We develop and present a quantum cryptography concept in which phase determinations are made from the time that a photon is detected, as opposed to where the photon is detected, and hence is a non-interferometric process. The phase-encoded quantum information is contained in temporal and polarization superpositions of single photon states, forming a complex qudit of Hilbert dimension D equal to or greater than 4. Based on this, we have developed a new quantum key distribution protocol that allows the generation of secret key in the presence of higher noise than is possible with other protocols.
@article{arxiv.0808.0686,
title = {Quantum cryptography with polarization, phase and time encoding},
author = {W. T. Buttler and S. K. Lamoreaux},
journal= {arXiv preprint arXiv:0808.0686},
year = {2008}
}