Abstract
We investigate the low loss acoustic motion of superfluid 4He parametrically coupled to a very low loss, superconducting Nb microwave resonator, forming a gram-scale, sideband resolved, optomechanical system. We demonstrate the detection of a series of acoustic modes with quality factors as high as . At higher temperatures, the lowest dissipation modes are limited by an intrinsic three phonon process. Acoustic quality factors approaching 1011 may be possible in isotopically purified samples at temperatures below 10 mK. A system of this type may be utilized to study macroscopic quantized motion and as a freqency tunable, ultra-sensitive sensor of extremely weak displacements and forces, such as continuous gravity wave sources.
Highlights
The study of the detection of motion at quantum mechanical limits has received great attention over the past 35 years [1,2,3] with much of the early thought and effort focused on the engineering of very large-scale, ultra-sensitive gravitational wave antennas
Superfluid 4He, a condensate which can be prepared in macroscopic quantities and demonstrates frictionless motion at zero-frequency [13], is an intriguing material to consider for the study of quantized macroscopic motion [3], quantized mechanical fields [14], and even Planck-scale physics [15, 16]
The coupling between the motion of the helium and the microwave field is relatively weak in comparison to nano- and micro-scale optomechanical realizations: the single quanta frequency shift is given by ΔPSQL = ω = 1 × 10−9 Pa is the amplitude of the zero point fluctuations of the acoustic field, Veff = 39.3 cm3 is the effective volume of the acoustic mode and ω = 2π × 8
Summary
The study of the detection of motion at quantum mechanical limits has received great attention over the past 35 years [1,2,3] with much of the early thought and effort focused on the engineering of very large-scale, ultra-sensitive gravitational wave antennas. The coupling between the motion of the helium and the microwave field is relatively weak in comparison to nano- and micro-scale optomechanical realizations: the single quanta frequency shift is given by ΔPSQL = ω (κHe Veff ) = 1 × 10−9 Pa is the amplitude of the zero point fluctuations of the acoustic field, Veff = 39.3 cm3 is the effective volume of the acoustic mode and ω = 2π × 8
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