We use the density matrix formalism to analyze the interaction of interferometer-type superconducting qubits with a high quality tank circuit, which frequency is well below the gap frequency of a qubit. We start with the ground state characterization of the superconducting flux and charge qubits. Then, by making use of a dressed state approach we describe the qubits' spectroscopy when the qubit is irradiated by a microwave field which is tuned to the gap frequency. The last section of the paper is devoted to continuous monitoring of qubit states by using a DC SQUID in the inductive mode.
@article{arxiv.0709.2459,
title = {Quantum theory of the low-frequency linear susceptibility of interferometer-type superconducting qubits},
author = {Ya. S. Greenberg and E. Il'ichev},
journal= {arXiv preprint arXiv:0709.2459},
year = {2008}
}
Comments
11 pages, 5 figures; the title and abstract are slightly changed; several typos are corrected; in order to make our argumentation more clear we added some comments in the introduction and other sections