Richard Lopp | Applied Math, University of Waterloo
Light-matter interactions without breaking Lorentz covariance
In investigating light-matter systems, i.e. the interaction between the electromagnetic field and atoms, approximations are often performed in the literature that break the Lorentz covariance of the model. These include the rotating-wave approximation, the single- or few-mode approximation, and dimensional reduction of the original space-time to an effective lower dimensional one. Often, these approximations require more justification than is usually given, especially when studying relativistic effects.
In particular, relating to previous research, we studied how quantum randomness generation based on unbiased measurements on a hydrogen-like atom can get compromised by the unavoidable coupling of the atom with the electromagnetic field. In contradistinction to intuition derived from quantum optical approximations, we show that preparing the atom in the ground state in the presence of no field excitations is not universally the safest state to generate randomness.
Moreover, we studied the signature of detectors (such as atoms) accelerating through an optical cavity. We found that the single-mode approximation and dimensional reduction suffer from non-negligible deviations from the true results already in the weak coupling limit. This is of particular interest as recent experimental proposals suggested detecting the Unruh effect in a cavity where one is required to work in relativistic regimes.
Further research will focus on the fully Lorentz covariant description of dynamical Casimir-Polder forces and quantum friction on atoms moving on arbitrary trajectories and considering realistic light-matter interactions.