Quantum Optomechanics

Speaker: Markus Aspelmeyer
Department: Kavli Colloqium
Subject: Quantum Optomechanics – exploring mechanical motion in the quantum regime
Location: TU Delft
Date: 01-03-2017
Author: Renée van der Winden

Markus Aspelmeyer came to talk to us about his research in establishing mechanical motion in the quantum regime. Techniques for this already exist, but only for single ions. Dr. Aspelmeyer wants to upscale this to up to 10^13 atoms. He first explained to us the basic and fundamental principle of his research. The setup for his experiments consists of a moveable mirror which is attached to a stationary wall with a spring. On the other side of the mirror, opposite the wall, is a lens through which light falls on the mirror. The photons that hit the mirror in this way, can cause it to be pushed back. This in turn changes the phase of the light in a nonlinear way. In this set-up the mirror functions as a harmonic oscillator. This leads to a position-dependent force and, because this is a retarded force, also a momentum-dependent force. This gives you control over the force and the movement of the mirror. However, photons leak to the environment and they leave the cavity between the lens and the mirror. This leads to decoherence and gives the need for a more isolated system.

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Figure 1: Very basic representation of the set-up used

The talk continued with a couple of applications. The technique can, amongst others, be used for mechanical memory and electromagnetically induced transparency. A surprise application that Dr. Aspelmeyer discovered in his lab was to improve the mechanical coating that is used in optomechanical systems. Right now these coatings are quite bad, which leads to a lot of dissipation to the environment. In fact, this is currently the limiting factor for systems such as optical clocks and gravitational wave detectors. Improving this coating will thus have a major influence on the operating of these systems.

I feel like I have not fully grasped the essence of the research that Dr. Aspelmeyer has done, because I did not really understand what it improved in relation to the current state of events. Nevertheless, I did enjoy the talk, not in the least because of Dr. Aspelmeyer’s enthusiasm about the subject. I do not intend on pursuing a career in physics, but the talk was still interesting.

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