arXiv:quant-ph/0403072

A quantum channel with additive minimum output entropy

Nilanjana Datta, Alexander Semenovich Holevo, Yuri Suhov

Published Mar 9, 2004• 19 citations

Abstract

We give a direct proof of the additivity of the minimum output entropy of a particular quantum channel which breaks the multiplicativity conjecture. This yields additivity of the classical capacity of this channel, a result obtained by a different method by Matsumoto and Yura [quant-ph/0306009]. Our proof relies heavily upon certain concavity properties of the output entropy which are of independent interest.

DOI: 10.48550/arxiv.quant-ph/0403072

Related papers

A counterexample to additivity of minimum output entropy

Matthew B. Hastings

We present a random construction of a pairs of channels which gives, with non-zero probability for sufficiently large dimensions, a counterexample to the minimum output entropy conjecture.As is known [4], this implies a violation of the additivity conjecture for the classical capacity of quantum channels.Thc violation of the minimum output cntropy conjecture is relatively small.

Physical Review LettersJan 1, 200821 citations

Additivity of the classical capacity of entanglement-breaking quantum channels

Peter W. Shor

arXiv:quant-ph/0201149Journal of Mathematical PhysicsSep 1, 2002170 citations

On some additivity problems in quantum information theory

Grigori Gennadievich Amosov, Alexander Semenovich Holevo, Reinhard F. Werner

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", and the "maximal output purity". All known results, including extensive numerical work, are consistent with the conjecture that these quantities are indeed additive (resp. multiplicative) with respect to tensor products of channels. A proof of this conjecture would have important consequences in quantum information theory. In particular, according to this conjecture, the classical capacity or the maximal purity of outputs cannot be increased by using entangled inputs of the channel. In this paper we state the additivity/multiplicativity problems, give some relations between them, and prove some new partial results, which also support the conjecture.

arXiv:math-ph/0003002Mar 4, 2000105 citations

Additivity of the Classical Capacity of Entanglement-Breaking Quantum Channels

Peter W. Shor

We show that for the tensor product of an entanglement-breaking quantum channel with an arbitrary quantum channel, both the minimum entropy of an output of the channel and the Holevo-Schumacher-Westmoreland capacity are additive. In addition, for the tensor product of two arbitrary quantum channels, we give a bound involving entanglement of formation for the amount of subadditivity (for minimum entropy output) or superadditivity (for classical capacity) that can occur. One of the more important open questions of quantum information theory is the determination of the capacity of a quantum channel for carrying classical information. This question has been only partially resolved. If entanglement between multiple inputs to the channel is not allowed, a formula for the classical capacity of a quantum channel has indeed been discovered [1, 2]. This capacity formula for a quantum channel Ψ is χ ∗ (Ψ) = max p i,ρ i H Ψ(piρi) − ∑

Jan 1, 2002157 citations

Additivity/Multiplicativity Communication Channels

Grigori Gennadievich Amosov, Alexander Semenovich Holevo, Reinhard F. Werner

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”, and the “maximal output purity”. All known results, including extensive numerical work, are consistent with the conjecture that these quantities are indeed additive (resp. multiplicative) with respect to tensor products of channels. A proof of this conjecture would have important consequences in quantum information theory. In particular, according to this conjecture, the classical capacity or the maximal purity of outputs cannot be increased by using entangled inputs of the channel. In this paper we state the additivity/multiplicativity problems, give some relations between them, and prove some new partial results, which also support the conjecture. These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Kluwer Academic Publishers eBooksFeb 24, 20060 citations

Revisiting additivity violation of quantum channels

Motohisa Fukuda

We prove additivity violation of minimum output entropy of quantum channels by straightforward application of ε-net argument and Lévy's lemma. The additivity conjecture was disproved initially by Hastings. Later, a proof via asymptotic geometric analysis was presented by Aubrun, Szarek and Werner, which uses Dudley's bound on Gaussian process (or Dvoretzky's theorem with Schechtman's improvement). In this paper, we develop another proof along Dvoretzky's theorem in Milman's view showing additivity violation in broader regimes than the existing proofs. Importantly, Dvoretzky's theorem works well with norms to give strong statements but these techniques can be extended to functions which have norm-like structures - positive homogeneity and triangle inequality. Then, a connection between Hastings' method and ours is also discussed. Besides, we make some comments on relations between regularized minimum output entropy and classical capacity of quantum channels.

Jan 1, 201415 citations