Effect of Strong Drives on the Inductively Shunted Transmon and its Impact on Readout

In the transmon, strong measurement drives can induce multiphoton resonances that lead to MIST/ionization, a process that compromises the quantum non-demolition character of readout and lowers fidelity. Moreover, this process is strongly dependent on offset charge, making it difficult to avoid at high readout power without actively stabilizing the charge. The inductively shunted transmon (IST) offers a promising alternative; its inductive shunt eliminates the dependency on gate charge and it could thus be more resilient to strong readout drives. Indeed, previous work has suggested that the IST is structurally stable under strong drives, exhibiting delayed onset of MIST/ionization compared to the conventional transmon. In this work, we investigate measurement-induced transitions in the IST, identifying the conditions under which ionization occurs and assessing its impact on readout speed and fidelity.