Entanglement and decoherence: fragile and robust entanglement

TL;DR

This paper analyzes how different types of entangled quantum states respond to decoherence, revealing that some are fragile and disentangle quickly, while others are robust and resist decoherence over time.

Contribution

It introduces a general decoherence model without weak-coupling or Markovian assumptions and classifies entangled states into fragile and robust categories based on their decoherence behavior.

Findings

Fragile states disentangle asymptotically despite remaining coherences.

Robust states only disentangle with perfect decoherence.

A criterion for classifying two-qubit entanglement into these classes.

Abstract

The destruction of entanglement of open quantum systems by decoherence is investigated in the asymptotic long-time limit. Starting from a general and analytically solvable decoherence model which does not involve any weak-coupling or Markovian assumption it is shown that two fundamentally different classes of entangled states can be distinguished. Quantum states of the first class are fragile against decoherence so that they can be disentangled asymptotically even if coherences between pointer states are still present. Quantum states of the second type are robust against decoherence. Asymptotically they can be disentangled only if also decoherence is perfect. A simple criterion for identifying these two classes on the basis of two-qubit entanglement is presented.