Quantum cryptography based on homodyne detection (vacuum-state cryptosystem)
S. N. Molotkov, S. S. Nazin · Journal of Experimental and Theoretical Physics Letters · 1997
A new protocol is proposed for quantum cryptography. The protocol is based on the use of a set of measurements which make it possible to reconstruct completely the density matrix — the information carrier — of a physical system. Such a protocol can be implemented by means of homodyne detection (well known in quantum optics) of an electromagnetic field. An example is given of a quantum cryptosystem in which the vacuum state of the photon field is used as one of two information states.