Patent ID: 7457548

Claim:
An optical transmitter, comprising: a quantum state generator having one light source as an exciting source; a modulator that superimposes a signal on a quantum state that is outputted from the quantum state generator to provide a signal light; a polarization controller for the signal light that is outputted from the modulator; an optical delay unit that adjusts an optical path length of a reference light which is a non-quantum light that is emitted from the quantum state generator; a polarization controller for the reference light; and a polarizing beam coupler that couples the signal light and the reference light whose polarizations are orthogonal to each other where the signal light and the reference light are spatially and temporally superimposed on each other, wherein the quantum state generator comprises a polarizing beam coupler, a first Faraday rotator, a means for delaying the two orthogonal components of polarized light, an optical path including an optical fiber and a second Faraday rotator, and a high-reflection mirror, and after a linearly polarized light is inputted to the polarizing beam coupler and an output light from the polarizing beam coupler is propagated in the optical path, the output light is returned to the identical optical path by the high-reflection mirror and propagated backward, and then the output light is returned to the polarizing beam coupler, and the linearly polarized light that is initially inputted and a squeezed light that is generated by light propagation in the series of optical paths are separated and extracted.