Interference system and an interference method

Patent metadata

Field	Value
Publication number	US-9696133-B2
Application number	US-201514824380-A
Country	US
Kind code	B2
Filing date	Aug 12, 2015
Priority date	Aug 14, 2014
Publication date	Jul 4, 2017
Grant date	Jul 4, 2017

Abstract

An interference system, comprising:
an interference apparatus, configured such that input light pulses interfere at an interference component; wherein the input of said interference apparatus is provided by a phase-randomized light source, said phase-randomized light source comprising: at least one slave light source; at least one master light source configured to intermittently generate master light pulses such that the phase of each master light pulse has a random relationship to the phase of each subsequently generated master light pulse, further configured to supply said master light pulses to the slave light source; and a controller, configured to apply a time varying drive signal to said at least one slave light source such that just one slave light pulse is generated during each period of time for which a master light pulse is received, such that the phase of each slave light pulse has a random relationship to the phase of each subsequently generated slave light pulse.

First claim

The invention claimed is:

1. An interference system, comprising:
an interference apparatus, configured such that input light pulses interfere at an interference component;
wherein the input of said interference apparatus is provided by a substantially phase-randomised light source, said substantially phase-randomised light source comprising:
at least one slave light source;
at least one master light source configured to intermittently generate master light pulses such that the phase of each master light pulse has a substantially random relationship to the phase of each subsequently generated master light pulse, further configured to supply said master light pulses to the slave light source; and
a controller, configured to apply a time varying drive signal to said at least one slave light source such that one slave light pulse is generated during each period of time for which a master light pulse is received, such that the phase of each slave light pulse has a substantially random relationship to the phase of each subsequently generated slave light pulse and such that each slave light pulse has a fixed phase relationship to the corresponding master light pulse.

2. The interference system of claim 1 , wherein light pulses generated by the at least one slave light source interfere at the interference component.

3. The interference system of claim 1 , said substantially phase-randomised light source further comprising a nonlinear crystal, configured such that when a slave light pulse is incident on the nonlinear crystal, a signal photon and an idler photon are generated through spontaneous parametric down conversion, wherein the interference system is configured such that signal light pulses interfere at the interference component.

4. The interference system of claim 1 , wherein the master light source and the slave light source are configured to generate a plurality of light pulses.

5. The interference system of claim 1 , wherein said controller is further configured to apply the time varying drive signal to said at least one master light source.

6. The interference system of claim 1 , further comprising a second controller, configured to apply a second time varying drive signal to said at least one master light source, wherein said time varying drive signal and said second time varying drive signal are synchronised.

7. The interference system of claim 1 , wherein said slave light source is a gain-switched laser.

8. The interference system of claim 1 , wherein said master light source is a gain-switched laser.

9. The interference system of claim 1 , wherein the interference apparatus comprises an interferometer, comprising first and second optical paths, wherein there is a difference in optical path length between the first and second optical paths.

10. The interference system of claim 9 , wherein the interference component is an exit beam splitter in the interferometer, and wherein the difference in optical path length corresponds to an integer multiple of the time between emission of a first slave light pulse and emission of a second slave light pulse, such that each slave light pulse interferes with a subsequently generated slave light pulse at the exit of the interferometer.

11. The interference system of claim 1 , wherein said at least one slave light source comprises a first slave light source and a second slave light source and wherein the interference component is a beam splitter configured such that each slave light pulse generated by the first slave light source interferes with a light pulse generated by the second slave light pulse at the beam splitter.

12. The interference system of claim 1 , wherein said substantially phase-randomised light source further comprises a spectral filter.

13. A quantum communication system, comprising the interference system of claim 1 , wherein the interference apparatus comprises;
an interferometer, comprising first and second optical paths, wherein there is a difference in optical path length between the first and second optical paths such that said slave light pulses interfere when exiting the interferometer.

14. The quantum communication system according to claim 13 , wherein the slave light source is in a sending unit and the interference component is in a receiving unit.

15. A quantum communication system, comprising the interference system of claim 1 , wherein said at least one slave light source comprises a first slave light source and a second slave light source; wherein the interference component is a beam splitter and wherein the interference system is configured such that each slave light pulse generated by the first slave light source interferes with a slave light pulse generated by the second slave light source at the beam splitter;
wherein the first slave light source is in a first sending unit, the second slave light source is in a second sending unit and the interference component is in a relay unit.

16. A quantum communication system, comprising the interference system of claim 1 , wherein the interference apparatus comprises;
a first interferometer, comprising first and second optical paths and having a difference in optical path length between the first and second optical paths;
a second interferometer, comprising third and fourth optical paths and having a difference in optical path length between the third and fourth optical paths;
wherein the delay caused by the first interferometer is reversed to the delay caused by the second interferometer such that a light pulse which is separated by the first interferometer recombines when exiting the second interferometer.

17. The quantum communication system according to claim 16 , wherein the first interferometer is in a sending unit and the second interferometer is in a receiving unit.

18. An interference method, comprising;
intermittently supplying master light pulses to a slave light source, wherein the phase of each master light pulse has a substantially random relationship to the phase of each subsequent master light pulse;
applying a time varying drive signal to said slave light source such that one slave light pulse is generated during each period of time for which a master light pulse is received, such that the phase of each slave light pulse has a substantially random relationship to the phase of each subsequently generated slave light pulse and such that each slave light pulse has a fixed phase relationship to the corresponding master light pulse; and
interfering said slave light pulses at an interference component.

19. A quantum communication method, comprising the interference method of claim 18 , further comprising:
encoding information in said slave light pulses; and
sending encoded slave light pulses from a sending unit to a receiving unit comprising an interferometer, comprising first and second optical paths, wherein there is a difference in optical path length between the first and second optical paths such that said slave light pulses interfere when exiting the interferometer.

Assignees

• Toshiba Kk

Inventors

• Yuan Zhiliang
• Lucamarini Marco
• Dynes James
• Frohlich Bernd Matthias
• Shields Andrew James
• Skiba-Szymanska Joanna Krystyna

Classifications

• H04B10/70 Primary

  Photonic quantum communication · CPC title

• H01S5/4006

  Injection locking · CPC title

• G01B9/0201 Primary

  using temporal phase variation · CPC title

• H01S5/06246

  controlling the phase · CPC title

• H01S5/06216

  Pulse modulation or generation · CPC title