Wednesday 13 October; Delft, Konrad Lehnert Sensing the quantum motion of a nanomechanical oscillator'



Time: 16:00 hrs

Location: Delft

The ability to both prepare a mechanical oscillator in a pure quantum state and measure its motion at the quantum limit provides a new opportunity to study quantum behavior in mechanical systems. A promising strategy for achieving this challenging goal is to use small mechanical oscillators embedded in optically or electrically resonant structures. In this talk, I will discuss how we implement this idea using micro- or nano- scale aluminum oscillators coupled to superconducting resonant circuits. By cooling these structures to 20 mK in a dilution refrigerator cryostat, we bring the MHz resonance frequency oscillators to a thermal occupancy of approximately 100 phonons. We further cool the mechanical oscillator towards its motional ground state by exciting the microwave resonant circuit at a frequency below its resonance, in close analogy to laser cooling of trapped ions. In order to detect the residual motion of the oscillator as it approaches its motional ground state, the microwave signal scattered from the resonant circuit must be detected close to the shot noise limit. We accomplish this measurement by developing a quantum efficient interferometric measurement based on a Josephson parametric amplifier.