  As a model of decohering environment, we show that quantum chaotic system
behave equivalently as many-body system. An approximate formula for the time
evolution of the reduced density matrix of a system interacting with a quantum
chaotic environment is derived. This theoretical formulation is substantiated
by the numerical study of decoherence of two qubits interacting with a quantum
chaotic environment modeled by a chaotic kicked top. Like the many-body model
of environment, the quantum chaotic system is efficient decoherer, and it can
generate entanglement between the two qubits which have no direct interaction.
