  Applied quantum optics stands to revolutionise many aspects of information
technology, provided performance can be maintained when scaled up. Silicon
quantum photonics satisfies the scaling requirements of miniaturisation and
manufacturability, but at 1.55 $\mu$m it suffers from unacceptable linear and
nonlinear loss. Here we show that, by translating silicon quantum photonics to
the mid-infrared, a new quantum optics platform is created which can
simultaneously maximise manufacturability and miniaturisation, while minimising
loss. We demonstrate the necessary platform components: photon-pair generation,
single-photon detection, and high-visibility quantum interference, all at
wavelengths beyond 2 $\mu$m. Across various regimes, we observe a maximum net
coincidence rate of 448 $\pm$ 12 Hz, a coincidence-to-accidental ratio of 25.7
$\pm$ 1.1, and, a net two photon quantum interference visibility of 0.993 $\pm$
0.017. Mid-infrared silicon quantum photonics will bring new quantum
applications within reach.
