Fig. 2: Experimental apparatus.
From: Experimental violation of n-locality in a star quantum network
a Four independent polarization-entangled photon pair sources and five measurement stations are available for the experimental realization of violation of the chained n-locality inequality (7) in a star-network configuration. b Physical location of the laboratories and scheme of the experimental apparatus. Distinct laboratories contain one source and one measurement station each, with the exception of Lab. 1, which also contains the central node B of the star-network on a separate optical table. c The entangled photon sources Λ1, Λ3, and Λ4 are realized using a Beta-Barium Borate (BBO) crystal, pumped in a pulsed regime, which emits photon pairs at 785 nm using spontaneous parametric down-conversion (SPDC) of type II. The source Λ2 instead is pumped in continuous-wave regime and employs a periodically poled KTP crystal placed inside a Sagnac interferometer to generate entangled photon pairs at 808 nm via a type II SPDC process. Single photons are then measured in polarization using a half-wave plate (HWP) followed by a polarizing beam splitter (PBS).
