Stabilization of Phase and Polarization in Multiplexed Entangled States Through Multi-Channel Optical Fibre Arrays

The second quantum revolution has driven rapid advancements in quantum technologies, particularly in quantum communication and computing, where the manipulation and distribution of quantum entanglement are crucial. Prior studies have explored entanglement distribution via multi-core fibres (MCF), which allow space-division multiplexing (SDM) and spatial information encoding. Particularly, in [1], polarization-entangled photon pairs from a spontaneous parametric down-conversion (SPDC)-based entangled photon source (EPS) were transmitted through opposite cores of a MCF. However, the ring-shaped intensity of the source output led to non-optimal core overlap, achieving coupling efficiencies below 1%. In this work, we focus on enhancing the coupling efficiency of 810 nm polarization-entangled photons into the six internal cores of a 19-core MCF designed for this wavelength. We achieve this by shaping the SPDC ring into Gaussian modes with a phase-only liquid crystal on Silicon (LCoS) spatial light modulator (SLM). The phase mask in Fig. 1(a) is used in the configuration shown in Fig. 1(b).