertainty relations in continuous variable quantum systems, as well as their applications to fundamental quantum physics and quantum information tasks. Our review is meant to be balanced in its content, since both theoretical considerations and experimental perspectives are put on an equal footing.
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Affiliation(s)
- Fabricio Toscano
- Instituto de Física, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, Rio de Janeiro 21941-972, Brazil
| | - Daniel S. Tasca
- Instituto de Física, Universidade Federal Fluminense, Niteroi 24210-346, Brazil
| | - Łukasz Rudnicki
- Max-Planck-Institut für die Physik des Lichts, Staudtstraße 2, Erlangen 91058, Germany
- Center for Theoretical Physics, Polish Academy of Sciences, Aleja Lotników 32/46, Warsaw 02-668, Poland
| | - Stephen P. Walborn
- Instituto de Física, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, Rio de Janeiro 21941-972, Brazil
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26
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Gómez ES, Riquelme P, Solís-Prosser MA, González P, Ortega E, Xavier GB, Lima G. Tunable entanglement distillation of spatially correlated down-converted photons. OPTICS EXPRESS 2018; 26:13961-13972. [PMID: 29877441 DOI: 10.1364/oe.26.013961] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2018] [Accepted: 05/07/2018] [Indexed: 06/08/2023]
Abstract
We report on a new technique for entanglement distillation of the bipartite continuous variable state of spatially correlated photons generated in the spontaneous parametric down-conversion process (SPDC), where tunable non-Gaussian operations are implemented and the post-processed entanglement is certified in real-time using a single-photon sensitive electron multiplying CCD (EMCCD) camera. The local operations are performed using non-Gaussian filters modulated into a programmable spatial light modulator and, by using the EMCCD camera for actively recording the probability distributions of the twin-photons, one has fine control of the Schmidt number of the distilled state. We show that even simple non-Gaussian filters can be finely tuned to a ∼67% net gain of the initial entanglement generated in the SPDC process.
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27
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Lange K, Peise J, Lücke B, Kruse I, Vitagliano G, Apellaniz I, Kleinmann M, Tóth G, Klempt C. Entanglement between two spatially separated atomic modes. Science 2018; 360:416-418. [PMID: 29700263 DOI: 10.1126/science.aao2035] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Accepted: 03/22/2018] [Indexed: 02/15/2024]
Abstract
Modern quantum technologies in the fields of quantum computing, quantum simulation, and quantum metrology require the creation and control of large ensembles of entangled particles. In ultracold ensembles of neutral atoms, nonclassical states have been generated with mutual entanglement among thousands of particles. The entanglement generation relies on the fundamental particle-exchange symmetry in ensembles of identical particles, which lacks the standard notion of entanglement between clearly definable subsystems. Here, we present the generation of entanglement between two spatially separated clouds by splitting an ensemble of ultracold identical particles prepared in a twin Fock state. Because the clouds can be addressed individually, our experiments open a path to exploit the available entangled states of indistinguishable particles for quantum information applications.
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Affiliation(s)
- Karsten Lange
- Institut für Quantenoptik, Leibniz Universität Hannover, Welfengarten 1, D-30167 Hannover, Germany
| | - Jan Peise
- Institut für Quantenoptik, Leibniz Universität Hannover, Welfengarten 1, D-30167 Hannover, Germany
| | - Bernd Lücke
- Institut für Quantenoptik, Leibniz Universität Hannover, Welfengarten 1, D-30167 Hannover, Germany
| | - Ilka Kruse
- Institut für Quantenoptik, Leibniz Universität Hannover, Welfengarten 1, D-30167 Hannover, Germany
| | - Giuseppe Vitagliano
- Institute for Quantum Optics and Quantum Information (IQOQI), Austrian Academy of Sciences, Boltzmanngasse 3, A-1090 Vienna, Austria
- Department of Theoretical Physics, University of the Basque Country UPV/EHU, Post Office Box 644, E-48080 Bilbao, Spain
| | - Iagoba Apellaniz
- Department of Theoretical Physics, University of the Basque Country UPV/EHU, Post Office Box 644, E-48080 Bilbao, Spain
| | - Matthias Kleinmann
- Department of Theoretical Physics, University of the Basque Country UPV/EHU, Post Office Box 644, E-48080 Bilbao, Spain
- Naturwissenschaftlich-Technische Fakultät, Universität Siegen, Walter-Flex-Straße 3, D-57068 Siegen, Germany
| | - Géza Tóth
- Department of Theoretical Physics, University of the Basque Country UPV/EHU, Post Office Box 644, E-48080 Bilbao, Spain
- Ikerbasque, Basque Foundation for Science, E-48013 Bilbao, Spain
- Wigner Research Centre for Physics, Hungarian Academy of Sciences, Post Office Box 49, H-1525 Budapest, Hungary
| | - Carsten Klempt
- Institut für Quantenoptik, Leibniz Universität Hannover, Welfengarten 1, D-30167 Hannover, Germany.
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28
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Kunkel P, Prüfer M, Strobel H, Linnemann D, Frölian A, Gasenzer T, Gärttner M, Oberthaler MK. Spatially distributed multipartite entanglement enables EPR steering of atomic clouds. Science 2018; 360:413-416. [DOI: 10.1126/science.aao2254] [Citation(s) in RCA: 125] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Accepted: 02/16/2018] [Indexed: 11/02/2022]
Abstract
A key resource for distributed quantum-enhanced protocols is entanglement between spatially separated modes. However, the robust generation and detection of entanglement between spatially separated regions of an ultracold atomic system remain a challenge. We used spin mixing in a tightly confined Bose-Einstein condensate to generate an entangled state of indistinguishable particles in a single spatial mode. We show experimentally that this entanglement can be spatially distributed by self-similar expansion of the atomic cloud. We used spatially resolved spin read-out to reveal a particularly strong form of quantum correlations known as Einstein-Podolsky-Rosen (EPR) steering between distinct parts of the expanded cloud. Based on the strength of EPR steering, we constructed a witness, which confirmed genuine 5-partite entanglement.
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Affiliation(s)
- Philipp Kunkel
- Kirchhoff-Institut für Physik, Universität Heidelberg, Im Neuenheimer Feld 227, 69120 Heidelberg, Germany
| | - Maximilian Prüfer
- Kirchhoff-Institut für Physik, Universität Heidelberg, Im Neuenheimer Feld 227, 69120 Heidelberg, Germany
| | - Helmut Strobel
- Kirchhoff-Institut für Physik, Universität Heidelberg, Im Neuenheimer Feld 227, 69120 Heidelberg, Germany
| | - Daniel Linnemann
- Kirchhoff-Institut für Physik, Universität Heidelberg, Im Neuenheimer Feld 227, 69120 Heidelberg, Germany
| | - Anika Frölian
- Kirchhoff-Institut für Physik, Universität Heidelberg, Im Neuenheimer Feld 227, 69120 Heidelberg, Germany
| | - Thomas Gasenzer
- Kirchhoff-Institut für Physik, Universität Heidelberg, Im Neuenheimer Feld 227, 69120 Heidelberg, Germany
| | - Martin Gärttner
- Kirchhoff-Institut für Physik, Universität Heidelberg, Im Neuenheimer Feld 227, 69120 Heidelberg, Germany
| | - Markus K. Oberthaler
- Kirchhoff-Institut für Physik, Universität Heidelberg, Im Neuenheimer Feld 227, 69120 Heidelberg, Germany
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29
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Chen SY, Chen LQ, Ou ZY, Hang W. Quantum non-demolition measurement of photon number with atom-light interferometers. OPTICS EXPRESS 2017; 25:31827-31839. [PMID: 29245853 DOI: 10.1364/oe.25.031827] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Accepted: 11/27/2017] [Indexed: 06/07/2023]
Abstract
When atoms are illuminated by an off-resonant field, the AC Stark effect will lead to phase shifts in atomic states. The phase shifts are proportional to the photon number of the off-resonant illuminating field. By measuring the atomic phase with newly developed atom-light hybrid interferometers, we can achieve quantum non-demolition measurement of the photon number of the optical field. In this paper, we analyze theoretically the performance of this QND measurement scheme by using the QND measurement criteria established by Holland et al [Phys. Rev. A 42, 2995 (1990)]. We find the quality of the QND measurement depends on the phase resolution of the atom-light hybrid interferometers. We apply this QND measurement scheme to a twin-photon state from parametric amplifier to verify the photon correlation in the twin beams. Furthermore, a sequential QND measurement procedure is analyzed for verifying the projection property of quantum measurement and for the quantum information tapping. Finally, we discuss the possibility for single-photon-number-resolving detection via QND measurement.
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Abstract
Occupying a position between entanglement and Bell nonlocality, Einstein-Podolsky-Rosen (EPR) steering has attracted increasing attention in recent years. Many criteria have been proposed and experimentally implemented to characterize EPR-steering. Nevertheless, only a few results are available to quantify steerability using analytical results. In this work, we propose a method for quantifying the steerability in two-qubit quantum states in the two-setting EPR-steering scenario, using the connection between joint measurability and steerability. We derive an analytical formula for the steerability of a class of X-states. The sufficient and necessary conditions for two-setting EPR-steering are presented. Based on these results, a class of asymmetric states, namely, one-way steerable states, are obtained.
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31
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Olsen MK. Controlled Asymmetry of Einstein-Podolsky-Rosen Steering with an Injected Nondegenerate Optical Parametric Oscillator. PHYSICAL REVIEW LETTERS 2017; 119:160501. [PMID: 29099216 DOI: 10.1103/physrevlett.119.160501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2017] [Indexed: 06/07/2023]
Abstract
We propose and analyze a nonlinear optical apparatus in which the direction of asymmetric steering is controllable within the apparatus, rather than by adding noise to measurements. Using a nondegenerate parametric oscillator with an injected signal field, we show how the directionality and extent of the steering can be readily controlled for output modes that can be up to one octave apart. The two down-converted modes, which exhibit the greater violations of the steering inequalities, can also be controlled to exhibit asymmetric steering in some regimes.
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Affiliation(s)
- M K Olsen
- School of Mathematics and Physics, University of Queensland, Brisbane, Queensland 4072, Australia and Quantum Science Otago and Dodd-Walls Centre for Photonic and Quantum Technologies, Department of Physics, University of Otago, Dunedin 9016, New Zealand
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32
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Robertson S, Michel F, Parentani R. Assessing degrees of entanglement of phonon states in atomic Bose gases through the measurement of commuting observables. Int J Clin Exp Med 2017. [DOI: 10.1103/physrevd.96.045012] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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33
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Kiesewetter S, Teh RY, Drummond PD, Reid MD. Pulsed Entanglement of Two Optomechanical Oscillators and Furry's Hypothesis. PHYSICAL REVIEW LETTERS 2017; 119:023601. [PMID: 28753370 DOI: 10.1103/physrevlett.119.023601] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2016] [Indexed: 06/07/2023]
Abstract
A strategy for generating entanglement between two separated optomechanical oscillators is analyzed, using entangled radiation produced from down-conversion and stored in an initiating cavity. We show that the use of pulsed entanglement with optimally shaped temporal modes can efficiently transfer quantum entanglement into a mechanical mode, then remove it after a fixed waiting time for measurement. This protocol could provide new avenues for testing for bounds on decoherence in massive systems that are spatially separated, as originally suggested by Furry not long after the discussion by Einstein-Podolsky-Rosen and Schrödinger of entanglement.
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Affiliation(s)
- S Kiesewetter
- Center for Quantum and Optical Science, Swinburne University of Technology, Melbourne 3122, Australia
| | - R Y Teh
- Center for Quantum and Optical Science, Swinburne University of Technology, Melbourne 3122, Australia
| | - P D Drummond
- Center for Quantum and Optical Science, Swinburne University of Technology, Melbourne 3122, Australia
| | - M D Reid
- Center for Quantum and Optical Science, Swinburne University of Technology, Melbourne 3122, Australia
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34
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Abstract
We introduce the concept of spatio-temporal steering (STS), which reduces, in special cases, to Einstein-Podolsky-Rosen steering and the recently-introduced temporal steering. We describe two measures of this effect referred to as the STS weight and robustness. We suggest that these STS measures enable a new way to assess nonclassical correlations in an open quantum network, such as quantum transport through nano-structures or excitation transfer in a complex biological system. As one of our examples, we apply STS to check nonclassical correlations among sites in a photosynthetic pigment-protein complex in the Fenna-Matthews-Olson model.
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35
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Cavalcanti D, Skrzypczyk P. Quantum steering: a review with focus on semidefinite programming. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2017; 80:024001. [PMID: 28008876 DOI: 10.1088/1361-6633/80/2/024001] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Quantum steering refers to the non-classical correlations that can be observed between the outcomes of measurements applied on half of an entangled state and the resulting post-measured states that are left with the other party. From an operational point of view, a steering test can be seen as an entanglement test where one of the parties performs uncharacterised measurements. Thus, quantum steering is a form of quantum inseparability that lies in between the well-known notions of Bell nonlocality and entanglement. Moreover, quantum steering is also related to several asymmetric quantum information protocols where some of the parties are considered untrusted. Because of these facts, quantum steering has received a lot of attention both theoretically and experimentally. The main goal of this review is to give an overview of how to characterise quantum steering through semidefinite programming. This characterisation provides efficient numerical methods to address a number of problems, including steering detection, quantification, and applications. We also give a brief overview of some important results that are not directly related to semidefinite programming. Finally, we make available a collection of semidefinite programming codes that can be used to study the topics discussed in this article.
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Affiliation(s)
- D Cavalcanti
- ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860 Castelldefels (Barcelona), Spain
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36
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Lee JC, Park KK, Zhao TM, Kim YH. Einstein-Podolsky-Rosen Entanglement of Narrow-Band Photons from Cold Atoms. PHYSICAL REVIEW LETTERS 2016; 117:250501. [PMID: 28036221 DOI: 10.1103/physrevlett.117.250501] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Indexed: 06/06/2023]
Abstract
Einstein-Podolsky-Rosen (EPR) entanglement introduced in 1935 deals with two particles that are entangled in their positions and momenta. Here we report the first experimental demonstration of EPR position-momentum entanglement of narrow-band photon pairs generated from cold atoms. By using two-photon quantum ghost imaging and ghost interference, we demonstrate explicitly that the narrow-band photon pairs violate the separability criterion, confirming EPR entanglement. We further demonstrate continuous variable EPR steering for positions and momenta of the two photons. Our new source of EPR-entangled narrow-band photons is expected to play an essential role in spatially multiplexed quantum information processing, such as, storage of quantum correlated images, quantum interface involving hyperentangled photons, etc.
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Affiliation(s)
- Jong-Chan Lee
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang 37673, Korea
| | - Kwang-Kyoon Park
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang 37673, Korea
| | - Tian-Ming Zhao
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang 37673, Korea
| | - Yoon-Ho Kim
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang 37673, Korea
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37
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Ji SW, Lee J, Park J, Nha H. Quantum steering of Gaussian states via non-Gaussian measurements. Sci Rep 2016; 6:29729. [PMID: 27411853 PMCID: PMC4944338 DOI: 10.1038/srep29729] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Accepted: 06/21/2016] [Indexed: 11/21/2022] Open
Abstract
Quantum steering—a strong correlation to be verified even when one party or its measuring device is fully untrusted—not only provides a profound insight into quantum physics but also offers a crucial basis for practical applications. For continuous-variable (CV) systems, Gaussian states among others have been extensively studied, however, mostly confined to Gaussian measurements. While the fulfilment of Gaussian criterion is sufficient to detect CV steering, whether it is also necessary for Gaussian states is a question of fundamental importance in many contexts. This critically questions the validity of characterizations established only under Gaussian measurements like the quantification of steering and the monogamy relations. Here, we introduce a formalism based on local uncertainty relations of non-Gaussian measurements, which is shown to manifest quantum steering of some Gaussian states that Gaussian criterion fails to detect. To this aim, we look into Gaussian states of practical relevance, i.e. two-mode squeezed states under a lossy and an amplifying Gaussian channel. Our finding significantly modifies the characteristics of Gaussian-state steering so far established such as monogamy relations and one-way steering under Gaussian measurements, thus opening a new direction for critical studies beyond Gaussian regime.
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Affiliation(s)
- Se-Wan Ji
- Department of Physics, Texas A&M University at Qatar, PO Box 23784, Doha, Qatar
| | - Jaehak Lee
- Department of Physics, Texas A&M University at Qatar, PO Box 23784, Doha, Qatar
| | - Jiyong Park
- Department of Physics, Texas A&M University at Qatar, PO Box 23784, Doha, Qatar
| | - Hyunchul Nha
- Department of Physics, Texas A&M University at Qatar, PO Box 23784, Doha, Qatar
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38
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Wang J, Cao H, Jing J, Fan H. Gaussian quantum steering and its asymmetry in curved spacetime. Int J Clin Exp Med 2016. [DOI: 10.1103/physrevd.93.125011] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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39
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Wollmann S, Walk N, Bennet AJ, Wiseman HM, Pryde GJ. Observation of Genuine One-Way Einstein-Podolsky-Rosen Steering. PHYSICAL REVIEW LETTERS 2016; 116:160403. [PMID: 27152777 DOI: 10.1103/physrevlett.116.160403] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2015] [Indexed: 06/05/2023]
Abstract
Within the hierarchy of inseparable quantum correlations, Einstein-Podolsky-Rosen steering is distinguished from both entanglement and Bell nonlocality by its asymmetry-there exist conditions where the steering phenomenon changes from being observable to not observable, simply by exchanging the role of the two measuring parties. While this one-way steering feature has been previously demonstrated for the restricted class of Gaussian measurements, for the general case of positive-operator-valued measures even its theoretical existence has only recently been settled. Here, we prove, and then experimentally observe, the one-way steerability of an experimentally practical class of entangled states in this general setting. As well as its foundational significance, the demonstration of fundamentally asymmetric nonlocality also has practical implications for the distribution of the trust in quantum communication networks.
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Affiliation(s)
- Sabine Wollmann
- Centre for Quantum Computation and Communication Technology and Centre for Quantum Dynamics, Griffith University, Brisbane, Queensland 4111, Australia
| | - Nathan Walk
- Centre for Quantum Computation and Communication Technology and Centre for Quantum Dynamics, Griffith University, Brisbane, Queensland 4111, Australia
- Department of Computer Science, University of Oxford, Oxford OX1 3QD, United Kingdom
| | - Adam J Bennet
- Centre for Quantum Computation and Communication Technology and Centre for Quantum Dynamics, Griffith University, Brisbane, Queensland 4111, Australia
| | - Howard M Wiseman
- Centre for Quantum Computation and Communication Technology and Centre for Quantum Dynamics, Griffith University, Brisbane, Queensland 4111, Australia
| | - Geoff J Pryde
- Centre for Quantum Computation and Communication Technology and Centre for Quantum Dynamics, Griffith University, Brisbane, Queensland 4111, Australia
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40
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Abstract
We investigate the steerability of two-qubit Bell-diagonal states under projective measurements by the steering party. In the simplest nontrivial scenario of two projective measurements, we solve this problem completely by virtue of the connection between the steering problem and the joint-measurement problem. A necessary and sufficient criterion is derived together with a simple geometrical interpretation. Our study shows that a Bell-diagonal state is steerable by two projective measurements iff it violates the Clauser-Horne-Shimony-Holt (CHSH) inequality, in sharp contrast with the strict hierarchy expected between steering and Bell nonlocality. We also introduce a steering measure and clarify its connections with concurrence and the volume of the steering ellipsoid. In particular, we determine the maximal concurrence and ellipsoid volume of Bell-diagonal states that are not steerable by two projective measurements. Finally, we explore the steerability of Bell-diagonal states under three projective measurements. A simple sufficient criterion is derived, which can detect the steerability of many states that are not steerable by two projective measurements. Our study offers valuable insight on steering of Bell-diagonal states as well as the connections between entanglement, steering, and Bell nonlocality.
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41
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Zhu H, Hayashi M, Chen L. Universal Steering Criteria. PHYSICAL REVIEW LETTERS 2016; 116:070403. [PMID: 26943513 DOI: 10.1103/physrevlett.116.070403] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Indexed: 06/05/2023]
Abstract
We propose a general framework for constructing universal steering criteria that are applicable to arbitrary bipartite states and measurement settings of the steering party. The same framework is also useful for studying the joint measurement problem. Based on the data-processing inequality for an extended Rényi relative entropy, we then introduce a family of steering inequalities, which detect steering much more efficiently than those inequalities known before. As illustrations, we show unbounded violation of a steering inequality for assemblages constructed from mutually unbiased bases and establish an interesting connection between maximally steerable assemblages and complete sets of mutually unbiased bases. We also provide a single steering inequality that can detect all bipartite pure states of full Schmidt rank. In the course of study, we generalize a number of results intimately connected to data-processing inequalities, which are of independent interest.
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Affiliation(s)
- Huangjun Zhu
- Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5, Canada
- Institute for Theoretical Physics, University of Cologne, Cologne 50937, Germany
| | - Masahito Hayashi
- Graduate School of Mathematics, Nagoya University, Nagoya 464-0814, Japan
- Centre for Quantum Technologies, National University of Singapore, Singapore 117543, Singapore
| | - Lin Chen
- School of Mathematics and Systems Science, Beihang University, Beijing 100191, China
- International Research Institute for Multidisciplinary Science, Beihang University, Beijing 100191, China
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42
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Satisfying the Einstein-Podolsky-Rosen criterion with massive particles. Nat Commun 2015; 6:8984. [PMID: 26612105 PMCID: PMC4674826 DOI: 10.1038/ncomms9984] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Accepted: 10/23/2015] [Indexed: 11/11/2022] Open
Abstract
In 1935, Einstein, Podolsky and Rosen (EPR) questioned the completeness of quantum mechanics by devising a quantum state of two massive particles with maximally correlated space and momentum coordinates. The EPR criterion qualifies such continuous-variable entangled states, where a measurement of one subsystem seemingly allows for a prediction of the second subsystem beyond the Heisenberg uncertainty relation. Up to now, continuous-variable EPR correlations have only been created with photons, while the demonstration of such strongly correlated states with massive particles is still outstanding. Here we report on the creation of an EPR-correlated two-mode squeezed state in an ultracold atomic ensemble. The state shows an EPR entanglement parameter of 0.18(3), which is 2.4 s.d. below the threshold 1/4 of the EPR criterion. We also present a full tomographic reconstruction of the underlying many-particle quantum state. The state presents a resource for tests of quantum nonlocality and a wide variety of applications in the field of continuous-variable quantum information and metrology. Continuous-variables EPR states present a resource for applications to quantum information processing and metrology, but these states have been created until now only with photon pairs. Here, the authors report the creation of an EPR-correlated two-mode squeezed states in an ultracold atomic ensemble.
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Kogias I, Skrzypczyk P, Cavalcanti D, Acín A, Adesso G. Hierarchy of Steering Criteria Based on Moments for All Bipartite Quantum Systems. PHYSICAL REVIEW LETTERS 2015; 115:210401. [PMID: 26636832 DOI: 10.1103/physrevlett.115.210401] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Indexed: 06/05/2023]
Abstract
Einstein-Podolsky-Rosen steering is a manifestation of quantum correlations exhibited by quantum systems that allows for entanglement certification when one of the subsystems is not characterized. Detecting the steerability of quantum states is essential to assess their suitability for quantum information protocols with partially trusted devices. We provide a hierarchy of sufficient conditions for the steerability of bipartite quantum states of any dimension, including continuous variable states. Previously known steering criteria are recovered as special cases of our approach. The proposed method allows us to derive optimal steering witnesses for arbitrary families of quantum states and provides a systematic framework to analytically derive nonlinear steering criteria. We discuss relevant examples and, in particular, provide an optimal steering witness for a lossy single-photon Bell state; the witness can be implemented just by linear optics and homodyne detection and detects steering with a higher loss tolerance than any other known method. Our approach is readily applicable to multipartite steering detection and to the characterization of joint measurability.
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Affiliation(s)
- Ioannis Kogias
- School of Mathematical Sciences, The University of Nottingham, University Park, Nottingham NG7 2RD, United Kingdom
- ICFO-The Institute of Photonic Sciences, Avenida Carl Friedrich Gauss, 3 08860 Castelldefels (Barcelona), Spain
| | - Paul Skrzypczyk
- ICFO-The Institute of Photonic Sciences, Avenida Carl Friedrich Gauss, 3 08860 Castelldefels (Barcelona), Spain
- H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, United Kingdom
| | - Daniel Cavalcanti
- ICFO-The Institute of Photonic Sciences, Avenida Carl Friedrich Gauss, 3 08860 Castelldefels (Barcelona), Spain
| | - Antonio Acín
- ICFO-The Institute of Photonic Sciences, Avenida Carl Friedrich Gauss, 3 08860 Castelldefels (Barcelona), Spain
| | - Gerardo Adesso
- School of Mathematical Sciences, The University of Nottingham, University Park, Nottingham NG7 2RD, United Kingdom
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Xiang Y, Sun FX, Wang M, Gong QH, He QY. Detection of genuine tripartite entanglement and steering in hybrid optomechanics. OPTICS EXPRESS 2015; 23:30104-30117. [PMID: 26698491 DOI: 10.1364/oe.23.030104] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Multipartite quantum entanglement is a key resource for ensuring security in quantum network. We show that by using a unified parameter in terms of reduced noise variances one can determine different types of tripartite entanglement of a given state generated in a hybrid optomechanical system, where an atomic ensemble is located inside a single-mode cavity with a movable mirror, with different thresholds for each type. In particular, the special quantum states which allow both entanglement and steering genuinely shared among atom-light-mirror modes can be observed, even though there is no direct interaction between the mirror and the atomic ensemble. We further show the robustness against mechanical thermal noise and damping, the relaxation time of atomic ensemble, as well as the effect of gain factors involved in the criteria. Our analysis provides an experimentally achievable method to determine the type of tripartite quantum correlation in a way.
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45
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He Q, Rosales-Zárate L, Adesso G, Reid MD. Secure Continuous Variable Teleportation and Einstein-Podolsky-Rosen Steering. PHYSICAL REVIEW LETTERS 2015; 115:180502. [PMID: 26565449 DOI: 10.1103/physrevlett.115.180502] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Indexed: 06/05/2023]
Abstract
We investigate the resources needed for secure teleportation of coherent states. We extend continuous variable teleportation to include quantum teleamplification protocols that allow nonunity classical gains and a preamplification or postattenuation of the coherent state. We show that, for arbitrary Gaussian protocols and a significant class of Gaussian resources, two-way steering is required to achieve a teleportation fidelity beyond the no-cloning threshold. This provides an operational connection between Gaussian steerability and secure teleportation. We present practical recipes suggesting that heralded noiseless preamplification may enable high-fidelity heralded teleportation, using minimally entangled yet steerable resources.
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Affiliation(s)
- Qiongyi He
- State Key Laboratory of Mesoscopic Physics, School of Physics, Peking University, Collaborative Innovation Center of Quantum Matter, Beijing 100871 China
- Centre for Quantum and Optical Science, Swinburne University of Technology, Melbourne 3122, Australia
| | - Laura Rosales-Zárate
- Centre for Quantum and Optical Science, Swinburne University of Technology, Melbourne 3122, Australia
| | - Gerardo Adesso
- School of Mathematical Sciences, University of Nottingham, Nottingham NG7 2RD, United Kingdom
| | - Margaret D Reid
- Centre for Quantum and Optical Science, Swinburne University of Technology, Melbourne 3122, Australia
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46
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Detecting the existence of an invisibility cloak using temporal steering. Sci Rep 2015; 5:15571. [PMID: 26493048 PMCID: PMC4616059 DOI: 10.1038/srep15571] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Accepted: 09/29/2015] [Indexed: 11/23/2022] Open
Abstract
An invisibility cloak provides a way to hide an object under the detection of waves. A good cloak guides the incident waves through the cloaking shell with few distortion. Even if one day a nearly perfect cloak is built, some important quantum effects, such as dephasing of the electron spin or photon polarization, may still remain. In this work, we consider the possibility that using the temporal steering of these degrees of freedom to detect the existence of an invisibility cloak.
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47
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Zhang Y, Okubo R, Hirano M, Eto Y, Hirano T. Experimental realization of spatially separated entanglement with continuous variables using laser pulse trains. Sci Rep 2015; 5:13029. [PMID: 26278478 PMCID: PMC4538399 DOI: 10.1038/srep13029] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2014] [Accepted: 07/15/2015] [Indexed: 11/09/2022] Open
Abstract
Spatially separated entanglement is demonstrated by interfering two high-repetition squeezed pulse trains. The entanglement correlation of the quadrature amplitudes between individual pulses is interrogated. It is characterized in terms of the sufficient inseparability criterion with an optimum result of in the frequency domain and in the time domain. The quantum correlation is also observed when the two measurement stations are separated by a physical distance of 4.5 m, which is sufficiently large to demonstrate the space-like separation, after accounting for the measurement time.
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Affiliation(s)
- Yun Zhang
- Department of Engineering Science, The University of Electro-Communications, 1-5-1 Chofugaoka, Chofu-shi, Tokyo 182-8585, Japan
| | - Ryuhi Okubo
- Department of Physics, Gakushuin University, 1-5-1 Mejiro, Toshima-ku, Tokyo, 171-8588, Japan
| | - Mayumi Hirano
- Department of Physics, Gakushuin University, 1-5-1 Mejiro, Toshima-ku, Tokyo, 171-8588, Japan
| | - Yujiro Eto
- Department of Physics, Gakushuin University, 1-5-1 Mejiro, Toshima-ku, Tokyo, 171-8588, Japan
| | - Takuya Hirano
- Department of Physics, Gakushuin University, 1-5-1 Mejiro, Toshima-ku, Tokyo, 171-8588, Japan
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48
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Yan Y, Li GX, Wu QL. Entanglement and Einstein-Podolsky-Rosen steering between a nanomechanical resonator and a cavity coupled with two quantum dots. OPTICS EXPRESS 2015; 23:21306-21322. [PMID: 26367979 DOI: 10.1364/oe.23.021306] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We propose a scheme for generation of the stationary continuous-variable entanglement and Einstein-Podolsky-Rosen (EPR) steering between an optical cavity mode and a nanomechanical resonator (NMR) mode. The cavity and the NMR are commonly coupled with two separated quantum dots (QDs), where the two QDs are driven simultaneously by a strong laser field. By adjusting the frequency of the strong laser field, the two QDs are nearly trapped on different dressed states, which is helpful to generate the entanglement between the cavity mode and the NMR mode. Due to the combined resonant interaction of the two QDs with the NMR-cavity subsystem, the photon and the phonon created and (or) annihilated are correlated. In this regime, the optimal entanglement of the two modes is obtained and the purity of the state of the NMR-cavity subsystem is near to 1. Furthermore, the coupling strength between the cavity and two QDs is different from the dot-NMR coupling strength, which leads to the different mean occupation numbers of the cavity and the NMR. In this case, one-way EPR steering is observed. In addition, through analyzing the purity, we find the conditions of the existence for the different types of EPR steering.
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49
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Wang M, Gong QH, Ficek Z, He QY. Efficient Scheme for Perfect Collective Einstein-Podolsky-Rosen Steering. Sci Rep 2015; 5:12346. [PMID: 26212901 PMCID: PMC4515746 DOI: 10.1038/srep12346] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Accepted: 06/25/2015] [Indexed: 11/08/2022] Open
Abstract
A practical scheme for the demonstration of perfect one-sided device-independent quantum secret sharing is proposed. The scheme involves a three-mode optomechanical system in which a pair of independent cavity modes is driven by short laser pulses and interact with a movable mirror. We demonstrate that by tuning the laser frequency to the blue (anti-Stokes) sideband of the average frequency of the cavity modes, the modes become mutually coherent and then may collectively steer the mirror mode to a perfect Einstein-Podolsky-Rosen state. The scheme is shown to be experimentally feasible, it is robust against the frequency difference between the modes, mechanical thermal noise and damping, and coupling strengths of the cavity modes to the mirror.
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Affiliation(s)
- M. Wang
- State Key Laboratory of Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, P. R. China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, P. R. China
| | - Q. H. Gong
- State Key Laboratory of Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, P. R. China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, P. R. China
| | - Z. Ficek
- The National Center for Applied Physics, KACST, P.O. Box 6086, Riyadh 11442, Saudi Arabia
| | - Q. Y. He
- State Key Laboratory of Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, P. R. China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, P. R. China
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50
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Rosołek K, Stobińska M, Wieśniak M, Żukowski M. Two copies of the Einstein-Podolsky-Rosen state of light lead to refutation of EPR ideas. PHYSICAL REVIEW LETTERS 2015; 114:100402. [PMID: 25815909 DOI: 10.1103/physrevlett.114.100402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Indexed: 06/04/2023]
Abstract
Bell's theorem applies to the normalizable approximations of original Einstein-Podolsky-Rosen (EPR) state. The constructions of the proof require measurements difficult to perform, and dichotomic observables. By noticing the fact that the four mode squeezed vacuum state produced in type II down-conversion can be seen both as two copies of approximate EPR states, and also as a kind of polarization supersinglet, we show a straightforward way to test violations of the EPR concepts with direct use of their state. The observables involved are simply photon numbers at outputs of polarizing beam splitters. Suitable chained Bell inequalities are based on the geometric concept of distance. For a few settings they are potentially a new tool for quantum information applications, involving observables of a nondichotomic nature, and thus of higher informational capacity. In the limit of infinitely many settings we get a Greenberger-Horne-Zeilinger-type contradiction: EPR reasoning points to a correlation, while quantum prediction is an anticorrelation. Violations of the inequalities are fully resistant to multipair emissions in Bell experiments using parametric down-conversion sources.
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Affiliation(s)
- Krzysztof Rosołek
- Institute of Theoretical Physics and Astrophysics, University of Gdańsk, Wita Stwosza 57, 80-952 Gdańsk, Poland
| | - Magdalena Stobińska
- Institute of Theoretical Physics and Astrophysics, University of Gdańsk, Wita Stwosza 57, 80-952 Gdańsk, Poland
- Institute of Physics, Polish Academy of Sciences, Aleja Lotników 32/46, 02-668 Warsaw, Poland
| | - Marcin Wieśniak
- Institute of Theoretical Physics and Astrophysics, University of Gdańsk, Wita Stwosza 57, 80-952 Gdańsk, Poland
| | - Marek Żukowski
- Institute of Theoretical Physics and Astrophysics, University of Gdańsk, Wita Stwosza 57, 80-952 Gdańsk, Poland
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