Two Photon Entanglement

via Efficient Spontaneous Parametric Downconversion


Entanglement is a unique quantum mechanical resource that plays a key role in many applications of quantum computation and communication. A member of our group (M. Pavicic) provided a theory of two and four photon entanglement [Pavicic, M., Phys. Rev. A 50 (1994); 3486, Pavicic, M. and J. Summhammer, Phys. Rev. Lett. 73 (1994); 3191, Pavicic, M., J. Opt. Soc. Am. B 12 (1995); 821]. Subsequent experiments with ultra bright sources of entangled photons based on spontaneous parametric downconversion in nonlinear crystals opened a whole field of research on the foundations of quantum mechanics. Practical quantum communication implementations, however, require as high a yield of the down-conversion processes as possible. We will address this question by probing new types of nonlinear crystals, using quantum cavities and femtosecond laser pulse techniques as well as investigating possibilities of building miniature entangled photon sources.

An unsymetric entanglement system with one fiber coupled arm and one air coupled arm.


A home-made laser driver used in the above entanglement setup.