Wigner-negative states in the steady-state emission of a two-level system driven by squeezed light
Phys. Rev. A 112, 013715 – Published 21 July, 2025
DOI: https://doi.org/10.1103/1kbt-kqjd
Abstract
Propagating modes of light with Wigner distributions exhibiting negativity are of fundamental interest in quantum optics and represent a key resource in the pursuit of optics-based quantum information technologies. Most schemes proposed or implemented for the generation of such modes are probabilistic in nature and rely on heralding by detection of a photon or on conditional methods where photons are separated from the original field mode by a beam splitter. We demonstrate theoretically, using a cascaded-quantum-system model, the possibility of deterministic generation of Wigner negativity in temporal modes of the steady-state emission of a two-level system driven by finite-bandwidth quadrature-squeezed light. Optimal negativity is obtained for a squeezing bandwidth similar to the linewidth of the transition of the two-level system. While the Wigner distribution associated with the incident squeezed light is Gaussian and everywhere positive, the Wigner functions of the outgoing temporal modes show distinct similarities and overlap with a superposition of displaced squeezed states.
