title: Quantum non-Gaussian Depth of Single-Photon States.
abstract: We introduce and experimentally explore the concept of the non-Gaussian depth of single-photon states with a positive Wigner function. The depth measures the robustness of a single-photon state against optical losses. The directly witnessed quantum non-Gaussianity withstands significant attenuation, exhibiting a depth of 18 dB, while the nonclassicality remains unchanged. Quantum non-Gaussian depth is an experimentally approachable quantity that is much more robust than the negativity of the Wigner function. Furthermore, we use it to reveal significant differences between otherwise strongly nonclassical single-photon sources.
authors.affiliation: Department of Optics, Palacký University, 17. listopadu 1192/12, 771 46 Olomouc, Czech Republic.
authors.forename: Ivo
authors.initials: I
authors.lastname: Straka
authors.affiliation: Institut für Experimentalphysik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria.
authors.forename: Ana
authors.initials: A
authors.lastname: Predojević
authors.affiliation: Institut für Experimentalphysik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria.
authors.forename: Tobias
authors.initials: T
authors.lastname: Huber
authors.affiliation: Department of Optics, Palacký University, 17. listopadu 1192/12, 771 46 Olomouc, Czech Republic.
authors.forename: Lukáš
authors.initials: L
authors.lastname: Lachman
authors.affiliation: Institut für Experimentalphysik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria.
authors.forename: Lorenz
authors.initials: L
authors.lastname: Butschek
authors.affiliation: Department of Optics, Palacký University, 17. listopadu 1192/12, 771 46 Olomouc, Czech Republic.
authors.forename: Martina
authors.initials: M
authors.lastname: Miková
authors.affiliation: Department of Optics, Palacký University, 17. listopadu 1192/12, 771 46 Olomouc, Czech Republic.
authors.forename: Michal
authors.initials: M
authors.lastname: Mičuda
authors.affiliation: Joint Quantum Institute, National Institute of Standards and Technology, and University of Maryland, Gaithersburg, Maryland 20849, USA.
authors.forename: Glenn S
authors.initials: GS
authors.lastname: Solomon
authors.affiliation: Institut für Experimentalphysik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria.
authors.forename: Gregor
authors.initials: G
authors.lastname: Weihs
authors.affiliation: Department of Optics, Palacký University, 17. listopadu 1192/12, 771 46 Olomouc, Czech Republic.
authors.forename: Miroslav
authors.initials: M
authors.lastname: Ježek
authors.affiliation: Department of Optics, Palacký University, 17. listopadu 1192/12, 771 46 Olomouc, Czech Republic.
authors.forename: Radim
authors.initials: R
authors.lastname: Filip