Abstract
We report a source of polarization-entangled photon pairs in the 1550-nm telecommunication band, which is based on non-collinear spontaneous parametric down-conversion in a periodically poled lithium niobate crystal pumped by picosecond pulses. This source is realized utilizing a polarization-based Sagnac interferometer employing a type-0 non-collinear quasi-phase-matching configuration. Polarization entanglement is verified through measurement of the polarization-correlation interference fringes with visibility >96% and by testing the experimental violation of the Clauser-Horne-Shimony-Holt (CHSH) form of Bell’s inequality. The CHSH-Bell parameter S is found to be 2.72 ± 0.04, with 18 standard deviations from the statistical uncertainty.
Highlights
Entangled photon-pair sources are widely recognized as key components for implementation of entanglement-based quantum information technology, such as linear optical quantum computing[1,2], quantum communication[3,4], and quantum metrology[5,6]
Combination of non-collinear quasi-phase matching (QPM)-spontaneous parametric down-conversion (SPDC) in a type-0 periodically poled lithium niobate (PPLN) with a highly stable interferometer is a promising method for efficient generation of polarization-entangled photon pairs with high brightness and intrinsic phase stability in the telecommunication band
Correlated photon pairs in the telecommunication band centred at 1550 nm were generated through a non-collinear QPM-SPDC process in a 10-mm-long type-0 PPLN crystal with a 19.2-μm grating period (Fig. 1(a))
Summary
Entangled photon-pair sources are widely recognized as key components for implementation of entanglement-based quantum information technology, such as linear optical quantum computing[1,2], quantum communication[3,4], and quantum metrology[5,6]. Over the past two decades, various source systems for entangled photon generation have been reported, which have been designed to satisfy the requirements of such quantum technology applications These systems are based on spontaneous parametric down-conversion (SPDC)[7], optical fibres[8], semiconductors[9], silicon waveguides[10], and atomic ensembles[11]. Combination of non-collinear QPM-SPDC in a type-0 PPLN with a highly stable interferometer is a promising method for efficient generation of polarization-entangled photon pairs with high brightness and intrinsic phase stability in the telecommunication band. A type-0 non-collinear QPM-SPDC in a PPKTP crystal operated in continuous mode was used to generate highly bright polarization-entangled photons at 810-nm wavelength[29]. We note that non-collinear geometry employing type-0 QPM-SPDC can significantly enhance the brightness of the photon-pair source, and aid development of new methods applicable to experimental quantum information science and technology
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