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Exploring the Macroscopic Quantum Physics of Motion with Superfluid He-4

Event Details

Event Dates: 

Friday, December 4, 2015 - 12:00pm

Seminar Location: 

  • JILA X317

Speaker Name(s): 

Laura De Lorenzo

Speaker Affiliation(s): 

Caltech
Seminar Type/Subject

Scientific Seminar Type: 

  • JILA Public Seminar

Event Details & Abstract: 

We demonstrate the utility of superfluid helium-4 as an extremely low loss optomechanical element.  We form an optomechanical system with a cylindrical niobium superconducting TE011 resonator whose 40 cm^3 inner cylindrical cavity is filled with He-4.  Coupling is realized via the variations in permittivity resulting from the density profile of the acoustic modes. Acoustic losses in helium-4 below 500 mK are governed by the intrinsic nonlinearity of sound, leading to an attenuation which drops as T^4, indicating the possibility of quality factors (Q) over 10^10 at 10 mK. In our lowest loss mode, we demonstrate this T^4 law at temperatures down to 50 mK, realizing an acoustic Q of 1.35*10^8 at 8.1 kHz.  When coupled with a low phase noise microwave source, we expect this system to be utilized as a probe of macroscopic quantized motion, for precision measurements to search for fundamental physical length scales, and as a continuous gravitational wave detector.  Our estimates suggest that a resonant superfluid acoustic system could exceed the sensitivity of current broad-band detectors for narrow-band sources such as pulsars.