Quantum and classical aspects of coincidence imaging

The differences between classical and quantum sources in the context of coincidence imaging are discussed. Consequently, a classical source must be configured to work with a particular reference geometry, whereas use of a quantum source allows the reference geometry to be chosen after the source is in place. It is shown how the fixed-basis limitation of a classical source can be compensated by a pair of lenses near the source, so that in practical terms a classical coincidence imaging setup will provide nearly the same flexibility as a quantum coincidence imaging setup.