Spontaneous patametric down-conversion sources for boson sampling

The next milestone in photonic quantum information processing is to
demonstrate an optical experiment at which the quantum device outperforms
any classical computer. This can be achieved by sending
single photons through a passive linear-optical network. However, this
requires the generation of many identical single photons, which is challenging
to realize. Spectral impurity reduces the visibility of quantum
interference of the photons, which can be mitigated by filtering at the
cost of optical losses. Unfortunately, these losses are also detrimental
to quantum interference.

We recently demonstrated how to analyze the role of imperfections in
multiphoton interference experiments [1]. We now apply these results
to the problem of constructing single-photon sources. In this work
we show that an optimum exists where we can outperform a classical
computer, using off-the-shelf parametric down-conversion photon
sources. These results show that demonstrating a quantum advantage
using photonics is difficult, but possible.
[1] J.J. Renema et al., arXiv: 1809.01953 (2018)