Single-photon nonlocality in quantum networks

Understand

The state obtained when a single photon impinges on a balanced beamsplitter is often known as single-photon entangled and its nonlocal properties have been the subject of intense debates in the quantum optics and foundations communities.

• It is however clear that a standard Bell test made only of passive optical elements cannot reveal the nonlocality of this state.
• We show that the nonlocality of single-photon entangled states can nevertheless be revealed in a quantum network made only of beamsplitters and photodetectors.
• In our protocol, three single-photon entangled states are distributed in a triangle network, introducing indeterminacy in the photons' paths and creating nonlocal correlations without the need for measurements choices.