Quantum receiver for large alphabet communication

Abstract

Quantum mechanics allows measurements that surpass the fundamental\nsensitivity limits of classical methods. To benefit from the quantum advantage\nin a practical setting, the receiver should use communication channels\nresources optimally; this can be done employing large communication alphabets.\nHere we show the fundamental sensitivity potential of a quantum receiver for\ncoherent communication with frequency shift keying. We introduce an adaptive\nquantum protocol for this receiver, show that its sensitivity outperforms other\nreceivers for alphabet sizes above 4 and scales favorably, whereas quantum\nreceivers explored to date suffer from degraded sensitivity with the alphabet\nsize. In addition, we show that the quantum measurement advantage allows the\nmuch better use of the frequency space in comparison to classical frequency\nkeying protocols and orthogonal frequency division multiplexing.\n