Tri-partite Entanglement Witnesses and Sudden Death

TL;DR

This paper investigates how entanglement witnesses detect three-qubit entanglement under dephasing, compares their effectiveness with other measures, and examines the impact of entanglement sudden death on quantum error correction.

Contribution

It introduces a comparison between entanglement witnesses and other entanglement measures during decoherence, revealing cases where witnesses detect entanglement despite other measures not doing so.

Findings

Entanglement witnesses can detect entanglement even when negativity and concurrence vanish.

A state was found with no concurrence or negativity but still entangled.

Entanglement sudden death impacts the effectiveness of quantum error correction.

Abstract

I explore entanglement dynamics in a three qubit system comparing the ability of entanglement witnesses to detect tri-partite entanglement to the phenomenon of entanglement sudden death (ESD). Using a system subject to dephasing I invoke entanglement witnesses to detect tri-partite GHZ and W-type entanglement and compare the evolution of their detection capabilites with the evolution of the negativity, bi-partite concurrence, and tri-partite negativity. Interestingly, I find a state in which there is no concurrence or tri-partite negativity but there is entanglement. Finally, I utilize a three qubit quantum error correction (QEC) code to address how ESD affects the abilities of quantum error correction.