Generation of photon pairs in topologically protected guided modes

We present a theoretical study on the generation of photon pairs via spontaneous four-wave mixing in a waveguide array supporting topologically protected guided modes. Following a statistical approach, we introduce incremental levels of disorder in the waveguide positions and analyze the effects in terms of photon path correlations and generation efficiency. For moderate level of disorder, we show that the generated two-photon state as well as the generation rate is preserved. However, we find that for higher level of disorder quantum correlations are significantly affected, despite the fact that the linear properties of the topological mode are still protected.