Engineering the Nonlinearity of Bosonic Modes with a Multi-loop SQUID

TL;DR

This paper presents a versatile superconducting circuit device that can engineer specific high-order nonlinearities in bosonic modes, advancing quantum error correction and state control.

Contribution

Introduction of the Nonlinearity-Engineered Multi-loop SQUID (NEMS) framework for arbitrary nonlinearities in superconducting circuits.

Findings

Demonstrated selective cubic, quartic, and quintic nonlinearities.

Suppressed parasitic couplings in engineered nonlinearities.

Potential for improved quantum gates and qubit stabilization.

Abstract

Engineering high-order nonlinearities while suppressing lower-order terms is crucial for quantum error correction and state control in bosonic systems, yet it remains an outstanding challenge. Here, we introduce a general framework of Nonlinearity-Engineered Multi-loop SQUID (NEMS) device, enabling the realization of arbitrary nonlinearities by tuning fluxes in multiple loops within superconducting circuits. We demonstrate specific examples of NEMS devices that selectively engineer pure cubic, quartic, and quintic interactions with suppressed parasitic couplings, showing great promise for realizing Kerr-cat bias-preserving {\scshape cnot} gates and stabilizing four-leg cat qubits. By opening new avenues for tailoring nonlinear Hamiltonians of superconducting devices, this work enables sophisticated and precise manipulation of bosonic modes, with potential applications in quantum computation, simulation, and sensing.