Fragility of quantum correlations and coherence in a multipartite photonic system

TL;DR

This paper experimentally investigates the fragility of quantum correlations and coherence in tripartite photonic states under controlled dephasing, confirming that entanglement is most fragile, followed by coherence and mutual information.

Contribution

It provides the first experimental confirmation of the hierarchy of fragility among quantum correlations, coherence, and mutual information in multipartite photonic systems.

Findings

Entanglement is most fragile under dephasing.

Quantum coherence is less fragile than entanglement.

Mutual information is the most robust among the three.

Abstract

Certain quantum states are well-known to be particularly fragile in the presence of decoherence, as illustrated by Schrodinger's famous gedanken cat experiment. It has been better appreciated more recently that quantum states can be characterized in a hierarchy of quantum quantities such entanglement, quantum correlations, and quantum coherence. It has been conjectured that each of these quantities have various degrees of fragility in the presence of decoherence. Here we experimentally confirm this conjecture by preparing tripartite photonic states and subjecting them to controlled amounts of dephasing. When the dephasing is applied to all the qubits, we find that the entanglement is the most fragile quantity, followed by the quantum coherence, then mutual information. This is in agreement with the widely held expectation that multipartite quantum correlations are a highly fragile manifestation of quantumness. We also perform dephasing on one out of the three qubits on star and $ W \bar{W} $ states. Here the distribution of the correlations and coherence in the state becomes more important in relation to the dephasing location.