The Roles of a Quantum Channel on a Quantum State

TL;DR

This paper investigates how quantum channels affect quantum states, introducing state-independent measures for fidelity, entanglement, and coherence, and analyzing their behaviors under various channels.

Contribution

It proposes novel state-independent quantities to quantify the influence of quantum channels on fidelity, entanglement, and coherence, with applications to qubit channels.

Findings

Fidelity decreases monotonically with decay rate.

Decoherence behavior varies significantly with different channels.

Entanglement is generally reduced by quantum channels.

Abstract

When a quantum state undergoes a quantum channel, the state will be inevitably influenced. In general, the fidelity of the state is reduced, so is the entanglement if the sub- systems go through the channel. However, the influence on the coherence of the state is quite different. Here we present some state-independent quantities to describe to what degree the fidelity, the entanglement and the coherence of the state are influenced. As applications, we consider some quantum channels on a qubit and find that the infidelity ability monotonically depends on the decay rate, but in usual the decoherence ability is not the case and strongly depends on the channel.