2013/01/31 by F Just, Felix Just, Andrea Cavanna +5
Computer Science · Physics and Astronomy · #Coherence (philosophical gambling strategy) #Field (mathematics) #Measure (data warehouse) #Parametric statistics #Phase (matter) #Photon #Quantum Electrodynamics and Casimir Effect #Quantum Information and Cryptography #Quantum Mechanics and Applications #Quantum entanglement #Spontaneous parametric down-conversion #Transverse plane #quant-ph
paper · pdf · doi:10.1088/1367-2630/15/8/083015
published as New J. Phys. 15 (2013) 083015 · 11 pages, 6 figures
openalex publication_date 2013/08/08 · arxiv created 2013/08/23 · arxiv updated 2015/06/12 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We measure the transverse entanglement of photon pairs on their propagation from the near to the far field of spontaneous parametric down-conversion (SPDC). The Fedorov ratio, depending on the widths of conditional and unconditional intensity measurements, is shown to be only able to characterize entanglement in the near and far field zones of the source. Therefore we also follow a different approach. By evaluating the first-order coherence of a subsystem of the state we can quantify its entanglement. Unlike previous measurements, which determine the Fedorov ratio via intensity correlations, our setup is sensitive to both phase and modulus of the biphoton state and thus always grants experimental access to the full transverse entanglement of the SPDC state. It is shown theoretically that this scheme represents a direct measurement of the Schmidt number.