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Remote quantum entanglement can enable numerous applications including distributed quantum computation, secure communication, and precision sensing. In this paper, we consider how a quantum network-nodes equipped with limited quantum…

We propose a new approach to implement quantum repeaters for long distance quantum communication. Our protocol generates a backbone of encoded Bell pairs and uses the procedure of classical error correction during simultaneous entanglement…

Networks of quantum devices with coherent control over their configuration offer promising advantages in quantum information processing. So far, the investigation of these advantages assumed that the control system was initially…

Quantum Physics · Physics 2024-05-21 Tamal Guha , Saptarshi Roy , Giulio Chiribella

As the field of superconducting quantum computing approaches maturity, optimization of single-device performance is proving to be a promising avenue towards large-scale quantum computers. However, this optimization is possible only if…

In quantum mechanics, a fundamental law prevents quantum communications to simultaneously achieve high rates and long distances. This limitation is well known for point-to-point protocols, where two parties are directly connected by a…

Quantum Physics · Physics 2020-04-06 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…

Our objective was to design a quantum repeater capable of achieving one million entangled pairs per second over a distance of 1000km. We failed, but not by much. In this letter we will describe the series of developments that permitted us…

Quantum Physics · Physics 2015-05-14 W. J. Munro , K. A. Harrison , A. M. Stephens , S. J. Devitt , Kae Nemoto

Device-independent quantum information is attracting significant attention, particularly for its applications in information security. This interest arises because the security of device-independent protocols relies solely on the observed…

Quantum Physics · Physics 2026-05-29 Matteo Padovan , Alessandro Rezzi , Lorenzo Coccia

We investigate quantum repeater protocols based upon atomic qubit-entanglement distribution through optical coherent-state communication. Various measurement schemes for an optical mode entangled with two spatially separated atomic qubits…

Quantum Physics · Physics 2010-12-14 Peter van Loock , Norbert Lütkenhaus , W. J. Munro , Kae Nemoto

The quantum repeater protocol is a promising approach to implement long-distance quantum communication and large-scale quantum networks. A key idea of the quantum repeater protocol is to use long-lived quantum memories to achieve efficient…

Quantum Physics · Physics 2022-01-31 Yunfei Pu , Sheng Zhang , Yukai Wu , Nan Jiang , Wei Chang , Chang Li , Luming Duan

The kind of information provided by a measurement is determined in terms of the correlation established between observables of the apparatus and the measured system. Using the framework of quantum measurement theory, necessary and…

Quantum Physics · Physics 2009-10-30 Paul Busch , Pekka Lahti

The impressive progress in fabricating and controlling superconducting devices for quantum information processing has reached a level where reliable theoretical predictions need to account for quantum correlations that are not captured by…

Quantum repeaters have long been established to be essential for distributing entanglement over long distances. Consequently, their experimental realization constitutes a core challenge of quantum communication. However, there are numerous…

Quantum Physics · Physics 2024-04-04 Julius Wallnöfer , Frederik Hahn , Fabian Wiesner , Nathan Walk , Jens Eisert

Quantum memory is a central component for quantum information processing devices, and will be required to provide high-fidelity storage of arbitrary states, long storage times and small access latencies. Despite growing interest in applying…

In this dissertation, we explore how quantum annealing (QA) and its applications behave in an open system setting. We give derivations and numerical recipes for effective parallel simulation methods for time-dependent open dynamics of…

Quantum Physics · Physics 2021-07-16 Ka Wa Yip

We consider the classical correlations that two observers can extract by measurements on a bipartite quantum state, and we discuss how they are related to the quantum mutual information of the state. We show with several examples how…

Quantum Physics · Physics 2009-09-19 Shengjun Wu , Uffe V. Poulsen , Klaus Mølmer

Within the framework of quantum memory channels we introduce the notion of repeatability of quantum channels. In particular, a quantum channel is called repeatable if there exist a memory device implementing the same channel on each…

Quantum Physics · Physics 2008-12-10 Tomas Rybar , Mário Ziman

We generalize measurement-device-independent quantum key distribution [ H.-K. Lo, M. Curty, and B. Qi, Phys. Rev. Lett. 108, 130503 (2012) ] to the scenario where the Bell-state measurement station contains also heralded quantum memories.…

Quantum Physics · Physics 2015-06-16 Silvestre Abruzzo , Hermann Kampermann , Dagmar Bruß

Uncertainty relations express the fundamental incompatibility of certain observables in quantum mechanics. Far from just being puzzling constraints on our ability to know the state of a quantum system, uncertainty relations are at the heart…

Quantum Physics · Physics 2012-08-30 Omar Fawzi

Long-distance quantum communication necessitates the use of quantum repeaters, which typically include highly coherent quantum memories. We provide a theoretical analysis of the secret key rates for a quantum repeater system incorporating…