Multi-photon propagation in connected structures - a quantum walk - offers the potential for simulating complex physical systems and provides a route to universal quantum computation. Increasing the complexity of quantum photonic networks where the walk occurs is essential for many applications. Here, we implement a quantum walk of indistinguishable photon pairs in a multimode fiber supporting 380 modes. Using wavefront shaping, we control the propagation of the two-photon state through the fiber in which all modes are coupled. Excitation of arbitrary output modes of the system is realized by controlling classical and quantum interferences. This experiment demonstrates a highly multimode platform for multi-photon interference experiments and provides a powerful method to program a general high-dimensional multiport optical circuit. This work paves the way for the next generation of photonic devices for quantum simulation, computing and communication.
@article{arxiv.1504.03178,
title = {Two-photon quantum walk in a multimode fiber},
author = {Hugo Defienne and Marco Barbieri and Ian A. Walmsley and Brian J. Smith and Sylvain Gigan},
journal= {arXiv preprint arXiv:1504.03178},
year = {2016}
}