Qubits, Cbits, Decoherence, Quantum Measurement and Environment

I present a tutorial review of the behavior of a simple 2-state quantum system (“bit”) in interaction with a dissipative environment, with particular attention to the questions of when we can regardthe system as effectively isolatedandof “true” versus “false” decoherence. The last lecture discusses the quantum measurement paradox in the light of recent experiments on Josephson systems.