Nanophotonic quantum memory
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.
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.