Single photon generator and single-photon generating method

Patent metadata

Field	Value
Publication number	US-9488897-B2
Application number	US-201514938308-A
Country	US
Kind code	B2
Filing date	Nov 11, 2015
Priority date	Dec 22, 2014
Publication date	Nov 8, 2016
Grant date	Nov 8, 2016

Abstract

The invention relates to a single-photon generator and a single-photon generating method, which theoretically makes it possible to precisely generate a single photon in real time. A three-level lambda system is formed of a coupled quantum dots group, which is a set of a number of coupled quantum dots where a couple of quantum dots having different ground quantum levels are coupled. The entirety is made in an exciton ground state through illumination with first excitation light. Then, the number of photons in the Raman scattering light through illumination with second excitation light is detected, and a single excited Dicke state is achieved. After that, a single photon is generated accompanying the transition from the single excited Dicke state to the exciton ground state through illumination with third excitation light.

First claim

What is claimed is:

1. A single-photon generator comprising: a coupled quantum dots group, which is a set of a number of coupled quantum dots made of a coupled pair of quantum dots having different ground quantum levels; a first pumping light illumination means for illuminating the coupled quantum dots group with first excitation light so that a multiple number of coupled quantum dots are made to be in an exciton ground state; a second pumping light illumination means for illuminating the coupled quantum dots group in the exciton ground state with second excitation light so that the coupled quantum dots group is made in the excited Dicke state through Raman scattering; a photon number detection means for detecting the number of photons in the Raman scattering light due to the Raman scattering; a control means for controlling the second pumping light illumination means so that the excited Dicke state becomes a single excited Dicke state using the detection results by the photon number detection means; and a third pumping light illumination means for illuminating the coupled quantum dots group in the single excited Dicke state with third excitation light so that a single photon is generated accompanying the transition of the coupled quantum dots group from the single excited Dicke state to the exciton ground state due to Raman scattering.

2. The single-photon generator according to claim 1 , wherein the second excitation light is a non-resonant laser beam.

3. The single-photon generator according to claim 1 , wherein the coupled quantum dots are linearly aligned along the respective optical axes of the first through third excitation light.

4. The single-photon generator according to claim 1 , wherein the coupled quantum dots in each pair are coupled quantum dots where a quantum dot in the first layer in a Stranski-Krastanov growth mode and a quantum dot in the second layer formed so as to be positionally aligned above the quantum dot in the first layer with a middle layer in between are coupled.

5. The single-photon generator according to claim 1 , wherein the linearly aligned coupled quantum dots group is placed inside an optical waveguide, which is either a mesa type optical waveguide or a photonic crystal optical waveguide.

6. The single-photon generator according to claim 5 , wherein the optical waveguide that includes the linearly aligned coupled quantum dots group is placed inside a Fabry-Perot type resonator.

7. The single-photon generator according to claim 5 , wherein the optical waveguide that includes the linearly aligned coupled quantum dots group is placed inside a ring type resonator.

8. A single-photon generating method, comprising: illuminating a coupled quantum dots group, which is a set of a number of coupled quantum dots where a couple of quantum dots having different ground quantum levels are coupled, with first excitation light so that a multiple number of coupled quantum dots are made in an exciton ground state; illuminating the coupled quantum dots group in the exciton ground state with second excitation light so that the exciton ground state becomes a single excited Dicke state using the detection results by a photon number detection means that detects the number of photons in the Raman scattering light due to Raman scattering; and illuminating the coupled quantum dots group in the single excited Dicke state with third excitation light so that a single photon is generated accompanying the transition of the coupled quantum dots group from the single excited Dicke state to the exciton ground state due to Raman scattering.

9. The single-photon generating method according to claim 8 , wherein three energy states, which are two exciton splitting energy states from among the four energy states of each coupled quantum dot and the higher energy state between the two exciton localized states, are used in the Raman scattering.

10. The single-photon generating method according to claim 8 , wherein the second excitation light is a non-resonant laser beam.

Assignees

• Fujitsu Ltd

Inventors

• Oshima Toshio

Classifications

• G02F1/365 Primary

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• G02F1/3556

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• H04L9/0852

  Quantum cryptography (transmission systems employing electromagnetic waves other than radio waves, e.g. light, infrared H04B10/00; wavelength-division multiplex systems H04J14/02; WDM arrangements H04J14/03) · CPC title

• H04B10/70

  Photonic quantum communication · CPC title