Decoherence and Entanglement Dynamics in Fluctuating Fields

TL;DR

This paper analyzes how pure phase damping caused by fluctuating fields affects entanglement and purity in two qubits, providing analytical insights into the dynamics and constraints in the concurrence-purity plane.

Contribution

It introduces an analytical method to determine entanglement and purity evolution under random unitary phase damping, clarifying the roles of initial states and dynamics.

Findings

RU phase damping constrains accessible regions in the CP diagram

Initial state and dynamics independently influence final entanglement

Analytical expressions for entanglement and purity evolution

Abstract

We study pure phase damping of two qubits due to fluctuating fields. As frequently employed, decoherence is thus described in terms of random unitary (RU) dynamics, i.e., a convex mixture of unitary transformations. Based on a separation of the dynamics into an average Hamiltonian and a noise channel, we are able to analytically determine the evolution of both entanglement and purity. This enables us to characterize the dynamics in a concurrence-purity (CP) diagram: we find that RU phase damping dynamics sets constraints on accessible regions in the CP plane. We show that initial state and dynamics contribute to final entanglement independently.