  We study the ultimate limits to the decoherence rate associated with
dephasing processes. Fluctuating chaotic quantum systems are shown to exhibit
extreme decoherence, with a rate that scales exponentially with the particle
number, thus exceeding the polynomial dependence of systems with fluctuating
$k$-body interactions. Our findings suggest the use of quantum chaotic systems
as a natural test-bed for spontaneous wave function collapse models. We further
discuss the implications on the decoherence of AdS/CFT black holes resulting
from the unitarity loss associated with energy dephasing.
