Effects of Quantum Error Correction on Entanglement Sudden Death

TL;DR

This paper explores how quantum error correction influences the timing and occurrence of entanglement sudden death in two-qubit systems under various damping errors, revealing complex effects on fidelity and entanglement.

Contribution

It extends previous studies by analyzing the impact of error correction on ESD for different damping channels and initial states, highlighting nuanced effects on entanglement and fidelity.

Findings

Error correction can delay or prevent ESD depending on initial states.

Fidelity and entanglement are affected differently by error correction.

Certain initial states see increased fidelity but decreased entanglement after correction.

Abstract

We investigate the effects of error correction on non-local quantum coherence as a function of time, extending the study by Sainz and Bj\"ork. We consider error correction of amplitude damping, pure phase damping and combinations of amplitude and phase damping as they affect both fidelity and quantum entanglement. Initial two-qubit entanglement is encoded in arbitrary real superpositions of both \Phi-type and \Psi-type Bell states. Our main focus is on the possibility of delay or prevention of ESD (early stage decoherence, or entanglement sudden death). We obtain the onset times for ESD as a function of the state-superposition mixing angle. Error correction affects entanglement and fidelity differently, and we exhibit initial entangled states for which error correction increases fidelity but decreases entanglement, and vice versa.