New Record for Photon Heralding

“Demonstrating highly symmetric single-mode, single-photon heralding efficiency in spontaneous parametric downconversion,” Marcelo Da Cunha Pereira, Francisco E Becerra, Boris L Glebov, Jingyun Fan, Sae Woo Nam, and Alan Migdall, Optics Letters, May 15, 2013.

A JQI/PFC experiment establishes a new record for symmetric single-mode, single-photon, heralding efficiency for a pair of entangled photons produced during parametric downconversion. About 84% of the time they observe photon A in one detector they also observe photon B just where it should be in a second detector, and vice versa. The aim of the JQI experiment is not itself to test the Bell criteria for entanglement (as it turns out the polarizations of photons A and B are known beforehand) but rather to optimize the process of heralding---the ability to say that if A is here then B is there. Some theorists hold that the heralding efficiency must be at least 82% if entanglement loopholes are to be closed. The JQI result has exceeded this criterion. The JQI detection scheme will be useful for a number of reasons: it should help experiments to tighten remaining loopholes over the fundamental sway of quantum reality; with the use of a shutter, it should help to establish a reliable source of single photons; and it might be an ingredient in the creation of a source of random numbers. Light produced in the process of spontaneous parametric down conversion.

(Illustration credit: NIST).