Single-photon characteristics of superposed weak coherent states

TL;DR

This paper investigates a superposed weak coherent state that mimics an ideal single photon, demonstrating its quantum properties and potential advantages in quantum key distribution over traditional methods.

Contribution

It introduces a superposed weak coherent state that closely resembles a single photon in photon number and phase, and applies it to enhance quantum key distribution.

Findings

Exhibits antibunching and Hong-Ou-Mandel interference.

Shows high fidelity to single-photon states.

Outperforms phase-randomized weak coherent states in QKD.

Abstract

We study a superposed weak coherent state that can fundamentally mimic an ideal single photon not only with respect to the number of photons but also in terms of an indeterminate phase. It is close to the single-photon state with high fidelity and exhibits fundamental features of single photons such as antibunching and Hong-Ou-Mandel interference. The emergence and vanishing of single-photon characteristics can be directly observed by changing two parameters, i.e., the mean photon number and number of phases. Our result shows that the uncertainty between the photon number and phase indeed constitutes the characteristics of single photons. Finally, we apply the superposed weak coherent state to quantum key distribution and demonstrate that it outperforms the typical approach using phase-randomized weak coherent states.