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The optimal positive operator-valued measure for state discrimination

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arXiv 2021年

Evaluating the amount of information obtained from non-orthogonal quantum states is an important topic in the field of quantum information. The commonly used evaluation method is Holevo bound, which only provides a loose upper bound for quantum measurement. In this paper, we provide a theoretical study of the positive operator-valued measure (POVM) for discriminating nonorthogonal states. We construct a generalized POVM measurement operation, and derive the optimal one for state discrimination by Lagrange multiplier method. With simulation, we find that the optimal POVM measurement provides a tight upper bound for state discrimination, which is significantly lower than that predicted by Holevo bound. The derivation of optimal POVM measurement will play an important role in the security research of quantum key distribution. Copyright © 2021, The Authors. All rights reserved.

关键词： Quantum cryptography

Phase matching quantum key distribution based on single-photon entanglement

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arXiv 2019年

作者： Li, Wei Wang, Le Zhao, Shengmei Nanjing University of Posts and Telecommunications Institute of Signal Processing and Transmission Nanjing210003 China Nanjing University of Posts and Telecommunications Key Lab Broadband Wireless Communication and Sensor Network Ministy of Education Nanjing210003 China National Laboratory of Solid State Microstructures Nanjing University Nanjing210093 China

Two time-reversal quantum key distribution (QKD) schemes are the quantum entanglement based device-independent (DI)-QKD and measurement-device-independent (MDI)-QKD. The recently proposed twin field (TF)-QKD, also known as phase-matching (PM)-QKD, has improved the key rate bound from O(η) to O(√η) with η the channel transmittance. In fact, TF-QKD is a kind of MDIQKD but based on single-photon detection. In this paper, we propose a different PM-QKD based on single-photon entanglement, referred to as SEPM-QKD, which can be viewed as a time-reversed version of the TF-QKD. Detection loopholes of the standard Bell test, which often occur in DI-QKD over long communication distances, are not present in this protocol because the measurement settings and key information are the same quantity which is encoded in the local weak coherent state. We give a security proof of SEPM-QKD and demonstrate in theory that it is secure against all collective attacks and beam-splitting attacks. The simulation results show that the key rate enjoys a bound of O (√η) with respect to the transmittance. SEPM-QKD not only helps us understand TF-QKD more deeply, but also hints at a feasible approach to eliminate detection loopholes in DI-QKD for long-distance communications. Copyright © 2019, The Authors. All rights reserved.

关键词： Quantum cryptography

Joint Cooperation Clustering and Downlink Power Control for Cell-Free Massive MIMO with Deep Reinforcement Learning

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Joint Cooperation Clustering and Downlink Power Control for ...

International Conference on communication technology (ICCT)

作者： Mingjun Du Xinghua Sun Yue Zhang Junyuan Wang Pei Liu School of Electronics and Communication Engineering Sun Yat-sen University Shenzhen China Department of Electronic Information Engineering Shantou University Shantou China College of Electronic and Information Engineering Tongji University Shanghai China School of Information Engineering Wuhan University of Technology Wuhan China Key Lab of Broadband Wireless Communication and Sensor Network Technology Ministry of Education Nanjing University of Posts and Telecommunications Nanjing China

Recently, numerous clustering and power control approaches have been developed to optimize network performance for cell-free massive multiple-input multiple-output (MIMO) systems. Notably, deep reinforcement learning (DRL) has emerged as a promising solution for network optimization. This paper investigates the joint cooperation clustering and downlink power control problem in cell-free massive MIMO, utilizing the deep deterministic policy gradient (DDPG) algorithm to maximize the long-term global average proportional fairness (PF). Our results demonstrate that the proposed DDPG method effectively outperforms the baselines in both clustering and power control. Furthermore, the proposed scheme exhibits robustness as it maintains superior performance even as the number of clusters varies.

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Outage Probability and Power Allocation Analysis of AmBC-Enabled NOMA for Future IoT

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Outage Probability and Power Allocation Analysis of AmBC-Ena...

International Conference on communication technology (ICCT)

作者： Chongye Wang Yang Liu Cheng-Xiang Wang School of Internet of Things Engineering Jiangnan University Wuxi China Key Lab of Broadband Wireless Communication and Sensor Network Technology Nanjing University of Posts and Telecommunications Ministry of Education Nanjing China National Mobile Communications Research Laboratory School of Information Science and Engineering Southeast University Nanjing China Purple Mountain Laboratories Nanjing China

Ambient backscatter communication (AmBC) combined with non-orthogonal multiple access (NOMA) presents superior energy reusability and higher sum rate. However, existing studies failed to utilize the information of backscatter links. Therefore, to explore the impact of backscatter link, this paper employs three-user NOMA to improve the spectral efficiency. We propose a simple distance power allocation method to accomplish successive interference cancellation. Based on the Monte Carlo method, the outage probability of the proposal is analyzed. Our work provides a scheme for coexistence between AmBC and NOMA systems in the future Internet of Things.

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A general deep reinforcement learning framework for grant-free NOMA optimization in mURLLC

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arXiv 2021年

作者： Liu, Yan Deng, Yansha Zhou, Hui Elkashlan, Maged Nallanathan, Arumugam Key Laboratory of Ministry of Education in Broadband Wireless Communication and Sensor Network Technology Nanjing University of Posts and Telecommunications Nanjing210003 China School of Electronic Engineering and Computer Science Queen Mary University of London London United Kingdom Department of Engineering King's College London London United Kingdom

Grant-free non-orthogonal multiple access (GF-NOMA) is a potential technique to support massive Ultra-Reliable and Low-Latency communication (mURLLC) service. However, the dynamic resource configuration in GF-NOMA systems is challenging due to random traffics and collisions, that are unknown at the base station (BS). Meanwhile, joint consideration of the latency and reliability requirements makes the resource configuration of GF-NOMA for mURLLC more complex. To address this problem, we develop a general learning framework for signature-based GF-NOMA in mURLLC service taking into account the multiple access signature collision, the UE detection, as well as the data decoding procedures for the K-repetition GF and the Proactive GF schemes. The goal of our learning framework is to maximize the long-term average number of successfully served users (UEs) under the latency constraint. We first perform a real-time repetition value configuration based on a double deep Q-network (DDQN) and then propose a Cooperative Multi-Agent learning technique based on the DQN (CMA-DQN) to optimize the configuration of both the repetition values and the contention-transmission unit (CTU) numbers. Our results show that the number of successfully served UEs under the same latency constraint in our proposed learning framework is up to ten times for the K-repetition scheme, and two times for the Proactive scheme, more than that with fixed repetition values and CTU numbers. In addition, the superior performance of CMA-DQN over the conventional load estimation-based approach (LE-URC) demonstrates its capability in dynamically configuring in long term. Importantly, our general learning framework can be used to optimize the resource configuration problems in all the signature-based GF-NOMA schemes. Copyright © 2021, The Authors. All rights reserved.

关键词： Deep learning

Multigrating design for integrated single-atom trapping, manipulation, and readout

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Physical Review A 2022年第5期105卷 053520-053520页

作者： Aiping Liu Jiawei Liu Wei Peng Xin-Biao Xu Guang-Jie Chen Xifeng Ren Qin Wang Chang-Ling Zou Institute of Quantum Information and Technology Nanjing University of Posts and Telecommunications Nanjing 210003 China Broadband Wireless Communication and Sensor Network Technology Key Laboratory of Ministry of Education Nanjing University of Posts and Telecommunications Nanjing 210003 China CAS Key Laboratory of Quantum Information University of Science and Technology of China Hefei 230026 China CAS Center for Excellence in Quantum Information and Quantum Physics University of Science and Technology of China Hefei 230026 China State Key Laboratory of Quantum Optics and Quantum Optics Devices and Institute of Opto-Electronics Shanxi University Taiyuan 030006 China

An on-chip multigrating device is proposed to interface single atoms and integrated photonic circuits, by guiding and focusing lasers to the area ∼10 μm above the chip for trapping, state manipulation, and readout of single rubidium atoms. For the optical dipole trap, two 850-nm laser beams are diffracted and overlapped to form the lattice of a single-atom dipole trap, with the diameter of the optical dipole trap being around 2.7 μm. Similar gratings are designed for guiding a 780-nm probe laser to excite and also collect the fluorescence of Rb87 atoms. Such a device provides a compact solution for future applications of single atoms, including the single-photon source, single-atom quantum register, and single-atom quantum sensor.

关键词： Atom optics Photonics

Asymmetric sending or not-sending twin-field quantum key distribution in practice

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arXiv 2019年

作者： Zhou, Xing-Yu Zhang, Chun-Hui Zhang, Chun-Mei Wang, Qin Institute of quantum information and technology Nanjing University of Posts and Telecommunications Nanjing210003 China "Broadband Wireless Communication and Senser Network Technology" Key Lab of Ministry of Education NUPT Nanjing210003 China "Telecommunication and Networks" National Engineering Research Center NUPT Nanjing210003 China

Quantum key distribution (QKD) offers a secret way to share keys between legitimate users which is guaranteed by the law of quantum mechanics. Most recently, the limitation of transmission distance without quantum repeaters was broken through by twin-field QKD [Nature (London) 557, 400 (2018)]. Based on its main idea, sending or not-sending (SNS) QKD protocol was proposed [Phys. Rev. A 98, 062323 (2018)], which filled the remaining security loopholes and can tolerate large misalignment errors. In this paper, we give a more general model for SNS QKD, where the two legitimate users, Alice and Bob, can possess asymmetric quantum channels. By applying the method present in the work, the legitimate users can achieve dramatically increased key generation rate and transmission distance compared with utilizing the original symmetric protocol. Therefore, our present work represents a further step along the progress of practical QKD. Copyright © 2019, The Authors. All rights reserved.

关键词： Quantum cryptography

Efficient passive measurement-device-independent quantum key distribution

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arXiv 2019年

作者： Zhang, Chun-Hui Zhang, Chun-Mei Wang, Qin Institute of quantum information and technology Nanjing University of Posts and Telecommunications Nanjing210003 China "Broadband Wireless Communication and Senser Network Technology" Key Lab of Ministry of Education NUPT Nanjing210003 China "Telecommunication and Networks"National Engineering Research Center NUPT Nanjing210003 China

The measurement-device-independent quantum key distribution (MDI-QKD) possesses the highest security among all practical quantum key distribution protocols. However, existing multiintensity decoy-state methods may cause loopholes when modulating light intensities with practical devices. In this paper, we propose a passive decoy-state MDI-QKD protocol based on a novel structure of heralded single-photon sources. It does not need to modulate the light source into different intensities and thus can avoid leaking modulation information of decoy states to eavesdroppers, enhancing the security of practical MDI-QKD. Furthermore, by combining the passive decoy states and biased basis choices, our protocol can exhibit distinct advantages compared with state-of-the art MDI-QKD schemes even when the finite key-size effect is taken into account. Therefore, our present passive decoy-state MDI-QKD seems a promising candidate for practical implementation of quantum key distributions in the near future. Copyright © 2019, The Authors. All rights reserved.

关键词： Quantum cryptography

Proposal for low-power atom trapping on a GaN-on-sapphire chip

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Physical Review A 2022年第3期106卷 033104-033104页

作者： Aiping Liu Lei Xu Xin-Biao Xu Guang-Jie Chen Pengfei Zhang Guo-Yong Xiang Guang-Can Guo Qin Wang Chang-Ling Zou Institute of Quantum Information and Technology Nanjing University of Posts and Telecommunications Nanjing 210003 China Broadband Wireless Communication and Sensor Network Technology Key Laboratory of Ministry of Education Nanjing University of Posts and Telecommunications Nanjing 210003 China CAS Key Laboratory of Quantum Information University of Science and Technology of China Hefei 230026 China CAS Center for Excellence in Quantum Information and Quantum Physics University of Science and Technology of China Hefei 230026 China State Key Laboratory of Quantum Optics and Quantum Optics Devices and Institute of Opto-Electronics Shanxi University Taiyuan 030006 China

Hybrid photon-atom integrated circuits, which include photonic microcavities and trapped single neutral atoms in their evanescent field, have great potential for quantum information processing. In this platform, the atoms provide single-photon nonlinearity and long-lived memory, which are complementary to the excellent passive photonic devices in conventional quantum photonic circuits. In this work, we propose a stable platform for realizing hybrid photon-atom circuits based on an unsuspended photonic chip. By introducing high-order modes in the microring, a feasible evanescent-field trap potential well ∼0.26mK could be obtained by only 10-mW-level power in the cavity, compared with the 100-mW-level power required in the scheme based on fundamental modes. Based on our scheme, stable single-atom trapping with relatively low laser power is feasible for future studies on high-fidelity quantum gates, single-photon sources, and many-body quantum physics based on a controllable atom array in a microcavity.

关键词： Cooling & trapping Photonics Relativistic & quantum electrodynamic effects in atoms, molecules,& ions