量子中继器是实现长距离量子通信的重要构建模块。然而，由于量子信息的脆弱性，这些中继器会受到损耗和操作错误的影响。先前的工作根据其使用概率性或近确定性方法来减轻这些错误，将中继器分为三大类。除了经典通信时间的差异外，这些方法在技术复杂性上也有所不同，近确定性方法需要更先进的硬件。最近内存可用性的增加和多路复用纠缠生成的进展促使人们重新比较单向和双向量子中继架构。在这项工作中，我们提出了一种双向中继协议，该协议将多路复用与应用感知的提纯相结合，专为具有足够高质量内存资源的环境而设计——反映了大规模网络部署中预期的架构假设。我们引入了一种递归公式来跟踪多路复用双向中继架构中 Bell 对的完整概率分布，从而能够对使用概率性 $n$-to-$k$ 提纯的多路复用中继方案进行性能分析。使用这个框架，我们在先前认为有利于后者的参数范围内将提出的双向协议与单向方案进行比较，并发现双向架构始终优于单向协议，同时需要较低的技术和资源开销。
英文摘要：
Quantum repeaters are an essential building block for realizing long-distance quantum communications. However, due to the fragile nature of quantum information, these repeaters suffer from loss and operational errors. Prior works have classified repeaters into three broad categories based on their use of probabilistic or near-deterministic methods to mitigate these errors. Besides differences in classical communication times, these approaches also vary in technological complexity, with near-deterministic methods requiring more advanced hardware. Recent increases in memory availability and advances in multiplexed entanglement generation motivate a fresh comparison of one-way and two-way repeater architectures.
In this work, we present a two-way repeater protocol that combines multiplexing with application-aware distillation, designed for a setting where sufficient high-quality memory resources are available -- reflecting architectural assumptions expected in large-scale network deployments. We introduce a recursive formulation to track the full probability distribution of Bell pairs in multiplexed two-way repeater architectures, enabling the performance analysis of multiplexed repeater schemes which use probabilistic $n$-to-$k$ distillation. Using this framework, we compare the proposed two-way protocol with one-way schemes in parameter regimes previously believed to favour the latter, and find that the two-way architecture consistently outperforms one-way protocols while requiring lower technological and resource overheads.
Quantum repeaters are essential ingredients for quantum networks that link distant quantum modules such as quantum computers and sensors. Motivated by distributed quantum computing and communication, quantum repeaters that relay discrete-variable quantum information have been extensively studied; while continuous-variable (CV) quantum information underpins a variety of quantum sensing and communication application, a quantum-repeater architecture for genuine CV quantum information remains largely unexplored. This paper reports a CV quantum-repeater architecture based on CV quantum teleportatio…
We propose a quantum repeater protocol and architecture that mitigates decoherence of the entangled states by optimizing the quantum memory buffer time. The protocol maximizes the rate of distillable entanglement in the average accessed state at all nesting levels. The achievable rate is higher by orders of magnitude in comparison to a canonical protocol that does not optimize the buffer time. The advantage of the proposed design is observed for all nesting levels of the repeater for technologically feasible memory quality, entanglement generation and swapping success probabilities.
Instruction-Set Architecture for Programmable NV-Center Quantum Repeater Nodes
University of Pisa（比萨大学）；Institute for Informatics and Telematics (IIT), National Research Council (CNR)（意大利国家研究委员会信息学与遥测研究所）；Technische Universität Dresden（德累斯顿工业大学）
Scalable entanglement distribution using encoded hybrid repeater chains
University of Texas at Arlington（阿灵顿得克萨斯大学）；Manning College of Information and Computer Sciences, University of Massachusetts Amherst（马萨诸塞大学阿姆赫斯特分校曼宁信息学与计算机科学学院）；Department of Electrical and Computer Engineering, University of Maryland College Park（马里兰大学帕克分校电气与计算机工程系）
The vision to develop quantum networks entails multi-user applications, which require the generation of long-distance multi-party entangled states. The current rapid experimental progress in building prototype-networks calls for new design concepts to guide future developments. Here we describe an experimentally feasible scheme implementing a two-dimensional repeater network for robust distribution of three-party entangled states of GHZ type in the presence of excitation losses and detector dark counts --- the main sources of errors in real-world hardware. Our approach is based on atomic or so…
We propose a quantum repeater architecture that can operate without cryogenics. Each node in our architecture builds on a cell of hot alkali atoms and noble-gas spins which offer a storage time as long as a few hours. Such a cell of hybrid gases is placed in a ring cavity, which allows us to suppress the detrimental four-wave mixing (FWM) noise in the system. We investigate the protocol based on a single-photon source made of an ensemble of the same hot alkali atoms. A single photon emitted from the source is either stored in the memory or transmitted to the central station to be detected. We …
We propose an architecture of quantum-error-correction-based quantum repeaters that combines techniques used in discrete- and continuous-variable quantum information. Specifically, we propose to encode the transmitted qubits in a concatenated code consisting of two levels. On the first level we use a continuous-variable GKP code encoding the qubit in a single bosonic mode. On the second level we use a small discrete-variable code. Such an architecture has two important features. Firstly, errors on each of the two levels are corrected in repeaters of two different types. This enables for achiev…
Realization of a globe-spanning quantum network is a current worldwide goal, where near and long term implementations will benefit from connectivity between platforms optimized for specific tasks. Towards this goal, a quantum network architecture is herewith proposed whereby quantum processing devices based on NV$^-$ colour centers act as quantum routers and, between which, long-distance entanglement distribution is enabled by spectrally-multiplexed quantum repeaters based on absorptive quantum memories in rare-earth ion-doped crystals and imperfect entangled photon-pair sources. The inclusion…
Scalable Repeater Architecture for Long-Range Quantum Energy Teleportation in Gapped Systems
University of Chinese Academy of Sciences（中国科学院大学）；Al-Azhar University（爱资哈尔大学）；China Three Gorges University（三峡大学）；Institute for Research in Fundamental Sciences (IPM)（伊朗基础科学研究所）；International Centre for Theoretical Physics Asia-Pacific, UCAS（亚太理论物理中心）
Entanglement recovery by reversing the effect of noise in quantum repeater
Korea Institute of Science and Technology (KIST)（韩国科学技术院）；Ewha Womans University（梨花女子大学）；Korea Institute for Advanced Study（韩国高等研究院）；Korea University of Science and Technology（韩国科学技术院）；Pohang University of Science and Technology (POSTECH)（浦项科技大学）
We propose a novel one-way quantum repeater architecture based on photonic tree-cluster states. Encoding a qubit in a photonic tree-cluster protects the information from transmission loss and enables long-range quantum communication through a chain of repeater stations. As opposed to conventional approaches that are limited by the two-way communication time, the overall transmission rate of the current quantum repeater protocol is determined by the local processing time enabling very high communication rates. We further show that such a repeater can be constructed with as little as two station…
Feasibility of satellite-augmented global quantum repeater networks
Airbus Central Research and Technology（空中客车中央研究与技术）；Institute for Quantum Physics and Center for Optical Quantum Technologies, University of Hamburg（汉堡大学量子物理研究所与光学量子技术中心）；Airbus Defence and Space（空中客车防务与航天）
SUPA Department of Physics, University of Strathclyde（斯特拉斯克莱德大学）；School of Mathematical and Physical Sciences, University of Sheffield（谢菲尔德大学）；Dahlem Center for Complex Quantum Systems, Freie Universität Berlin（柏林自由大学）；Fraunhofer Centre for Applied Photonics（弗劳恩霍夫应用光子学中心）
Long-distance entanglement is a very precious resource, but its distribution is very difficult due to the exponential losses of light in optical fibres. A possible solution consists in the use of quantum repeaters, based on entanglement swapping or quantum error correction. Alternatively, satellite-based free-space optical links can be exploited, achieving better loss-distance scaling. We propose to combine these two ingredients, quantum repeaters and satellite-based links, into a scheme that allows to achieve entanglement distribution over global distances with a small number of intermediate …
Trapped ions form an advanced technology platform for quantum information processing with long qubit coherence times, high-fidelity quantum logic gates, optically active qubits, and a potential to scale up in size while preserving a high level of connectivity between qubits. These traits make them attractive not only for quantum computing but also for quantum networking. Dedicated, special-purpose trapped-ion processors in conjunction with suitable interconnecting hardware can be used to form quantum repeaters that enable high-rate quantum communications between distant trapped-ion quantum com…
Uniting Quantum Processing Nodes of Cavity-coupled Ions with Rare-earth Quantum Repeaters Using Single-photon Pulse Shaping Based on Atomic Frequency Comb
We examine the viability of quantum repeaters based on two-species trapped ion modules for long distance quantum key distribution. Repeater nodes comprised of ion-trap modules of co-trapped ions of distinct species are considered. The species used for communication qubits has excellent optical properties while the other longer lived species serves as a memory qubit in the modules. Each module interacts with the network only via single photons emitted by the communication ions. Coherent Coulomb interaction between ions is utilized to transfer quantum information between the communication and me…
1Department of Computer Science, School of Computing \& Information, University of Pittsburgh, Pittsburgh, PA 15260, USA；2Department of Informatics \& Networked Systems, School of Computing \& Information, University of Pittsburgh, Pittsburgh, PA 15260, USA
We propose a scheme for fault-tolerant long-range entanglement generation at the ends of a rectangular array of qubits of length $R$ and a square cross section of size $d\times d$ with $d=O(\log R)$. Up to an efficiently computable Pauli correction, the scheme generates a maximally entangled state of two qubits using a depth-$6$ circuit consisting of nearest-neighbor Clifford gates and local measurements only. Compared with existing fault-tolerance schemes for quantum communication, the protocol is distinguished by its low latency: starting from a product state, the entangled state is prepared…
