Quantum optical transmission device and quantum optical generator device therefor
View Patent ↗A squeezed light generator comprises an arbitrary optical fiber, a means for temporally separating two linearly polarized components, two Faraday rotators and a high-reflection mirror. Pulse lights that are temporally separated into two orthogonally polarized components at an intensity ratio of 50:50 are reciprocatively propagated in the optical fiber, and the polarized light is rotated by 90° in an outward transmission. Since those two polarized components pass through the optical paths which are accurately equal to each other in the outward and homeward transmissions, those two polarized components interfere with each other accurately at 50:50 after reciprocation through the fiber. The interfered beam is separated by a polarizing beam splitter that is high in an extinction ratio. When the polarized lights before inputting the fiber and after reciprocating coincide with each other, it is unnecessary to maintain the polarization in the fiber propagation, and an arbitrary fiber can be used.
1. 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.
2. The optical transmitter according to claim 1 , wherein the optical path has a λ/2 waveplate disposed at the post- or pre-stage of the first Faraday rotator.
3. The optical transmitter according to claim 1 , wherein the means for delaying the two orthogonal components of polarized light, which constitutes the optical paths, comprises a polarization maintaining optical fiber.
4. The optical transmitter according to claim 1 , wherein the means for delaying the two orthogonal components of polarized light, which constitutes the optical paths, comprises a polarization maintaining optical fiber, and the polarization maintaining optical fiber is spliced with the optical fiber.
5. The optical transmitter according to claim 1 , wherein the means for delaying the two orthogonal components of polarized light, which constitutes the optical paths, comprises two polarizing beam splitters, a first polarizing beam splitter separates the optical path into two optical paths, a delay is given the two optical paths, and polarized beams are re-coupled by a second polarizing beam splitter.
6. An optical transmitter wherein, in the quantum state generator according to claim 1 , the first Faraday rotator and the means for delaying the two orthogonal components of polarized light are omitted, and the optical fiber and the second Faraday rotator are replaced by a polarization maintaining waveguide and a λ/4 waveplate, respectively, and the quantum state generator comprises an optical path including the polarizing beam coupler, the polarization maintaining waveguide, and the λ/4 waveplate, and a high-reflection mirror, and
after 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 the squeezed light that is generated by light propagation in the series of optical paths are separated and extracted.
7. The optical transmitter according to claim 6 , wherein the optical path has a λ/2 waveplate at a pre-stage of the waveguide.
8. The optical transmitter according to claim 6 , wherein the waveguide comprises a planar lightwave circuit (PLC).
9. The optical transmitter according to claim 6 , wherein the λ/4 waveplate comprises a fiber-type device functioning a λ/4 waveplate.
10. An optical transmitter/receiver system, comprising:
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;
an optical fiber that transmits a signal transmitted from the optical transmitter; and
an optical receiver that detects, with the transmitted reference light, the transmitted quantum light that has been modulated by a transmission signal, and that reproduces the transmission signal from the detection signal, 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.
11. The optical transmitter/receiver system according to claim 10 , wherein the optical path has a λ/2 waveplate is disposed at a post- or pre-stage of the first Faraday rotator.
12. The optical transmitter/receiver system according to claim 10 , wherein the means for delaying the two orthogonal components of polarized light, which constitutes the optical paths, comprises a polarization maintaining optical fiber.
13. The optical transmitter/receiver system according to claim 10 , wherein the means for delaying the two orthogonal components of polarized light, which constitutes the optical paths, comprises a polarization maintaining optical fiber, and the polarization maintaining optical fiber is spliced with the optical fiber.
14. The optical transmitter/receiver system according to claim 10 , wherein the means for delaying the two orthogonal components of polarized light, which constitutes the optical paths, comprises two polarizing beam splitters, a first polarizing beam splitter separates the optical path into two optical paths, a delay is given the two optical paths, and polarized beams are re-coupled by a second polarizing beam splitter.
15. An optical transmitter/receiver system, wherein, in the quantum state generator according to claim 10 , the first Faraday rotator and the means for delaying the two orthogonal components of polarized light are omitted, and the optical fiber and the second Faraday rotator are replaced by a polarization maintaining waveguide and a λ/4 waveplate, respectively, and the quantum state generator comprises an optical path including the polarizing beam coupler, the polarization maintaining waveguide, and the λ/4 waveplate, and a high-reflection mirror, and
after 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 the squeezed light that is generated by light propagation in the series of optical paths are separated and extracted.
16. A quantum optical generator comprising:
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, wherein
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.
17. The quantum optical generator according to claim 16 , wherein a λ/2 waveplate is disposed at a post- or pre-stage of the first Faraday rotator.
18. The quantum optical generator according to claim 16 , wherein the means for delaying the two orthogonal components of polarized light comprises a polarization maintaining optical fiber.
19. The quantum optical generator according to claim 16 , wherein the means for delaying the two orthogonal components of polarized light comprises a polarization maintaining optical fiber, and the polarization maintaining optical fiber is spliced with the optical fiber of a post stage.
20. The quantum optical generator according to claim 16 , wherein the means for delaying the two orthogonal components of polarized light comprises two polarizing beam splitters, a first polarizing beam splitter separates the optical path into two optical paths, a delay is given the two optical paths, and polarized beams are re-coupled by a second polarizing beam splitter.