Nanophotonic quantum memory

Patent metadata

Field	Value
Publication number	US-12014246-B2
Application number	US-202017623757-A
Country	US
Kind code	B2
Filing date	Jul 16, 2020
Priority date	Jul 17, 2019
Publication date	Jun 18, 2024
Grant date	Jun 18, 2024

Abstract

Systems and methods are disclosed for making a quantum network node. A plurality of scoring function F values are calculated for an array of at least two photonic crystal cavity unit cells, each having a lattice constant a and a hole having a length Hx and a width Hy. A value of a, a value of Hx, and a value of Hy are selected for which a scoring function value is at a maximum. A waveguide region and the array of at least two photonic crystal cavity unit cells based on the selected values are formed on a substrate. At least one ion between a first photonic crystal cavity unit cell and a second photonic crystal cavity unit cell are implanted and annealed into a quantum defect. A coplanar microwave waveguide is formed on the substrate in proximity to the array of at least two photonic crystal cavity unit cells.

First claim

The invention claimed is:

1. A method of making a quantum network node comprising:
calculating a plurality of scoring function F values for an array of at least two photonic crystal cavity unit cells, each photonic crystal cavity unit cell having a lattice constant α and a hole having a length H x and a width H y , wherein the scoring function comprises:
F =min( Q,Q cutoff )/( Q cutoff ×V mode )

wherein Q is a cavity quality factor, Q cutoff is an estimated maximum realizable Q, and V mode is a cavity mode volume;
selecting a value of α, a value of H x , and a value of H y for which the scoring function value meets a scoring function value criteria;
forming, on a substrate, a waveguide region and the array of at least two photonic crystal cavity unit cells based on the selected value a, the selected value H z , and the selected value H y ;
implanting at least one ion between a hole of a first photonic crystal cavity unit cell and a second photonic crystal cavity unit cell;
annealing the at least one implanted ion into at least one quantum defect; and
forming a coplanar microwave waveguide on the substrate configured to be electromagnetically coupled to the array of at least two photonic crystal cavity unit cells.

2. The method of claim 1 , wherein the scoring function value criteria comprises one or more of a maximum scoring function value of the plurality of scoring function F values, a threshold value exceeded by at least one of the plurality of scoring function F values, and a maximum scoring function value of the plurality of scoring function F values after a predetermined number of iterations calculating scoring function F values.

3. The method of claim 1 , further comprising:
tapering an input end of the waveguide region;
connecting the tapered input end of the waveguide region to a tapered optical fiber to optically couple the optical fiber to the array of at least two photonic crystal cavity unit cells.

4. The method of claim 3 , further comprising coupling the tapered optical fiber to at least one probing light source and to at least one single photon detector.

5. The method of claim 1 , wherein the substrate comprises a diamond substrate.

6. The method of claim 5 , wherein the implanted ion is a silicon ion and wherein the at least one quantum defect is a silicon-vacancy color center.

7. The method of claim 1 , wherein Q cutoff is not greater than 5 x 10 5 .

8. The method of claim 1 , further comprising:
forming a mask, after the forming the array of at least two photonic crystal cavity unit cells, on the array of at least two photonic crystal cavity unit cells;
etching, with an ion beam, the substrate, at two or more angles, to form a tapered column between the hole of a first photonic crystal cavity unit cell and the second photonic crystal cavity unit cell.

9. The method of claim 1 , wherein the implanting the at least one ion further comprises:
forming a mask on the array of at least two photonic crystal cavity unit cells;
forming at least one aperture in the mask at a location between the hole of a first photonic crystal cavity unit cell and the second photonic crystal cavity unit cell; and
implanting the at least one ion through the at least one aperture in the mask, wherein ions are not implanted through the mask.

10. The method of claim 1 , further comprising mounting the substrate in a refrigeration unit, wherein the refrigeration unit is configured to cool the substrate to less than 100 mK such that the spin coherence time T 2 of the at least one quantum defect is extended.

11. A quantum network device comprising:
a substrate;
an array of at least two photonic crystal cavity unit cells on the substrate, wherein each photonic crystal cavity unit cell has a lattice constant α and a hole having a length H x and a width H y , wherein a value of α, a value of H x , and a value of H y are selected so that a scoring function F value meets a scoring function value criteria, and wherein the scoring function comprises:
F =min( Q,Q cutoff )/( Q cutoff ×V mode )

wherein Q is a cavity quality factor, Q cutoff is an estimated maximum realizable Q, and V mode is a cavity mode volume;
at least one quantum defect in the substrate between a first photonic crystal cavity unit cell in the array of at least two photonic crystal cavity unit cells and a second photonic crystal cavity unit cell in the array of at least two photonic crystal cavity unit cells; and
a coplanar microwave waveguide disposed on the substrate configured to be electromagnetically coupled to the array of at least two photonic crystal cavity unit cell.

12. The device of claim 11 , wherein the scoring function value criteria comprises one or more of a maximum scoring function value of the plurality of scoring function F values, a threshold value exceeded by at least one of the plurality of scoring function F values, and a maximum scoring function value of the plurality of scoring function F values after a predetermined number of iterations calculating scoring function F values.

13. The device of claim 11 , wherein the coplanar microwave waveguide comprises a tapered input end, and wherein the tapered input end is connected to a tapered optical fiber to optically couple the optical fiber to the array of at least two photonic crystal cavity unit cells.

14. The device of claim 11 , further comprising at least one probing light source and at least one single photon detector.

15. The device of claim 11 , wherein the substrate comprises a diamond substrate.

16. The device of claim 11 , wherein the quantum defect is a silicon-vacancy color center.

17. The device of claim 11 , further comprising a refrigeration unit, wherein the refrigeration unit is configured to cool the substrate to less than 100 mK such that a spin coherence time T 2 of the at least one quantum defect is extended.

18. A method of operating the quantum network device of claim 14 , the method comprising:
receiving, with the at least one single photon detector, at least two photons; and
in response to the receipt of two photons, measuring the state of the quantum defect using the probing light source.

19. The method of claim 18 , wherein the receiving, with the at least one single photon detector, at least two photons and the measuring the state of the quantum defect with the laser comprises a Bell-state measurement.

20. A method of encoding of quantum information using the quantum network device of claim 11 , comprising:
for n time-bin qubits comprising n+1 optical pulses, applying phase control with a phase modulator to each optical pulse, wherein each time-bin qubit stores quantum information in a relative amplitude and phase between a pair of neighboring optical pulses among the n+1 optical pulses;
guiding the n+1 optical pulses to the at least one quantum defect;
alternating, with each pulse, coherent microwave control of the quantum defect; and
interfering, with a time-delay interferometer, each pulse with a previous optical pulse, wherein the time-delay interferometer delays the previous optical pulse by the time between the pulse and the previous optical pulse.

Assignees

• Harvard College

Inventors

• Bhaskar Mihir Keshav
• Sukachev Denis D
• Nguyen Christian Thieu
• Machielse Bartholomeus
• Levonian David S
• Riedinger Ralf
• Lukin Mikhail D
• Loncar Marko

Classifications

• G02B6/1225

  comprising photonic band-gap structures or photonic lattices · CPC title

• B82Y20/00

  Nanooptics, e.g. quantum optics or photonic crystals · CPC title

• B82Y10/00

  Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic · CPC title

• G02B6/30

  for use between fibre and thin-film device · CPC title

• G06N10/70 Primary

  Quantum error correction, detection or prevention, e.g. surface codes or magic state distillation · CPC title