# Collective effects in Casimir-Polder forces

## TL;DR

This paper investigates how collective quantum states of emitters near a surface can modify Casimir-Polder forces, revealing that super- and subradiant states can enhance or suppress these forces through cooperative effects.

## Contribution

It introduces the concept that collective quantum states can be used to control and tailor vacuum fluctuation-induced forces in surface-emitter systems.

## Key findings

- Superradiant states enhance Casimir-Polder forces.
- Subradiant states suppress Casimir-Polder forces.
- Force modifications depend on surface response at emitter resonance.

## Abstract

We study cooperative phenomena in the fluctuation-induced forces between a surface and a system of neutral two-level quantum emitters prepared in a coherent collective state, showing that the total Casimir-Polder 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. Such cooperative fluctuation forces depend singularly on the surface response at the resonance frequency of the emitters, thus being easily maneuverable. Our results demonstrate the potential of collective phenomena as a new tool to selectively tailor vacuum forces.