UC Santa Barbara

There are several unknown aspects about the decoherence mechanisms that cause the

transition of a system from the quantum to the classical regime. In this work we present

optomechanical systems, in which light couples to mechanical motion, as a suitable platform

for the study of decoherence in macroscopic systems.

We start by discussing some of the features of optomechanical systems, focusing on

the membrane-in-the-middle configuration. We then explain how optomechanical systems

can be extended to include multiple modes, which enables different state transfer

mechanisms, and we show an experimental demonstration of two such transfer schemes.

We also explain how multimode systems can exhibit an enhanced optomechanical coupling

rate for individual and collective mechanical modes.

Later we introduce periodic structures and how they can be applied at different scales

in order to improve the performance of our optomechanical devices. We first analyze the

vibrational modes of a thin membrane within the framework of linear elasticity and

proceed to show how a phononic crystal reduces the dissipation of mechanical energy in

the membrane. Next, we investigate an interference model for how a photonic crystal

can enhance the reflectivity of a membrane for out-of-plane propagating radiation. We

move on to outline the fabrication process for our optomechanical membrane devices.

We conclude with a theoretical proposal for a measurement of decoherence in a macroscopic

superposition state. This proposal relies on the state transfer techniques discussed

earlier and should be possible to implement with current technologies.