25 August 2005 Measurement of the spectral properties of the two-photon state generated via type-II spontaneous parametric down-conversion
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Proceedings Volume 5893, Quantum Communications and Quantum Imaging III; 58930L (2005); doi: 10.1117/12.613611
Event: Optics and Photonics 2005, 2005, San Diego, California, United States
Abstract
Spontaneous parametric down-conversion (SPDC) is the most often used source of entangled photon states in quantum optics. Recently, it has been suggested in theory that the reduction of polarization entanglement between the photon pair generated via the type-II SPDC process pumped by a ultrafast laser is due to the asymmetry in the joint spectrum function, which is the indicative of the frequency entanglement between the two photons. In this paper, we report the measurement of the joint spectrum function (i.e., direct observation of the degree of frequency entanglement) of the two-photon state of type-II SPDC in both cw- and ultrafast-laser pumping conditions. We observed that, in agreement with the theory, the degree of frequency entanglement (the shape of the joint spectrum function) is indeed different for cw- and ultrafast-pumped type-II SPDC. Our results are of importance in "engineering" the two-photon state for specific quantum applications, such as quantum cryptography.
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Yoon-Ho Kim, Warren P. Grice, "Measurement of the spectral properties of the two-photon state generated via type-II spontaneous parametric down-conversion", Proc. SPIE 5893, Quantum Communications and Quantum Imaging III, 58930L (25 August 2005); doi: 10.1117/12.613611; https://doi.org/10.1117/12.613611
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KEYWORDS
Ultraviolet radiation

Ultrafast phenomena

Crystals

Quantum cryptography

Laser crystals

Monochromators

Photon polarization

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