I want to know the answer to the following question:
What are simply lowest quantum mechanical energy state of photons?
All the background I'm provided with is that "Virtual photons (which are simply lowest quantum mechanical energy state of photons) are also responsible for electrostatic interaction between electric charges (which results in Coulomb law), for spontaneous radiative decay of exited atomic and nuclear states, for the Casimir force, for van der Waals bond forces and some other observable phenomena.". Is that enough to answer the question?