  The Polyakov loop of an operator in the anti-symmetric representation in N=4
SYM theory on spacial R^3 is calculated, to leading order in 1/N and at large
't Hooft coupling, by solving the saddle point equations of the corresponding
quantum impurity model. Agreement is found with previous results from the
supergravity dual, which is given by a D5-brane in an asymptotically AdS_5 x
S^5 black brane background. It is shown that the azimuth angle, at which the
dual D5-brane wraps the S^5, is related to the spectral asymmetry angle in the
spectral density associated with the Green's function of the impurity fermions.
Much of the calculation also applies to the Polyakov loop on spacial S^3 or
H^3.
