Single photons: Is there a 90° offset of the electric to the magnetic component in the direction of propagation?

Single photons: Is there a 90° offset of the electric to the magnetic component in the direction of propagation?

Answer

If you ask whether there is a phase difference of 90° between the electric field and the magnetic field, the answer is yes. The electric field and the magnetic field oscillate in quadrature. You can see that from the conservation of the total electromagnetic energy during one oscillation cycle, or as you mentioned it, to conserve the energy of a "single photon" during a cycle.

Plug quickly $$E = E_0 cos(\omega t)$$ and $$B = B_0 sin(\omega t)$$ in the instantaneous electromagnetic energy density), remembering that $$cos(\omega t)^2 + sin(\omega t)^2 = 1 $$ and $$ B_0 = E_0/c $$ in the present case of transverse electromagnetic waves propagating in free-space.