Conditional Transformation Operator for Near State Generation

We show that by minor modification of the previously proposed procedure for the generation of near-coherent states, one can produce “near states” even from a mixed input state. In this study, we consider this procedure as a conditional quantum-state transformation and find the explicit form of the non-unitary transformation operator. We demonstrate that even in mixed states, this quantum process can produce nonclassical states with a smooth non-positive P-function.