Testing Quantum Mechanics by Measuring the High-Amplitude Motion of a Massive Oscillator

ABSTRACT

I will describe measurements of the individual phonons in a 1 ng body of superfluid helium. When this body is in equilibrium, its phonon correlations are consistent with a thermal state having a mean occupancy ~ 1 phonon. These thermal fluctuations remain essentially unchanged even when the system is in a state of coherent motion corresponding to ~100,000 phonons. I will describe how these results can be used to constrain a certain class of nonlinear extensions of quantum mechanics. Somewhat surprisingly, this data places constraints at roughly the same level as experiments at the Large Hadron Collider.

BIOGRAPHY

Jack Harris is a professor of physics and applied physics at Yale University and a member of the Yale Quantum Institute. Professor Harris studies the quantum aspects of motion in macroscopic objects that combine mechanical, optical, and superfluid components. His group’s experiments use ultrasensitive force detectors to measure quantum fluctuations of objects that are visible to the naked eye. He received his undergraduate degree from Cornell University and his Ph.D. from UCSB, where he developed ultrasensitive micromechanical sensors and used them to study quantum Hall systems in the group of David Awschalom. He was a postdoctoral fellow at the Harvard/MIT Center for Ultracold Atoms, where he worked with John Doyle and Wolfgang Ketterle on a cryogenic atom-trapping experiment. Since joining the Yale faculty in 2004, his group has developed novel approaches to the field of quantum optomechanics, including the “membrane-in-the-middle” device, and various means for combining high-finesse optical cavities with superfluid helium.