Quantum walks of correlated particles offer the possibility to study large-scale quantum interference, simulate biological, chemical and physical systems, and a route to universal quantum computation. Here we demonstrate quantum walks of two identical photons in an array of 21 continuously evanescently-coupled waveguides in a SiOxNy chip. We observe quantum correlations, violating a classical limit by 76 standard deviations, and find that they depend critically on the input state of the quantum walk. These results open the way to a powerful approach to quantum walks using correlated particles to encode information in an exponentially larger state space.
@article{arxiv.1006.4764,
title = {Quantum walks of correlated particles},
author = {Alberto Peruzzo and Mirko Lobino and Jonathan C. F. Matthews and Nobuyuki Matsuda and Alberto Politi and Konstantinos Poulios and Xiao-Qi Zhou and Yoav Lahini and Nur Ismail and Kerstin Wörhoff and Yaron Bromberg and Yaron Silberberg and Mark G. Thompson and Jeremy L. O'Brien},
journal= {arXiv preprint arXiv:1006.4764},
year = {2011}
}