Quantum entanglement dynamics due to dynamical Lamb effect

We investigate the dynamics of a system of N qubits coupled to a common resonator with time-dependent coupling. The instantaneous switching on and off of the qubit/cavity coupling gives rise to the dynamical Lamb effect. The dynamical Lamb effect is the parametric excitation of the qubits, and the creation of cavity photons, due to the sudden change in Lamb shift of the qubit. In the absence of dissipation, the Schrodinger equation which describes the dynamics of the N qubits is solved within a perturbative approach. When dissipation is taken into account, the Lindblad equation for the system of N qubits is solved numerically. Different measures of entanglement compatible with pure and mixed states are adopted. The concurrence and the negativity are obtained in the two-qubit case; the three-π and the negativity are obtained in the three-qubit case. It is demonstrated that the different measures show different level of details of the entanglement between the qubits. We find that the dynamical Lamb effect can be used to create Greenberger-Horne-Zeilinger states even in presence of dissipation. Furthermore, the dynamical Lamb effect can be used as a fast entangling gate between two qubits.