  We propose a new duality relation between codimension two space-like surfaces
in gravitational theories and quantum states in dual Hilbert spaces. This
surface/state correspondence largely generalizes the idea of holography such
that we do not need to rely on any existence of boundaries in gravitational
spacetimes. The present idea is motivated by the recent interpretation of
AdS/CFT in terms of the tensor networks so called MERA. Moreover, we study this
correspondence from the viewpoint of entanglement entropy and information
metric. The Cramer-Rao bound in quantum estimation theory implies that the
quantum fluctuations of radial coordinate of the AdS is highly suppressed in
the large N limit.
