Multimode coupler to control interaction between quantum bits

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.

A device, comprising:

• a first superconducting transmon quantum bit;
• a second superconducting transmon quantum bit;
• and
• a superconducting multimode coupler circuit coupled between the first superconducting transmon quantum bit and the second superconducting transmon quantum bit, wherein the superconducting 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 a 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;
• wherein the first superconducting transmon quantum bit is coupled to the first superconducting pad and to the second superconducting pad of the superconducting multimode coupler circuit;
• and
• wherein the second superconducting transmon quantum bit is coupled to the third superconducting pad of the superconducting multimode coupler circuit.