System and method for generating heralded single photon

Patent metadata

Field	Value
Publication number	US-11630373-B2
Application number	US-202017260241-A
Country	US
Kind code	B2
Filing date	Aug 19, 2020
Priority date	Sep 5, 2019
Publication date	Apr 18, 2023
Grant date	Apr 18, 2023

Abstract

It discloses a system and a method for generating heralded single photons, wherein the system comprises a high-quality optical ring cavity, a PPKTP nonlinear crystal, a polarization beam splitter, a dichroic mirror, a light filtering device, a reflector module, an atomic vapor cell and a single photon detector, wherein: the high-quality optical ring cavity is formed by a first plano-concave reflector, a second plano-concave reflector, a third plano-concave reflector and a fourth plano-concave reflector; the PPKTP nonlinear crystal and the polarization beam splitter are positioned in an optical path between the first plano-concave reflector and the second plano-concave reflector; the dichroic mirror is positioned in an optical path behind a reflecting end of the polarization beam splitter.

First claim

What is claimed is:

1. A system for generating heralded single photons, comprising: a high-quality optical ring cavity, a PPKTP nonlinear crystal, a polarization beam splitter, a dichroic mirror, a light filtering device, a reflector module, an atomic vapor cell and a single photon detector, wherein: the high-quality optical ring cavity is formed by a first plano-concave reflector, a second plano-concave reflector, a third plano-concave reflector and a fourth plano-concave reflector; the PPKTP nonlinear crystal and the polarization beam splitter are positioned in an optical path between the first plano-concave reflector and the second plano-concave reflector; the dichroic mirror, the light filtering device and the single photon detector are sequentially positioned in an optical path behind the second plano-concave reflector; the atomic vapor cell is positioned in an optical path between the third plano-concave reflector and the fourth plano-concave reflector; the reflector module is used to reflect a control light and comprises a first reflector and a second reflector; an axis formed by the first reflector and the second reflector is kept at an angle of 3-5 degrees to an axis formed by the atomic vapor cell and the high-quality optical ring cavity, and the reflected control light is allowed to pass through the atomic vapor cell.

2. The system for generating heralded single photons according to claim 1 , wherein: a pump light is incident into a plane of the first plano-concave reflector; concave surfaces and planes of the first plano-concave reflector and the second plano-concave reflector are each coated with a pump light anti-reflection film; concave surfaces of the first plano-concave reflector, the second plano-concave reflector, the third plano-concave reflector and the fourth plano-concave reflector are each coated with a parametric light reflective film, and planes thereof are each coated with a parametric light anti-reflection film; reflectivity values of the parametric light reflective films coated on the concave surfaces of the first plano-concave reflector, the third plano-concave reflector and the fourth plano-concave reflector are the same and greater than that of the parametric light reflective film coated on the concave surface of the second plano-concave reflector.

3. The system for generating heralded single photons according to claim 1 , wherein: the PPKTP nonlinear crystal is used to generate a pair of polarization orthogonal parametric lights, i.e., an idle light and a signal light, and both front and rear end faces of the PPKTP nonlinear crystal are coated with pump light and parametric light anti-reflection films.

4. The system for generating heralded single photons according to claim 1 , wherein the PPKTP nonlinear crystal is specifically a type II quasi-phase-matched PPKTP nonlinear crystal with a domain-periodic inversion structure.

5. The system for generating heralded single photons according to claim 1 , wherein the polarization beam splitter reflects a signal light and transmits an idle light and a pump light, and both front and rear end faces of the polarization beam splitter are coated with pump light and parametric light anti-reflection films.

6. The system for generating heralded single photons according to claim 1 , wherein the dichroic mirror reflects a pump light and transmits an idle light, and front and rear end faces of the dichroic mirror are each coated with an idle light anti-reflection film.

7. The system for generating heralded single photons according to claim 1 , wherein the light filtering device is used to filter out the control light scattered into an idle light.

8. The system for generating heralded single photons according to claim 1 , wherein the atomic vapor cell is specifically N energy level atomic vapor cell.

9. A method for generating heralded single photons, comprising:
step 1: forming an optical ring cavity by a first plano-concave reflector, a second plano-concave reflector, a third plano-concave reflector and a fourth plano-concave reflector;
step 2: enabling normal incidence of a pump pulsed light through a plane of the first plano-concave reflector;
step 3: providing a PPKTP nonlinear crystal behind the first plano-concave reflector, such that the incident pump light, when passing through the PPKTP nonlinear crystal, generates a spontaneous parametric down-conversion process to control pump light intensity and pulse length, and a pair of polarization orthogonal parametric photons, i.e., an idle photon and a signal photon, are generated with a probability close to 1;
step 4: providing a polarization beam splitter behind the PPKTP nonlinear crystal, wherein the polarization beam splitter reflects a vertically polarized signal light in the parametric light emitted by the PPKTP nonlinear crystal and transmits a horizontally polarized idle light therein;
step 5: allowing the second plano-concave reflector to transmit the pump light having passed through the PPKTP nonlinear crystal and the polarization beam splitter successively, and reflect the idle light transmitted by the polarization beam splitter back to the first plano-concave reflector via the third plano-concave reflector and the fourth plano-concave reflector, so as to form a stable cavity mode, wherein the idle light cavity mode is transmitted through the second plano-concave reflector and detected by a single photon detector after passing through a dichroic mirror and a light filtering device;
step 6: providing an atomic vapor cell in an optical path of the idle light between the third plano-concave reflector and the fourth plano-concave reflector, and allowing the control light to pass through the atomic vapor cell by reflecting with a reflector module to induce a strong self-Kerr nonlinear optical effect of the idle light, wherein the reflector module comprises a first reflector and a second reflector, and an axis formed by the first reflector and the second reflector is kept at an angle of 3-5 degrees to an axis formed by the atomic vapor cell and the high-quality optical ring cavity;
step 7: providing the dichroic mirror behind the second plano-concave reflector, wherein the dichroic mirror reflects the pump light and transmits the idle light;
step 8: providing the light filtering device behind the dichroic mirror, wherein the light filtering device filters out the control light scattered into the idle light; and
step 9: providing a single photon detector behind the light filtering device, wherein the single photon detector, on the premise of triggering a signal light, is used to measure idle light photons, and obtain heralded signal single photons if the measurement succeeds.

Assignees

• Nanjing University Of Technology

Inventors

• Xia Keyu
• Wu Yang
• Zhang Han

Classifications

• G02F1/3553 Primary

  having the formula MTiOYO4, where M=K, Rb, TI, NH4 or Cs and Y=P or As, e.g. KTP · CPC title

• G02F1/3503 Primary

  Structural association of optical elements, e.g. lenses, with the non-linear optical device · CPC title

• G02F1/3511 Primary

  Self-focusing or self-trapping of light; Light-induced birefringence; Induced optical Kerr-effect · CPC title