Can we observe the gravitational quantum states of Positronium?

TL;DR

This paper explores the possibility of observing gravitational quantum states of positronium using techniques similar to those used with neutrons, aiming to measure gravitational effects on antimatter with current or near-future technology.

Contribution

It proposes a feasible experimental scheme for detecting gravitational quantum states of positronium, outlining necessary technological milestones and estimating expected signal rates.

Findings

Most required techniques are currently available.

Key milestones include focusing positron beams, Stark deceleration, and excitation of positronium.

Estimated signal rates suggest potential for experimental observation.

Abstract

In this paper we consider the feasibility of observing the gravitational quantum states of positronium. The proposed scheme employs the flow-throw technique used for the first observation of this effect with neutrons. Collimation and Stark deceleration of Rydberg positronium atoms allow to select the required velocity class. If this experiment could be realized with positronium it would lead to a determination of g for this matter-antimatter system at the few % level. As discussed in this contribution, most of the required techniques are currently available but important milestones have to be demonstrated experimentally before such an experiment could become reality. Those are: the efficient focusing of a bunched positron beam, Stark deceleration of Rydberg positronium and its subsequent excitation into states with large angular momentum. We provide an estimate of the efficiencies we expect for these steps and assuming those could be confirmed we calculate the signal rate.