Quantum reflection of antihydrogen from a liquid helium film

TL;DR

This paper investigates how ultracold antihydrogen atoms quantum reflect off liquid helium surfaces, revealing potential for extended antihydrogen lifetimes useful in gravity experiments.

Contribution

It provides detailed calculations of quantum reflection and Casimir-Polder potentials for antihydrogen on helium films, introducing a Liouville transformation analysis of scattering interferences.

Findings

Antihydrogen can be trapped for over 1 second on liquid helium surfaces.

Quantum reflection probabilities depend on helium film thickness and substrate.

Interference effects in scattering are explained via Liouville transformation.

Abstract

We study the quantum reflection of ultracold antihydrogen atoms bouncing on the surface of a liquid helium film. The Casimir-Polder potential and quantum reflection are calculated for different thicknesses of the film supported by different substrates. Antihydrogen can be protected from anni- hilation for as long as 1.3s on a bulk of liquid 4He, and 1.7s for liquid 3He. These large lifetimes open interesting perspectives for spectroscopic measurements of the free fall acceleration of antihydrogen. Variation of the scattering length with the thickness of a film of helium shows interferences which we interpret through a Liouville transformation of the quantum reflection problem.