Ask HN: Do all mental processes have a physical existence?

If a unique idea or concept is created by a mind, it undeniably exists (albeit in an abstract sense).

Does it then have a physical existence? Does it propagate into space (electromagnetism)? Theoretically, could an idea/experience be reconstructed from the private thoughts of an individual?

If all mental workings have a physical component, would that mean that there is an encoding mechanism for subjective experience?

I could be asking the wrong questions here. My knowledge of physics and neuroscience in borderline nonexistent.

Thanks!