Errors in quantum state identification with ultrashort pulses

From the nonclassicality of photon superbunching to the basic property of intensity, we characterize light with correlation and coherence functions. The correlation functions for nonstationary sources, such as short pulses, depend deterministically on the time dependent shape of the field and change the probability of the ensemble in time. We start from the fundamental principles of detection and show how nonstationary fields result in a coherence function that depends not only on the statistics of the field but also on the field shape. This means that observations of bunching and superbunching with ultrafast sources are not indicative of the quantum state of the field.