Quantum optomechanics with nanomechanical oscillators

Tobias J. Kippenberg
École Polytechnique Fédérale de Lausanne, Switzerland

Nanomechanical resonators are exquisite force sensors, and have recently (and surprisingly) emerged as a potential quantum technology. In this talk I will discuss measurements in which we have reached a regime where the inteferometric position measurement  of a nanomechanical oscillator via an optical cavity field, takes place in a regime where the measurement quantum backaction cannot be neglected. This regime, as experimentally demonstrated for a near field coupled opto-nanomechanical system, enables to generate squeezed state of light, which lend themselves to quantum enhanced for sensing, using a technique called variational measurements. This technique, as shown experimentally at room temperature, allows quantum enhanced sensitivity as first described theoretically in the context of gravitational wave detectors. Moreover, the talk will discuss a new phononic engineering techniques based on soft-clamping and elastic stress engineering, that have made it possible to realize unprecedented room temperature mechanical quality factors of up to 800 million for a mechanical oscillator, and with potential for orders of magnitude improvement. The devices are also intriguing as macroscopic quantum systems, as they undergo 100s of oscillations in their thermal decoherence time even at ambient temperature.