Suppressing the instabilities of RF driven transmon by a kinetic inductive shunt - Part 2: Experimental results*

The transmon is ubiquitous in circuit QED experiments due to its remarkable coherence properties and simplicity of design and fabrication. However, when strongly driven at microwave frequencies, the transmon exhibits various kinds of instabilities. Floquet-Markov theory indeed predicts such instabilities. Shunting the transmon with a linear inductance qualitatively changes the potential seen by the phase, thus increasing the device stability under certain conditions. We call the resulting qubit the inductively-shunted transmon (IST) to distinguish it from the RF SQUID. Comparison of driven transmons and ISTs with different implementations offers insights in eliminating these instabilities, and also sheds light on the fundamental problem of chaos in a strongly driven dissipative quantum system. This talk will focus on recent experimental results for such investigations.