Catching light one particle at a time is like hearing a whisper in a roaring factory. An electron-multiplying camera (EMCCD) can do exactly that: it turns a single photon hitting a pixel into an avalanche of electrons that can be measured. These cameras are mounted on telescopes to spot a barely visible planet next to a dazzling star.
But the avalanche comes at a price. As an electron passes through the amplifier, it can randomly spawn extra electrons, as if someone coughed in a quiet corridor and the cough was mistaken for a voice. This noise is called clock-induced charge, and the higher the gain, the more often it occurs. In the new work, the author rewrote the program that simulates the operation of such a camera for the future Roman Space Telescope.
Now the program calculates the gain exactly, as if flipping a coin for each electron: whether it will multiply or not. This will make it easier to separate real light from noise and to fine-tune the camera before the telescope's launch.
A single photon of visible light carries energy of about a few electron-volts, but an electron-multiplying camera can amplify the signal from it thousands of times, turning it into a measurable electrical pulse.
In Stanislaw Lem's novel Solaris, the planet's ocean reacts to the slightest changes, and here the camera reacts to individual photons — sensitivity on the edge of the possible.