Holevo's bound from a general quantum fluctuation theorem

TL;DR

This paper derives a refined version of Holevo's bound by applying a quantum fluctuation theorem, accounting for measurement back action and non-unitary evolution, resulting in a tighter information inequality.

Contribution

It introduces a general formalism of quantum fluctuation theorems for two-time measurements that leads to a measurement-dependent correction to Holevo's bound.

Findings

Derived a measurement-dependent correction to Holevo's bound.

Provided conditions under which the bound becomes tight.

Linked quantum fluctuation theorems with quantum information bounds.

Abstract

We give a novel derivation of Holevo's bound using an important result from nonequilibrium statistical physics, the fluctuation theorem. To do so we develop a general formalism of quantum fluctuation theorems for two-time measurements, which explicitly accounts for the back action of quantum measurements as well as possibly non-unitary time evolution. For a specific choice of observables this fluctuation theorem yields a measurement-dependent correction to the Holevo bound, leading to a tighter inequality. We conclude by analyzing equality conditions for the improved bound.