Superconducting coupler with exponentially large on-off ratio

TL;DR

This paper introduces a superconducting coupler that exponentially suppresses all two-qubit interactions without fine-tuning, enhancing control in quantum processors by leveraging a nonlinear resonator mode and drive-induced effects.

Contribution

A novel superconducting coupler design that achieves broad, tunable suppression of two-qubit interactions using a nonlinear resonator and drive-induced displacement.

Findings

Achieves exponential on-off ratio for two-qubit couplings.

Does not require fine-tuning of parameters.

Supports practical superconducting circuit implementation.

Abstract

Tunable two-qubit couplers offer an avenue to mitigate errors in multiqubit superconducting quantum processors. However, most couplers operate in a narrow frequency band and target specific couplings, such as the spurious $ZZ$ interaction. We introduce a superconducting coupler that alleviates these limitations by suppressing all two-qubit interactions with an exponentially large on-off ratio and without the need for fine-tuning. Our approach is based on a bus mode supplemented by an ancillary nonlinear resonator mode. Driving the ancillary mode leads to a coupler-state-dependent field displacement in the resonator which, in turn, results in an exponential suppression of real and virtual two-qubit interactions with respect to the drive power. A superconducting circuit implementation supporting the proposed mechanism is presented.