High sensitivity, directional dc-SQUID magnetometer

• US 20030098455A1
• Filed: 03/31/2001
• Published: 05/29/2003
• Est. Priority Date: 03/31/2001
• Status: Active Grant

• Current Assignee: D-Wave Systems Inc. (D-Wave Quantum, Inc.)
• Original Assignee: D-Wave Systems Inc. (D-Wave Quantum, Inc.)
• Inventors: Rose, Geordie, Hilton, Jeremy P., Amin, Mohammad H.S., Omelyanchouk, Alexander, Zagoskin, Alexandre, Duty, Timothy
• Granted Patent: US 6,627,916 B2
• Time in Patent Office: Days
• US Class Current: 257/31
• CPC Class Codes: G01R 33/0354 SQUIDS
• CPC Class Codes: H10N 60/0941 comprising high-Tc ceramic materials
• CPC Class Codes: H10N 60/124 comprising high-Tc ceramic materials
• CPC Class Codes: Y10S 505/874 with josephson junction, e.g. squid
• CPC Class Codes: Y10S 977/933 Spintronics or quantum computing

Abstract

A solid state dc-SQUID includes a superconducting loop containing a plurality of Josephson junctions, wherein an intrinsic phase shift is accumulated through the loop. In an embodiment of the invention, the current-phase response of the dc-SQUID sits in a linear regime where directional sensitivity to flux through the loop occurs. Changes in the flux passing through the superconducting loop stimulates current which can be quantified, thus providing a means of measuring the magnetic field. Given the linear and directional response regime of the embodied device, an inherent current to phase sensitivity is achieved that would otherwise be unobtainable in common dc-SQUID devices without extrinsic intervention.

Claims

1. A Josephson device, comprising:

a superconducting loop;

a plurality of Josephson junctions in the superconducting loop; and

wherein a superconducting current in the SQUID loop experiences an accumulated intrinsic phase shift over the path of the SQUID loop.

2. The device of claim 1, wherein the plurality of Josephson junctions includes two junctions.

3. The device of claim 2, wherein the plurality of Josephson junctions are formed along a grain boundary, the grain boundary having a bend from a straight path at a point inside the superconducting loop.

4. The device of claim 3, wherein the two junctions includes a 0 junction and a π

/2 junction.

5. The device of claim 4, wherein the π

/2 junction is an asymmetric junction.

6. The device of claim 4, wherein the 0 junction is a symmetric junction.

7. The device of claim 6, wherein the symmetric junction is a symmetric, 22.5°

grain boundary Josephson junction.

8. The device of claim 3, wherein the superconducting material at the grain boundary has a lattice mismatch.

9. The device of claim 8, wherein the lattice mismatch is about 45°

.

10. The device of claim 2, wherein the bend is approximately 22.5°

from a straight path.

11. The device of claim 1, wherein the superconducting material is a high temperature superconductor.

12. The device of claim 11, wherein the high temperature superconducting material is YBa₂Cu₃O₇₋

x, where x is some value greater than or equal to 0 and less than about 0.6.

13. The device of claim 1, wherein the superconducting material is a p-wave superconductor.

14. The device of claim 13, wherein the superconducting material is Sr₂RuO₄.

15. The device of claim 4, wherein branches of the superconducting loop are on the order of 1 micrometer in width.

16. The device of claim 15, wherein the width of the loop is much longer than the width of the junctions.

17. The device of claim 15, wherein the widths of each branch in the loop are not the same.

18. A method of producing a SQUID magnetometer, comprising:

depositing a seed layer on a substrate;

depositing a first buffer layer on the seed layer;

etching the seed layer and the first buffer layer to form a boundary separating a first portion having the seed layer and the first buffer and a second portion where the seed layer and the first buffer are substantially removed;

depositing a second buffer layer on the second portion;

depositing a superconducting material on the first buffer layer and the second buffer layer; and

etching the superconducting material to form a SQUID loop with Josephson junctions at the boundary.

19. The method of claim 18, wherein the substrate is of sapphire.

20. The method of claim 18, wherein the substrate is of SrTiO₃.

21. The method of claim 18, wherein the seed layer is of MgO.

22. The method of claim 18, wherein the first buffer layer is of CeO₂.

23. The method of claim 18, wherein the second buffer layer is of CeO₂.

24. The method of claim 18, wherein the superconducting material is YBa₂Cu₃O₇₋

x where x is greater than or equal to 0 and less than about 0.6.

25. The method of claim 18, wherein the superconducting material is Bi₂Sr₂Ca_n−

1Cu_nO_2n+4, where n is an integer.

26. The method of claim 18, wherein the superconducting material is Sr₂RuO₄.

27. The method of claim 18, wherein depositing the seed layer is performed bi-epitaxially.

28. The method of claim 18, wherein depositing the first buffer layer is performed bi-epitaxially.

29. The method of claim 18, wherein depositing the second layer is performed bi-epitaxially.

30. The method of claim 18, wherein depositing the superconducting material is performed bi-epitaxially.

31. The method of claim 18, wherein etching the seed layer and the first buffer layer is accomplished with a milling process.

32. The method of claim 18, wherein etching the superconducting material can be accomplished with a milling process.

33. A method of measuring a magnetic field, comprising:

providing a SQUID magnetometer having an intrinsic phase shift;

positioning the SQUID magnetometer in proximity with a magnetic source; and

monitoring changes in the current through the SQUID magnetometer in order to monitor magnetic changes in the magnetic source.

34. The method of claim 33, wherein the magnetic source is a flux qubit.

35. The method of claim 33, wherein the magnetic source is an electronic circuit.

36. The method of claim 35, wherein the electronic circuit is semi-conducting.

37. The method of claim 35, wherein the electronic circuit is superconducting.

38. A magnetometer array, comprising:

a plurality of superconducting loops having an intrinsic phase shift, each superconducting loop of the plurality of superconducting loops including a superconducting material with a plurality of Josephson junctions in the loop.

39. The device of claim 38, wherein a plurality of arrays are coupled to create a multi-dimensional magnetometer array.