Monday, January 16, 2012

LWP: Polariton Mott insulator with trapped ions or circuit QED

by M. Hohenadler, M. Aichhorn, L. Pollet and S. Schmidt
Physical Review A 85, 013810 (2012)

The authors address an extended Jaynes-Cummings-Hubbard model where photons in 1D or 2D arrays of coupled resonators—each of them holding a two-level system—can hop beyond nearest neighbors. This particular model is of relevance in circuit-QED—where 1D and 2D arrays of qubit+stripline resonators can capacitively couple—and in trapped ions&mdahs;where dipole interactions are long range—. So, the model are basically 1D or 2D arrays of polaritons—qubit+fied excitation—with short and long range coupling.

They study a 1D frustrated long-range hopping model in the context of trapped ions and the same in 2D by assuming a circuit-QED model. The first is studied using a variational cluster approach and a quantum Monte Carlo method (ALPS 1.3 implementation), the second only the quantum Monte Carlo method. Analytically, Metzner's local cumulants are used to calculate a photonic Matsubara Green's function for the system within a random phase approximation.

The authors find a Mott-superfluid transition by changing the hopping to qubit-field coupling ratio as usual with these models. Their results show that the Mott lobes characteristic for this transition are enlarged/reduced in the case of trapped ions/circuit-QED but they realize that neither the quantum Monte Carlo, nor the variational cluster approaches provide any evidence of a change of the universality class of phase transition in the presence of long-range hopping.

This is one of those papers that would take long to duplicate but are nice to read and learn the physics of the studied system and even more interesting if you like anything Jaynes-Cummings.

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