title: Measurement of the transverse spatial quantum state of light at the single-photon level.
abstract: We present an experimental method to measure the transverse spatial quantum state of an optical field in coordinate space at the single-photon level. The continuous-variable measurements are made with a photon-counting, parity-inverting Sagnac interferometer based on all-reflecting optics. The technique provides a large numerical aperture without distorting the shape of the wavefront, does not introduce astigmatism, and allows for characterization of fully or partially coherent optical fields at the single-photon level. Measurements of the transverse spatial Wigner functions for highly attenuated coherent beams are presented and compared with theoretical predictions.
authors.affiliation: Oregon Center for Optics, Department of Physics, University of Oregon, Eugene, Oregon 97403, USA. bsmith4@uoregon.edu
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Smith
authors.forename: Bryan
authors.initials: B
authors.lastname: Killett
authors.forename: M G
authors.initials: MG
authors.lastname: Raymer
authors.forename: I A
authors.initials: IA
authors.lastname: Walmsley
authors.forename: K
authors.initials: K
authors.lastname: Banaszek