Abstract

Free-space optical links promise vastly higher communication rates compared to radio or microwave spectrum standards. However, the prohibitive cost of large-aperture telescopes or adaptive optics systems limits the collected fraction of the signal, especially for ultra-long haul links operated in the power-limited regime. Instead, the approach of coherent beam combination can be used to utilize light collected by several apertures to yield a stronger signal [1]. However, when the power received at a single aperture approaches the few-photon level, the quantum optical shot noise inherent to the photodetection process may limit the efficiency of such a technique [2,3].

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