The Margolus–Levitin theorem, named for Norman Margolus

Norman Margolus

Norman H. Margolus is an Canadian-American physicist and computer scientist, known for his work on cellular automata and reversible computing...

 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

Joule

The joule ; symbol J) is a derived unit of energy or work in the International System of Units. It is equal to the energy expended in applying a force of one newton through a distance of one metre , or in passing an electric current of one ampere through a resistance of one ohm for one second...

 of energy. Or stating the bound for one micro system:

A quantum system of energy E needs at least a time of to go from one state to an orthogonal state, where h = 6.626 × 10⁻³⁴ joules/hertz is Planck's constant.

The theorem is also of interest outside of quantum computation, e.g. it relates to the holographic principle

Holographic principle

The holographic principle is a property of quantum gravity and string theories which states that the description of a volume of space can be thought of as encoded on a boundary to the region—preferably a light-like boundary like a gravitational horizon...

,
digital physics

Digital physics

In physics and cosmology, digital physics is a collection of theoretical perspectives based on the premise that the universe is, at heart, describable by information, and is therefore computable...

, simulated reality

Simulated reality

Simulated reality is the proposition that reality could be simulated—perhaps by computer simulation—to a degree indistinguishable from "true" reality. It could contain conscious minds which may or may not be fully aware that they are living inside a simulation....

, the mathematical universe hypothesis and pancomputationalism.