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entanglement purification for memory nodes in a quantum network

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Science China(Physics,Mechanics & Astronomy) 2020年第2期63卷 47-54页

作者： GuanYu Wang GuiLu Long State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics Tsinghua UniversityBeijing 100084China Tsinghua National Laboratory of Information Science and Technology Beijing 100084China Collaborative Innovation Center of Quantum Matter Beijing 100084China

The entanglement between quantum memory nodes is a prerequisite in a quantum network, and the diamond nitrogen-vacancy(NV) center is a promising candidate serving as a quantum memory node. Here, we investigate the possibility of achieving an entanglement purification protocol(EPP) for entangled NV centers in distant diamonds. To construct the EPP, we design a nondestructive parity-check detector(PCD) utilizing an auxiliary polarization-entangled photon pair, which makes our EPP less time consuming and insensitive to the phase fluctuation of the optical path length. The satisfied fidelity of an NV center pair after purification and efficiency of obtaining a purified NV center pair with our EPP can be obtained with current experimental techniques in the realistic condition. This EPP is useful for a quantum network in which NV centers are used as quantum memory nodes.

关键词： entanglement purification memory nodes quantum network nitrogen-vacancy center system parity-check detectors

Self-error-rejecting multipartite entanglement purification for electron systems assisted by quantum-dot spins in optical microcavities

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Chinese Physics B 2022年第5期31卷 113-121页

作者：刘永婷吴一鸣杜芳芳 Science and Technology on Electronic Test and Measurement Laboratory North University of ChinaTaiyuan 030051China

We present a self-error-rejecting multipartite entanglement purification protocol(MEPP)for N-electron-spin entangled states,resorting to the single-side cavity-spin-coupling system.Our MEPP has a high efficiency containing two steps.One is to obtain high-fidelity N-electron-spin entangled systems with error-heralded parity-check devices(PCDs)in the same parity-mode outcome of three electron-spin pairs,as well as M-electron-spin entangled subsystems(2≤Mentanglement link.Moreover,the quantum circuits of PCDs make our MEPP works faithfully,due to the practical photon-scattering deviations from the finite side leakage of the microcavity,and the limited coupling between a quantum dot and a cavity mode,converted into a failed detection in a heralded way.

关键词： quantum communication entanglement purification electron-spin system

Multi-copy entanglement purification with practical spontaneous parametric down conversion sources

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Chinese Physics B 2017年第6期26卷 53-60页

作者：张帅帅祁舒周澜盛宇波 Key Laboratory of Broadband Wireless Communication and Sensor Network Technology of Ministry of Education Nanjing University of Posts and Telecommunications Bell Honors School Nanjing University of Posts and Telecommunications College of Mathematics & Physics Nanjing University of Posts and Telecommunications

entanglement purification is to distill the high quality entanglement from the low quality entanglement with local operations and classical communications. It is one of the key technologies in long-distance quantum communication. We discuss an entanglement purification protocol（EPP） with spontaneous parametric down conversion（SPDC） sources, in contrast to previous EPP with multi-copy mixed states, which requires ideal entanglement sources. We show that the SPDC source is not an obstacle for purification, but can benefit the fidelity of the purified mixed state. This EPP works for linear optics and is feasible in current experiment technology.

关键词： quantum communication entanglement entanglement purification

Efficient entanglement purification in quantum repeaters

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Chinese Physics B 2012年第3期21卷 67-73页

作者：盛宇波周澜程维文巩龙龑赵生妹郑宝玉 Institute of Signal Processing Transmission Nanjing University of Posts and Telecommunications College of Telecommunications & Information Engineering Nanjing University of Posts and Telecommunications Key Laboratory of Broadband Wireless Communication and Sensor Network Technology of Ministry of Education Nanjing University of Posts and Telecommunications Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of Sciences

We present an efficient entanglement purification protocol （EPP） with controlled-not （CNOT） gates and linear optics. With the CNOT gates, our EPP can reach a higher fidelity than the conventional one. Moreover, it does not require the fidelity of the initial mixed state to satisfy 1 2. If the initial state is not entangled, it still can be purified. With the linear optics, this protocol can get pure maximally entangled pairs with some probabilities. Meanwhile, it can be used to purify the entanglement between the atomic ensembles in distant locations. This protocol may be useful in long-distance quantum communication.

关键词： quantum communication entanglement entanglement purification quantum repeater

Design and Implementation of Quantum Repeaters:Insights on Quantum entanglement purification

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Journal of Quantum Computing 2023年第1期5卷 25-40页

作者： Karoki A.Mugambi Geoffrey O.Okeng’o The Astrophysics and Space Science Research Group Department of PhysicsFaculty of Science and TechnologyUniversity of NairobiNairobiKenya

Quantum communication is a groundbreaking technology that is driving the future of information transmission and communication technologies to a new paradigm.It relies on quantum entanglement to facilitate the transmission of quantum states between parties.Quantum repeaters are crucial for facilitating long-distance quantum communication.These quantum devices act as intermediaries between adjacent communication channel segments within a fragmented quantum network,allowing for entanglement swapping between the channel segments.This entanglement swapping process establishes entanglement links between the endpoints of adjacent segments,gradually creating a continuous entanglement connection over the entire length of the transmission channel.The established quantum link can be utilized for secure and efficient quantum communication between distant sender and receiver nodes.This study focuses on quantum entanglement purification,a protocol aimed at maintaining high fidelity entangled states above the operational threshold of the communication channel.This study investigates the optimal stage for executing the purification protocol and applies optimization schemes to evaluate various purification protocols.We use IBM Qiskit for circuit implementation and simulation.The results offer valuable insights into future approaches to implementing practical quantum repeaters and shed light on existing and anticipated challenges.

关键词： Quantum repeaters quantum entanglement entanglement purification quantum communication entanglement swapping