Quantum receiver for quadrature phase-shift keying at the single photon level
Jasminder S. Sidhu, Shuro Izumi, Jonas Schou Neergaard-Nielsen, Cosmo Lupo, Ulrik L. Andersen · arXiv (Cornell University) · 2020
Quantum enhanced receivers are endowed with resources to achieve higher sensitivities than conventional technologies. For application in optical communications, they provide improved discriminatory capabilities for multiple non-orthogonal quantum states. In this work, we propose and experimentally demonstrate a new decoding scheme for quadrature phase-shift encoded signals. Our receiver surpasses the standard quantum limit and outperforms all previously known non-adaptive detectors at low input powers. Unlike existing approaches, our receiver only exploits auxiliary coherent-state fields, linear optics, and on-off photo-detection. This circumvents the requirement for challenging feed-forward operations that limit communication transmission rates and can be readily implemented with current technology.