Fidelity preserving and decoherence for mixed unitary quantum channels

TL;DR

This paper studies mixed unitary quantum channels and identifies conditions under which they preserve fidelity and distinguishability of quantum states, addressing decoherence effects in quantum systems.

Contribution

It characterizes the structure of quantum channels that preserve fidelity and distinguishability, especially under decoherence, providing insights into quantum state preservation.

Findings

Identifies conditions for fidelity preservation in mixed unitary channels

Analyzes the impact of phase damping on quantum state fidelity

Explores the structure of channels that maintain distinguishability

Abstract

Distinguishable and non-distinguishable quantum states are fundamental resources in quantum mechanics and quantum technologies. Interactions with the environment often induce decoherence, impacting both the distinguishability and non-distinguishability between quantum states. In this paper, we investigate mixed unitary quantum channels and the conditions under which fidelity, a measure of quantum state closeness, is preserved. More precisely, for quantum channels in the form $\Phi(\rho) = \sum_{i=1}^N p_i U_i \rho U_i^*$, we analyze their effect on quantum state $|\varphi\rangle$ through the associated purification $|\Psi\rangle$, explore the structure of such quantum channels that preserve either distinguishable or non-distinguishable states and then discuss the challenges of maintaining fidelity, particularly under the influence of phase damping.