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

TL;DR

This paper explores multi-photon transitions and dressing in an anharmonic superconducting multi-level circuit, demonstrating higher-order effects and their impact on readout, with results aligning with theoretical models.

Contribution

It presents the first detailed experimental observation of multi-photon dressing and higher-order Rabi sidebands in an anharmonic superconducting circuit, advancing understanding of multi-level quantum dynamics.

Findings

Observation of multi-photon transitions up to the fifth excited state

Quantitative analysis of back-action on the readout resonator

Experimental demonstration of multi-photon dressing and Autler-Townes splittings

Abstract

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. 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.