Engineering Progressive Decoherence with Quantum Jumps in Charge Qubit

For the Josephson junction charge qubits with macroscopically quantum natures, we propose a theoretical scheme to observe the loss of quantum coherence through coupling such qubit system to an engineered reservoir, the harmonic oscillator mode in the LC circuit formed by the inductor and the separated capacitors. Similar to the usual cavity QED system in form, this charge qubit system with engineered couplings shows the quantum jumps (C.P.Sun et al Fortschr. Phys. \textbf{43}, 585 (1995))in a progressive decoherence process. Corresponding to two components of superposition of two charge states, the inductor evolves simultaneously towards two distinct quasi-classical states entangling with two states of the charge qubit. Then it induces the quantum decoherence for the induced squeezing macroscopically in the LC mode.