  The Margolus-Levitin Theorem is a limitation on the minimal evolving time of
a quantum system from its initial state to its orthogonal state. It also
supplies a bound on the maximal operations or events can occur within a volume
of spacetime. We compare Margolus-Levitin Theorem with other form of limitation
on minimal evolving time, and present covariant versions of Margolus-Levitin
Theorem in special and general relativity respectively. The relation among
entropy bound, maximum information flow and computational limit are discussed,
by applying the covariant versions of Margolus-Levitin Theorem.
