Photon pair sources with controlled frequency correlation

Development of efficient and well-controlled nonclassical photon sources is one of the keys in the quantum information and communication technology. We present our recent activities to develop advanced sources of photon pairs having controlled frequency correlation, by use of quasi-phase matching (QPM) and extended phase-matching (EPM). First, we present the generation of polarization and frequency entangled photons using QPM having two poling periods. We also demonstrate the photon pair generation with controlled frequency correlation and its application to making heralded single photons with intrinsically pure spectrotem-