Reversibility and energetics in optical computing
H. John Caulfield, Jacques E. Ludman, Pál Greguss, Joseph Shamir · Optics Letters · 1990
Computer operations that conserve energy do not, from an information viewpoint, increase entropy and therefore have no minimum energy cost associated with them. An information-conserving operation must be reversible in principle; reversible optical gates inevitably incur losses. The energy per calculation may have many meanings, as we show. The energy expended by a single photon in a conservative optical operation is negligible, much less than kT.