http://www.digitaljournal.com/tech-and-science/science/light-stored-as-sound-for-the-first-time/article/502866

Light stored as sound for the first time

Posted Sep 19, 2017 by Tim Sandle
The capturing and storing of light as sound is not just remarkable in itself, it is also part of the future development of super-fast, light-based computers.
Optical components configured to produce photons in a high-dimensional GHZ entangled state  in an ex...
Optical components configured to produce photons in a high-dimensional GHZ entangled state, in an experiment designed by the computer algorithm called Melvin.
M. Malik/Univ. of Vienna
In new research that will have implications for the development of computers, scientists have successfully stored light-based information in the form of sound waves. These sound recordings have been placed onto a computer. This feat is a step towards the development of light-based (or ‘photonic’) computers. The conceptual difference is that data will be held in the form of photons as opposed to the current storage systems, which are based on elections.
The reason why there’s so much interest in photonic computers is due to the potential for such machines to operate at speeds up to 20 times faster than conventional computers. Moreover, these devices are predicted to be more energy efficient in terms of not producing much in the way of heat. These theoretical devices have sparked the interest of major technology players like IBM and Intel.
Despite considerable investment, developing the technology has proved complex. The first phase involved finding a way to encode information into photons, which has been achieved — the process is similar to passing data along an optical fiber.
What has proved more challenging is designing a computer chip to retrieve and process information stored as photons. This is because light moves too fast for current computing technology to read. Some of these complexities are outlined in the following video:
Attempting a different course, researchers from the University of Sydney have assessed that if the photons are converted into sound then the considerably slower speed that sound moves at can be reliably read by computers.
According to lead researcher, Dr. Birgit Stiller, who was speaking with Science Alert: “The information in our chip in acoustic form travels at a velocity five orders of magnitude slower than in the optical domain.” Drawing on a meteorological analogy, the researcher added, “It is like the difference between thunder and lightning.”
Central to the research was the development of a memory system that can transfer between light and sound waves across a photonic microchip. This type of chip will be critical for the development of next generation light-based computers.
With the process, photonic data enters the chip in the form of yellow pulses of light. Here it interacts with a 'write' pulse (which is blue light). This then leads to the generation of an acoustic wave that stores the data. To extract the data, a blue pulse of light (the 'read' pulse) accesses this sound data and transmits as light back as yellow light.
The research is published in the journal Nature Communications, under the title “A chip-integrated coherent photonic-phononic memory.”