Something I've never quite understood: Photon frequency is quantized, but amplitude is not. So what distinguishes two coherent photons from one photon with twice the amplitude? In both cases, the waveform would be identical, but the two coherent photons have twice the energy of the single double-amplitude photon, since energy depends only on frequency.
Or is it wrong that photon amplitude is non-quantized? If it is quantized, what's the amplitude quantum?
@Austin_Dern well, the problem is that there is no such something in the uncertainty principle and there are well-documented cases of coherent photons. There are probably about a dozen in your vicinity, even! Lasers.
@Austin_Dern well, that helps a little bit! I had thought the number and electric field operators did commute.
