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We consider compound as well as arbitrarily varying classical-quantum channel models. For classical-quantum compound channels, we give an elementary proof of the direct part of the coding theorem. A weak converse under average error…

Quantum Physics · Physics 2016-08-14 Igor Bjelaković , Holger Boche , Gisbert Janßen , Janis Nötzel

We demonstrate superadditivity of one-shot zero-error classical capacity in an asymmetric communication setting where a noisy classical channel is used in parallel with a perfect quantum channel. Each channel individually supports only a…

Quantum Physics · Physics 2026-02-10 Ambuj , Anushko Chattopadhyay , Kunika Agarwal , Rakesh Das , Amit Mukherjee

The thermodynamic resourcefulness of quantum channels primarily depends on their underlying causal structure and their ability to generate quantum correlations. We quantify this interplay within the resource theory of athermality for…

Quantum Physics · Physics 2026-04-02 Himanshu Badhani , Siddhartha Das

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 introduce potential capacities of quantum channels in an operational way and provide upper bounds for these quantities, which quantify the ultimate limit of usefulness of a channel for a given task in the best possible context.…

Quantum Physics · Physics 2016-02-17 Andreas Winter , Dong Yang

We provide lower and upper bounds on the information transmission capacity of one single use of a classical-quantum channel. The lower bound is expressed in terms of the Hoeffding capacity, that we define similarly to the Holevo capacity,…

Quantum Physics · Physics 2009-07-24 Milan Mosonyi , Nilanjana Datta

We prove that the minimal Renyi entropy of order 2 (RE2) output of a positive-partial-transpose(PPT)-inducing channel joint to an arbitrary other channel is equal to the sum of the minimal RE2 output of the individual channels. PPT-inducing…

Quantum Physics · Physics 2009-11-13 B. Dierckx , M. Fannes , C. Vandenplas

Determining whether a noisy quantum channel can be used to reliably transmit quantum information at a non-zero rate is a challenging problem in quantum information theory. This is because it requires computation of the channel's coherent…

Quantum Physics · Physics 2024-10-24 Satvik Singh , Nilanjana Datta

We prove that quantum thermal Gaussian input states minimize the output entropy of the multi-mode quantum Gaussian attenuators and amplifiers that are entanglement breaking and of the multi-mode quantum Gaussian phase contravariant channels…

Quantum Physics · Physics 2019-08-20 Giacomo De Palma

We consider the image of some classes of bipartite quantum states under a tensor product of random quantum channels. Depending on natural assumptions that we make on the states, the eigenvalues of their outputs have new properties which we…

Mathematical Physics · Physics 2019-02-27 Benoit Collins , Motohisa Fukuda , Ion Nechita

The additivity of both the entanglement of formation and the classical channel capacity is known to be a consequence of the strong superadditivity conjecture. We show that, conversely, the strong superadditivity conjecture follows from the…

Quantum Physics · Physics 2007-05-23 Andrei Pomeransky

The quantum analog of the classical erasure channel provides a simple example of a channel whose asymptotic capacity for faithful transmission of intact quantum states, with and without the assistance of a two-way classical side channel,…

Quantum Physics · Physics 2008-11-26 Charles H. Bennett , David P. DiVincenzo , John A. Smolin

The capacity of classical channels is convex. This is not the case for the quantum capacity of a channel: the capacity of a mixture of different quantum channels exceeds the mixture of the individual capacities and thus is non-convex. Here…

Quantum Physics · Physics 2016-10-26 David Elkouss , Sergii Strelchuk

A recent method to certify the classical capacity of quantum communication channels is applied for general damping channels in finite dimension. The method compares the mutual information obtained by coding on the computational and a…

Quantum Physics · Physics 2020-10-23 Chiara Macchiavello , Massimiliano F. Sacchi , Tito Sacchi

In this paper, we compute the exact values of the minimum output entropy and the completely bounded minimal entropy of very large classes of quantum channels acting on matrix algebras $\mathrm{M}_n$. Our new and simple approach relies on…

Operator Algebras · Mathematics 2025-02-06 Cédric Arhancet

The quantum capacity of a quantum channel captures its capability for noiseless quantum communication. It lies at the heart of quantum information theory. Unfortunately, our poor understanding of nonadditivity of coherent information makes…

Quantum Physics · Physics 2018-12-07 Felix Leditzky , Debbie Leung , Graeme Smith

Recently Hastings proved the existence of random unitary channels which violate the additivity conjecture. In this paper we use Hastings' method to derive new bounds for the entanglement of random subspaces of bipartite systems. As an…

Quantum Physics · Physics 2014-11-27 Motohisa Fukuda , Christopher King

Based on the resource theory for quantifying the coherence of quantum channels, we introduce a new coherence quantifier for quantum channels via maximum relative entropy. We prove that the maximum relative entropy for coherence of quantum…

In the present paper we study the entropy gain $H(\Phi [\rho])-H(\rho)$ for infinite-dimensional channels $\Phi$. We show that unlike finite-dimensional case where the minimal entropy gain is always nonpositive \cite{al}, there is a plenty…

Mathematical Physics · Physics 2010-11-23 A. S. Holevo

For a partially degradable (PD) channel, the channel output state can be used to simulate the degraded environment state. The quantum capacity of a PD channel has been proven to be additive. Here, we show that the private classical capacity…

Quantum Physics · Physics 2015-06-16 Laszlo Gyongyosi