1306.2757 (Hou Ian)

Quasi-lattice chains and multipartite entanglement in a cavity    [PDF]

Hou Ian

Unlike atoms in a lattice, the spacings between neighboring qubits in a superconducting qubit chain are not uniform. Inside a circuit cavity, the interaction between this quasi-lattice chain of qubits and the cavity field is geometrically dependent on the particular circuit layout. The quasi-particle excitation modes that arise in the chain cannot be derived using traditional models. By proposing a projection-deformation method, we analytically give the eigenstates of the excitation modes of arbitrary distribution of coupling strengths. We further show that the quasi-particle permits a set of multi-photon resonances between different photon Fock states and quasi-lattice angular momentum states, which preserves the total number of excitations in the cavity. Such resonances lead to simultaneous generation of different types of multipartite entanglement states, such as the GHZ state and the W state. Using concurrence and 3-tangle as metrics, we find that non-uniformity increases the generated entanglement through the asynchronous excitations of the qubits.

View original: http://arxiv.org/abs/1306.2757