Mode-selective couplers for frequency collision reduction

Patent metadata

Field	Value
Publication number	US-11626555-B2
Application number	US-202016895677-A
Country	US
Kind code	B2
Filing date	Jun 8, 2020
Priority date	Jun 8, 2020
Publication date	Apr 11, 2023
Grant date	Apr 11, 2023

Abstract

Systems and techniques that facilitate mode-selective couplers for frequency collision reduction are provided. In various embodiments, a device can comprise a control qubit. In various aspects, the device can comprise a first target qubit coupled to the control qubit by a first mode-selective coupler. In various instances, the first mode-selective coupler can facilitate A-mode coupling between the control qubit and the first target qubit. In various embodiments, the device can comprise a second target qubit coupled to the control qubit by a second mode-selective coupler. In various aspects, the second mode selective coupler can facilitate B-mode coupling between the control qubit and the second target qubit. In various embodiments, the first mode-selective coupler can comprise a capacitor that capacitively couples a middle capacitor pad of the control qubit to a middle capacitor pad of the first target qubit. In various embodiments, the second mode-selective coupler can comprise a first capacitor that capacitively couples an end capacitor pad of the control qubit to an end capacitor pad of the first target qubit and can comprise a second capacitor that capacitively couples the end capacitor pad of the control qubit to a middle capacitor pad of the second target qubit.

First claim

What is claimed is:

1. A device, comprising:
a control qubit coupled to a first mode-selective coupler and a second mode-selective coupler;
a first target qubit coupled to the first mode-selective coupler, wherein the first mode-selective coupler allows A-mode coupling between the control qubit and the first target qubit, and prevents B-mode coupling between the control qubit and the first target qubit; and
a second target qubit coupled to the second mode-selective coupler, wherein the second mode-selective coupler allows the B-mode coupling between the control qubit and the second target qubit, and prevents the A-mode coupling between the control qubit and the second target qubit.

2. The device of claim 1 , wherein the control qubit, the first target qubit, and the second target qubit are two-junction transmon qubits.

3. The device of claim 2 , wherein the first mode-selective coupler comprises a capacitor that capacitively couples a middle capacitor pad of the control qubit to a middle capacitor pad of the first target qubit.

4. The device of claim 3 , wherein the capacitor has a capacitance that is less than shunting capacitance values of the control qubit and less than shunting capacitance values of the first target qubit.

5. The device of claim 2 , wherein the second mode-selective coupler comprises a first capacitor that capacitively couples an end capacitor pad of the control qubit to an end capacitor pad of the second target qubit and comprises a second capacitor that capacitively couples the end capacitor pad of the control qubit to a middle capacitor pad of the second target qubit.

6. The device of claim 5 , wherein the first capacitor has a first capacitance that is less than shunting capacitance values of the control qubit and less than shunting capacitance values of the second target qubit, and wherein the second capacitor has a second capacitance that is half the first capacitance.

7. The device of claim 1 , wherein the first target qubit and the second target qubit are degenerate targets.

8. The device of claim 7 , wherein the first target qubit entangles with the control qubit when the control qubit is driven by a first microwave tone corresponding to an A-mode excitation frequency of the degenerate targets, and wherein the second target qubit entangles with the control qubit when the control qubit is driven by a second microwave tone corresponding to a B-mode excitation frequency of the degenerate targets.

9. A method, comprising:
providing a control qubit;
coupling the control qubit to a first target qubit by a first mode-selective coupler that allows A-mode coupling between the control qubit and the first target qubit, and prevents B-mode coupling between the control qubit and the first target qubit; and
coupling the control qubit to a second target qubit by a second mode-selective coupler that allows the B-mode coupling between the control qubit and the second target qubit, and prevents the A-mode coupling between the control qubit and the second target qubit, wherein the second mode-selective coupler couples an end capacitor pad of the control qubit to a middle capacitor pad of the second target qubit.

10. The method of claim 9 , wherein the control qubit, the first target qubit, and the second target qubit are two-junction transmon qubits.

11. The method of claim 10 , wherein the first mode-selective coupler comprises a capacitor that capacitively couples a middle capacitor pad of the control qubit to a middle capacitor pad of the first target qubit.

12. The method of claim 11 , wherein the capacitor has a capacitance that is less than shunting capacitance values of the control qubit and less than shunting capacitance values of the first target qubit.

13. The method of claim 10 , wherein the second mode-selective coupler comprises a first capacitor that capacitively couples an end capacitor pad of the control qubit to an end capacitor pad of the second target qubit and comprises a second capacitor that capacitively couples the end capacitor pad of the control qubit to a middle capacitor pad of the second target qubit.

14. The method of claim 13 , wherein the first capacitor has a first capacitance that is less than shunting capacitance values of the control qubit and less than shunting capacitance values of the second target qubit, and wherein the second capacitor has a second capacitance that is half the first capacitance.

15. The method of claim 9 , wherein the first target qubit and the second target qubit are degenerate targets.

16. The method of claim 15 , further comprising:
driving the control qubit with a first microwave tone corresponding to an A-mode excitation frequency of the degenerate targets, thereby entangling the first target qubit with the control qubit; and
driving the control qubit with a second microwave tone corresponding to a B-mode excitation frequency of the degenerate targets, thereby entangling the second target qubit with the control qubit.

17. An apparatus, comprising:
a control qubit;
a first mode-selective coupler that allows A-mode coupling between the control qubit and a first target qubit, and prevents B-mode coupling between the control qubit and the first target qubit; and
a second mode-selective coupler that allows the B-mode coupling between the control qubit and a second target qubit, and prevents the A-mode coupling between the control qubit and the second target qubit, wherein the second mode-selective coupler couples an end capacitor pad of the control qubit to a middle capacitor pad of the second target qubit.

18. The apparatus of claim 17 , wherein the first mode-selective coupler comprises a capacitor that couples a middle capacitor pad of the control qubit to a middle capacitor pad of the first target qubit, wherein a capacitance of the capacitor is less than shunting capacitance values of the control qubit and less than shunting capacitance values of the second target qubit.

19. The apparatus of claim 17 , wherein the second mode-selective coupler comprises a first capacitor that couples an end capacitor pad of the control qubit to an end capacitor pad of the second target qubit and comprises a second capacitor that couples the end capacitor pad of the control qubit to a middle capacitor pad of the second target qubit, wherein a first capacitance of the first capacitor is less than shunting capacitance values of the control qubit and less than shunting capacitance values of the second target qubit, and wherein a second capacitance of the second capacitor is half the first capacitance.

20. The apparatus of claim 17 , wherein the first target qubit and the second target qubit are degenerate targets, wherein the first target qubit entangles with the control qubit when the control qubit is driven by a first microwave tone corresponding to an A-mode excitation frequency of the degenerate targets, and wherein the second target qubit entangles with the control qubit when the control qubit is driven by a second microwave tone corresponding to a B-mode excitation frequency of the degenerate targets.

Assignees

• IBM

Inventors

• Finck Aaron
• Blair John

Classifications

• G06N10/40

  Physical realisations or architectures of quantum processors or components for manipulating qubits, e.g. qubit coupling or qubit control · CPC title

• H10N69/00 Primary

  Integrated devices, or assemblies of multiple devices, comprising at least one superconducting element covered by group H10N60/00 · CPC title

• H10N60/805 Primary

  for Josephson-effect devices · CPC title

• H10N60/12

  Josephson-effect devices · CPC title

• H10N60/0912

  of Josephson-effect devices · CPC title