Mitigating charge noise sensitivity of higher levels with an inductively shunted transmon - Part 1

The transmon qubit is a fundamental building block for large scale superconducting quantum processors. In these circuits, strong microwave drives enable fast readout and control operations. However, recent works have shown that strong drives can induce unwanted state transitions in the transmon, often involving higher excited states. Further, the spectrum of these resonances can be significantly blurred and broadened by temporal fluctuations in the transmon gate charge (n_g), drastically increasing the susceptibility to these transitions. In this work we build an inductively shunted transmon (IST), where the superconducting island is shunted with a low loss linear inductor made from granular aluminum (grAl). This inductive shunt eliminates n_g from the problem, provides stability to all higher energy levels and increases design flexibility for strong drives.

 

In part 1 of this talk, we introduce the grAl IST circuit design and discuss the predicted multiphoton transitions due to off resonant drives in this system, while highlighting the key differences from a transmon.