The A Satellite-to-Ground Quantum Key Distribution Protocol Based on Orbital Angular Momentum of Light

Abstract

The orbital angular momentum (OAM) of light has been considered as a promising degree of freedom (DoF) that gives access to a higher-dimensional Hilbert space, which may lead to potential higher capacity quantum communications. Due to the fragility of the OAM state, the traditional view is that turbulence will make OAM-QKD infeasible in satellite-to-ground channels. However, based on the detailed phase screen simulations of the expected atmospheric turbulence, we find that quantum key distribution (QKD) using OAM of the light is feasible in certain system configurations, especially if quantum channel in-formation is utilized in the processing of post-selected states. Therefore, we propose a satellite-to-ground quantum key distribution protocol based on the orbital angular momentum of the light, which uses the principle that OAM-QKD can only be used in high-altitude ground stations with larger receiver apertures with-out using classic optical probes. At the same time, the classically entangled light is used as a probe of the quantum channel and reasonably-sized transmitter-receiver apertures are also employed. Numerical simulation results show that this protocol can lead to positive secret key rates even under circumstances where a sea-level ground station with a reasonable-sized aperture is used. We also found that quantum channel conjugation enables a key rate advantage provided by the higher dimensions of the protocol to be realized.