Large-Alphabet Encoding Schemes for Floodlight Quantum Key Distribution

Floodlight quantum key distribution (FL-QKD) uses binary phase-shift keying (BPSK) of multiple optical modes to achieve Gbps secret-key rates (SKRs) at metropolitan-area distances. We show that FL-QKD's SKR can be doubled by using 32-ary PSK.Comment: 2 pages, 2 figure

Squeezing-enhanced phase-shift-keyed binary communication in noisy channels

We address binary phase-shift-keyed communication channels based on Gaussian states and prove that squeezing improves state discrimination at fixed energy of the channel, also in the presence of phase diffusion. We then assess performances of homodyne detection against the ultimate quantum limits to discrimination, and show that homodyning achieves optimality in large noise regime. Finally, we consider noise in the preparation of the seed signal (before phase encoding) and show that also in this case squeezing may improve state discrimination in realistic conditions.Comment: 6 pages, 5 figure

Programming the Kennedy Receiver for Capacity Maximization versus Minimizing One-shot Error Probability

We find the capacity attained by the Kennedy receiver for coherent-state BPSK when the symbol prior p and pre-detection displacement are optimized. The optimal displacement is different than what minimizes error probability for single-shot BPSK state discrimination.Comment: Updating email address format for this replacement submissio