  We propose a simple experimental test of the quantum equivalence principle
introduced by Zych and Brukner [arXiv:1502.00971], which generalises the
Einstein equivalence principle to superpositions of internal energy states. We
consider a harmonically-trapped spin-$\frac12$ atom in the presence of both
gravity and an external magnetic field and show that when the external magnetic
field is suddenly switched off, various violations of the equivalence principle
would manifest as otherwise forbidden transitions. Performing such an
experiment would put bounds on the various phenomenological violating
parameters. We further demonstrate that the classical weak equivalence
principle can be tested by suddenly putting the apparatus into free fall,
effectively 'switching off' gravity.
