We describe a quantum cryptography protocol with up to twenty four-dimensional (D=4) states generated by a polarization-, phase- and time-encoding transmitter. This protocol can be experimentally realized with existing technology, drawing from time-encoded and polarization-encoded systems. The protocol is error tolerant and has a quantum bit-rate of 2 per transmission/detection, which when combined with state detection efficiency yields a qubit efficiency of up to 1 or double that of BB84-{\it like} protocols.
@article{arxiv.1003.0484,
title = {Quantum dense coding without entanglement},
author = {W. T. Buttler and S. K. Lamoreaux and J. R. Torgerson},
journal= {arXiv preprint arXiv:1003.0484},
year = {2010}
}
Comments
New title, 6 pages, 3 figures. Submitted to PRL: 12/23/09. Includes PRL response. Possible it will not be published in PRL; PRA next likely. Nominally related to arXiv:0808.0686, but uniquely different. Tell us (buttler@lanl.gov) if you find an error.