Rydberg Atomic Receiver for Quantum-Enhanced Underwater Wireless Optical Communications

Abstract

This paper introduces the first Rydberg atomic quantum receiver (RAQR) for underwater wireless optical communications (UWOC). Unlike conventional RF-oriented Rydberg receivers, the proposed architecture exploits direct optical excitation of an atomic transition, enabling a compact threelevel configuration in which the received optical signal and an internally generated local oscillator jointly form the coupling field. The proposed receiver eliminates the dedicated coupling laser required by conventional four-level architectures while providing intrinsic spectral selectivity and strong rejection of ambient optical interference. A comprehensive analytical framework incorporating underwater attenuation, turbulence-induced fading, pointing errors, and angle-of-arrival interruptions is developed. Closed-form expressions for the outage probability, ergodic capacity, and bit error rate are derived, together with a quantum-advantage condition relative to a classical silicon photomultiplier (SiPM) receiver. Numerical results using experimentally demonstrated cesium parameters and representative oceanic channels demonstrate significant SNR and capacity gains over conventional direct-detection UWOC receivers, particularly under severe attenuation.