  We explore the cosmological implications of quantum entanglement between two
causally disconnected universes in the multiverse. We first consider two
causally separated de Sitter spaces with a state which is initially entangled.
We derive the reduced density matrix of our universe and compute the spectrum
of vacuum fluctuations. We then consider the same system with an initially
non-entangled state. We find that scale dependent modulations may enter the
spectrum for the case of initially non-entangled state due to quantum
interference. This gives rise to the possibility that the existence of causally
disconnected universes may be experimentally tested by analyzing correlators in
detail.
