Driving dark modes to facilitate entanglement

Patent metadata

Field	Value
Publication number	US-11620562-B2
Application number	US-202117409425-A
Country	US
Kind code	B2
Filing date	Aug 23, 2021
Priority date	Aug 23, 2021
Publication date	Apr 4, 2023
Grant date	Apr 4, 2023

Abstract

Systems and techniques that facilitate entanglement via driving dark modes are provided. In various embodiments, a method can comprise accessing a first multi-mode qubit and a second multi-mode qubit. In various cases, the first multi-mode qubit can be coupled to the second multi-mode qubit by a mode-selective coupler. In various aspects, the method can further comprise exciting a dark mode of the first multi-mode qubit. In various cases, the exciting the dark mode can entangle the first multi-mode qubit with the second multi-mode qubit.

First claim

What is claimed is:

1. A method, comprising:
accessing a first multi-mode qubit that is coupled by a mode-selective coupler to a second multi-mode qubit; and
exciting a dark mode of the first multi-mode qubit, wherein the exciting the dark mode entangles the first multi-mode qubit with the second multi-mode qubit.

2. The method of claim 1 , wherein the exciting the dark mode of the first multi-mode qubit comprises:
applying a pi-pulse to the first multi-mode qubit.

3. The method of claim 2 , wherein the exciting the dark mode of the first multi-mode qubit further comprises:
idling for a predetermined time period after the applying the pi-pulse; and
applying a negative pi-pulse to the first multi-mode qubit based on the predetermined time period elapsing.

4. The method of claim 3 , wherein the mode-selective coupler couples the dark mode of the first multi-mode qubit to another dark mode of the second multi-mode qubit, and wherein the mode-selective coupler leaves a bright mode of the first multi-mode qubit uncoupled from another bright mode of the second multi-mode qubit.

5. The method of claim 4 , wherein the first multi-mode qubit and the second multi-mode qubit are two-junction transmon qubits.

6. The method of claim 5 , wherein the mode-selective coupler is a capacitor that directly couples a middle capacitor pad of the first multi-mode qubit to another middle capacitor pad of the second multi-mode qubit.

7. The method of claim 5 , wherein the mode-selective coupler is a bus resonator that capacitively couples a middle capacitor pad of the first multi-mode qubit to another middle capacitor pad of the second multi-mode qubit.

8. The method of claim 3 , further comprising:
applying an echo pi-pulse to a third multi-mode qubit that is coupled to the first multi-mode qubit.

9. A device, comprising:
a first multi-mode qubit and a second multi-mode qubit; and
a mode-selective coupler that couples the first multi-mode qubit to the second multi-mode qubit, wherein the mode-selective coupler is configured to, upon excitation of a dark mode of the first multi-mode qubit, entangle the first multi-mode qubit with the second multi-mode qubit.

10. The device of claim 9 , wherein the dark mode of the first multi-mode qubit is excited via application of a pi-pulse to the first multi-mode qubit.

11. The device of claim 10 , wherein the dark mode of the first multi-mode qubit is de-excited via application of a negative pi-pulse to the first multi-mode qubit, and wherein the negative pi-pulse is applied after a predetermined time period has elapsed following the application of the pi-pulse.

12. The device of claim 11 , wherein the mode-selective coupler couples the dark mode of the first multi-mode qubit to another dark mode of the second multi-mode qubit, and wherein the mode-selective coupler leaves a bright mode of the first multi-mode qubit uncoupled from another bright mode of the second multi-mode qubit.

13. The device of claim 12 , wherein the first multi-mode qubit and the second multi-mode qubit are two-junction transmon qubits.

14. The device of claim 13 , wherein the mode-selective coupler is a capacitor that directly couples a middle capacitor pad of the first multi-mode qubit to another middle capacitor pad of the second multi-mode qubit.

15. The device of claim 13 , wherein the mode-selective coupler is a bus resonator that capacitively couples a middle capacitor pad of the first multi-mode qubit to another middle capacitor pad of the second multi-mode qubit.

16. The device of claim 11 , further comprising:
a third multi-mode qubit that is coupled to the first multi-mode qubit, wherein an echo pi-pulse is applied to the third multi-mode qubit.

17. A method, comprising:
accessing a first two-junction transmon qubit and a second two-junction transmon qubit, wherein a middle capacitor pad of the first two-junction transmon qubit is capacitively coupled to another middle capacitor pad of the second two-junction transmon qubit; and
entangling the first two-junction transmon qubit with the second two-junction transmon qubit, by driving the first two-junction transmon qubit with a dark mode excitation pulse sequence.

18. The method of claim 17 , wherein the middle capacitor pad of the first two-junction transmon qubit being capacitively coupled to the another middle capacitor pad of the second two-junction transmon qubit causes the dark mode of the first two-junction transmon qubit to be coupled to another dark mode of the second two-junction transmon qubit, and wherein the middle capacitor pad of the first two-junction transmon qubit being capacitively coupled to the another middle capacitor pad of the second two-junction transmon qubit causes a bright mode of the first two-junction transmon qubit to remain uncoupled from another bright mode of the second two-junction transmon qubit.

19. The method of claim 17 , wherein the dark mode excitation pulse sequence includes a first pi-pulse, a first idle time, and a first negative pi-pulse.

20. The method of claim 19 , wherein the dark mode excitation pulse sequence further includes a second pi-pulse, a second idle time, and a second negative pi-pulse, wherein the first negative pi-pulse and the second pi-pulse are separated by an echo pi-pulse applied to a third two-junction transmon qubit that is coupled to the first two-junction transmon qubit.

Assignees

• IBM

Inventors

• Finck Aaron
• Blair John
• Carniol April

Classifications

• G06N10/00 Primary

  Quantum computing, i.e. information processing based on quantum-mechanical phenomena · CPC title

• H03K3/38

  by the use, as active elements, of superconductive devices · CPC title

• G06N10/40 Primary

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