Contextuality with vanishing coherence and maximal robustness to dephasing

TL;DR

This paper investigates the robustness of quantum contextuality against dephasing noise, showing that even minimal coherence can demonstrate contextuality and providing proofs resilient to significant dephasing, unlike depolarizing noise.

Contribution

It introduces a scenario where contextuality remains robust under arbitrary partial dephasing, highlighting a new resilience property of quantum contextuality.

Findings

Minimal coherence suffices to demonstrate contextuality.

Contextuality proof is robust to arbitrary partial dephasing.

Partially depolarizing noise always destroys contextuality.

Abstract

Generalized contextuality is a resource for a wide range of communication and information processing protocols. However, contextuality is not possible without coherence, and so can be destroyed by dephasing noise. Here, we explore the robustness of contextuality to partially dephasing noise in a scenario related to state discrimination (for which contextuality is a resource). We find that a vanishing amount of coherence is sufficient to demonstrate the failure of noncontextuality in this scenario, and we give a proof of contextuality that is robust to arbitrary amounts of partially dephasing noise. This is in stark contrast to partially depolarizing noise, which is always sufficient to destroy contextuality.