Laser annealing of qubits with structured illumination

• US 10,170,681 B1
• Filed: 11/28/2017
• Issued: 01/01/2019
• Est. Priority Date: 11/28/2017
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Rosenblatt, Sami, Orcutt, Jason S.
• Primary Examiner(s): Sandvik, Benjamin
• Application Number:
  US15/823,713
• Time in Patent Office: 399 Days
• CPC Class Codes: G06N 10/00 Quantum computing, i.e. information processing based on quantum-mechanical phenomena
• CPC Class Codes: H10N 60/0912 of Josephson-effect devices
• CPC Class Codes: H10N 60/12 Josephson-effect devices
• CPC Class Codes: H10N 60/805 for Josephson-effect devices
• CPC Class Codes: H10N 69/00 Integrated devices, or assemblies of multiple devices, comprising at least one superconducting element covered by group H10N60/00

Abstract

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.

Claims

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.