Quantum aspects of cavity optomechanics with atomic ensembles and ensemble arrays

Lele Zhai, Jin‐Liang Guo

Qinghong Liao, Jian Sun, Zhihui Liu +1 more

Thierry Botter, Daniel W. C. Brooks, Sydney Schreppler +2 more

We create an ultracold-atom-based cavity optomechanical system in which the center-of-mass modes of motion of as many as six distinguishable atomic ensembles are prepared and optically detected near their ground states. We demonstrate that the collective motional state of one atomic ensemble can be selectively addressed while preserving neighboring ensembles near their ground states to better than 95% per excitation quantum. We also show that our system offers nanometer-scale spatial resolution of each atomic ensemble via optomechanical imaging. This technique enables the in situ parallel sensing of potential landscapes, a capability relevant to active research areas of atomic physics and force-field detection in optomechanics.

Nathaniel Brahms, Daniel W. C. Brooks, Sydney Schreppler +2 more

Dan Stamper-Kurn

Thierry Botter

An exciting scientific goal, common to many fields of research, is the development of ever-larger physical systems operating in the quantum regime. Relevant to this dissertation is the objective of preparing and observing a mechanical object in its motional quantum ground state. In order to sense the object's zero-point motion, the probe itself must have quantum-limited sensitivity. Cavity optomechanics, the interactions between light and a mechanical object inside an optical cavity, provides an elegant means to achieve the quantum regime. In this dissertation, I provide context to the successful cavity-based optical detection of the quantum-ground-state motion of atoms-based mechanical elements; mechanical elements, consisting of the collective center-of-mass (CM) motion of ultracold atomic ensembles and prepared inside a high-finesse Fabry-P'erot cavity, were dispersively probed with an average intracavity photon number as small as 0.1. I first show that cavity optomechanics emerges from the theory of cavity quantum electrodynamics when one takes into account the CM motion of one or many atoms within the cavity, and provide a simple theoretical framework to model optomechanical interactions. I then outline details regarding the apparatus and the experimental methods employed, highlighting certain fundamental aspects of optical detection along the way. Finally, I describe background information, both theoretical and experimental, to two published results on quantum cavity optomechanics that form the backbone of this dissertation. The first publication shows the observation of zero-point collective motion of several thousand atoms and quantum-limited measurement backaction on that observed motion. The second publication demonstrates that an array of near-ground-state collective atomic oscillators can be simultaneously prepared and probed, and that the motional state of one oscillator can be selectively addressed while preserving the near-zero-point motion of neighboring oscillators.