# Does universality of free-fall apply to the motion of quantum probes?

## TL;DR

This paper investigates whether quantum particles obey the weak equivalence principle and finds that, while globally they do not, local assessments show some agreement, with implications for quantum-based mass sensing.

## Contribution

It provides a detailed analysis showing quantum particles do not fully satisfy the weak equivalence principle, but exhibit local agreement, highlighting nuanced interactions between quantum mechanics and gravity.

## Key findings

- Quantum particles do not satisfy the weak equivalence principle globally.
- Local assessments show some agreement with the principle.
- Implications for quantum mass sensing are discussed.

## Abstract

Can quantum-mechanical particles propagating on a fixed spacetime background be approximated as test bodies satisfying the weak equivalence principle? We ultimately answer the question in the negative but find that, when universality of free-fall is assessed locally, a nontrivial agreement between quantum mechanics and the weak equivalence principle exists. Implications for mass sensing by quantum probes are discussed in some details.