Laser annealing of qubits with structured illumination
View Patent ↗A qubit may be formed by forming a Josephson junction between two capacitive plates. The Josephson junction may be annealed with a thermal source. The thermal source may be a laser that generates a Gaussian beam. An axicon lens may be exposed to the Gaussian beam. Annealing the Josephson junction may alter the resistance of the Josephson junction.
1. A method for forming a qubit, the method comprising:
forming a Josephson junction between two capacitive plates; and
annealing the Josephson junction with a thermal source, wherein the thermal source is a laser that generates a Gaussian beam, wherein an axicon lens is exposed to the Gaussian beam, and wherein annealing the Josephson junction alters a resistance of the Josephson junction.
2. The method of claim 1 , wherein the Josephson junction is an aluminum/aluminum-oxide/aluminum trilayer Josephson junction on a substrate.
3. The method of claim 2 , wherein the substrate is a Silicon substrate.
4. The method of claim 2 , wherein the substrate is a sapphire substrate.
5. The method of claim 2 , wherein the substrate is a magnesium oxide substrate.
6. The method of claim 2 , wherein each aluminum layer of the aluminum/aluminum-oxide/aluminum trilayer is connected to a respective niobium capacitive plate.
7. The method of claim 1 , wherein the axicon lens includes an apex angle of 0.5 degrees.
8. The method of claim 1 , wherein exposing the axicon lens to the Gaussian beam reshapes the Gaussian beam into an annular beam.
9. The method of claim 8 , wherein the annular beam has a 532 nm wavelength.
10. The method of claim 9 , wherein the annular beam includes an illuminated outer ring and a non-illuminated center.
11. The method of claim 10 , wherein the annular beam has an annulus diameter that is greater than a diameter of the Josephson junction.
12. The method of claim 11 , wherein the illuminated outer ring has a 10-micron radius.
13. The method of claim 12 , wherein the annular beam is positioned on the Josephson junction.
14. The method of claim 13 , wherein the annular beam heats the substrate.
15. The method of claim 14 , wherein the illuminated outer ring heats the aluminum portions of the aluminum/aluminum-oxide/aluminum trilayer Josephson junction.
16. The method of claim 15 , wherein the illuminated outer ring indirectly heats the aluminum-oxide portion of the aluminum/aluminum-oxide/aluminum trilayer Josephson junction.
17. The method of claim 8 , wherein annealing the Josephson junction with the thermal source includes the annular beam uniformly increasing the temperature of the Josephson junction.
18. The method of claim 17 , wherein uniformly increasing the temperature of the Josephson junction comprises applying the thermal source to the Josephson junction as a function of time and a power level of the thermal source.
19. The method of claim 17 , wherein annealing the Josephson junction to alter the resistance of the Josephson junction increases the resistance of the Josephson junction.