They have high quantum efficiency and are able to detect single photons in the visible range of the electromagnetic spectrum.
The ability to count the exact number of photons detected is extremely important for quantum key distribution.
Rockwell International's Science Center had previously announced the "Solid-State Photomultiplier" (SSPM), a wide-band (0.4–28 μm) detector.
[1] In the late 1980s a collaboration – initially consisting of Rockwell and UCLA – began developing scintillating-fiber particle trackers for use at the Superconducting Super Collider,[2][3] based on a dedicated variant of the SSPM that came to be known as the Visible Light Photon Counter.
[4] The operating principles are similar to APDs but based on impurity-band conduction.