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The derivation of ultimate limits to communication over certain quantum repeater networks have provided extremely valuable benchmarks for assessing near-term quantum communication protocols. However, these bounds are usually derived in the…

Quantum Physics · Physics 2022-06-02 Riccardo Laurenza , Nathan Walk , Jens Eisert , Stefano Pirandola

Quantum key distribution allows for the generation of a secret key between distant parties connected by a quantum channel such as optical fibre or free space. Unfortunately, the rate of generation of a secret key by direct transmission is…

Satellite-based quantum repeaters are a promising means to reach global distances in quantum networking due to the polynomial decrease of optical transmission with distance in free space, in contrast to the exponential decrease in optical…

Quantum Physics · Physics 2024-11-15 V. Domínguez Tubío , M. Badás Aldecocea , J. van Dam , A. S. Sørensen , J. Borregaard

Quantum repeaters are used to overcome the exponential photon loss scaling that quantum states acquire as they are transmitted over long distances. While repeaters for discrete variable encodings of quantum information have existed for some…

Quantum Physics · Physics 2022-08-08 Josephine Dias , Matthew S. Winnel , William J. Munro , Timothy C. Ralph , Kae Nemoto

We analyze an entanglement-based quantum key distribution (QKD) architecture that uses a linear chain of quantum repeaters employing photon-pair sources, spectral-multiplexing, linear-optic Bell-state measurements, multi-mode quantum…

Quantum repeaters, which are indispensable for long-distance quantum communication, are necessary for extending the entanglement from short distance to long distance; however, high-rate entanglement distribution, even between adjacent…

Quantum Physics · Physics 2021-07-26 Daisuke Yoshida , Kazuya Niizeki , Shuhei Tamura , Tomoyuki Horikiri

Quantum repeaters promise to deliver long-distance entanglement overcoming noise and loss in realistic quantum channels. A promising class of repeaters, based on atomic ensemble quantum memories and linear optics, follow the proposal by…

Quantum Physics · Physics 2010-04-05 Jonatan Bohr Brask , Anders Sondberg Sorensen

Quantum repeater is one of the important building blocks for long distance quantum communication network. The previous quantum repeaters based on atomic ensembles and linear optical elements can only be performed with a maximal success…

Quantum Physics · Physics 2015-11-03 Tao Li , Fu-Guo Deng

Quantum communication enables the implementation of tasks that are unachievable with classical resources. However, losses on the communication channel preclude the direct long-distance transmission of quantum information in many relevant…

Quantum Physics · Physics 2021-11-02 Boxi Li , Tim Coopmans , David Elkouss

We investigate the influence of memory errors in the quantum repeater scheme for long-range quantum communication. We show that the communication distance is limited in standard operation mode due to memory errors resulting from unavoidable…

Quantum Physics · Physics 2007-05-23 L. Hartmann , B. Kraus , H. -J. Briegel , W. Dür

A full-fledged quantum network relies on the formation of entangled links between remote location with the help of quantum repeaters. The famous Duan-Lukin-Cirac-Zoller quantum repeater protocol is based on long distance single-photon…

Quantum Physics · Physics 2024-11-27 Chen-Long Li. Hua-Lei Yin , Zeng-Bing Chen

Quantum communication relies on the existence of entanglement between two nodes of a network. However, due to its fragile nature, it is nearly impossible to establish entanglement at large distances through the direct transmission of…

Quantum Physics · Physics 2021-10-18 Sowmitra Das , Md. Saifur Rahman , Mahbub Majumdar

We present an exact rate analysis for a secret key that can be shared among two parties employing a linear quantum repeater chain. One of our main motivations is to address the question whether simply placing quantum memories along a…

Quantum Physics · Physics 2022-03-22 Lars Kamin , Evgeny Shchukin , Frank Schmidt , Peter van Loock

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…

Quantum Physics · Physics 2021-05-18 Carlo Liorni , Hermann Kampermann , Dagmar Bruss

Long-distance quantum communication via entanglement distribution is of great importance for the quantum internet. However, scaling up to such long distances has proved challenging due to the loss of photons, which grows exponentially with…

Quantum repeaters are critical to the development of quantum networks, enabling rates of entanglement distribution beyond those attainable by direct transmission. We consider multiple continuous-variable, squeezed light-based entanglement…

Quantum Physics · Physics 2023-01-24 Ian J. Tillman , Allison Rubenok , Saikat Guha , Kaushik P. Seshadreesan

We present a quantum repeater scheme based on the recently proposed qubit amplifier [N. Gisin, S. Pironio and N. Sangouard, Phys. Rev. Lett. 105, 070501 (2010)]. It relies on a on-demand entangled-photon pair source which uses on-demand…

Quantum Physics · Physics 2015-06-03 Jiří Minář , Hugues de Riedmatten , Nicolas Sangouard

Despite the tremendous progress of quantum cryptography, efficient quantum communication over long distances (>1000km) remains an outstanding challenge due to fiber attenuation and operation errors accumulated over the entire communication…

In the absence of quantum repeaters, quantum communication proved to be nearly impossible across optical fibres longer than $\gtrsim 20\text{ km}$ due to the drop of transmissivity below the critical threshold of $1/2$. However, if the…

Quantum Physics · Physics 2025-12-29 Francesco Anna Mele , Ludovico Lami , Vittorio Giovannetti

Long-distance quantum communication requires reliable entanglement distribution, but direct generation with protocols such as Barrett--Kok suffers from exponentially decreasing success probability with distance, making it impractical over…

Quantum Physics · Physics 2025-10-10 Wenhan Li , Shiyu Zhang