Stationary entanglement in strongly coupled qubits

Abstract

The dynamics of two superconducting flux qubits coupled to each other and to a common bath is discussed. We focus on the case in which the qubit-qubit coupling strength dominates over the respective qubit transition frequencies. We derive the master equation including collective effect by modeling the bath as 1D open space in this ultra-strong coupling regime, and find that the coupling greatly modifies both the coherent and the incoherent dynamics of the system, giving rise to qualitatively different properties. By analyzing the steady-state and the dynamics governed by the master equation, we show that ground state entanglement and maximum coherence between the two qubits can be induced by the environment alone. By employing in addition a single external driving field, both the entangled anti-symmetric and symmetric collective states can be populated and preserved with high fidelity. Similarly, entangled states can be prepared using adiabatic passage techniques using two external fields. Our results could find applications in entangling quantum gates and quantum memories free from the decoherence.

19 pages, 21 figures

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• Input-output theory for waveguide QED with an ensemble of inhomogeneous atoms
• Designing frequency-dependent relaxation rates and Lamb shift for a giant artificial atom
• Steady state entanglement of two superconducting qubits engineered by dissipation
• Non-Markovian quantum input-output networks
• Quantum routing of single optical photons with a superconducting flux qubit
• Shot noise in magnetic tunnel junctions from first principles
• Steady-state entanglement enhanced by a dissipative ancilla
• Entanglement versus cooling in the system of a driven pair of two-level qubits longitudinally coupled with a boson mode field