Entanglement harvesting from the electromagnetic vacuum with hydrogenlike atoms

Abstract

We study how two fully-featured hydrogenlike atoms harvest entanglement from the electromagnetic field vacuum, even when the atoms are spacelike separated. We compare the electromagnetic case -qualitatively and quantitatively-with previous results that used scalar fields and featureless, idealized atomic models. Our study reveals the new traits that emerge when we relax these idealizations, such as anisotropies in entanglement harvesting and the effect of exchange of angular momentum. We show that, under certain circumstances, relaxing previous idealizations makes vacuum entanglement harvesting more efficient.

General relativistic quantum optics: Finite-size particle detector models in curved spacetimes

“…For concreteness, we are going to focus on free scalar field quantization and on particle detectors that couple linearly to the field. This scenario is paramount in many studies in quantum field theory in curved spacetimes, relativistic quantum information, and in quantum optics, since scalar particle detector models such as the Unruh-DeWitt (UDW) [4,5] detector have been proven to be good models for the light-matter interaction in most regimes [9,18]. The theory of a free scalar field in an arbitrary curved spacetime in D = n + 1 dimensions is described by an action given by…”

Faster-than-light signaling in the rotating-wave approximation

“…To increase the physicality of the model at the same time as avoiding spurious divergences, the interaction used will be a spatially smeared Unruh-DeWitt interaction that, as has been discussed, captures all the fundamental features of the light-matter interaction when exchange of angular momentum between atoms and light is not relevant [2,3]:…”

“…where χ(t) is a switching function controlling the duration of the interaction and its adiabaticity or suddenness, λ is the interaction strength,σ ± are the detector raising and lower operators, Ω is the detector's energy gap and F (y), which has dimensions of [L] −3 , is the detector's smearing that can be associated to the wavefunctions of the excited and ground state of the atom being modelled [2,3]. We will assume that the smearing function is only non-negligible for a length scale R (the size of the atom).…”

Directional dependence of the Unruh effect for spatially extended detectors

“…We ask whether the temperature seen by these observers is still independent of the direction. The question is nontrivial: while a spatially pointlike detector with a monopole coupling is known to be a good approximation for the interaction between the quantum electromagnetic field and electrons on atomic orbitals in processes where the angular momentum interchange is insignificant [8,9], finite size effects can be expected to have a significant role in more general situations [10,11,12,13,14,15]. Also, the notion of a finite size accelerating body has significant subtlety: while a rigid body undergoing uniform linear acceleration in Minkowski spacetime can be defined in terms of the boost Killing vector, different points on the body have differing values of the proper acceleration, and the body as a whole does not have an unambiguous value of 'acceleration'.…”