Testing general relativity at the quantum level

It is shown that the effect of a gravitational field on a hydrogen atom is to admix states of opposite parity such as 2Ssub(1/2) and 2Psub(1/2). The phase of this admixture is such as to produce circular polarization of the radiation emitted in transitions such as 2Ssub(1/2) → 1Ssub(1/2) +γ which arises from the interference between the gravity-induced amplitude and that due to the weak neutral current. The predicted magnitude of the circular polarization, which could be sufficiently large to be detected in white dwarfs or in certain binary systems, varies from theory to theory. It is thus possible that a study of this effect could provide a feasible means of testing general relativity at the quantum level. (author)