  We present two methods for computing two-time correlation functions or
Green's functions from real time bold-line continuous time quantum Monte Carlo.
One method is a formally exact generalized auxiliary lead formalism by which
spectral properties may be obtained from single-time observables. The other
involves the evaluation of diagrams contributing to two-time observables
directly on the Keldysh contour. Additionally, we provide a detailed
description of the bold-line Monte Carlo method. Our methods are general and
numerically exact, and able to reliably resolve high-energy features such as
band edges. We compare the spectral functions obtained from real time methods
to analytically continued spectral functions obtained from imaginary time Monte
Carlo, thus probing the limits of analytic continuation.
