With the high intensities available from bright squeezed vacuum sources, there has been much recent interest in the quantum state of ultrashort pulse generation processes, such as high harmonic generation. To keep the deterministic time dependence used to describe ultrashort pulses, all of the statistical dependence of the light is included in the quantum state. However this introduces a fundamental change to the measurement of coherence. We address the change to coherence for light with a deterministic time dependence and how this affects both the coherence length and superbunching considered in experiments.