Ultrastrong-coupling circuit QED in the radio-frequency regime

摘要: We study a circuit QED setup where multiple superconducting qubits are ultrastrongly coupled to single radio-frequency resonator. In this extreme parameter regime of cavity the dynamics electromagnetic mode is very slow compared all other relevant timescales and can be described as an effective particle moving in adiabatic energy landscape defined by qubits. The focus work placed on settings with two or qubits, different types symmetry-breaking transitions ground- excited-state potentials occur. Specifically, we show how change level structure wave packet associated these transition points probed via conventional excitation spectra Ramsey measurements performed at GHz frequencies. More generally, analysis demonstrates that state-of-the-art systems used access whole range particle-like quantum mechanical phenomena beyond usual paradigm oscillators.