Quantum and thermal noise in optomechanical systems
Thomas Purdy, National Institute of Standards and Technology

Recently there has been much experimental progress in understanding the interaction of light with solid state mechanical resonators at the quantum level in systems ranging from nano-optomechanical systems to large-scale interferometric gravitational wave observatories. I will begin by reviewing the basics of quantum noise limits of optical detection of mechanical motion, which are mostly captured by Heisenberg's-Microscope-like uncertainty trade offs. I will highlight the central role of correlations in quantum noise introduced by the optomechanical interactions by discussing their manifestations in recent nano/micro-optomechanics experiments: For example the spectrum of light produced when a mechanical resonator comes to a thermal equilibrium with the optical force noise bath of the vacuum fluctuations of an optical cavity mode. I will discuss a recent experiment where we measure the extremely weak signature of Heisenberg measurement backaction in the form of optical quantum correlations on light probing a nanomechanical resonator, even while the mechanics is strongly coupled to the ambient environment -- room temperature and atmospheric pressure [1]. We use the scale of these quantum correlations relative to the measured thermal motion to absolutely calibrate the resonator temperature, demonstrating a route toward an on-chip primary thermometry referenced to fundamental constants.

[1] T. P. Purdy, K. E. Grutter, K. Srinivasan, J. M. Taylor, Science 356, 1265 (2017).