Testing nonlocality of a single photon without a shared reference frame

TL;DR

This paper proposes a simple, feasible method to demonstrate the nonlocality of a single photon without needing a shared reference frame, simplifying quantum communication protocols.

Contribution

It introduces a scheme that shows Bell inequality violation with unaligned devices, even with fluctuating reference frames, advancing single-photon nonlocality testing.

Findings

Bell inequality violation achieved without shared reference frame

Scheme is robust to device misalignment and frame fluctuations

Feasible with current quantum technology

Abstract

The question of testing the nonlocality of a single photon has raised much debate over the last years. The controversy is intimately related to the issue of providing a common reference frame for the observers to perform their local measurements. Here we address this point by presenting a simple scheme for demonstrating the nonlocality of a single photon which does not require a shared reference frame. Specifically, Bell inequality violation can be obtained with certainty with unaligned devices, even if the relative frame fluctuates between each experimental run of the Bell test. Our scheme appears feasible with current technology, and may simplify the realization of quantum communication protocols based on single-photon entanglement.