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Information capacity enhancement through the coherent control of channels has attracted much attention of late, with work exploring the effect of coherent control of channel causal orders, channel superpositions, and information encoding.…

Channel capacity describes the size of the nearly ideal channels, which can be obtained from many uses of a given channel, using an optimal error correcting code. In this paper we collect and compare minor and major variations in the…

Quantum Physics · Physics 2009-11-10 Dennis Kretschmann , Reinhard F Werner

We analyze different aspects of multiparty communication over quantum memoryless channels and generalize some of key results known from bipartite channels to that of multiparty scenario. In particular, we introduce multiparty versions of…

Quantum Physics · Physics 2009-11-13 Maciej Demianowicz , Pawel Horodecki

We study subadditivity of the minimum output entropy ($H_{min}$) of quantum multiple access channels (MACs). We provide an example of violation of the additivity theorem for $H_{min}$ known in classical information theory. Our result is…

Quantum Physics · Physics 2012-03-14 Lukasz Czekaj

We determine the secrecy capacities of AVQCs (arbitrarily varying quantum channels). Both secrecy capacity with average error probability and with maximal error probability are derived. Both derivations are based on one common code…

Information Theory · Computer Science 2018-06-13 Holger Boche , Minglai Cai , Christian Deppe , Janis Nötzel

A direct proof of the relation between the one-shot classical capacity and the minimal output entropy for covariant quantum channels is suggested. The structure of covariant channels is described in some detail. A simple proof of a general…

Quantum Physics · Physics 2007-05-23 A. S. Holevo

We show the equivalence of two different notions of quantum channel capacity: that which uses the entanglement fidelity as its criterion of success in transmission, and that which uses the minimum fidelity of pure states in a subspace of…

Quantum Physics · Physics 2016-11-18 H. Barnum , E. Knill , M. A. Nielsen

We prove that a broad array of capacities of a quantum channel are continuous. That is, two channels that are close with respect to the diamond norm have correspondingly similar communication capabilities. We first show that the classical…

Quantum Physics · Physics 2009-09-09 Debbie Leung , Graeme Smith

Quantum channel capacities give the fundamental performance limits for information flow over a communication channel. However, the prevalence of superadditivity is a major obstacle to understanding capacities, both quantitatively and…

Quantum Physics · Physics 2025-09-10 Graeme Smith , Peixue Wu

It is known that the number of different classical messages which can be communicated with a single use of a classical channel with zero probability of decoding error can sometimes be increased by using entanglement shared between sender…

Quantum Physics · Physics 2012-03-30 Debbie Leung , Laura Mancinska , William Matthews , Maris Ozols , Aidan Roy

In quantum Shannon theory, the way information is encoded and decoded takes advantage of the laws of quantum mechanics, while the way communication channels are interlinked is assumed to be classical. In this Letter we relax the assumption…

Quantum Physics · Physics 2018-03-28 Daniel Ebler , Sina Salek , Giulio Chiribella

In Shannon information theory the capacity of a memoryless communication channel cannot be increased by the use of feedback. In quantum information theory the no-cloning theorem means that noiseless copying and feedback of quantum…

Quantum Physics · Physics 2016-11-17 Garry Bowen

The computational problem of distinguishing two quantum channels is central to quantum computing. It is a generalization of the well-known satisfiability problem from classical to quantum computation. This problem is shown to be…

Quantum Physics · Physics 2009-09-24 Bill Rosgen

We prove the equivalence of an arbitrary single-mode Gaussian quantum channel and a newly defined fiducial channel preceded by a phase shift and followed by a Gaussian unitary operation. This equivalence implies that the energy-constrained…

We study extensions of a quantum channel whose one-way capacities are described by a single-letter formula. This provides a simple technique for generating powerful upper bounds on the capacities of a general quantum channel. We apply this…

Quantum Physics · Physics 2009-02-20 Graeme Smith , John A. Smolin

We consider a scenario where a party, say, Alice prepares a pure two-qubit (either maximally entangled or non-maximally entangled) state and sends one half of this state to another distant party, say, Bob through a qubit (either unital or…

Quantum Physics · Physics 2021-05-19 Arkaprabha Ghosal , Debarshi Das , Subhashish Banerjee

For any quantum transmission line, with smaller output dimension than its input, the number of classical symbols that can be reliably encoded is strictly suboptimal. In other words, if the channel outputs a lesser number of symbols than it…

Quantum Physics · Physics 2025-09-12 Snehasish Roy Chowdhury , Sutapa Saha , Subhendu B. Ghosh , Ranendu Adhikary , Tamal Guha

This paper shows that it is possible to piggyback classical information on a stream of qubits protected by quantum error correcting codes. The piggyback channel can be created by introducing intentional errors corresponding to a controlled…

Quantum Physics · Physics 2020-07-21 Marco Chiani , Andrea Conti , Moe Z. Win

Communication over a quantum multiple access channel (MAC) is considered with classical feedback. Since the no-cloning prohibits universal copying of arbitrary quantum states, classical feedback is generated through measurement. An…

Quantum Physics · Physics 2026-02-20 Elina Levi , Uzi Pereg

We present a method to detect lower bounds to the classical capacity of quantum communication channels by means of few local measurements (i.e. without complete process tomography), reconstruction of sets of conditional probabilities, and…

Quantum Physics · Physics 2019-08-30 Chiara Macchiavello , Massimiliano F. Sacchi