Multiphoton dressing of an anharmonic superconducting many-level quantum circuit
Jochen Braumüller, Joel Cramer, Steffen Schlör, Hannes Rotzinger, Lucas Radtke, Alexander V. Lukashenko, Ping Yang, Sebastian T. Skacel, Sebastian Probst, Michael Marthaler, Lingzhen Guo, Alexey Vladimirovich Ustinov, Martin P. Weides · Physical Review B · 2015
We report on the investigation of a superconducting anharmonic multilevel circuit that is coupled to a harmonic readout resonator. We observe multiphoton 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 multiphoton dressing within our anharmonic circuit which is dynamically coupled by a weak probe tone. The emerging higher-order Rabi sidebands and associated Autler-Townes splittings involving up to five levels of the investigated anharmonic circuit are observed. Experimental results are in good agreement with master-equation simulations.