Possible experimental test of photon non-locality from a one-photon state

Tanumoy Pramanik, Satyabrata Adhikari, A. S. Majumdar +1 more

A scheme is formulated for testing nonlocality of single photons by considering the state of a single photon that could be located within one of two spatially separated cavities. The outcomes of four experiments on this state involving the resonant interactions of two-level atoms with these cavities and a couple of other auxiliary ones is shown to lead to a contradiction with the criterion of locality.

Chris Erven, Evan Meyer-Scott, Kent Bonsma-Fisher +13 more

Chiara Vitelli, Nicolò Spagnolo, Fabio Sciarrino +8 more

A Bell test is performed on a Micro‐Macroscopic photon system obtained by parametric amplification of a spin‐1 entangled photon state. The optical parametric amplification leads to the creation of a Micro‐Macroscopic entangled system consisting of N≃3.5×104. The performed Bell’s inequality non locality test involves the adoption of a positive operator valued measurement (POVM) strategy for a sharper identification of the amplified states. This is obtained through a local filtering technique and the experimental data are found to violate the Bell’s inequality albeit with a loophole similar to the detection efficiency one in photon counting experiments.

Dipankar Home, G. S. Agarwal

Tanumoy Pramanik, Satyabrata Adhikari, A. S. Majumdar +1 more

Morteza Moradi, Juan Camilo López Carreño, Adam Buraczewski +4 more

Abstract Optical hybrid entanglement can be created between two qubits, one encoded in a single photon and another one in coherent states with opposite phases. It opens the path to a variety of quantum technologies, such as heterogeneous quantum networks, merging continuous- and discrete-variable encoding, and enabling the transport and interconversion of information. However, reliable characterization of the non-local nature of this quantum state is limited so far to full quantum state tomography. Here, we perform a thorough study of Clauser–Horne–Shimony–Holt Bell inequality tests, enabling practical verification of quantum nonlocality for optical hybrid entanglement. We show that a practical violation of this inequality is possible with simple photon number on/off measurements if detection efficiencies stay above 82%. Another approach, based on photon-number parity measurements, requires 94% efficiency but works well in the limit of higher photon populations. Both tests use no postselection of the measurement outcomes and they are free of the fair-sampling hypothesis. Our proposal paves the way to performing loophole-free tests using feasible experimental tasks such as coherent state interference and photon counting.