Physicists from the University of Oregon have successfully changed the color of individual photons within a fiber optic cable. They were able to do so by focusing a dual-color burst of light from two lasers onto an optical cable carrying a single photon of a distinct color. Through a process known as Bragg scattering, a small amount of energy was exchanged between the laser light and the photon, causing the photon to change color. The achievement could pave the way for transferring and receiving high volumes of secured electronic data.
Individual bits of data are currently represented by many electrons, and are optically transmitted via pulses of infrared light containing many photons. In the promising future technology of quantum computing, those same bits could be represented by individual electrons, and transmitted via individual photons. Being able to change the color of those photons could greatly facilitate that process.
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“In today's fiber optic lines one frequency of light may carry a phone conversation, while others may carry TV channels or emails, all traveling in separate channels across the Internet,” explained U Oregon physicist Michael G. Raymer. “At the level of single photons, we would like to send data in different channels – colors or wavelengths – at the same time.”
Raymer added that such technology would be impervious to hacking, and would expand users’ ability to search large databases.
Changing the color of photons in this manner is known as quantum frequency translation, and it has been achieved before, but not within a fiber optic cable. “Other researchers have done this frequency translation using certain types of crystals,” Raymer said. “Using optical fibers instead creates the translated photons already having the proper shape that allows them to be transmitted in a communication fiber.”
The research was published in the journal Physical Review Letters.