Abstract:
We consider non-unitary operations of photon addition (ρ→a†ρa) and photon subtraction (ρ→aρa†), which can be realized by selective measurements. Modifying the measurement, it is possible to implement a coherent superposition of those operations (ρ→(μa+νa†)ρ(μ∗a†+ν∗a)) that reduces to the differentiator if μ=−ν. Further, we discuss the possibility of wavefunction reconstruction based on non-unitary tomography.