Multimode coupler to control interaction between quantum bits

Patent metadata

Field	Value
Publication number	US-12555015-B2
Application number	US-202217835511-A
Country	US
Kind code	B2
Filing date	Jun 8, 2022
Priority date	Jun 8, 2022
Publication date	Feb 17, 2026
Grant date	Feb 17, 2026

Abstract

A device comprises first and second superconducting quantum bits, and a multimode coupler circuit coupled between the first and second superconducting quantum bits. The multimode coupler circuit comprises a first mode and a second mode, and is configured to operate in one of a first state and a second state, in response to a flux tuning control signal. In the first state, the first superconducting quantum bit is exchange coupled to the first mode, and the second superconducting quantum bit is exchange coupled to the second mode, to suppress interaction between the first and second superconducting quantum bits. In the second state, the first and second superconducting quantum bits are exchange coupled to both the first and second modes, to enable an interaction between the first and second superconducting quantum bits and perform an entanglement gate operation.

First claim

What is claimed is:

1 . A device, comprising:
a first superconducting quantum bit; a second superconducting quantum bit; and a multimode coupler circuit coupled between the first superconducting quantum bit and the second superconducting quantum bit; wherein the multimode coupler circuit comprises a first mode and a second mode, and is configured to operate in one of a first state and a second state, in response to a flux tuning control signal applied to the multimode coupler circuit; wherein in the first state of the multimode coupler circuit, the first superconducting quantum bit is exchange coupled to the first mode, and the second superconducting quantum bit is exchange coupled to the second mode, to suppress interaction between the first superconducting quantum bit and the second superconducting quantum bit; and wherein in the second state of the multimode coupler circuit, the first superconducting quantum bit and the second superconducting quantum bit are exchange coupled to both the first mode and the second mode, to enable interaction between the first superconducting quantum bit and the second superconducting quantum bit and perform an entanglement gate operation.

2 . The device of claim 1 , wherein the first superconducting quantum bit and the second superconducting quantum bit each comprise a fixed-frequency transmon quantum bit with different transition frequencies.

3 . The device of claim 1 , wherein the first superconducting quantum bit comprises a superconducting quadrupole transmon quantum bit.

4 . The device of claim 1 , wherein:
the multimode coupler circuit comprises a first superconducting tunnel junction device, and a second superconducting tunnel junction device, which are coupled to form a superconducting loop; and the multimode coupler circuit is tuned to operate in one of the first state and the second state, in response to the flux tuning control signal applied to the superconducting loop.

5 . The device of claim 1 , wherein the multimode coupler circuit comprises a superconducting tunable coupler quantum bit.

6 . The device of claim 1 , wherein the multimode coupler circuit comprises:
a first superconducting pad; a second superconducting pad; a third superconducting pad, disposed between the first superconducting pad and the second superconducting pad; a superconducting quantum interference device comprising a first superconducting tunnel junction device and second superconducting tunnel junction device, coupled to and between the first superconducting pad and the third superconducting pad and forming a superconducting loop; and a third superconducting tunnel junction device coupled to and between the second superconducting pad and the third superconducting pad.

7 . The device of claim 6 , wherein:
the first superconducting quantum bit comprises:
a first node coupled to the first superconducting pad of the multimode coupler circuit; and
a second node coupled to the second superconducting pad of the multimode coupler circuit; and
the second superconducting quantum bit comprises a first node coupled to the third superconducting pad of the multimode coupler circuit.

8 . The device of claim 6 , wherein:
the superconducting quantum interference device comprises a critical current that is tunable in response to the flux tuning control signal applied to the superconducting loop; the third superconducting tunnel junction device comprises a critical current that is fixed; the multimode coupler circuit is configured to operate in the first state by applying the flux tuning control signal to the superconducting loop to tune the critical current of the superconducting quantum interference device to be the same or substantially the same as the fixed critical current of the third superconducting tunnel junction device; and the multimode coupler circuit is configured to operate in the second state by applying the flux tuning control signal to the superconducting loop to tune the critical current of the superconducting quantum interference device to be greater than the fixed critical current of the third superconducting tunnel junction device.

9 . A system, comprising;
a quantum processor comprising an array of superconducting quantum bits; and a control system configured to generate control signals to control the quantum processor; wherein the array of superconducting quantum bits comprises:
a first superconducting quantum bit;
a second superconducting quantum bit; and
a multimode coupler circuit coupled between the first superconducting quantum bit and the second superconducting quantum bit;
wherein the multimode coupler circuit comprises a first mode and a second mode, and is configured to operate in one of a first state and a second state, in response to a flux tuning control signal applied to the multimode coupler circuit;
wherein in the first state of the multimode coupler circuit, the first superconducting quantum bit is exchange coupled to the first mode, and the second superconducting quantum bit is exchange coupled to the second mode, to suppress interaction between the first superconducting quantum bit and the second superconducting quantum bit; and
wherein in the second state of the multimode coupler circuit, the first superconducting quantum bit and the second superconducting quantum bit are exchange coupled to both the first mode and the second mode, to enable interaction between the first superconducting quantum bit and the second superconducting quantum bit and perform an entanglement gate operation.

10 . The system of claim 9 , wherein the first superconducting quantum bit and the second superconducting quantum bit each comprise a fixed-frequency transmon quantum bit with different transition frequencies.

11 . The system of claim 9 , wherein:
the first superconducting quantum bit comprises a superconducting quadrupole transmon quantum bit; and the array of superconducting quantum bits further comprises: a second multimode coupler circuit coupled to the superconducting quadrupole transmon quantum bit; a third multimode coupler circuit coupled to the superconducting quadrupole transmon quantum bit; a third superconducting quantum bit coupled to the second multimode coupler circuit; and a fourth superconducting quantum bit coupled to the third multimode coupler circuit.

12 . The system of claim 11 , wherein the array of superconducting quantum bits comprises a hexagonal lattice structure.

13 . The system of claim 9 , wherein:
the multimode coupler circuit comprises a first superconducting tunnel junction device, and a second superconducting tunnel junction device, which are coupled to form a superconducting loop; and the multimode coupler circuit is tuned to operate in one of the first state and the second state, in response to the flux tuning control signal applied to the superconducting loop.

14 . The system of claim 9 , wherein:
the multimode coupler circuit comprises:
a first superconducting pad;
a second superconducting pad;
a third superconducting pad, disposed between the first superconducting pad and the second superconducting pad;
a superconducting quantum interference device comprising a first superconducting tunnel junction device and second superconducting tunnel junction device, coupled to and between the first superconducting pad and the third superconducting pad and forming a superconducting loop;
a third superconducting tunnel junction device coupled to and between the second superconducting pad and the third superconducting pad;
the first superconducting quantum bit comprises:
a first node coupled to

Assignees

• IBM

Inventors

• Finck Aaron
• Mckay David C
• Stehlik Jiri
• Blair John

Classifications

• H10N60/11

  Single-electron tunnelling devices · CPC title

• H10N60/128

  having three or more electrodes, e.g. transistor-like structures · CPC title

• G06N10/20

  Models of quantum computing, e.g. quantum circuits or universal quantum computers · 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