Harris, Jack

Date:    Tuesday May 23, 2023
Time:    14:00
Place:   ETH Campus Hönggerberg, HPF G6
Host:    Yiwen Chu

Counting phonons and measuring their coherences in a superfluid optomechanical device

Jack Harris - Yale University

Abstract: I will describe measurements of individual photons that are scattered inelastically from superfluid helium. We use these photon counts to study the phonons in a single acoustic mode of the superfluid. When this acoustic mode is in equilibrium, its phonon-phonon correlations are consistent (up to 4th order) with a thermal state of mean occupancy ~ 1. We find that the mode's purity is preserved even when it is driven to a coherent state with an amplitude corresponding to ~1E5 phonons. I will describe applications of these results to testing models of spacetime discreteness, and to distributing entanglement over kilometer-scale optical fiber networks.