  Since euclidean global AdS_2 space represented as a strip has two boundaries,
the state / operator correspondence in the dual CFT_1 reduces to the standard
map from the operators acting on a single copy of the Hilbert space to states
in the tensor product of two copies of the Hilbert space. Using this picture we
argue that the corresponding states in the dual string theory living on AdS_2 x
K are described by twisted version of the Hartle-Hawking states, the twists
being generated by a large unitary group of symmetries that this string theory
must possess. This formalism makes natural the dual interpretation of the black
hole entropy, -- as the logarithm of the degeneracy of ground states of the
quantum mechanics describing the low energy dynamics of the black hole, and
also as an entanglement entropy between the two copies of the same quantum
theory living on the two boundaries of global AdS_2 separated by the event
horizon.
