Evaluation of polarization entanglement generated by pulsed spontaneous parametric down-conversion with multi-pairs using four single-photon detectors for quantum state tomography |
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| Authors: | Akio Yoshizawa Daiji Fukuda Hidemi Tsuchida |
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| Affiliation: | 1. RCPTM, Joint Laboratory of Optics of Palacký University and Institute of Physics of Academy of Sciences of the Czech Republic, 17. listopadu 12, 771 46 Olomouc, Czech Republic;2. Institute of Physics of Academy of Sciences of the Czech Republic, Joint Laboratory of Optics of PU and IP AS CR, 17. listopadu 50A, 772 07 Olomouc, Czech Republic;1. Department of Material Science and Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan;2. Department of Polymer Engineering Mechanical Engineering Technology, College of Industrial Technology, King Mongkut''s University of Technology North Bangkok, Bangkok 10800, Thailand;1. Rheumatology Department, Faculty of Medicine, Cairo University, Egypt;2. Clinical Pathology Department, Faculty of Medicine, Cairo University, Egypt;1. Department of Chemistry and Biochemistry, Duquesne University, 600 Forbes Avenue, Pittsburgh, PA 15282, USA;2. Chemical and Engineering Materials Division, Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA;3. International Centre for Diffraction Data, 12 Campus Boulevard, Newtown Square, PA 19073-3273, USA;4. University of Michigan, Department of Materials Science and Engineering, Laboratory of Emerging Energy and Electronic Materials LE3M, Ann Arbor, MI 48109, USA;1. College of Physics and Electronic Engineering, Hengyang Normal University, Hengyang, 421002 China;2. Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education, Hunan Normal University, Changsha, 410081 China;3. Synergetic Innovation Center for Quantum Effects and Applications, Hunan Normal University, Changsha, 410081 China;4. CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Beijing, 100190 China |
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| Abstract: | Quantum state tomography (QST) is widely used to evaluate entanglement generated by spontaneous parametric down-conversion. Two-fold coincidence counts for 16 different configurations have been measured using single-photon detectors to estimate the fidelity (i.e., the probability overlap between ideal and real states) from the reconstructed density matrix. However, multi-pair emission events degrade the fidelity. Here, we numerically analyze pulse-pumped polarization-entangled photon pairs for single-photon detectors that can or cannot count the number of incident photons to estimate the fidelity given by QST. Threshold single-photon detectors are desirable for QST from a practical point of view. Our analysis suggests that using four threshold single-photon detectors for two-fold coincidence measurements offers almost the same fidelity as that given by four photon-number-resolving single-photon detectors. The fidelity estimated by QST becomes poor and loss independent when two threshold single-photon detectors are used. |
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