Heralded Photon Purification

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Science  02 May 2008:
Vol. 320, Issue 5876, pp. 587
DOI: 10.1126/science.320.5876.587b

Quantum information processing requires techniques for the generation and transportation of quantum data. The use of photons as the carriers of that quantum information, with the data encoded as different polarization states of the light, is particularly appealing because photons are robust against decoherence effects and can be transported over long distances. The photons, however, need to be indistinguishable; i.e., identical and in a pure quantum state. Although techniques exist for the generation for single photons, determining whether they are in fact indistinguishable and pure has generally required a postselection or spectral filtering process that compromises their quantum utility. By careful design of the parametric downconversion process, in which a single photon is divided into two entangled photons, Mosley et al. show that restricting the optical modes into which the photon pairs emerge can provide a method for the generation of heralded (by measurement of one member of the pair) indistinguishable single photons of high purity. — ISO

Phys. Rev. Lett. 100, 133601 (2008).

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