Tunable polarization-entangled near-infrared photons from orthogonal GaAs nanowires

Quantum entanglement is a fundamental resource for emerging quantum technologies, enabling secure communication and enhanced sensing. For decades, generating polarization entangled states has been mainly achieved using bulk crystals with spontaneous parametric down conversion (SPDC), preventing scalability and on-chip integration. Miniaturizing the quantum source provides access to more versatility and tunability while enabling an easier integration to other devices, notably necessary for satellite-based quantum communication, and eventually reducing fabrication costs. This challenging task can be achieved with Zinc Blende GaAs nanowires. They already have shown an efficient photon pairs generation via SPDC at 1550 nm. Here we demonstrate that a pair of orthogonal GaAs nanowires constitutes a new nanoscale platform to control the quantum state at telecommunication wavelength, enabling a transition from polarization entangled to separable states as a function of the pump polarization, with fidelities reaching 90%