For Valeria Saggio to boot up the computer in her former Vienna lab, she needed a special crystal, only as big as her fingernail. Saggio would place it gently into a small copper box, a tiny electric oven, which would heat the crystal to 77 degrees Fahrenheit. Then she would switch on a laser to bombard the crystal with a beam of photons. This crystal, at this precise temperature, would split some of those photons into two photons. One of these would go straight to a light detector, its journey finished; the other would travel into a tiny silicon chip -- a quantum computing processor.

Artificial intelligence is part of our modern life by enabling machines to learn useful processes such as speech recognition and digital personal assistants. A crucial question for practical applications is how fast such intelligent machines can learn. An experiment at the University of Vienna has answered this question, showing that quantum technology enables a speed-up in the learning process. The physicists, in an international collaboration within Austria, Germany, the Netherlands, and the USA, have achieved this result by using a quantum processor for single photons as a robot. This work, which con-tributes to the advancement of quantum artificial intelligence for future applications, is published in the current issue of the journal "Nature".

Machine learning, a process used to train artificial intelligences, can take an extremely long time – but a quantum trick could massively speed things up for tasks involving particles of light called photons. In reinforcement learning, an algorithm runs through the same problem over and over again and is given a numerical reward only when it reaches the correct answer. That process teaches it to find the correct answer more quickly when pitted against similar problems later on. Now Valeria Saggio at the University of Vienna in Austria and her colleagues have added a quantum twist to accelerate this process. They set up an experiment involving a photon moving through a wave guide and ending up in one of four possible states.