arXiv:1303.3367 · Physical Review A

Ground state of a resonant two-qubit cavity system in the ultrastrong-coupling regime

Kelvin M. C. Lee, C. K. Law

Published Jul 8, 2013• 21 citations

Abstract

We examine a generalized Rabi model formed by two identical qubits interacting with a common oscillator mode. In the near-resonance configuration where the oscillator frequency is close to the transition frequency of the qubit, we determine the ground state of the model approximately by using a variational method and a transformation method. Both methods are shown to approximate the ground state accurately for a range of coupling strengths in the ultrastrong-coupling regime. In addition, the accuracy of the approximation can be further improved by using perturbation theory. We also characterize the ground-state entanglement between the two qubits by calculating the negativity.

DOI: 10.1103/physreva.88.015802

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