Distilling N00N-like components of two-mode quantum states of light

The set of efficiently produced quantum states of light is limited. Particularly difficult to produce are non-classical non-Gaussian super-positions. Nevertheless, with quantum state engineering certain properties of accessible states can be modified. We propose a filter that diminishes the contributions of components with approximately equal population to a two-mode quantum state of light. In return, N00N-like contributions to the quantum state are enhanced. The main feature of our method is that it works symmetrically on components with different mode occupation and thus does preserve super-positions. Furthermore, the filter is especially suitable for macroscopic states of light and can be implemented easily with beam splitters and photon detectors only. We discuss its applications to several quantum states and present first experimental results on the filters working principle.