Closing objectivity loophole in Bell tests on a public quantum computer

TL;DR

This paper presents a Bell test on a public quantum computer emphasizing outcome objectivity, demonstrating the feasibility of such tests on current quantum hardware despite some loopholes and signaling issues.

Contribution

It introduces a Bell test focusing on outcome objectivity and benchmarks entanglement distribution on IBM Quantum and IonQ devices.

Findings

Successfully performed Bell test on IBM Quantum and IonQ devices

Demonstrated the presence of entanglement across multiple qubits

Identified communication loopholes and residual signaling in the tests

Abstract

We have constructed and run a Bell test of local realism focusing on the objectivity criterion. The objectivity means that the outcomes are confirmed macroscopically by a few observers at each party. The IBM Quantum and IonQ devices turn out to be sufficiently accurate to pass such an extended Bell-type test, although at the price of communication loopholes and residual but statistically significant signaling. The test also serves as the benchmark of entanglement spread across larger sets of qubits.