One of the outstanding “Big Questions” in physics is: How does the apparently classical world of macroscopic objects emerge from a universe that is fundamentally quantum mechanical?

In recent decades it has become clear that the laws of quantum mechanics predict that quantum effects (such as entanglement, superposition, and the Heisenberg Uncertainty Principle) can be observed in macroscopic objects, provided that these objects are sufficiently isolated from dissipation. One promising approach to testing this prediction has been to couple the photons trapped inside an optical cavity to the motion of a macroscopic mechanical oscillator. If the photons and the mechanical oscillator both have sufficiently low dissipation, this coupling provides a natural way to generate and observe quantum effects in the mechanical oscillator’s motion.

The goal of this project is to realize an entirely new type of optomechanical device that will achieve vastly lower dissipation than any existing device. To do this, we will fully exploit the unique properties of superfluid liquid helium. Specifically, we will use magnetic levitation to suspend a drop of superfluid liquid helium in vacuum. The millimeter-scale drop will serve both as an optical cavity (via its whispering gallery modes) and as a mechanical element (via its vibrations and rotation).

As related in the Project Description, this device will provide unprecedentedly low damping for photons as well as for the mechanical motion, allowing it to reach the “single quantum strong coupling regime”, an outstanding goal in this field. The ability of the drop to rotate freely will also realize a unique type of optomechanical coupling ideally suited to detecting quantum effects in the drop’s motion. Lastly, this project will achieve these goals in an object roughly three orders of magnitude more massive than any device that has demonstrated quantum behavior.