Mass-energy equivalence in atom-light interactions and fundamental tests with composite particles

Abstract

Composite particles (e.g. atoms and molecules) are excellent tools for tests of joint quantum and general relativistic effects, such as time dilation of quantum clocks, tests of gravity in the mesoscopic regime, and coupling of quantum particles to various environments.

A two-level system coupled to a field is a simple but powerful model of a quantum system interacting with an external environment. As the system’s internal state can change in response to the field, e.g. its internal energy increases at the expense of absorbing a particle from the field, the model is often called a `particle detector’. Simple such models, with a point-like two-level system on a classical trajectory, are called Unruh-DeWitt detectors. Recent models incorporating quantum effects of the detector’s centre of mass have produced interesting results, however they cannot yet capture known relativistic effects required in typical applications of the model—such as in atom-light interactions.

We have addressed this problem by incorporating quantisation of the centre of mass and the internal mass-energy into the Unruh-DeWitt model. We show that internal energy changes due to emission or absorption are relevant even in the lowest energy limit—corrections to transition rates due to the detector’s mass changing cannot be ignored unless the entirety of the centre of mass dynamics is also ignored. Our results imply that one cannot have a consistent model of a massive particle interacting with a relativistic quantum field without including relativistic mass-energy equivalence, at the least, in the particle’s dynamics.

In this talk, I will discuss these recent results and others from our group, as well as some open problems arising from this research.

Carolyn Wood

Postdoctoral Scientist

Carolyn Wood is a postdoctoral researcher at the University of Queensland, in Brisbane, Australia focusing on quantum machine learning and physics at the interface between quantum mechanics and general relativity.