Temporal Entanglement and Witnesses of Non-Classicality

TL;DR

This paper links information-theoretic witnesses of non-classicality with temporal entanglement, proposing a protocol to detect non-classical features in systems via a qubit probe, supported by NMR experiments.

Contribution

It introduces a novel protocol connecting temporal Bell inequality violations with non-classicality, applicable across various physical contexts.

Findings

Violating temporal Bell inequalities indicates non-classicality.

Experimental validation using NMR quantum computer.

Protocol is robust under minimal assumptions.

Abstract

The universality of quantum theory has been questioned ever since it was proposed. Key to this long-unsolved question is to test whether a given physical system has non-classical features. Here we connect recently proposed witnesses of non-classicality, based on information-theoretic ideas, with the theory of temporal entanglement. We provide a protocol to witness the non-classicality of a system by probing it with a qubit: we show that, assuming a general conservation law, violating temporal Bell inequalities on the qubit probe implies the non-classicality of the system under investigation. We also perform proof-of-principle experimental emulations of the proposed witness of non-classicality, using a three qubit Nuclear Magnetic Resonance quantum computer. Our result is robust, as it relies on minimal assumptions, and remarkably it can be applied in a broad range of contexts, from quantum biology to quantum gravity.