Patent ID: 9722784
Date: 2017-08-01
CPC Classifications: H04L

Claim:
1. A quantum cryptographic key distribution system comprising: an optical source configured to generate a plurality of optical pulses; a first optical beam splitter having a first, a second, a third and a fourth port and configured to generate, starting from each optical pulse, a first and a second optical sub-pulse, respectively on the third and fourth ports; a first and a second peripheral devices; and an optical path that optically couples the first and second peripheral devices to each other through the first optical beam splitter, said optical path having a first and a second end which are respectively connected to the third and fourth ports of the first optical beam splitter, said optical path extending through the first and second peripheral devices and also being configured to be traversed in a first and a second direction between the first and second peripheral devices through the first optical beam splitter, respectively by the first and second optical sub-pulses, said first and second directions being opposite to one another, so that the first and second optical sub-pulses respectively impinge on the fourth and third ports of the first optical beam splitter through the optical path; wherein the first peripheral device is configured to randomly phase shift the second optical sub-pulse by a first phase, and the second peripheral device is configured to randomly phase shift the first optical sub-pulse by a second phase; and wherein, in use, the first and second optical sub-pulses impinge concurrently on the first optical beam splitter, thereby causing interference in the first optical beam splitter between the first and second optical sub-pulses, said interference generating an optical signal in a deterministic manner on the first or the second port of the first optical beam splitter, or in an non-deterministic manner, as a function of a relation between the first and second phases; and wherein each of the first and second peripheral devices is configured to generate a cryptographic key on the basis of whether said optical signal, when generated in a deterministic manner, is generated on the first or the second port of the first optical beam splitter.