The two slit experiment, fundamentally requires more than one particle, as the slits themselves are made of matter. While one photon travels through the experi

The two slit experiment, fundamentally requires more than one particle, as the slits themselves are made of matter. While one photon travels through the experiment at a time, there are many particles interacting and influencing the fields that the photon travels through. In the information theory of Physics there are thought experiments about deep space, where one particle may be essentially all alone, in such cases the particle's decoherence becomes quite dramatic.