QIS is to count how many electrons are set free by photons and thus effectively count photons. This is particularly important in very low light applications, such as in life science microscopy, photography, or even possibly quantum cryptography and the Internet of Things. "When we build an image sensor, we build a chip that is also sensitive to these photons. We were able to build a new kind of pixel with a sensitivity so high we could see one electron above all the background noise."
The new pixels are considerably smaller than regular pixels since they are designed to sense only one photon, but many more are placed on the sensor to capture the same amount of total photons from the image. "We'd like to have 1 billion pixels on the sensor and we'll still keep the sensor the same size," says Ma.
These new pixels are able to sense and count a single electron for the first time, without resorting to extreme measures, such as cooling the sensor to -60 C and/or avalanche multiplication. "Avalanche multiplication may be thought of as an electrically-induced chain reaction, but the strong electric fields necessary lead to reliability issues and it is difficult to make small pixels." says Fossum.