Sideband-resolved resonator electromechanics on the single-photon level based on a nonlinear Josephson inductance

TL;DR

This paper demonstrates a highly sensitive, tunable inductively coupled electromechanical system using a SQUID integrated into a microwave resonator, achieving sideband resolution and strong coupling at the single-photon level.

Contribution

It introduces a novel SQUID-based inductive coupling scheme for electromechanics, enabling vacuum coupling rates up to 1.62 kHz and sub-aN Hz-1/2 force sensitivities.

Findings

Achieved sideband-resolved electromechanical interaction.

Demonstrated tunable vacuum coupling rate of 1.62 kHz.

Confirmed large coupling via microwave resonator frequency splitting.

Abstract

Light-matter interaction in optomechanical systems is the foundation for ultra-sensitive detection schemes [1,2] as well as the generation of phononic and photonic quantum states [3-10]. Electromechanical systems realize this optomechanical interaction in the microwave regime. In this context, capacitive coupling arrangements demonstrated interaction rates of up to 280 Hz [11]. Complementary, early proposals [12-15] and experiments [16,17] suggest that inductive coupling schemes are tunable and have the potential to reach the vacuum strong-coupling regime. Here, we follow the latter approach by integrating a partly suspended superconducting quantum interference device (SQUID) into a microwave resonator. The mechanical displacement translates into a time varying flux in the SQUID loop, thereby providing an inductive electromechanical coupling. We demonstrate a sideband-resolved electromechanical system with a tunable vacuum coupling rate of up to 1.62 kHz, realizing sub-aN Hz-1/2 force sensitivities. Moreover, we study the frequency splitting of the microwave resonator for large mechanical amplitudes confirming the large coupling. The presented inductive coupling scheme shows the high potential of SQUID-based electromechanics for targeting the full wealth of the intrinsically nonlinear optomechanics Hamiltonian.