Classical capacity of a qubit depolarizing channel with memory

TL;DR

This paper investigates how memory effects in a quantum depolarizing channel influence its classical capacity, revealing that increased noise correlations can enhance the channel's information transmission ability.

Contribution

It introduces a model of a forgetful quantum channel with Markov switching, providing a method to compute capacity considering non-Markovian noise correlations.

Findings

Memory correlations can increase channel capacity

Capacity computation reduces to entropy of a Markov process

Reformulation using algebraic measures enables calculation

Abstract

The classical product state capacity of a noisy quantum channel with memory is investigated. A forgetful noise-memory channel is constructed by Markov switching between two depolarizing channels which introduces non-Markovian noise correlations between successive channel uses. The computation of the capacity is reduced to an entropy computation for a function of a Markov process. A reformulation in terms of algebraic measures then enables its calculation. The effects of the hidden-Markovian memory on the capacity are explored. An increase in noise-correlations is found to increase the capacity.