Sure, CPT theorem/the least action principle/Feynman ensembles only say equations are symmetric, not solution.
Like symmetric lake surface - breaking this symmetry in solution e.g. by throwing a rock.
The "rock" causing our 2nd law of thermodynamics entropy growth was e.g. the Big Bang - everything was localized, so entropy was low, causing the observed entropy growth.
In Rabi cycle laser causes periodically excitation and deexcitation of external target (which switch in CPT perspective) ...
and Rabi is analogous to coupled pendula like below:
- laser is large pumped directional resonator,
- atom is tiny isotropic resonator,
- they are coupled with EM field.
Clearly energy/photons travel in both directions, we can prevent one of them with optical isolator.
... and being CPT symmetric, laser -> atom causes its excitation later, but laser <- should cause its deexcitation earlier.
