For the purpose of this discussion there are two types of noise in electronics: shot noise and thermal noise.
Shot noise is discrete noise that happens when single electrons are emitted and adsorbed. Shot noise is quantum noise and can't be reduced by cooling and don't vary with frequency.
Thermal noise is noise that depends on the temperature of the circuit. Temperature increases the energy of material and this energy allows electrons to bounce around more creating noise.
For the purpose of QRNG, you don't have to separate shot noise from thermal noise if you know the shot noise to thermal noise ratio. We are not interested of knowing actual bits generated by shot noise. We just want to collect enough random bits so that we can guarantee that there is enough quantum randomness to make the quality equal to just quantum bits. For example, if the ratio is 1/100, we collect more than 100 bits and mix them together to get one bit of quantum randomness. Shot noise is amplified and has easily detectable effects in in p-n junctions (diodes, photodectectors).
That sounds reasonable. For a camera sensor, the noise budget is made up of four primary terms:
1. So called "fixed pattern noise," i.e., a pixel by pixel pattern in the measured value that isn't reduced by averaging. This pattern would be a "fingerprint" of the camera, probably long term if not forever. You can make a well averaged measurement of the fixed pattern (somewhat temperature dependent) and subtract it from subsequent exposures.
2. Thermal noise of the amplifier that converts charge into a signal that can be read by the analog-to-digital converter. This is referred to as "readout noise."
3. Shot noise in "good" photocurrent, i.e., photons from the scene being converted into charge. This becomes dominant at higher light levels, as it's proportional to the square root of photocurrent.
4. Shot noise in "bad" photocurrent, i.e., a constant leakage current in the light sensitive elements, whose magnitude is temperature dependent.
Shot noise is discrete noise that happens when single electrons are emitted and adsorbed. Shot noise is quantum noise and can't be reduced by cooling and don't vary with frequency.
Thermal noise is noise that depends on the temperature of the circuit. Temperature increases the energy of material and this energy allows electrons to bounce around more creating noise.
For the purpose of QRNG, you don't have to separate shot noise from thermal noise if you know the shot noise to thermal noise ratio. We are not interested of knowing actual bits generated by shot noise. We just want to collect enough random bits so that we can guarantee that there is enough quantum randomness to make the quality equal to just quantum bits. For example, if the ratio is 1/100, we collect more than 100 bits and mix them together to get one bit of quantum randomness. Shot noise is amplified and has easily detectable effects in in p-n junctions (diodes, photodectectors).