Programmable photonic processing

• US 10,619,993 B2
• Filed: 06/06/2019
• Issued: 04/14/2020
• 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, Steinbrecher, Greg
• Primary Examiner(s): Pak, Sung H
• Application Number:
  US16/433,649
• Publication Number:
  US 20190310070A1
• Time in Patent Office: 313 Days
• 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 a linear 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 linear optical transformation;

a plurality of output detectors, fabricated in the semiconductor substrate in optical communication with the plurality of output waveguides, the plurality of output detectors comprising at least one output detector in optical communication with a first output waveguide of at least one of the interconnected variable beam splitters and configured to measure an optical power of light present in the first output waveguide; and

control circuitry, operably coupled to the plurality of interconnected variable beam splitters to control the plurality of interconnected variable beam splitters.

2. The photonic device of claim 1, wherein the control circuitry is configured to calibrate the plurality of interconnected variable beam splitters by:

preparing a first known optical power distribution at the plurality of input waveguides;

controlling settings of a first layer of variable beam splitters of the plurality of interconnected variable beam splitters; and

determining, using the at least one output detector to detect light from the first known optical power distribution, a first set of matrix values as a function of the settings of the first layer of variable beam splitters.

3. The photonic device of claim 2, wherein the control circuitry is further configured to calibrate the plurality of interconnected variable beam splitters by:

preparing a second known optical power distribution at the plurality of input waveguides of a second layer of variable beam splitters of the plurality of interconnected variable beam splitters based on the first set of matrix values; and

determining, using the at least one output detector to detect light from the second known optical power distribution, a second set of matrix values as a function of the settings of the second layer of variable beam splitters.

4. The photonic device of claim 2, wherein the control circuitry is further configured to calibrate the plurality of interconnected variable beam splitters by:

iteratively preparing a subsequent known optical power distribution at the input waveguides of a subsequent layer of variable beam splitters of the plurality of interconnected variable beam splitters based on previously determined sets of matrix values; and

iteratively determining, using the at least one output detector to detect light from the subsequent known optical power distribution, a subsequent set of matrix values as a function of the settings of the subsequent layer of variable beam splitters.

5. The photonic device of claim 1, wherein the control circuitry is configured to calibrate the plurality of interconnected variable beam splitters by:

modulating at least one interconnected variable beam splitter in the plurality of interconnected variable beam splitters at a known frequency; and

determining an identity of the at least one variable beam splitter based on detection signals from at least output detector of the plurality of output detectors,

wherein the control circuitry is further configured to determine a control setting of the at least one variable beam splitter based on the identity of the at least one interconnected variable beam splitter.

6. The photonic device of claim 1, where in the control circuitry is configured to calibrate the plurality of interconnected variable beam splitters by:

inserting a known optical signal into a single input waveguide of the plurality of input waveguides; and

determining identities of a subset of the plurality of output detectors that receive a portion of the known optical signal,

wherein the control circuitry is further configured to determine a control setting of at least one variable beam splitter of the plurality of interconnected variable beam splitters based on the determined identities.

7. The photonic device of claim 6, wherein the control circuitry is further configured to calibrate the plurality of interconnected variable beam splitters by:

modulating at least one interconnected variable beam splitter of the plurality of interconnected variable beam splitters at a known frequency; and

determining an identity of the at least one interconnected variable beam splitter based on detection signals from at least output detector of the plurality of output detectors,

wherein the control circuitry is further configured to determine a control setting of the at least one interconnected variable beam splitter based on the identity of the at least one interconnected variable beam splitter.

8. The photonic device of claim 1, wherein at least one interconnected variable beam splitter of the plurality of interconnected variable beam splitters is configured to mix modes of light with different polarizations, different frequencies and/or different temporal locations.

9. The photonic device of claim 1, wherein the plurality of output waveguides is configured to emit light into free space.

10. The photonic device of claim 9, wherein the control circuitry, is configured to implement the linear optical transformation for use in a phased array.

11. The photonic device of claim 1, further comprising a plurality of temperature sensors configured to measure temperatures at different location of the photonic device.

12. The photonic device of claim 1, wherein the linear optical transformation comprises mode-crossings, identity transformations, and/or mode mixing.

13. The photonic device of claim 1, wherein at least one interconnected variable beam splitter of the plurality of interconnected variable beam splitters comprises an electro-mechanical device.

14. The photonic device of claim 1, further comprising at least one light source fabricated in the semiconductor substrate and in optical communication with the plurality of input waveguides.

15. The photonic device of claim 1, further comprising a plurality of transistors fabricated in the semiconductor substrate.

16. The photonic device of claim 1, wherein the at least one optical mode is coupled to at least one vacuum mode using the plurality of interconnected variable beam splitters.

17. The photonic device of claim 1, further comprising a plurality of optical nonlinearity elements fabricated in the semiconductor substrate, wherein each of the plurality of optical nonlinearity elements is coupled to at least one corresponding interconnected variable beam splitter of the plurality of interconnected variable beam splitters.

18. The photonic device of claim 1 wherein at least one of the output detectors is switchable.

19. The photonic device of claim 1 wherein at least one of the plurality of input waveguides and plurality of output waveguides is formed in the semiconductor substrate.

20. A photonic device comprising:

a semiconductor substrate;

a plurality of interconnected variable beam splitters, fabricated in the semiconductor substrate, configured to perform a linear 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 linear optical transformation;

a plurality of integrated output detectors, fabricated in the semiconductor substrate, in optical communication with the plurality of output waveguides;

at least one output detector in optical communication with a first output waveguide of at least one of the variable beam splitters of the interconnected beam splitters and configured to measure an optical power of light present in the first output waveguide; and

control circuitry configured to implement an optimization process to determine settings of the plurality of interconnected variable beam splitters to implement the linear optical transformation.

21. The photonic device of claim 20, wherein a number of interconnected variable beam splitters in the plurality of interconnected variable beam splitters is larger than a minimum number of variable beam splitters needed to implement the linear optical transformation, and including the larger number of interconnected variable beam splitters in the optimization process increases the fidelity of the linear optical transformation relative to including only the minimum number of interconnected variable beam splitters in the optimization process.

22. A photonic device comprising:

a semiconductor substrate;

a plurality of interconnected variable beam splitters, fabricated in the semiconductor substrate, configured to perform a linear 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 linear 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 linear optical transformation; and

a plurality of switches, each switch of the plurality of switches positioned at a corresponding output waveguide of the plurality of output waveguides, configured to switch light from the output waveguides between the plurality of detectors and the plurality of input waveguides.

23. The photonic device of claim 22, further comprising a plurality of modulators, each modulator of the plurality of modulators positioned at a corresponding input waveguide of the plurality of input waveguides, configured to modulate light received by the plurality of input waveguides.