The darkened collective mode in strongly coupled transmons

Weichen chien^1*, Raveendharan Sundaram¹, Watson Kuo¹

¹Department of physics, National Chung Hsing University, Taichung, Taiwan

* Presenter:Weichen chien, email:melcwc@gmail.com

In our work, we focus on the optical effect of strongly coupled transmons. We study its energy spectrum by utilizing a resonator as a dispersive readout. We were able to observe higher excited states via 2-photon processes and these observations were well explained by capacitively coupled transmons. As the flux bias approaches the degenerate point, the Rabi frequency of the ATS splitting at the same driving amplitude decreases from 230 MHz to 35 MHz. The measurement of relaxation time indicates that as the system approaches to the degenerate point, the T1 of the |0⟩-|1⟩ transition becomes longer. Both results conclude that the excited state |1⟩ of the coupled system is resilient to external microwave influences near the degenerate point.

Keywords: Transmon , Artificial atom, Autler townes splitting