Photon source and method of operating a photon source

• US 20030218143A1
• Filed: 03/11/2003
• Published: 11/27/2003
• Est. Priority Date: 03/11/2002
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Shields, Andrew James, Stevenson, Richard Mark
• Granted Patent: US 6,960,779 B2
• Time in Patent Office: Days
• US Class Current: 250/493.1
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: H01L 33/382 the electrode extending partially in or entirely through the semiconductor body
• CPC Class Codes: H01S 5/0424 lateral current injection
• CPC Class Codes: H01S 5/183 having only vertical cavities, e.g. vertical cavity surface-emitting lasers [VCSEL]
• CPC Class Codes: H01S 5/18319 comprising a periodical structure in lateral directions
• CPC Class Codes: H01S 5/18341 Intra-cavity contacts
• CPC Class Codes: H01S 5/3412 quantum box or quantum dash
• CPC Class Codes: H04L 9/0858 Details about key distillation or coding, e.g. reconciliation, error correction, privacy amplification, polarisation coding or phase coding
• CPC Class Codes: Y10S 977/95 Electromagnetic energy

Abstract

A photon source for emitting entangled photons, the source comprising:

at least one quantum dot having a degenerate exciton level; and

exciton creation means to create a biexciton or higher order exciton within the at least one quantum dot.

Claims

1. A photon source for emitting entangled photons, the source comprising:

a photon source body comprising at least one quantum dot having a degenerate exciton level; and

exciton creation means for creating a biexciton or higher order exciton within the at least one quantum dot.

2. The photon source of claim 1, wherein said quantum dot has a nondegenerate exciton level, said source further comprising at least one electrical contact configured to apply an electric field to said photon source and to make said nondegenerate exciton level degenerate.

3. The photon source of claim 2, wherein said at least one quantum dot is provided within a layer and said at least one electrical contact is configured to apply said field within the plane of the layer.

4. The photon source of claim 2, wherein said at least one quantum dot is provided within a layer and said at least one electrical contact is configured to apply said field perpendicular to the plane of the layer.

5. The photon source of claim 2, wherein said at least one electrical contact is configured to tune the applied electric field in any direction within a plane.

6. The photon source of claim 2 comprising 3 pairs of electric contacts, arranged so as to apply the field in any selected direction.

7. The photon source of claim 6, wherein said 3 pairs of electrical contacts are configured to tune the applied electric field in any direction within a three dimensional volume.

8. The photon source of claim 1, wherein said quantum dot has a non-degenerate exciton level, said source further comprising a source of magnetic field configured to apply a magnetic field to said at least one quantum dot to make said non-degenerate exciton level degenerate.

9. The photon source of claim 8, wherein said at least one quantum dot is provided in a quantum dot layer and said source of magnetic field is configured to apply a magnetic field perpendicular to the plane of the said layer.

10. The photon source of claim 9, wherein said source of magnetic field comprises a solenoid, said quantum dot layer being provided within said solenoid and arranged substantially perpendicular to the axis of said solenoid.

11. The photon source of claim 8, wherein said at least one quantum dot is provided in a quantum dot layer and said source of magnetic field is configured to apply a magnetic field parallel to the plane of the layers.

12. The photon source of claim 11, wherein said source of magnetic field comprises a pair of spaced apart solenoids, said quantum dot layer being provided between said solenoids and oriented substantially parallel to the axes of the solenoids.

13. The photon source of claim 8, wherein said first means comprises a conducting or superconducting track provided on or within said photon source body or an electromagnet.

14. The photon source of claim 1, wherein said quantum dot has a non-degenerate exciton level, said source further comprising means to vary the temperature of said photon source to make said non-degenerate exciton level degenerate.

15. The photon source of claim 1, wherein said quantum dot has a non-degenerate exciton level, said source further comprising means to vary pressure applied to said photon source body to make said non-degenerate exciton level degenerate.

16. The photon source of claim 15, wherein the at least one quantum dot is provided in quantum dot layer and said means to vary pressure is configured to apply strain in the plane of the quantum dot layer.

17. The photon source of claim 1, wherein said exciton creation means comprises incident radiation to irradiate said photon source to provide optically excited carriers to said at least one quantum dot.

18. The photon source of claim 1, wherein said exciton means comprises means to electrically inject carriers into said at least one quantum dot.

19. The photon source of claim 1, further comprising a filter configured to filter unwanted emissions from said photon source body.

20. The photon source of claim 19, wherein said filter comprises an optical cavity.

21. The photon source of claim 20, wherein optical confinement in two dimensions is provided by a photonic band gap structure.

22. The photon source of claim 1, further comprising separating means for directing one photon of an entangled photon pair in a first direction and the other photon from the entangled photon pair in a second direction.

23. The photon source of claim 1, wherein said source comprises an optical cavity, configured to emit one photon of an entangled photon pair from said photon source body in a first optical mode and said other photon of the entangled photon pair in a second optical mode.

24. A method of operating a photon source, said photon source comprising at least one quantum dot, the method comprising:

forcing the single exciton energy levels within the quantum dot to form a degenerate single exciton level;

forming a biexciton or higher order exciton within said at least one quantum dot.