Light is the fastest thing in the universe. That makes it ideal for conveying information over long distances. Indeed, much of the information flowing across the internet travels in the form of light pulsing through optical fibres. When that light reaches the end of the fibre, however, things slow down. The data have to be converted into electrical signals for processing and then converted back into light if they need to be sent on their way again. That increases costs and complexity. If a way to eliminate the need for this conversion could be found it would both simplify things and speed them up. It would also help lay the foundations for new forms of computing, such as those that employ quantum bits, or qubits.rnThe main reason that all-optical networks and light-driven computers have not yet been built is that the speed of light is non-negotiable. An electron can be speeded up, slowed down or even stopped. A photon cannot-at least, nowhere near so easily. To create a memory, however, things have to stay put. Hence the need to transfer data from photons to electrons to build such memories.
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