Quantum bouncer: theory and experiment

TL;DR

This paper analyzes an experiment attempting to observe quantum states of neutrons in Earth's gravity, concluding that the data do not sufficiently support the claim of observing the quantum bouncer phenomenon.

Contribution

The paper critically evaluates the experimental setup and data, clarifying limitations in detecting vertical quantum states of neutrons in gravitational fields.

Findings

Experimental data are not sensitive to vertical quantum probability density.

The claim of observing neutron quantum states in Earth's gravity is not justified by the data.

The experimental design does not provide conclusive evidence of the quantum bouncer phenomenon.

Abstract

The quantum bouncer (QB) concept is a known QM textbook example of confined particle, namely, a solution to the 1D Schroedinger equation for a linear potential (the so-called Airy equation). It would be a great methodological challenge to create such a QM object in laboratory. An attempt of observation of the QB ``running'' in the horizontal direction was recently made by the international team at the Laue-Langevin Institute, Grenoble. The experiment was performed with ultra-cold neutrons. In this paper, the experiment is analyzed in view of the authors' claim that ``neutron quantum states in Earth gravitational field'' are observed. The experimental apparatus is designed for measurements of horizontal flux of neutrons passing through an absorbing wave guide with a variable height of absorber. From our analysis, it follows, however, that in such a layout measured data are not sensitive to quantum probability density in the vertical direction. The overall conclusion is made that the experimental data do not contain sufficient information to justify the claim.