  We discuss generalizations of the TFD to a density matrix on the doubled
Hilbert space. We suggest that a semiclassical wormhole corresponds to a
certain class of such density matrices, and specify how they are constructed.
Different semi-classical profiles correspond to different non-overlapping
density matrices. We show that this language allows for a finer criteria for
when the wormhole is semiclassical, which goes beyond entanglement. Our main
tool is the SYK model. We focus on the simplest class of such density matrices,
in a scaling limit where the ER bridge is captured by chords going from one
space to another, encoding correlations in the microscopic Hamiltonian. The
length of the wormhole simply encodes the extent these correlations are eroded
when flowing from one side to the other.
