Three-tone coherent microwave electromechanical measurement of a superfluid Helmholtz resonator
S. Spence (University of Alberta)
E. Varga (Charles University)
C.A. Potts (TU Delft - QN/Steele Lab, Kavli institute of nanoscience Delft)
J. P. Davis (University of Alberta)
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Abstract
We demonstrate electromechanical coupling between a superfluid mechanical mode and a microwave mode formed by a patterned microfluidic chip and a 3D cavity. The electric field of the chip-cavity microwave resonator can be used to both drive and detect the motion of a pure superflow Helmholtz mode, which is dictated by geometric confinement. The coupling is characterized using a coherent measurement technique developed for measuring weak couplings deep in the sideband unresolved regime. The technique is based on two-probe optomechanically induced transparency/amplification using amplitude modulation. Instead of measuring two probe tones separately, they are interfered to retain only a signal coherent with the mechanical motion. With this method, we measure a vacuum electromechanical coupling strength of g 0 = 2 p × 23.3 µ Hz, three orders of magnitude larger than previous superfluid electromechanical experiments.