The Margolus–Levitin theorem, named for Norman Margolus and Lev B. Levitin, gives a fundamental limit on quantum computation (strictly speaking on all forms on computation). The processing rate cannot be higher than 6 × 1033 operations per second per joule of energy. Or stating the bound for one micro system:
The theorem is also of interest outside of quantum computation, e.g. it relates to the holographic principle, digital physics, simulated reality, the mathematical universe hypothesis and pancomputationalism.