  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.
