量子電腦 - 中研院物理研究所

Decoherence
• Process by which h a quantum superposition state
t
decays into a classical, statistical mixture of
state.
• In system-environment models, decoherence is
caused by interactions between the system and
its environments.
• As the system and bath evolve under the total
Hamiltonian, they become entangled.
• By tracing over the environmental degrees of
freedom, the reduced density matrix of the
system of interest at later times is no longer pure
and the system is said to have decohered.