Quantum theory of the low-frequency linear susceptibility of interferometer-type superconducting qubits

Abstract

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.

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

References in corpus (7)

• Nondestructive readout for a superconducting flux qubit
• Multiphoton transitions in a macroscopic quantum two-state system
• Four-qubit device with mixed couplings
• Low-frequency measurement of the tunneling amplitude in a flux qubit
• Direct Josephson coupling between superconducting flux qubits
• Reading-out the state inductively and microwave spectroscopy of an interferometer-type charge qubit
• Low frequency Rabi spectroscopy for a dissipative two-level system