Equivalence principle, quantum mechanics, and atom-interferometric tests

TL;DR

The paper critically examines a recent proposal to reinterpret atom interferometry experiments, highlighting its conflicts with fundamental principles of General Relativity and Quantum Mechanics, and concludes it is not tenable.

Contribution

It provides a detailed analysis of the equivalence principle's role in quantum mechanics and evaluates the validity of the controversial reinterpretation proposal.

Findings

The reinterpretation proposal faces significant compatibility issues.

Current experiments do not support the claimed reduction in bounds for violations.

The proposal is deemed too problematic to support its claims.

Abstract

That gravitation can be understood as purely metric phenomenon depends crucially on the validity of a number of hypotheses which are summarised by the Einstein Equivalence Principle, the least well tested part of which being the Universality of Gravitational Redshift. A recent and currently widely debated proposal (Nature 463 (2010) 926-929) to re-interpret some 10-year old experiments in atom interferometry would imply, if tenable, substantial reductions on upper bounds for possible violations of the Universality of Gravitational Redshift by four orders of magnitude. This interpretation, however, is problematic and raises various compatibility issues concerning basic principles of General Relativity and Quantum Mechanics. I review some relevant aspects of the equivalence principle and its import into quantum mechanics, and then turn to the problems raised by the mentioned proposal. I conclude that this proposal is too problematic to warrant the claims that were launched with it.