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We show that entanglement is a useful resource to enhance the mutual information of the depolarizing channel when the noise on consecutive uses of the channel has some partial correlations. We obtain a threshold in the degree of memory,…

Quantum Physics · Physics 2009-11-07 Chiara Macchiavello , G. Massimo Palma

Shared entanglement is a resource available to parties communicating over a quantum channel, much akin to public coins in classical communication protocols. Whereas shared randomness does not help in the transmission of information, or…

Quantum Physics · Physics 2018-03-22 Ashwin Nayak , Julia Salzman

The capacity of a channel is known to be equivalent to the highest rate at which it can generate entanglement. Analogous to entanglement, the notion of a causality measure characterises the temporal aspect of quantum correlations. Despite…

Quantum Physics · Physics 2020-02-24 Robert Pisarczyk , Zhikuan Zhao , Yingkai Ouyang , Vlatko Vedral , Joseph F. Fitzsimons

A class of problems in quantum information theory, having an elementary formulation but still resisting solution, concerns the additivity properties of various quantities characterizing quantum channels, notably the "classical capacity",…

Mathematical Physics · Physics 2007-05-23 G. G. Amosov , A. S. Holevo , R. F. Werner

A random unitary channel is one that is given by a convex combination of unitary channels. It is shown that the conjectures on the additivity of the minimum output entropy and the multiplicativity of the maximum output $p$-norm can be…

Quantum Physics · Physics 2008-10-15 Bill Rosgen

The additivity problem asks if the use of entanglement can boost the information-carrying capacity of a given channel beyond what is achievable by coding with simple product states only. This has recently been shown not to be the case for…

Quantum Physics · Physics 2018-04-10 Stefan Huber , Robert Koenig

A minimal model for gene expression, consisting of a switchable promoter together with the resulting messenger RNA, is equivalent to a Poisson channel with a binary Markovian input process. Determining its capacity is an optimization…

Molecular Networks · Quantitative Biology 2021-01-06 Mark Sinzger , Maximilian Gehri , Heinz Koeppl

We discuss the estimation of channel parameters for a noisy quantum channel - the so-called Pauli channel - using finite resources. It turns out that prior entanglement considerably enhances the fidelity of the estimation when we compare it…

Quantum Physics · Physics 2009-11-07 Dietmar G. Fischer , Holger Mack , Markus A. Cirone , Matthias Freyberger

All communication channels are at bottom quantum mechanical. Quantum mechanics contributes both obstacles to communication in the form of noise, and opportunities in the use of intrinsically quantum representations for information. This…

Quantum Physics · Physics 2007-05-23 Seth Lloyd

The squashed entanglement of a quantum channel is an additive function of quantum channels, which finds application as an upper bound on the rate at which secret key and entanglement can be generated when using a quantum channel a large…

Quantum Physics · Physics 2016-04-26 Kaushik P. Seshadreesan , Masahiro Takeoka , Mark M. Wilde

Gaussian quantum channels have recently attracted a growing interest, since they may lead to a tractable approach to the generally hard problem of evaluating quantum channel capacities. However, the analysis performed so far has always been…

Quantum Physics · Physics 2010-02-18 Nicolas J. Cerf , Julien Clavareau , Jérémie Roland , Chiara Macchiavello

We consider the problem of trying to send a single classical bit through a noisy quantum channel when two transmissions through the channel are available as a resource. Classically, two transmissions add nothing to the receiver's capability…

Quantum Physics · Physics 2007-05-23 Charles H. Bennett , Christopher A. Fuchs , John A. Smolin

Quantum communication theory focuses on the study of quantum channels for transmitting quantum information, where the transmission rate is measured by quantum channel capacity. This quantity exhibits several intriguing properties, such as…

Quantum Physics · Physics 2025-01-14 Changchun Zhong

The problem of communication and state estimation is considered in the context of channels with actiondependent states. Given the message to be communicated, the transmitter chooses an action sequence that affects the formation of the…

Information Theory · Computer Science 2012-02-07 Chiranjib Choudhuri , Urbashi Mitra

Arbitrarily varying channels offer a powerful framework for analyzing the robustness of quantum communication systems, especially for classical-quantum models, where the analysis displays strengths or weaknesses of specific signal…

Quantum Physics · Physics 2025-07-25 Janis Nötzel , Florian Seitz

In a quantum communication network, links represent entanglement between qubits located at different nodes. Even if two nodes are not directly linked by shared entanglement, communication channels can be established between them via quantum…

Quantum Physics · Physics 2025-03-07 Xiangyi Meng , Bingjie Hao , Balázs Ráth , István A. Kovács

In this work we design a specific simulation tool for quantum channels which is based on the use of a control system. This allows us to simulate an average quantum channel which is expressed in terms of an ensemble of channels, even when…

Quantum Physics · Physics 2018-12-19 Stefano Pirandola , Riccardo Laurenza , Leonardo Banchi

Transmission of quantum entanglement will play a crucial role in future networks and long-distance quantum communications. Quantum Key Distribution, the working mechanism of quantum repeaters and the various quantum communication protocols…

Quantum Physics · Physics 2013-10-08 Laszlo Gyongyosi

We simplify some conjectures in quantum information theory; the additivity of minimal output entropy, the multiplicativity of maximal output p-norm and the superadditivity of convex closure of output entropy. We construct a unital channel…

Quantum Physics · Physics 2007-08-21 Motohisa Fukuda

Quantum communication schemes widely use dielectric four-port devices as basic elements for constructing optical quantum channels. Since for causality reasons the permittivity is necessarily a complex function of frequency, dielectrics are…

Quantum Physics · Physics 2007-05-23 S. Scheel , L. Knoll , T. Opatrny , D. -G. Welsch