Testing Bell inequalities with weak measurements

TL;DR

This paper proposes a novel experimental method using weak measurements to test Bell inequalities, allowing all observables to be measured on each system and potentially maximizing violation detection.

Contribution

It introduces a feasible approach with weak measurements to test Bell inequalities on all ensemble members simultaneously, enhancing experimental capabilities.

Findings

Bell inequalities can be maximally violated with weak measurements on each system

Weak measurements produce small disturbance but less accurate results

Adding precise measurements verifies the absence of hidden variable interference

Abstract

Quantum theory is inconsistent with any local hidden variable model as was first shown by Bell. To test Bell inequalities two separated observers extract correlations from a common ensemble of identical systems. Since quantum theory does not allow simultaneous measurements of noncommuting observables, on each system every party measures a single randomly chosen observable out of a given set. Here we suggest a different approach for testing Bell inequalities that is experimentally realizable by current methods. We show that Bell inequalities can be maximally violated even when all observables are measured on each member of the ensemble. This is possible by using weak measurements that produce small disturbance, at the expense of accuracy. However, our approach does not constitute an independent test of quantum nonlocality since the local hidden variables may correlate the noise of the measurement instruments. Nevertheless, by adding a randomly chosen precise measurement at the end of every cycle of weak measurements, the parties can verify that the hidden variables were not interfering with the noise, and thus validate the suggested test.