Photons meet with three-way split

A method that generates photon triplets could be a boon for quantum information.

Generating three photons from one is now a reality, opening the door to demonstrating entanglement.Karl Dolenc/iStockphoto

A single photon can now be split into three, thanks to the work of an international team of physicists. The achievement could open up new avenues in the field of quantum information.

The ability to split photons may not sound as extraordinary as other achievements in quantum physics, but for decades it has proved crucial to the success of many experiments. Often researchers need to know that photons are emitted at precisely the same time and are in phase with each other, and this is almost impossible if the photons come from separate sources.

In the past, devices have been able to split a photon only into two. In the typical method used to achieve this, known as parametric down-conversion, a laser beam is shone into a special ‘non-linear’ crystal — crystals that exhibit unusual optical effects under intense laser light. Occasionally, a single photon from the beam converts into two photons, each with a portion of the original’s energy and momentum.

Researchers have known that, in theory, it would be possible to split one of these new photons again in a ‘cascaded down-conversion’, making a total of three photons. But there has been a catch: the probability of one photon splitting is normally just one in a billion, making the probability of it happening twice in succession one in a billion billion. Experimentally, this has been too small to contemplate.

Technology has improved over time, however, and now Thomas Jennewein of the University of Waterloo in Ontario, Canada, and his colleagues have made three-photon generation a reality.

via Jon Cartwright Photons meet with three-way split : Nature News.

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