Experimental Test of Contextuality based on State Discrimination with a Single Qubit

TL;DR

This paper experimentally demonstrates quantum contextuality in a single qubit system by violating a non-contextuality inequality through minimum error state discrimination on a single ion, highlighting quantum advantages over classical models.

Contribution

It extends the experimental test of contextuality to a minimal two-level quantum system, using state discrimination on a single ion, which was previously limited to systems with three or more levels.

Findings

Significant violation of a non-contextuality inequality observed.

Quantum contextual advantage in state discrimination quantified.

Results show robustness against quantum noise.

Abstract

Exploring quantum phenomena beyond predictions of any classical model has fundamental importance to understand the boundary of classical and quantum descriptions of nature. As a typical property that a quantum system behaves distinctively from a classical counterpart, contextuality has been studied extensively and verified experimentally in systems composed of at least three levels (qutrit). Here we extend the scope of experimental test of contextuality to a minimal quantum system of only two states (qubit) by implementing the minimum error state discrimination on a single $^{171}$Yb$^+$ ion. We observe a substantial violation of a no-go inequality derived by assuming non-contextuality, and firmly conclude that the measured results of state discrimination cannot be reconciled with any non-contextual description. We also quantify the contextual advantage of state discrimination and the tolerance against quantum noises.