Anomalous dynamics of superconducting qubits coupled to strongly driven readout resonators

Experimental realization of rapid qubit readout in superconducting circuits usually relies on the application of strong readout pulses to dispersively coupled readout resonators. However, the optimal pulse strength is severely limited by the emergence of anomalous qubit dynamics in the presence of a strong readout drive. Interestingly, these anomalous dynamics cannot be explained by the Purcell decay or other conventional models of qubit dissipation. In this talk, we discuss several mechanisms for these drive-induced anomalous dynamics, from coherent multi-level or multi-photon transitions to incoherent jumps induced by the resonator photons. Using the theoretical framework of perturbative time-coarse-graining [1], we derive effective master equations for the qubit dynamics, and thereby produce simulated heterodyne histograms which are then compared with real data from transmon readout experiments. Finally, we propose some strategies for mitigating these drive-induced anomalous qubit dynamics.



[1] https://github.com/leonbello/QuantumGraining.jl