Dynamics of trade-off relations between quantum information resources in two qubits interacting individually and nonlinearly with a cavity: Decoherence model

The dynamics of trade-off relations between quantum information resources are investigated in a system of two non-interacting qubits, each individually and nonlinearly coupled to coherent cavity fields through intensity-dependent coupling. The qubits are initially prepared in a maximally entangled Bell state, while the cavity fields are assumed to be in coherent states. An exact analytical treatment of the reduced two-qubit density matrix is presented under qubit–cavity detuning and intrinsic decoherence governed by the Milburn model. The time evolutions of first-order coherence, concurrence, intrinsic concurrence and purity are analyzed to elucidate the redistribution of quantum resources. The results confirm that intrinsic concurrence and first-order coherence obey a complementary trade-off relation governed by the purity of the two-qubit state, with standard concurrence acting as a lower bound for intrinsic concurrence throughout the dynamics. The roles of the initial coherent field intensity, qubit–cavity detuning and intrinsic decoherence are examined, showing that nonlinear atom–cavity interactions induce regular oscillatory behavior accompanied by entanglement sudden death and revival phenomena. Increasing the coherent field intensity enhances coherence generation and accelerates entanglement degradation of the generated two-qubit states.