Four-body coupler for superconducting qubits based on Josephson parametric oscillators

TL;DR

This paper proposes a theoretical design for a four-body coupler for superconducting qubits using Josephson parametric oscillators, enhancing interaction strength through circuit parameter tuning.

Contribution

It introduces a novel four-body coupler circuit based on JPOs, generalizing previous designs and clarifying how to optimize the coupling strength via circuit parameters.

Findings

Four-body coupling constant can be significantly increased by tuning capacitance.

The coupler circuit is a specific setup of SNAIL with a superconducting loop.

The design allows for enhanced multi-qubit interactions in superconducting circuits.

Abstract

We theoretically propose a circuit of the four-body coupler for superconducting qubits based on Josephson parametric oscillators (JPOs). Our coupler for the four-body interaction has a superconducting loop, similar to a capacitively shunted flux qubit, where an external magnetic flux set to half a flux quantum is threaded. This coupler circuit is a specific setup of the circuit called superconducting nonlinear asymmetric inductive elements (SNAIL) and also is a generalization of the previously proposed one for the four-body interaction of JPOs. We clarify roles of circuit parameters in the four-body interaction and, in particular, show that the four-body coupling constant in our circuit can be significantly increased by tuning capacitance of the coupler or the area ratio of the Josephson junctions of the coupler.