Physics Colloquium - Look, But Don't Touch: Mechanically Detecting and Evading the Quantum Measurement Back-Action of a Microwave Field

Event Date: 

Tuesday, April 22, 2014 - 4:00pm

Event Location: 

  • Broida 1640

Event Contact: 


Keith Schwab, Caltech


In the 1970's, during the theoretical investigation of the ultimate sensitivity of gravitational wave detectors, it was understood that quantum fluctuations of the electro-magnetic field used to probe the motion, would produce a force noise which would limit the sensitivity.  After this was understood, people developed schemes to avoid this limitation by giving up complete knowledge of the motion.  In our recent experiments with micron-scale mechanical structures coupled to microwave resonators at milli-Kelvin temperatures, we detect this force noise generated by the quantum fluctuations of a microwave field, and show how to avoid this stochastic noise by measuring a single quadrature of motion.  We will also show our recent work to cool a mechanical resonator to a state near the ground state of motion and how to manipulate the mechanical zero point fluctuations.