Science: Four groups have recently demonstrated the feasibility of a new form of quantum computation known as photonic boson sampling. The technique entails sending photons through a network of criss-crossing channels and observing which of several exits they emerge from. Thanks to the photons’ quantum mechanical interactions and to the network’s topology, the number of photons recorded at each exit correspond, together, to a matrix function known as the permanent. By using three input channels, the four groups determined the permanents of 3 × 3 matrices. That’s hardly a feat of computational power, but if the technique could be scaled up to 25 × 25 and bigger matrices, it could be used to determine permanents faster than a classical computer could. The four groups that demonstrated photonic boson sampling are those of Andrew White at the University of Queensland in Brisbane, Australia, Ian Walmsley of the University of Oxford in the UK, Philip Walther of the University of Vienna, Austria, and Roberto Osellame of the Polytechnic University of Milan, Italy.