Quantum Correlations in a Two-Qubit Heisenberg XX Model under Intrinsic Decoherence

Taking into account the intrinsic decoherence, we have investigated quantum correlations in a two-qubit Heisenberg XX model when a nonuniform magnetic field is included. We compare entanglement measured by entan- glement of formation, quantum discord and measurement-induced measurement （MID） and illustrate their different characteristics. Quantum discord and MID show the same features and always exist even though there is no entangle- ment in the long time limit. In the time evolution, quantum discord could be generated or enhanced to the stable value, while MID just decreases to the stable value.