Superconducting Nanoelectromechanical Transducer Resilient to Magnetic Fields

Abstract

Nanoscale electromechanical coupling provides a unique route towards control of mechanical motions and microwave fields in superconducting cavity electromechanical devices. Though their successes in utilizing the optomechanical or electromechanical back-action effects for various purposes, aluminum imposes severe constraints on their operating conditions with its low superconducting critical temperature (1.2 K) and magnetic field (0.01 T). To extend the potential of the devices, here we fabricate a superconducting electromechanical device employing niobium and demonstrate a set of cavity electromechanical dynamics including back-action cooling and amplification, and electromechanically induced reflection at 4.2 K and in strong magnetic fields up to 0.8 T. This device could be used to realize electromechanical microwave components for quantum technologies by integrating amplifiers, converters, and circulators on a single chip that can be installed at the 4K stage of dilution refrigerators.Moreover, with its ability to control and readout nanomechanical motions simultaneously, this niobium electromechanical transducer could provide powerful nanomechanical sensing platforms.

On-Chip Microwave Frequency Combs in a Superconducting Nanoelectromechanical Device

“…A superconducting microwave system involving a nanomechanical resonator can exhibit strong dispersive electromechanical coupling that forms an ideal host for optomechanical phenomena. − This coupling, in general, is realized through a vacuum-gap capacitor within the nanomechanical resonator. When the resonator is electrically displaced by a microwave pump, a change of capacitance shifts the microwave resonant frequency.…”

“…(b) Scanning electron microscope image of the mechanical resonator (top) and the capacitance bridges (bottom). The top SEM image is adapted and modified from ref . Copyright 2021 American Chemical Society.…”

“…To explore the nonlinear optomechanical phenomena, we apply a blue-detuned microwave pump at ω d = ω c + Ω m to drive our device and measure the sideband power spectrum S v (ω), around ω c (Figure a). This power spectrum can be converted to the displacement spectral density S x (ω) = 2 πS v (ω) k B T mode /( mΩ m 2 ∫ S v (ω) d ω ), and we study its behavior for different pump powers P d (Figure a). Note that T mode is the effective temperature of the mechanical mode.…”

“…Here, we explore the dynamics of microwave frequency combs in such a niobium-based superconducting electromechanical device. 29 Thanks to the high superconducting critical temperature (∼9 K) of niobium, we perform all measurements at 4.2 K. We study the effects of pump detuning and the decay rate of the microwave resonator on the features of the frequency comb, and inform our findings by numerically solving coupled nonlinear equations considering electromechanical coupling as well as mechanical nonlinearities.…”

“…Figure 1a shows the system under investigation, an LC microwave resonator incorporating a niobium nanomechanical resonator. The fabrication details of our device are described in ref 29. The LC resonator is capacitively coupled to input and output ports, which are connected to measurement instruments at room temperature.…”