Programmable photonic processing

• US 10,359,272 B2
• Filed: 09/26/2017
• Issued: 07/23/2019
• Est. Priority Date: 06/06/2014
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Mower, Jacob C., Harris, Nicholas C., Englund, Dirk R., Steinbrecher, Greg
• Primary Examiner(s): Pak, Sung H
• Application Number:
  US15/716,196
• Publication Number:
  US 20180274900A1
• Time in Patent Office: 665 Days
• Field of Search: None
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: G01B 9/02049 characterised by particular mechanical design details
• CPC Class Codes: G01B 9/02083 characterised by particular signal processing and presentation
• CPC Class Codes: G06N 10/00 Quantum computing, i.e. information processing based on quantum-mechanical phenomena
• CPC Class Codes: G06N 20/00 Machine learning

Abstract

A programmable photonic integrated circuit implements arbitrary linear optics transformations in the spatial mode basis with high fidelity. Under a realistic fabrication model, we analyze programmed implementations of the CNOT gate, CPHASE gate, iterative phase estimation algorithm, state preparation, and quantum random walks. We find that programmability dramatically improves device tolerance to fabrication imperfections and enables a single device to implement a broad range of both quantum and classical linear optics experiments. Our results suggest that existing fabrication processes are sufficient to build such a device in the silicon photonics platform.

Claims

1. A photonic device comprising:

a semiconductor substrate;

a plurality of interconnected variable beam splitters, fabricated in the semiconductor substrate, configured to perform an arbitrary unitary optical transformation on at least one optical mode, the plurality of interconnected variable beam splitters having a plurality of input waveguides configured to receive the at least one optical mode and a plurality of output waveguides configured to output the at least one optical mode after the arbitrary unitary optical transformation;

a plurality of detectors, in optical communication with the plurality of output waveguides, configured to measure the at least one optical mode after the arbitrary unitary optical transformation; and

control circuitry, operably coupled to the plurality of interconnected variable beam splitters and to the plurality of detectors, configured to determine a density distribution of the at least one optical mode at the plurality of output waveguides and configured to adjust at least one setting of at least one variable beam splitter in the plurality of interconnected variable beam splitters so as to change the density distribution of the at least one optical mode at the plurality of output waveguides.

2. The photonic device of claim 1, wherein the control circuitry is operably coupled to the plurality of detectors and configured to determine a measurement result from the plurality of detectors.

3. The photonic device of claim 2, wherein the control circuitry is further configured to adjust the at least one setting of the at least one variable beam splitter based on the measurement result.

4. The photonic device of claim 1, wherein at least one variable beam splitter of the plurality of interconnected variable beam splitters comprises a Mach-Zehnder interferometer comprising two input arms, two output arms, two intermediary arms, and at least one phase shifter.

5. The photonic device of claim 4, wherein the control circuitry controlling the at least one setting comprises controlling a phase shift of the at least one phase shifter.

6. The photonic device of claim 5, wherein the at least one phase shifter comprises a first phase shifter in one of the two intermediary arms and a second phase shifter in one of the two output arms.

7. The photonic device of claim 6, wherein the controller is configured to adjust a first phase shift of the first phase shifter and adjust a second phase shift of the second phase shifter such that the Mach-Zehnder interferometer implements an arbitrary 2×

2 unitary operation.

8. The photonic device of claim 1, further comprising at least one light source configured to generate the at least one optical mode.

9. The photonic device of claim 8, wherein the at least one light source is fabricated in the semiconductor substrate.

10. The photonic device of claim 8, further comprising a plurality of routing waveguides configured to route the at least one optical mode from the at least one light source to the plurality of input waveguides.

11. The photonic device of claim 8, wherein the at least one light source comprises an off-chip light source.

12. The photonic device of claim 11, further comprising at least one free-space optic and/or at least one optical fiber configured to route the at least one optical mode from the at least one light source to the plurality of input waveguides.

13. The photonic device of claim 8, where the at least one light source comprises a laser.

14. A method of performing optical processing, the method comprising:

(A) coupling at least one optical mode into a plurality of input waveguides of a plurality of interconnected variable beam splitters fabricated in a semiconductor substrate so as to perform an arbitrary unitary optical transformation on the at least one optical mode;

(B) detecting the at least one optical mode at a plurality of output waveguides of the plurality of interconnected variable beam splitters after the arbitrary unitary optical transformation; and

(C) determining a measurement result from (B);

(D) adjusting at least one setting of at least one variable beam splitter in the plurality of interconnected variable beam splitters so as to change the arbitrary unitary optical transformation.

15. The method of claim 14, wherein (D) comprises adjusting the at least one setting of the at least one variable beam splitter based on the measurement result.

16. The method of claim 15, wherein at least one variable beam splitter of the plurality of interconnected variable beam splitter comprises a Mach-Zehnder interferometer comprising two input arms, two output arms, two intermediary arms, and at least one phase shifter.

17. The method of claim 16, wherein (D) comprises adjusting a phase shift of the at least one phase shifter.

18. The method of claim 17, wherein the at least one phase shifter comprises a first phase shifter in one of the two intermediary arms and a second phase shifter in one of the two output arms.

19. The method of claim 18, wherein (D) comprises adjusting a first phase shift of the first phase shifter and adjusting a second phase shift of the second phase shifter such that the Mach-Zehnder interferometer implements an arbitrary 2×

2 unitary operation.

20. The method of claim 14, wherein (A) comprises routing the at least one optical mode from a light source to the plurality of input waveguides using at least one optical component selected from the group consisting of a routing waveguide, a free-space optic, and an optical fiber.