# Contextuality Test of the Nonclassicality of Variational Quantum Eigensolvers

## TL;DR

This paper introduces a practical test for assessing the nonclassicality of variational quantum eigolvers (VQEs) through contextuality, revealing that some experimental VQEs exhibit quantum features while others do not.

## Contribution

We develop an efficiently computable contextuality test for VQEs and apply it to experimental data to evaluate their quantum nature.

## Key findings

- Some VQE implementations are contextual, indicating quantum behavior.
- Not all experimental VQEs pass the contextuality test, suggesting classical features.
- The test provides a new way to verify quantum resources in VQEs.

## Abstract

Contextuality is an indicator of non-classicality, and a resource for various quantum procedures. In this paper, we use contextuality to evaluate the variational quantum eigensolver (VQE), one of the most promising tools for near-term quantum simulation. We present an efficiently computable test to determine whether or not the objective function for a VQE procedure is contextual. We apply this test to evaluate the contextuality of experimental implementations of VQE, and determine that several, but not all, fail this test of quantumness.