Since the laws of quantum physics are reversible in time, we shall have to consider computing engines which obey such reversible laws. Feynman RP. Foundations of Physics, Volume 16, Number 6, 507-531, DOI: 10.1007/Dec.
Now he has departed from this strange world a little ahead of me. That means nothing. People like us, who believe in physics, know that the distinction between past, present, and future is only a stubbornly persistent illusion. — Albert Einstein on the occasion of his friend Michele Besso’s death…and three weeks before Einstein’s death.