The nanowire localizes the photons in space, time, and energy. APDs can't do energy. The cryogenics allow using cryogenic-level bandgaps/carrier-energies, so e

The nanowire localizes the photons in space, time, and energy. APDs can't do energy. The cryogenics allow using cryogenic-level bandgaps/carrier-energies, so each optical photon turns into many carriers which then flow out the wire in both directions, the delay between the pulse on both ends localizes the impact along the wire.