Decoherence and Entanglement Dynamics of Coupled Qubits

          @misc{ pirsa_PIRSA:09030047,
            doi = {10.48660/09030047},
            url = {https://pirsa.org/09030047},
            author = {Hamma, Alioscia},
            keywords = {Quantum Information},
            language = {en},
            title = {Decoherence and Entanglement Dynamics of Coupled Qubits},
            publisher = {Perimeter Institute},
            year = {2009},
            month = {mar},
            note = {PIRSA:09030047 see, \url{https://pirsa.org}}
          }
          

Abstract

We study the entanglement dynamics and relaxation properties of a system of two interacting qubits in the two cases (I) two independent bosonic baths and (II) one common bath, at temperature $T$. The entanglement dynamics is studied in terms of the concurrence C(t) between the two spins and of the von Neumann entropy S(t) with respect to the bath, as a function of time. We prove that the system does thermalize. In the case (II) of a single bath, the existence of a decoherence-free (DFS) subspace makes entanglement dynamics very rich. We show that when the system is initially in a state with a component in the DFS the relaxation time is surprisingly long, showing the existence of semi-decoherence free subspaces. The equilibrium state in this case is not the Gibbs state. The entanglement dynamics for the single bath case is also studied as a function of temperature, coupling strength with the environment and strength of tunneling coupling. The case of the mixed state is finally shown and discussed.