Direct generation of photon triplets using cascaded photon-pair sources by Hannes Hübel, Deny Hamel, Sven Ramelow, Alessandro Fedrizzi, Kevin Resch, and Thomas Jennewein was published today in Nature.
Parametric down-conversion is the most common source of entangled photon pairs. It uses a nonlinear optical process to split a pump photon, typically from a laser, into two lower energy photons. It is only natural to ask whether we can find an analogous process for converting one photon into three. Many different physical mechanisms have been considered for this, but none have proven feasible until now. Taking advantage of advances in nonlinear optical materials, we have demonstrated, for the first time, production of photon triplets using a cascade of two down-conversion processes. These photon triplets will find application in quantum information technologies and serve as an interesting new system for fundamental studies.
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