Quantum key distribution based on time coding

Summary form only given. An alternative protocol to polarization coding or phase coding is proposed for quantum key distribution. It is based on a time coding technique which is expected to be robust against propagation medium disturbances. The information is coded on one photon pulses of duration T and with a chosen time delay with respect to a time reference. The possible delays are chosen by Alice so that possible pulses may overlap. Bob uses photon counters with a time resolution much better than the pulse duration and he measures the detection time with respect to the reference. He can perform only one measurement which may lead to an ambiguity on the delay evaluation.