Anderson localization of composite particles and decoherence

We investigate the effect of coupling between translational and internal degrees of freedom of composite quantum particles on their localization in a random potential.

Anderson localization can be understood as interference phenomena between multiple scattering paths. The dynamics of the composite particle is, however, affected by couplings to internal states that provide which-way information, that may suppress quantum interferences thus affecting localization in the spatial dimension. We illustrate that the coupling has a dramatic effect on localization properties, even with a small number of internal states participating in quantum dynamics. The model can be applied to quantum walk and Anderson localization of photons with orbital angular momentum.