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A conjecture arising naturally in the investigation of additivity of classical information capacity of quantum channels states that the maximal purity of outputs from a quantum channel, as measured by the p-norm, should be multiplicative…

Quantum Physics · Physics 2015-06-26 R. F. Werner , A. S. Holevo

We establish a strong converse bound for the private classical capacity of anti-degradable quantum channels. Specifically, we prove that this capacity is zero whenever the error $\epsilon > 0$ and privacy parameter $\delta > 0$ satisfy the…

Quantum Physics · Physics 2025-07-22 Zahra Baghali Khanian , Christoph Hirche

We present a general model for quantum channels with memory, and show that it is sufficiently general to encompass all causal automata: any quantum process in which outputs up to some time t do not depend on inputs at times t' > t can be…

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

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

We study the properties of the quantum information transmission channel that emerges from the quantum dynamics of particles interacting with a black hole horizon. We calculate the quantum channel capacity in two limiting cases where a…

Quantum Physics · Physics 2014-08-20 Kamil Bradler , Christoph Adami

Quantum addition channels have been recently introduced in the context of deriving entropic power inequalities for finite dimensional quantum systems. We prove a reverse entropy power equality which can be used to analytically prove an…

Quantum Physics · Physics 2026-04-13 Chiranjib Mukhopadhyay , Arun Kumar Pati , Sk Sazim

A quantum channel physically is a unitary interaction between the information carrying system and an environment, which is initialized in a pure state before the interaction. Conventionally, this state, as also the parameters of the…

Quantum Physics · Physics 2016-10-25 Siddharth Karumanchi , Stefano Mancini , Andreas Winter , Dong Yang

Quantum channels represent a broad spectrum of operations crucial to quantum information theory, encompassing everything from the transmission of quantum information to the manipulation of various resources. In the domain of states, the…

Quantum Physics · Physics 2025-05-15 Gilad Gour , Doyeong Kim , Takla Nateeboon , Guy Shemesh , Goni Yoeli

The property of the optimal signal ensembles of entanglement assisted channel capacity is studied. A relationship between entanglement assisted channel capacity and one-shot capacity of unassisted channel is obtained. The data processing…

Quantum Physics · Physics 2009-11-10 Heng Fan

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 study the additivity problems for the classical capacity of quantum channels, the minimal output entropy and its convex closure. We show for each of them that additivity for arbitrary pairs of channels holds iff it holds for arbitrary…

Quantum Physics · Physics 2007-08-21 Motohisa Fukuda , Michael M. Wolf

The nonadditivity of channel capacity is a defining feature that distinguishes quantum communication from classical communication. In the quantum realm, the channel capacity is determined by coherent information, which is defined through…

Quantum Physics · Physics 2026-05-19 Yu Guo , Bo-Xuan Wang , Xiao-Min Hu , Yun-Feng Huang , Chuan-Feng Li , Guang-Can Guo , Bi-Heng Liu

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…

Capacities of quantum channels are fundamental quantities in the theory of quantum information. A desirable property is the additivity for a capacity. However, this cannot be achieved for a few quantities that have been established as…

Quantum Physics · Physics 2025-05-20 D. -S. Wang

We prove that, when two local quantum channels are used paralleled, the quantum-correlating power (QCP) of the composed channel is no less than the sum of QCP of the two channels. For local channels with zero QCP, the super-activation of…

Quantum Physics · Physics 2013-07-23 Xueyuan Hu , Heng Fan , D. L. Zhou , Wu-Ming Liu

In this paper we address the issue of universal or robust communication over quantum channels. Specifically, we consider memoryless communication scenario with channel uncertainty which is an analog of compound channel in classical…

Quantum Physics · Physics 2009-11-13 I. Bjelakovic , H. Boche , J. Noetzel

The present work continues investigation of the capacities of measurement (quantum-classical) channels in the most general setting, initiated in~\cite{HCT}. The proof of coding theorems is given for the classical capacity and…

Quantum Physics · Physics 2014-08-15 A. A. Kuznetsova , A. S. Holevo

We consider quantum channels with two senders and one receiver. For an arbitrary such channel, we give multi-letter characterizations of two different two-dimensional capacity regions. The first region is comprised of the rates at which it…

Quantum Physics · Physics 2011-10-25 Jon Yard , Igor Devetak , Patrick Hayden

A quantum channel is conjugate degradable if the channel's environment can be simulated up to complex conjugation using the channel's output. For all such channels, the quantum capacity can be evaluated using a single-letter formula. In…

Quantum Physics · Physics 2010-07-19 Kamil Bradler , Nicolas Dutil , Patrick Hayden , Abubakr Muhammad

For a continuous-input-continuous-output arbitrarily distributed quantum channel carrying classical information, the channel capacity can be computed in terms of the distribution of the channel envelope, received signal strength over a…

Information Theory · Computer Science 2022-06-09 Mouli Chakraborty , Harun Siljak , Indrakshi Dey , Nicola Marchetti