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Updated: Aug 13, 2026

Quantum State Engineering of Light with Continuous-wave Optical Parametric Oscillators
Published on: May 30, 2014
Measurement of the transverse spatial quantum state of light at the single-photon level
Brian J Smith1, Bryan Killett, M G Raymer
1Oregon Center for Optics, Department of Physics, University of Oregon, Eugene, Oregon 97403, USA. bsmith4@uoregon.edu
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.
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