Various aspects of modern coherence theory are studied in quantum optics. So, some elementary experiences eg the double slit experience are often used to illustrate the particle-wave duality of the light.
However, the theory of partially coherent light is very sufficient to describe and predict the results of these experiences. In the theory of partially coherent light, there are no particles at all ; only waves, statistics and uncertainty. In the both theories, the global phase is an unobservable parameter, but the amplitude of a wave function is only important for the theory of partial coherent light and is commonly normalized away in quantum-mechanics.