Practical four-dimensional quantum key distribution without entanglement
W. T. Buttler, S. K. Lamoreaux, Justin R. Torgerson · Quantum Information and Computation · 2012
We describe a four-dimensional ($\mathcal{D} = 4$) single-photon quantum cryptography protocol with up to twenty ($\mathcal{D} \times (2^2 + 1)$) possible states generated by a polarization-, phase- and time-encoding transmitter. This protocol can be experimentally realized with existing technology, drawing from time- and polarization-encoded systems. The protocol is error tolerant and has a maximum raw bit rate of two raw bits per detection, which when combined with state detection efficiency yields a qubit rate of up to one per transmission under ideal assumptions, or up to twice the raw bit rate of two-dimensional protocols such as the well-known BB84 protocol.