Squeezed Vibrational States in Superfluid Helium

TL;DR

This paper reports on ultrafast birefringence oscillations in superfluid helium, revealing anisotropic quantum squeezing of quasiparticle pairs across multiple vibrational modes.

Contribution

It provides experimental evidence of quantum squeezing in superfluid helium and analyzes the multimode interference effects on the observed response.

Findings

Ultrafast birefringence oscillations indicate quantum squeezing.

Dominant vibrational modes include rotons, maxons, and Pitaevskii's plateau.

Initial phase results from multimode interference.

Abstract

Ultrafast birefringence oscillations observed in superfluid helium provide evidence for anisotropic quantum squeezing of quasiparticle pairs. The measured response is a superposition of contributions from all vibrational modes, with dominant contributions from rotons, maxons, and Pitaevskii's plateau. The nonzero initial phase follows naturally from multimode interference.