Performance of a quantum key distribution protocol with dual-rail displaced photon states

We propose a scheme for a quantum key distribution (QKD) protocol with dual-rail displaced photon states. Displaced single-photon states with different amplitudes carry bit values of code that may be extracted, while coherent states carry nothing and only provide an inconclusive outcome. A real resource of single photons is used, involving imperfections associated with experimental technique that result in a photon state with an admixture of the vacuum state. The protocol is robust against the loss of a single photon and the inefficiency of the detectors. Pulses with large amplitudes, unlike the conventional QKD relying on faint laser pulses, are used that may approximate it to standard telecommunication and may show resistance to eaves-dropping even in settings with high attenuation. Information leakage to the eavesdropper is determined from comparison of the output distributions of the outcomes with ideal ones that are defined by two additional parameters accessible to only those send the pulses. Robustness to some possible eavesdropping attacks is shown.