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Characterization of State-Preparation Uncertainty in quantum Key Distribution

Physical Review Applied 2023年第1期19卷 014048-014048页

作者： Anqi Huang Akihiro Mizutani Hoi-Kwong Lo Vadim Makarov Kiyoshi Tamaki Institute for Quantum Information & State Key Laboratory of High Performance Computing College of Computer Science and Technology National University of Defense Technology Changsha 410073 People’s Republic of China Graduate School of Engineering Science Osaka University Toyonaka Osaka 560-8531 Japan Department of Electrical & Computer Engineering and Department of Physics Centre for Quantum Information and Quantum Control (CQIQC) University of Toronto Toronto Ontario M5S 3G4 Canada Department of Physics University of Hong Kong Pokfulam Hong Kong Quantum Bridge Technologies Inc. 100 College Street Toronto Ontario M5G 1L5 Canada Russian Quantum Center Skolkovo Moscow 121205 Russia Shanghai Branch National Laboratory for Physical Sciences at Microscale and CAS Center for Excellence in Quantum Information University of Science and Technology of China Shanghai 201315 People’s Republic of China NTI Center for Quantum Communications National University of Science and Technology MISiS Moscow 119049 Russia Faculty of Engineering University of Toyama Gofuku 3190 Toyama 930-8555 Japan

To achieve secure quantum key distribution, all imperfections in the source unit must be incorporated in a security proof and measured in the lab. Here we perform a proof-of-principle demonstration of the experimental techniques for characterizing the source phase and intensity fluctuation in commercial quantum key distribution systems. When we apply the measured phase-fluctuation intervals to the security proof that takes into account fluctuations in the state preparation, it predicts a key distribution distance of over 100km of fiber. The measured intensity fluctuation intervals are, however, so large that the proof predicts zero key, indicating a source improvement may be needed. Our characterization methods pave the way for a future certification standard.

关键词： Fluctuations & noise Optical quantum information processing quantum cryptography quantum engineering quantum state engineering

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Maximal coin-walker entanglement in a ballistic quantum walk

arXiv

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arXiv 2022年

作者： Zhang, Rong Yang, Ran Guo, Jian Sun, Chang-Wei Duan, Jia-Chen Zhou, Heng Xie, Zhenda Xu, Ping Gong, Yan-Xiao Zhu, Shi-Ning National Laboratory of Solid State Microstructure School of Physics School of Electronic Science and Engineering Collaborative Innovation Center of Advanced Microstructures Nanjing University Nanjing210093 China College of Electronic and Optical Engineering Nanjing University of Posts and Telecommunication Nanjing210023 China School of Information and Communication Engineering University of Electronic Science and Technology of China Chengdu611731 China Institute for Quantum Information State Key Laboratory of High Performance Computing College of Computing National University of Defense Technology Changsha410073 China

We report the position-inhomogeneous quantum walk (IQW) can be utilized to produce the maximal high dimensional entanglement while maintaining the quadratic speedup spread of the wave-function. Our calculations show that the maximal coin-walker entanglement can be generated in any odd steps or asymptotically in even steps, and the nearly maximal entanglement can be obtained in even steps after 2. We implement the IQW by a stable resource-saving time-bin optical network, in which a polarization Sagnac loop is employed to realize the precisely tunable phase shift. Our approach opens up an efficient way for high-dimensional entanglement engineering as well as promotes investigations on the role of coin-walker interactions in QW based applications. Copyright © 2022, The Authors. All rights reserved.

关键词： quantum entanglement

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Arbitrary coherent distributions in a programmable quantum walk

arXiv

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arXiv 2022年

作者： Zhang, Rong Yang, Ran Guo, Jian Sun, Chang-Wei Liu, Yi-Chen Zhou, Heng Xu, Ping Xie, Zhenda Gong, Yan-Xiao Zhu, Shi-Ning National Laboratory of Solid State Microstructure School of Physics School of Electronic Science and Engineering Collaborative Innovation Center of Advanced Microstructures Nanjing University Nanjing210093 China College of Electronic and Optical Engineering Nanjing University of Posts and Telecommunication Nanjing210023 China School of Information and Communication Engineering University of Electronic Science and Technology of China Chengdu611731 China Institute for Quantum Information State Key Laboratory of High Performance Computing College of Computing National University of Defense Technology Changsha410073 China

The coherent superposition of position states in a quantum walk (QW) can be precisely engineered towards the desired distributions to meet the need of quantum information applications. The coherent distribution can make full use of quantum parallel in computation and simulation. Particularly, the uniform superposition provides the robust non-locality, which has wide applications such as the generation of genuine multi-bit random numbers without post-processing. We experimentally demonstrate that the rich dynamics featured with arbitrary coherent distributions can be obtained by introducing different sets of the time- and position-dependent operations. Such a QW is realized by a resource-constant and flexible optical circuit, in which the variable operation is executed based on a Sagnac interferometer in an intrinsically stable and precisely controlled way. Our results contribute to the practical realization of quantum-walk-based quantum computation, quantum simulations and quantum information protocols. Copyright © 2022, The Authors. All rights reserved.

关键词： quantum optics

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Loophole-free test of macroscopic realism via high-order correlations of measurement

arXiv

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arXiv 2024年

作者： Wang, Ping Chen, Chong Liao, Hao Vorobyov, Vadim V. Wrachtrup, Jörg Liu, Ren-Bao College of Education for the Future Beijing Normal University Zhuhai519087 China Department of Physics The Chinese University of Hong Kong New Territories Shatin Hong Kong Centre for Quantum Coherence The Chinese University of Hong Kong New Territories Shatin Hong Kong The Hong Kong Institute of Quantum Information Science and Technology The Chinese University of Hong Kong New Territories Shatin Hong Kong National Engineering Laboratory on Big Data System Computing Technology Guangdong Province Engineering Center of China-made High Performance Data Computing System College of Computer Science and Software Engineering Shenzhen University Shenzhen518060 China 3rd Institute of Physics Research Center SCoPE and IQST University of Stuttgart Stuttgart70569 Germany New Cornerstone Science Laboratory The Chinese University of Hong Kong New Territories Shatin Hong Kong

Test of macroscopic realism (MR) is key to understanding the foundation of quantum mechanics. Due to the existence of the non-invasive measurability loophole and other interpretation loopholes, however, such test remains an open question. Here we propose a general inequality based on high-order correlations of measurements for a loophole-free test of MR at the weak signal limit. Importantly, the inequality is established using the statistics of raw data recorded by classical devices, without requiring a specific model for the measurement process, so its violation would falsify MR without the interpretation loophole. The non-invasive measurability loophole is also closed, since the weak signal limit can be verified solely by measurement data (using the relative scaling behaviors of different orders of correlations). We demonstrate that the inequality can be broken by a quantum spin model. The inequality proposed here provides an unambiguous test of the MR principle and is also useful to characterizing quantum coherence. Copyright © 2024, The Authors. All rights reserved.

关键词： quantum theory

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Bright photon-pair source based on a silicon dual-Mach-Zehnder microring

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Science China(Physics,Mechanics & Astronomy) 2020年第2期63卷 3-6页

作者： Chao Wu YingWen Liu XiaoWen Gu XinXin Yu YueChan Kong Yang Wang XiaoGang Qiang JunJie Wu ZhiHong Zhu XueJun Yang Ping Xu Institute for Quantum Information and State Key Laboratory of High Performance Computing College of ComputerCollege of Advanced Interdisciplinary StudiesNational University of Defense TechnologyChangsha 410073China Science and Technology on Monolithic Integrated Circuits and Modules Laboratory Nanjing Electronic Devices InstituteNanjing 210016China National Laboratory of Solid State Microstructures and School of Physics Nanjing UniversityNanjing 210093China

Single photons and photon pairs are typically generated by spontaneous parametric down conversion or quantum dots;however,spontaneous four-wave mixing(SFWM)in silicon microring resonators[1]is also an appealing source of entangled photons,offering a strong cavity-enhanced nonlinear interactions while maintaining features,such as compact,simple to fabricate,and allowing for thermal ***,silicon ring-resonators usually suffer from a trade-off between providing a high pair generation rate(PGR)and high extraction *** achieve high PGR,devices are generally operated with the signal and idler photons in the undercoupling regime and pump photons at the critical coupling point,while high extraction rates require the converted photons to be ***,the optimal conditions for achieving maximal output photon pair flux are critical coupling for the pump photons and overcoupling for the converted photons[2,3].

关键词： coupling photon converted

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Redshift-Space Distortions in Massive Neutrinos Cosmologies

arXiv

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arXiv 2025年

作者： Verdiani, Francesco Bellini, Emilio Moretti, Chiara Sefusatti, Emiliano Carbone, Carmelita Viel, Matteo SISSA - International School for Advanced Studies Via Bonomea 265 Trieste34136 Italy Istituto Nazionale di Astrofisica Osservatorio Astronomico di Trieste via Tiepolo 11 Trieste34143 Italy Institute for Fundamental Physics of the Universe Via Beirut 2 Trieste34151 Italy Istituto Nazionale di Fisica Nucleare Sezione di Trieste via Valerio 2 Trieste34127 Italy Center for Astrophysics and Cosmology University of Nova Gorica Nova Gorica Slovenia Istituto Nazionale di Astrofisica Istituto di Astrofisica Spaziale e Fisica cosmica di Milano Via Alfonso Corti 12 Milano20133 Italy ICSC - Centro Nazionale di Ricerca in High Performance Computing Big Data e Quantum Computing Via Magnanelli 2 Bologna Italy

We study the Kaiser formula for biased tracers in massive neutrino cosmologies by comparing its predictions with a large set of N-body simulations. In particular, we examine the ambiguity in the definition of the peculiar velocity contribution at linear level, whether it should be expressed in terms of the total matter velocity field or only the cold-matter component, comprised of cold dark matter and baryons. We revisit and extend previous qualitative studies on the topic with larger statistics and including a full fit of halo power spectrum and halo-matter cross-power spectrum measurements. We find clear evidence that the clustering of halos in redshift space is correctly described assuming that halo velocity is tracing the velocity field of cold-matter. The opposite assumption provides a worse fit to the simulated data and can lead to a spurious running of nuisance parameters in the perturbative galaxy power spectrum model. © 2025, CC BY.

关键词： Neutrons

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Protecting Fiber-Optic quantum Key Distribution Sources against Light-Injection Attacks

引用

PRX quantum 2022年第4期3卷 040307-040307页

作者： Anastasiya Ponosova Daria Ruzhitskaya Poompong Chaiwongkhot Vladimir Egorov Vadim Makarov Anqi Huang Russian Quantum Center Skolkovo Moscow 121205 Russia NTI Center for Quantum Communications National University of Science and Technology MISiS Moscow 119049 Russia Institute for Quantum Computing University of Waterloo Waterloo Ontario N2L 3G1 Canada Department of Physics and Astronomy University of Waterloo Waterloo Ontario N2L 3G1 Canada Department of Physics Faculty of Science Mahidol University Bangkok 10400 Thailand Quantum technology foundation (Thailand) Bangkok 10110 Thailand Leading research center for Quantum internet ITMO University Birzhevaya line 14 St. Petersburg 199034 Russia SMARTS-Quanttelecom LLC 6 liniya V.O. 59 St. Petersburg 199178 Russia Shanghai Branch National Laboratory for Physical Sciences at Microscale and CAS Center for Excellence in Quantum Information University of Science and Technology of China Shanghai 201315 People’s Republic of China Institute for Quantum Information & State Key Laboratory of High Performance Computing College of Computer Science and Technology National University of Defense Technology Changsha 410073 China

A well-protected and characterized source in a quantum key distribution system is needed for its security. Unfortunately, the source is vulnerable to light-injection attacks, such as Trojan-horse, laser-seeding, and laser-damage attacks, in which an eavesdropper actively injects bright light to hack the source unit. The hacking laser could be a high-power one that can modify properties of components via the laser-damage attack and also further help the Trojan-horse and other light-injection attacks. Here we propose a countermeasure against the light-injection attacks, consisting of an additional sacrificial component placed at the exit of the source. This component should either withstand high-power incoming light while attenuating it to a safe level that cannot modify the rest of the source, or get destroyed into a permanent high-attenuation state that breaks up the line. We demonstrate experimentally that off-the-shelf fiber-optic isolators and circulators have these desired properties, at least under attack by a continuous-wave high-power laser.

关键词： quantum communication quantum cryptography

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Nonequilibrium dynamics of the localization-delocalization transition in the non-Hermitian Aubry-André model

arXiv

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arXiv 2022年

作者： Zhai, Liang-Jun Huang, Guang-Yao Yin, Shuai Department of Physics Nanjing University Nanjing210093 China The School of Mathematics and Physics Jiangsu University of Technology Changzhou213001 China Institute for Quantum Information State Key Laboratory of High Performance Computing College of Computer Science and Technology National University of Defense Technology Changsha410073 China School of Physics Sun Yat-Sen University Guangzhou510275 China

In this paper, we investigate the driven dynamics of the localization transition in the non-Hermitian Aubry-André model with the periodic boundary condition. Depending on the strength of the quasi-periodic potential λ, this model undergoes a localization-delocalization phase transition. We find that the localization length ξ satisfies ξ ∼ Ε−ν with Ε being the distance from the critical point and ν = 1 being a universal critical exponent independent of the non-Hermitian parameter. In addition, from the finite-size scaling of the energy gap between the ground state and the first excited state, we determine the dynamic exponent z as z = 2. The critical exponent of the inverse participation ratio (IPR) for the nth eigenstate is also determined as s = 0.1197. By changing Ε linearly to cross the critical point, we find that the driven dynamics can be described by the Kibble-Zurek scaling (KZS). Moreover, we show that the KZS with the same set of the exponents can be generalized to the localization phase transitions in the excited states. Copyright © 2022, The Authors. All rights reserved.

关键词： Excited states

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Large-scale full-programmable quantum walk and its applications

arXiv

引用

arXiv 2022年

作者： Wang, Yizhi Liu, Yingwen Zhan, Junwei Xue, Shichuan Zheng, Yuzhen Zeng, Ru Wu, Zhihao Wang, Zihao Zheng, Qilin Wang, Dongyang Shi, Weixu Fu, Xiang Xu, Ping Wang, Yang Liu, Yong Ding, Jiangfang Huang, Guangyao Yu, Chunlin Huang, Anqi Qiang, Xiaogang Deng, Mingtang Xu, Weixia Lu, Kai Yang, Xuejun Wu, Junjie Institute for Quantum Information State Key Laboratory of High Performance Computing College of Computer Science and Technology National University of Defense Technology Changsha410073 China National Innovation Institute of Defense Technology AMS Beijing100071 China China Greatwall Research Institute China Greatwall Technology Group CO. LTD. Shenzhen518057 China

With photonics, the quantum computational advantage has been demonstrated on the task of boson sampling. Next, developing quantum-enhanced approaches for practical problems becomes one of the top priorities for photonic systems. quantum walks are powerful kernels for developing new and useful quantum algorithms. Here we realize large-scale quantum walks using a fully programmable photonic quantum computing system. The system integrates a silicon quantum photonic chip, enabling the simulation of quantum walk dynamics on graphs with up to 400 vertices and possessing full programmability over quantum walk parameters, including the particle property, initial state, graph structure, and evolution time. In the 400-dimensional Hilbert space, the average fidelity of random entangled quantum states after the whole on-chip circuit evolution reaches as high as 94.29±1.28%. With the system, we demonstrated exponentially faster hitting and quadratically faster mixing performance of quantum walks over classical random walks, achieving more than two orders of magnitude of enhancement in the experimental hitting efficiency and almost half of the reduction in the experimental evolution time for mixing. We utilize the system to implement a series of quantum applications, including measuring the centrality of scale-free networks, searching targets on Erdös-Rényi networks, distinguishing non-isomorphic graph pairs, and simulating the topological phase of higher-order topological insulators. Our work shows one feasible path for quantum photonics to address applications of practical interests in the near future. Copyright © 2022, The Authors. All rights reserved.

关键词： Mixing

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Multi-wavelength properties of z 6 LISA detectable events

arXiv

引用

arXiv 2025年

作者： Chakraborty, Srija Gallerani, Simona Di Mascia, Fabio Zana, Tommaso Valentini, Milena Carniani, Stefano Vito, Fabio Bhatt, Maulik Scuola Normale Superiore Piazza dei Cavalieri 7 PI Pisa56126 Italy Dipartimento di Fisica Sapienza Universita di Roma Piazzale Aldo Moro 5 Roma00185 Italy Dipartimento di Fisica dell’Universita di Trieste Sez. di Astronomia via Tiepolo 11 TriesteI-34131 Italy INAF Osservatorio Astronomico di Trieste via Tiepolo 11 TriesteI-34131 Italy INFN Instituto Nazionale di Fisica Nucleare Via Valerio 2 TriesteI-34127 Italy ICSC - Italian Research Center on High Performance Computing Big Data and Quantum Computing via Magnanelli 2 Casalecchio di Reno40033 Italy INAF - Osservatorio Astronomico di Bologna via Piero Gobetti 93/3 BolognaI-40129 Italy

We investigate the intrinsic and observational properties of z 6 galaxies that host the coalescence of massive (MBH ∼ 105−6 M☉) black holes (MBHs) giving rise to gravitational waves (GWs) detectable with the Laser Interferometer Space Antenna (LISA). We adopt a zoom-in cosmological hydrodynamical simulation of galaxy formation and black hole (BH) co-evolution, based on the GADGET-3 code, zoomed-in on a Mℎ ∼ 1012 M☉ dark matter halo at z = 6, which hosts a fast accreting (M¤ ∼ 35 M☉ yr−1) super-massive black hole (SMBH, MBH ∼ 109 M☉) and a star-forming galaxy (SFR ∼ 100 M☉ yr−1). Following the SMBH formation backward in time, we identify the merging events that concurred to its formation and we pick up the ones that are detectable with LISA. Among these LISA detectable events (LDEs), we select those that, based on their intrinsic properties (M¤ , SFR, gas metallicity, and dust mass), are expected to be bright in one or more electromagnetic (EM) bands, e.g. rest-frame X-ray, ultra-violet (UV) and far-infrared (FIR). We further restrict our selection to those LDEs that, after considering the effect of delay due to dynamical friction in the MBH coalescence, are still occurring at z 6. We find that ∼20-30% of the LDEs and their host galaxies are also detectable with EM telescopes. We post-process these events with dust radiative transfer calculations to make accurate predictions about their spectral energy distributions (SEDs) and continuum maps in the JWST to ALMA wavelength range. We compare the spectra arising from galaxies hosting the merging MBHs with those arising from AGN powered by single accreting BHs. We find that it will be impossible to identify an LDE from the continuum SEDs because of the absence of specific imprints from the merging MBHs. Finally, we compute the profile of the Hα line arising from LDEs, taking into account both the contribution from their star-forming regions and the accreting MBHs. We find that the presence of two accreting MBHs would be

关键词： Dark Matter

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