CQOM Colloquium - Andreas Næsby and Albert Schliesser
Info about event
Andreas Næsby, IFA
Title: Optomechanical sandwiches for sensing
Abstract: Optomechanical sandwiches made of high-quality suspended silicon nitride thin films will be introduced as a promising and versatile design for ultrasensitive sensing. Pressure sensing as well as tailoring of the optomechanical properties of such sandwiches will be discussed as examples.
15:15-15:30 Questions and coffee/tea and cake
Albert Schliesser, Nils Bohr Institute, Copenhagen
Title: Quantum measurement and control of an ultracoherent nanomechanical resonator
Abstract: Using measurements to control the quantum state of a massive object’s motion is a goal shared by communities as diverse as atomic physics, nanomechanics, and gravitational wave astronomy. The key challenge is to make the measurement both strong and efficient. That is, one must acquire sufficient information about the motional state before the environment decoheres it. Simultaneously, one must gain the largest possible amount of information per decoherence induced by measurement backaction. We address these challenges with an ultracoherent (quality factor Q=1 billion) nanomechanical membrane resonator, whose motion we monitor with a near-ideal optomechanical transducer. Operating within 35% of the Heisenberg measurement-disturbance uncertainly relation, and the standard quantum limit (SQL), it allows us to follow the resonator’s quantum trajectory with unprecedented resolution. Via electronic feedback, we can then cool the resonator to the quantum ground state (residual occupation 0.3). Disabling the feedback abruptly, we observe re-heating with rates as low as ~1 phonon per millisecond. Exploiting quantum correlations, we are furthermore able to perform motion measurements with a sensitivity (all noises included) 1.5 dB below the SQL. These advances open the door to a range of applications of ultracoherent mechanical resonators in quantum information processing and sensing.