Collective effects in Casimir-Polder forces*

Fluctuation forces between neutral objects due to the quantum fluctuations of the electromagnetic field are a fascinating feature of quantum electrodynamics. When considering atom-surface interactions at nanoscales, such forces become an imperative element of consideration in understanding nanophotonic systems. It is then an important question whether and how these forces can be tailored to achieve better control and coherence of quantum systems interacting at nanoscales. In this talk we introduce the use of collective effects as a means to tailor Casimir-Polder (CP) forces.
We analyze the fluctuation forces between a surface and a system of neutral two-level quantum emitters, showing that the total CP force on the emitters can be modified via their mutual correlations. Particularly, we find that a collection of emitters prepared in a super- or subradiant state experiences an enhanced or suppressed collective vacuum-induced force, respectively. The collective nature of dispersion forces can be understood as resulting from the interference between the different processes contributing to the surface-modified resonant dipole-dipole interaction. Our results demonstrate the potential of collective phenomena as a new tool to selectively modify vacuum forces.