en اپتیک کوانتمی، مخابرات کوانتمی و کامپیوترهای اپتیکی Quantum Optics, Quantum Communications, Quantom Computing پژوهشي Research <span style="font-size:11pt"><span new="" roman="" style="font-family:" times=""><span style="font-weight:bold"><span style="color:#000000"><span style="font-style:normal"><span style="white-space:normal"><span style="text-decoration:none">This paper describes the second-order coherence degree of photons produced in SPDC. First, the nonlinear BBO crystal generates the twin correlated signal and idler photons in the experimental setup. Then, g² (0) is obtained experimentally via Hanbury Brown-Twiss set-up for investigation of the light source nature. The results show this value is less than 1 which verifies the generated photons are in the heralded single photon (HSP) regime.</span></span></span></span></span></span></span> Spontaneous parametric down-conversion, Heralded Single Photon, Second-order degree of coherence. 145 152 http://ijop.ir/browse.php?a_code=A-10-898-1&slc_lang=en&sid=1 Hoda Sadat Lotfipour hodalotfipoor@gmail.com 10031947532846004661 10031947532846004661 Yes Photonics and Quantum Technologies Research School, Nuclear Science and Technology Research Institute (NSTRI) Majid Khodabandeh majidkh92@gmail.com 10031947532846004662 10031947532846004662 No Quantum BioPhotonics Group, Iranian Center for Quantum Technologies (ICQTs), Tehran, Iran Zahra Bagheri bagheri.zahra110@gmail.com 10031947532846004663 10031947532846004663 No Quantum BioPhotonics Group, Iranian Center for Quantum Technologies (ICQTs), Tehran, Iran Hassan Sobhani hassan960SOB@yahoo.com 10031947532846004664 10031947532846004664 No Photonics and Quantum Technologies Research School, Nuclear Science and Technology Research Institute (NSTRI)