Multi-photon dressing of an anharmonic superconducting many-level quantum circuit

Understand

We report on the investigation of a superconducting anharmonic multi-level circuit that is coupled to a harmonic readout resonator.

• We observe multi-photon transitions via virtual energy levels of our system up to the fifth excited state.
• The back-action of these higher-order excitations on our readout device is analyzed quantitatively and demonstrated to be in accordance with theoretical expectation.
• By applying a strong microwave drive we achieve multi-photon dressing within our anharmonic circuit which is dynamically coupled by a weak probe tone.