  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.

Quantum Physics