Frozonium: Freezing Anharmonicity in Floquet Superconducting Circuits

TL;DR

This paper introduces the 'frozonium' artificial atom, a superconducting circuit that leverages Floquet engineering to dynamically suppress anharmonicity, enabling enhanced control and noise protection for quantum memory applications.

Contribution

It demonstrates how Floquet drives can effectively linearize the dynamics of a superconducting Josephson junction, with potential for improved quantum control and noise resilience.

Findings

Floquet drives can tune the frozonium to behave like a linear oscillator.

Suppression of nonlinear corrections at high drive frequencies.

Enhanced protection against external noise sources.

Abstract

Floquet engineering is a powerful method that can be used to modify the properties of interacting many-body Hamiltonians via the application of periodic time-dependent drives. Here we consider the physics of an inductively shunted superconducting Josephson junction in the presence of Floquet drives in the fluxonium regime and beyond, which we dub the frozonium artificial atom. We find that in the vicinity of special ratios of the drive amplitude and frequency, the many-body dynamics can be tuned to that of an effectively linear bosonic oscillator, with additional nonlinear corrections that are suppressed in higher powers of the drive frequency. By analyzing the inverse participation ratios between the time-evolved frozonium wavefunctions and the eigenbasis of a linear oscillator, we demonstrate the ability to achieve a novel dynamical control using a combination of numerical exact diagonalization and Floquet-Magnus expansion. We discuss the physics of resonances between quasi-energy states induced by the drive, and ways to mitigate their effects. We also highlight the enhanced protection of frozonium against external sources of noise present in experimental setups. This work lays the foundation for future applications in quantum memory and bosonic quantum control using superconducting circuits.