  A classical analogue of the entanglement entropy is calculated on the system
boundary of the two-dimensional Edwards-Anderson model, where the
nearest-neighbor interaction is stochastically chosen from +J and -J. The
boundary spin distribution is obtained by means of the time-evolving block
decimation (TEBD) method, where the random ensemble is created from the
successive multiplications of position-dependent transfer matrices, whose width
is up to N = 300. The random average of the entanglement entropy is calculated
on the Nishimori line, and it is confirmed that the entanglement entropy shows
critical singularity at the Nishimori point. The central charge of the boundary
state is estimated.
