Experimental boson sampling

Universal quantum computers 1 promise a dramatic increase in speed over classical computers, but their full-size realization remains challenging 2 . However, intermediate quantum computational models 3 , 4 , 5 have been proposed that are not universal but can solve problems that are believed to be classically hard. Aaronson and Arkhipov 6 have shown that interference of single photons in random optical networks can solve the hard problem of sampling the bosonic output distribution. Remarkably, this computation does not require measurement-based interactions 7 , 8 or adaptive feed-forward techniques 9 . Here, we demonstrate this model of computation using laser-written integrated quantum networks that were designed to implement unitary matrix transformations. We characterize the integrated devices using an in situ reconstruction method and observe three-photon interference 10 , 11 , 12 that leads to the boson-sampling output distribution. Our results set a benchmark for a type of quantum computer with the potential to outperform a conventional computer through the use of only a few photons and linear-optical elements 13 . The boson-sampling problem is experimentally solved by implementing Aaronson and Arkhipov's model of computation with photons in integrated optical circuits. These results set a benchmark for a type of quantum computer that can potentially outperform a conventional computer by using only a few photons and linear optical elements.