Multi-signal spectroscopy of qubit–resonator systems

Some unique properties of superconducting devices are promising for the development of modern quantum technologies. Superconducting quantum circuits use large coupling constants and provide good scalability and controllability due to their macroscopic dimensions. Still, micro-fabrication methods have some hardship with reproducibility of identical superconducting quantum circuits. The dressed state approach presents some possibility to reduce influence of non-identity of qubits. We study a qubit-resonator system, when the qubit interacts with three signals. Such system configuration adds additional flexibility for circuit tunability. A particular realization of such a system is a superconducting flux qubit coupled to a transmission-line resonator driven by three signals. We describe this triply-driven system in terms of the dressed qubit states and conclude that using several signals can be beneficial for both system spectroscopy and tunability. Such study of a qubit based system, coupled to both classical and quantum fields, can be useful for detection of individual itinerant microwave photons. (author)