Two-Photon Coincident-Frequency Entanglement via Extended Phase Matching
Onur Kuzucu, Marco Fiorentino, Marius A. Albotǎ, Franco N. C. Wong, Franz X. Kärtner · Physical Review Letters · 2005
We demonstrate a new class of frequency-entangled states generated via spontaneous parametric down-conversion under extended phase-matching conditions. Biphoton entanglement with coincident signal and idler frequencies is observed over a broad bandwidth in periodically poled KTiOPO4. We demonstrate high visibility in Hong-Ou-Mandel interferometric measurements under pulsed pumping without spectral filtering, which indicates excellent frequency indistinguishability between the down-converted photons. The coincident-frequency entanglement source is useful for quantum information processing and quantum measurement applications.