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Bright-light detector control emulates the local bounds of Bell-type inequalities

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arXiv 2019年

作者： Sajeed, Shihan Sultana, Nigar Lim, Charles Ci Wen Makarov, Vadim Institute for Quantum Computing University of Waterloo WaterlooONN2L 3G1 Canada Department of Physics and Astronomy University of Waterloo WaterlooONN2L 3G1 Canada Department of Electrical and Computer Engineering University of Toronto M5S 3G4 Canada Centre for Quantum Technologies National University of Singapore Singapore Department of Electrical & Computer Engineering National University of Singapore Singapore Russian Quantum Center Skolkovo Moscow121205 Russia Shanghai Branch National Laboratory for Physical Sciences at Microscale CAS Center for Excellence in Quantum Information University of Science and Technology of China Shanghai201315 China NTI Center for Quantum Communications National University of Science and Technology MISiS Moscow119049 Russia

It is well-known that no local model—in theory—can simulate the outcome statistics of a Bell-type experiment as long as the detection efficiency is higher than a threshold value. For the Clauser-Horne-Shimony-Holt (CHSH) Bell inequality this theoretical threshold value is ηT = 2(√2−1) ≈ 0.8284. On the other hand, Phys. Rev. Lett. 107, 170404 (2011) outlined an explicit practical model that can fake the CHSH inequality for a detection efficiency of up to 0.5. In this work, we close this gap. More specifically, we propose a method to emulate a Bell inequality at the threshold detection efficiency using existing optical detector control techniques. For a Clauser-Horne-Shimony-Holt inequality, it emulates the CHSH violation predicted by quantum mechanics up to ηT. For the Garg-Mermin inequality—re-calibrated by incorporating non-detection events—our method emulates its exact local bound at any efficiency above the threshold. This confirms that attacks on secure quantum communication protocols based on Bell violation is a real threat if the detection efficiency loophole is not closed. Copyright © 2019, The Authors. All rights reserved.

关键词： Bells

Broadcasting of Non-locality

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arXiv 2019年

作者： Patel, Dhrumil Roy, Arup Chakrabarty, Indranil Ganguly, Nirman Department of Computer Science Cornell University IthacaNY14853 United States Center for Security Theory and Algorithmic Research International Institute of Information Technology Hyderabad Gachibowli Telangana Hyderabad500032 India Department of Physics A B N Seal College West Bengal Cooch Behar736 101 India Centre for Quantum Science and Technology International Institute of Information Technology Hyderabad Gachibowli Telangana Hyderabad500032 India Department of Mathematics Birla Institute of Technology and Science Pilani Hyderabad Campus Telangana 500078 India

Bell nonlocality and steering are archetypal characteristics of quantum mechanics that mark a significant departure from conventional classical notions. They basically refer to the presence of quantum correlations between separated systems which violate a nonlocal inequality, the violation otherwise not possible if we restrict ourselves only to classical correlations. In view of the importance of such unique correlations one may be interested to generate more states exhibiting nonlocality starting from a few, a protocol which is termed as broadcasting. However, in the present submission, we show using universal Buzek-Hillary(BH) quantum cloning machine that, if one restricts to broadcasting through local quantum cloning, then such nonlocality cannot be broadcasted. Our study is done in the purview of the Bell-CHSH inequality and the CJWR (E.G. Cavalcanti, S.J. Jones, H.M Wiseman and M.D. Reid, Phys. Rev.A 80, 032112(2009)) steering inequality. It is observed that when number of measurement settings is greater than 6, some of the output states are steerable after the application of local optimal B-H cloners. We find that, under some restrictions, if the Werner and Bell diagonal states are subjected to such procedures, then the resultant state is rendered unsteerable. We extend this study to three qubit systems and find that genuine tripartite nonlocality cannot be broadcasted using universal BH local quantum cloners, when we consider the Svetlichny’s inequality. For two qubit systems, we have considered 105 simulated general local unitaries over Werner and Bell-diagonal states and find that for none of these states broadcasting on nonlocality and 3-steerability is possible. Copyright © 2019, The Authors. All rights reserved.

关键词： Broadcasting

Mitigating realistic noise in practical noisy intermediate-scale quantum devices

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arXiv 2020年

作者： Sun, Jinzhao Yuan, Xiao Tsunoda, Takahiro Vedral, Vlatko Benjamin, Simon C. Endo, Suguru Clarendon Laboratory University of Oxford Parks Road OxfordOX1 3PU United Kingdom Center on Frontiers of Computing Studies Department of Computer Science Peking University Beijing100871 China Stanford Institute for Theoretical Physics Stanford University StanfordCA94305 United States Department of Materials University of Oxford Parks Road OxfordOX1 3PH United Kingdom Centre for Quantum Technologies National University of Singapore Singapore117543 Singapore NTT Secure Platform Laboratories NTT Corporation Musashino180-8585 Japan

quantum error mitigation (QEM) is vital for noisy intermediate-scale quantum (NISQ) devices. While most conventional QEM schemes assume discrete gate-based circuits with noise appearing either before or after each gate, the assumptions are inappropriate for describing realistic noise that may have strong gate-dependence and complicated nonlocal effects, and general computing models such as analog quantum simulators. To address these challenges, we first extend the scenario, where each computation process, being either digital or analog, is described by a continuous time evolution. For noise from imperfections of the engineered Hamiltonian or additional noise operators, we show it can be effectively suppressed by a novel stochastic QEM method. Since our method only assumes accurate single qubit controls, it is applicable to all digital quantum computers and various analog simulators. Meanwhile, errors in the mitigation procedure can be suppressed by leveraging the Richardson extrapolation method. As we numerically test our method with various Hamiltonians under energy relaxation and dephasing noise and digital quantum circuits with additional two-qubit crosstalk, we show an improvement of simulation accuracy by two orders. We assess the resource cost of our scheme and conclude the feasibility of accurate quantum computing with NISQ devices. Copyright © 2020, The Authors. All rights reserved.

关键词： Hamiltonians

A platform for high performance photon correlation measurements

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arXiv 2020年

作者： Zadeh, Iman Esmaeil Los, Johannes W.N. Gourgues, Ronan B.M. Chang, Jin Elshaari, Ali W. Zichi, Julien van Staaden, Yuri J. Swens, Jeroen Kalhor, Nima Guardiani, Antonio Meng, Yun Zou, Kai Dobrovolskiy, Sergiy Fognini, Andreas W. Schaart, Dennis R. Dalacu, Dan Poole, Philip J. Reimer, Michael E. Hu, Xiaolong Pereira, Silvania F. Zwiller, Val Dorenbos, Sander N. Optics Research Group ImPhys Department Faculty of Applied Sciences Delft University of Technology Delft2628 CJ Netherlands Single Quantum B.V. Delft2628 CJ Netherlands Optics Research Group Imphys Department Faculty of Applied Sciences Delft University of Technology Delft2628 CJ Netherlands Stockholm106 91 Sweden School of Precision Instrument and Optoelectronic Engineering Tianjin University Tianjin300072 China Key Laboratory of Optoelectronic Information Science and Technology Ministry of Education Tianjin300072 China Medical Physics & Technology Radiation Science & Technology Department Faculty of Applied Sciences Delft University of Technology National Research Council of Canada OttawaONK1A 0R6 Canada Institute for Quantum Computing Department of Electrical & Computer Engineering University of Waterloo WaterlooONN2L 3G1 Canada

A broad range of scientific and industrial disciplines require precise optical measurements at very low light levels. Single-photon detectors combining high efficiency and high time resolution are pivotal in such experiments. By using relatively thick films of NbTiN (8-11 nm) and improving the pattern fidelity of the nano-structure of the superconducting nanowire single-photon detectors (SNSPD), we fabricated devices demonstrating superior performance over all previously reported detectors in the combination of efficiency and time resolution. Our findings prove that small variations in the nanowire width, in the order of a few nanometers, can lead to a significant penalty on their temporal response. Addressing these issues, we consistently achieved high time resolution (best device 7.7 ps, other devices ∼10-16 ps) simultaneously with high system detection efficiencies (80 − 90%) in the wavelength range of 780-1000 nm, as well as in the telecom bands (1310-1550 nm). The use of thicker films allowed us to fabricate large-area multi-pixel devices with homogeneous pixel performance. We first fabricated and characterized a 100 × 100 µm2 16-pixel detector and showed there was little variation among individual pixels. Additionally, to showcase the power of our platform, we fabricated and characterized 4-pixel multimode fiber-coupled detectors and carried out photon correlation experiments on a nanowire quantum dot resulting in g2(0) values lower than 0.04. The multi-pixel detectors alleviate the need for beamsplitters and can be used for higher order correlations with promising prospects not only in the field of quantum optics, but also in bio-imaging applications, such as fluorescence microscopy and positron emission tomography. Copyright © 2020, The Authors. All rights reserved.

关键词： quantum optics

A two-kind-boson mixture honeycomb Hamiltonian of bloch exciton-polaritons

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arXiv 2021年

作者： Pan, Haining Winkler, K. Powlowski, Mats Xie, Ming Schade, A. Emmerling, M. Kamp, M. Klembt, S. Schneider, C. Byrnes, Tim Höfling, S. Kim, Na Young Institute for Quantum Computing University of Waterloo 200 University Ave. West WaterlooONN2L 3G1 Canada Condensed Matter Theory Center Joint Quantum Institute Department of Physics University of Maryland College ParkMD20742 United States Technische Physik Physikalisches Institut Universität Würzbug WürzburgD-97074 Germany Department of Electrical and Computer Engineering University of Waterloo 200 University Ave. West WaterlooONN2L 3G1 Canada Department of Physics The University of Texas at Austin AustinTX78712 United States State Key Laboratory of Precision Spectroscopy School of Physical and Material Sciences East China Normal University Shanghai200062 China New York University Shanghai 1555 Century Ave. Pudong Shanghai200122 China NYU-ECNU Institute of Physics NYU Shanghai 366 Zhongshan Road North Shanghai200062 China Department of Physics New York University New YorkNY10003 United States School of Physics and Astronomy University of St. Andrews St. AndrewsKY16 9SS United Kingdom Department of Physics and Astronomy University of Waterloo 200 University Ave. West WaterlooONN2L 3G1 Canada Department of Chemistry University of Waterloo 200 University Ave. West WaterlooONN2L 3G1 Canada

The electronic bandstructure of a solid is a collection of allowed bands separated by forbidden bands, revealing the geometric symmetry of the crystal structures. Comprehensive knowledge of the bandstructure with band parameters explains intrinsic physical, chemical and mechanical properties of the solid. Here we report the artificial polaritonic bandstructures of two-dimensional honeycomb lattices for microcavity exciton-polaritons using GaAs semiconductors in the wide-range detuning values, from cavity-photon-like (red-detuned) to exciton-like (blue-detuned) regimes. In order to understand the experimental bandstructures and their band parameters, such as gap energies, bandwidths, hopping integrals and density of states, we originally establish a polariton band theory within an augmented plane wave method with two-kind-bosons, cavity photons trapped at the lattice sites and freely moving excitons. In particular, this two-kind-band theory is absolutely essential to elucidate the exciton effect in the bandstructures of blue-detuned exciton-polaritons, where the flattened exciton-like dispersion appears at larger in-plane momentum values captured in our experimental access window. We reach an excellent agreement between theory and experiments in all detuning values. © 2021, CC BY-NC-SA.

关键词： Honeycomb structures

Advances in space quantum communications

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arXiv 2021年

作者： Sidhu, Jasminder S. Joshi, Siddarth K. Gündogan, Mustafa Brougham, Thomas Lowndes, David Mazzarella, Luca Krutzik, Markus Mohapatra, Sonali Dequal, Daniele Vallone, Giuseppe Villoresi, Paolo Ling, Alexander Jennewein, Thomas Mohageg, Makan Rarity, John Fuentes, Ivette Pirandola, Stefano Oi, Daniel K.L. SUPA Department of Physics University of Strathclyde 107 Rottenrow GlasgowG4 0NG United Kingdom Quantum Engineering Technology Labs H. H. Wills Physics Laboratory Department of Electrical and Electronic Engineering University of Bristol Merchant Venturers Building Woodland Road BristolBS8 1UB United Kingdom Institüt für Physik Humboldt-Universität zu Berlin Newtonstr. 15 Berlin12489 Germany Jet Propulsion Laboratory California Institute of Technology United States Scientific Research Unit Agenzia Spaziale Italiana Matera Italy Dipartimento di Ingegneria dell'Informazione Università degli Studi di Padova Padova35131 Italy Dipartimento di Fisica e Astronomia Università degli Studi di Padova Padova35131 Italy Centre for Quantum Technologies National University of Singapore S15-02-10 3 Science Drive 2 Singapore117543 Singapore Department of Physics 2 Science Drive 3 Blk S12 Level 2 Singapore117551 Singapore Institute for Quantum Computing University of Waterloo WaterlooONN2L 3G1 Canada Department of Physics and Astronomy University of Waterloo WaterlooONN2L 3G1 Canada School of Physics and Astronomy University of Southampton SouthamptonSO17 1BJ United Kingdom Department of Computer Science University of York YorkYO10 5GH United Kingdom Craft Prospect Ltd. Suite 4A Fairfield 1048 Govan Road GlasgowG51 4XS United Kingdom

Concerted efforts are underway to establish an infrastructure for a global quantum internet to realise a spectrum of quantum technologies. This will enable more precise sensors, secure communications, and faster data processing. quantum communications are a front-runner with quantum networks already implemented in several metropolitan areas. A number of recent proposals have modelled the use of space segments to overcome range limitations of purely terrestrial networks. Rapid progress in the design of quantum devices have enabled their deployment in space for in-orbit demonstrations. We review developments in this emerging area of space-based quantum technologies and provide a roadmap of key milestones towards a complete, global quantum networked landscape. Small satellites hold increasing promise to provide a cost effective coverage required to realised the quantum internet. We review the state of art in small satellite missions and collate the most current in-field demonstrations of quantum cryptography. We summarise important challenges in space quantum technologies that must be overcome and recent efforts to mitigate their effects. A perspective on future developments that would improve the performance of space quantum communications is included. We conclude with a discussion on fundamental physics experiments that could take advantage of a global, space-based quantum network. Copyright © 2021, The Authors. All rights reserved.

关键词： quantum cryptography

Bayesian inference analysis of jet quenching using inclusive jet and hadron suppression measurements

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Physical Review C 2025年第5期111卷 054913-054913页

作者： R. Ehlers Y. Chen J. Mulligan Y. Ji A. Kumar S. Mak P. M. Jacobs A. Majumder A. Angerami R. Arora S. A. Bass R. Datta L. Du H. Elfner R. J. Fries C. Gale Y. He B. V. Jacak S. Jeon F. Jonas L. Kasper M. Kordell, II R. Kunnawalkam-Elayavalli J. Latessa Y.-J. Lee R. Lemmon M. Luzum A. Mankolli C. Martin H. Mehryar T. Mengel C. Nattrass J. Norman C. Parker J.-F. Paquet J. H. Putschke H. Roch G. Roland B. Schenke L. Schwiebert A. Sengupta C. Shen M. Singh C. Sirimanna D. Soeder R. A. Soltz I. Soudi Y. Tachibana J. Velkovska G. Vujanovic X.-N. Wang X. Wu W. Zhao Department of Physics University of California Berkeley California 94270 USA Nuclear Science Division Lawrence Berkeley National Laboratory Berkeley California 94270 USA Laboratory for Nuclear Science Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA Department of Physics Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA Department of Physics and Astronomy Vanderbilt University Nashville Tennessee 37235 USA Department of Statistical Science Duke University Durham North Carolina 27708 USA Department of Physics University of Regina Regina Saskatchewan S4S 0A2 Canada Department of Physics McGill University Montréal Québec H3A2T8 Canada Department of Physics and Astronomy Wayne State University Detroit Michigan 48201 USA Lawrence Livermore National Laboratory Livermore California 94550 USA Department of Computer Science Wayne State University Detroit Michigan 48202 USA Department of Physics Duke University Durham North Carolina 27708 USA GSI Helmholtzzentrum für Schwerionenforschung 64291 Darmstadt Germany Institute for Theoretical Physics Goethe University 60438 Frankfurt am Main Germany Frankfurt Institute for Advanced Studies 60438 Frankfurt am Main Germany Cyclotron Institute Texas A&M University College Station Texas 77843 USA Department of Physics and Astronomy Texas A&M University College Station Texas 77843 USA Guangdong Provincial Key Laboratory of Nuclear Science Institute of Quantum Matter South China Normal University Guangzhou 510006 China Guangdong-Hong Kong Joint Laboratory of Quantum Matter Southern Nuclear Science Computing Center South China Normal University Guangzhou 510006 China Daresbury Laboratory Daresbury Warrington Cheshire WA44AD United Kingdom Instituto de Fìsica Universidade de São Paulo C.P. 66318 05315-970 São Paulo SP Brazil. Department of Physics and Astronomy University of Tennessee Knoxville Tennessee 37996 USA Oliver Lodge Laboratory University of Liverpo

The JETSCAPE Collaboration reports a new determination of the jet transport parameter q̂ in the quark-gluon plasma (QGP) using Bayesian inference, incorporating all available inclusive hadron and jet yield suppression data measured in heavy-ion collisions at the BNL Relativistic Heavy Ion Collider (RHIC) and the CERN Large Hadron Collider (LHC). This multi-observable analysis extends the previously published JETSCAPE Bayesian inference determination of q̂, which was based solely on a selection of inclusive hadron suppression data. jetscape is a modular framework incorporating detailed dynamical models of QGP formation and evolution, and jet propagation and interaction in the QGP. Virtuality-dependent partonic energy loss in the QGP is modeled as a thermalized weakly coupled plasma, with parameters determined from Bayesian calibration using soft-sector observables. This Bayesian calibration of q̂ utilizes active learning, a machine-learning approach, for efficient exploitation of computing resources. The experimental data included in this analysis span a broad range in collision energy and centrality, and in transverse momentum. In order to explore the systematic dependence of the extracted parameter posterior distributions, several different calibrations are reported, based on combined jet and hadron data; on jet or hadron data separately; and on restricted kinematic or centrality ranges of the jet and hadron data. Tension is observed in comparison of these variations, providing new insights into the physics of jet transport in the QGP and its theoretical formulation.

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Classifying single-qubit noise using machine learning

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arXiv 2019年

作者： Scholten, Travis L. Liu, Yi-Kai Young, Kevin Blume-Kohout, Robin IBM T.J. Watson Research Center Yorktown HeightsNY10598 United States National Institute of Standards and Technology GaithersburgMD20899 United States Joint Center for Quantum Information and Computer Science University of Maryland College ParkMD20742 United States Quantum Performance Lab Sandia National Laboratories LivermoreCA94550 United States Quantum Performance Lab and Center for Computing Research Sandia National Laboratories AlbuquerqueNM87185 United States Center for Quantum Information and Control University of New Mexico AlbuquerqueNM87131 United States

quantum characterization, validation, and verification (QCVV) techniques are used to probe, characterize, diagnose, and detect errors in quantum information processors (QIPs). An important component of any QCVV protocol is a mapping from experimental data to an estimate of a property of a QIP. Machine learning (ML) algorithms can help automate the development of QCVV protocols, creating such maps by learning them from training data. We identify the critical components of "machine-learned" QCVV techniques, and present a rubric for developing them. To demonstrate this approach, we focus on the problem of determining whether noise affecting a single qubit is coherent or stochastic (incoherent) using the data sets originally proposed for gate set tomography. We leverage known ML algorithms to train a classifier distinguishing these two kinds of noise. The accuracy of the classifier depends on how well it can approximate the "natural" geometry of the training data. We find GST data sets generated by a noisy qubit can reliably be separated by linear surfaces, although feature engineering can be necessary. We also show the classifier learned by a support vector machine (SVM) is robust under finite-sample noise. Copyright © 2019, The Authors. All rights reserved.

关键词： quantum optics

Encoding classical information into quantum resources

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arXiv 2019年

作者： Korzekwa, Kamil Puchala, Zbigniew Tomamichel, Marco Zyczkowski, Karol International Centre for Theory of Quantum Technologies University of Gdansk Gdańsk80-308 Poland Faculty of Physics Astronomy and Applied Computer Science Jagiellonian University Kraków30-348 Poland Institute of Theoretical and Applied Informatics Polish Academy of Sciences Gliwice44-100 Poland Centre for Quantum Technologies National University of Singapore Singapore117543 Singapore Department of Electrical and Computer Engineering National University of Singapore Singapore117583 Singapore Centre for Quantum Software and Information School of Software University of Technology Sydney SydneyNSW2007 Australia Center for Theoretical Physics Polish Academy of Sciences Warszawa02-668 Poland

We introduce and analyse the problem of encoding classical information into different resources of a quantum state. More precisely, we consider a general class of communication scenarios characterised by encoding operations that commute with a unique resource destroying map and leave free states invariant. Our motivating example is given by encoding information into coherences of a quantum system with respect to a fixed basis (with unitaries diagonal in that basis as encodings and the decoherence channel as a resource destroying map), but the generality of the framework allows us to explore applications ranging from super-dense coding to thermodynamics. For any state, we find that the number of messages that can be encoded into it using such operations in a one-shot scenario is upper bounded in terms of the information spectrum relative entropy between the given state and its version with erased resources. Furthermore, if the resource destroying map is the twirling channel over some unitary group, we find matching one-shot lower bounds as well. In the asymptotic setting where we encode into many copies of the resource state, our bounds yield an operational interpretation of resource monotones such as the relative entropy of coherence and its corresponding relative entropy variance. Copyright © 2019, The Authors. All rights reserved.

关键词： quantum optics