Realization of four-state qudits using biphotons
arXiv:quant-ph/0601091
Abstract
The novel experimental realization of four-level optical quantum systems (ququarts) is presented. We exploit the polarization properties of frequency non-degenerate biphoton field to obtain such systems. A simple method that does not rely on interferometer is used to generate and measure the sequence of states that can be used in quantum key distribution (QKD) protocol.
4 pages, 3 figures