Excluding the local hidden variable theory with time-reversal Bell test

TL;DR

This paper proposes a time-reversal Bell test protocol that can exclude local hidden variable theories without requiring high detection efficiency, advancing experimental tests of quantum nonlocality.

Contribution

The authors introduce a novel time-reversal Bell test protocol that prevents local hidden variables from exchanging information, enabling loophole-free Bell violation demonstration.

Findings

Bell violation achieved without high detection efficiency

Protocol prevents local hidden variables from exchanging information

Feasible with current technology

Abstract

A time-reversal Bell test protocol is proposed. The quantum states are prepared by faraway separated partners and transferred to the third partner who carries out Bell basis measurement on them to post-select the Einstein-Podolsky-Rosen (EPR) pairs. If some loopholes open, similar as that in normal Bell test, the Bell violation in the present protocol is apt to be interpreted with local hidden variable (lhv) theory. With some modifications on the protocol, the lhvs at both sides are prevented to exchange their information. Thus they only function locally and cannot affect the behaviors of the states at the other sides. However, Bell violation can still be obtained in this case. It means that Bell violation is realized with the lhv theory excluded. Because high detection efficiency is not compulsory, this protocol can be realized with present technology.