Interactions and time evolutions of atoms are governed by quantum mechanics Quantum mechanics is all about certainities at microcosmic level
The very existence of atoms owes everything not to the chaotic uncertainties of classicalmechanics, but rather to the certainties of quantum mechanics with the Pauli exclusion principle and well-defined and stable atomic energy levels!
Indeed without our quantum understanding of the solid state and the band theory of metals, insulators and semiconductors, the whole of the semiconductor industry with its transistors and integrated circuits could not have developed.
The same can be said about quantum optics and lasers: huge industries - from optical communications to music and video CDs - have their basis in these intrinsically quantum technologies.
In 1973, Charles Bennett of IBM Research made a remarkable discovery. Classical computation can be broken down into a series of steps, each logically reversible, and this in turn allows physical reversibility of the computation. This result has implications for the energy dissipated by thecomputation. Rolf Landauer, Bennett's long-term colleague and mentor, had earlier shown that it is the act of discarding information that incurs an unavoidable energy loss
Bennett's result means that we can arrange our computer to calculate reversibly, very slowly, with an energy as small as we please. In his lectures on computation in the 1980's, Feynman discusses a reversible computer that calculates for a few steps, then drifts back a bit, ‘uncalculating’ as it goes, before it drifts forward again to eventually complete the calculation with almost zero energy loss.