Collective quantum decoherence induced by qubit–electron interaction

We investigate a model of quantum register composed of N   qubits coupling with itinerant electrons by adopting the Born–Markov master equation. Decoherence induced by this coupling is studied for various initial states. By solving the master equation for N=4N=4 with the numerical integration, we obtain time evolution of fidelity and linear entropy of the register. The decoherence rate of this model is proportional to |J′|2|J′|2 with J′J′ being the exchange coupling strength of electrons and qubits. We also investigate the decoherence free subspace which provides a possible routine of applications in quantum computation.