In circuit quantum electrodynamics (QED), qubits are typically measured using dispersively-coupled readout resonators. Coupling between each readout resonator and its electrical environment however reduces the qubit lifetime via the Purcell effect. Inserting a Purcell filter counters this effect while maintaining high readout fidelity, but reduces measurement bandwidth and thus limits multiplexing readout capacity. In this letter, we develop and implement a multi-stage bandpass Purcell filter that yields better qubit protection while simultaneously increasing measurement bandwidth and multiplexed capacity. We report on the experimental performance of our transmission-line--based implementation of this approach, a flexible design that can easily be integrated with current scaled-up, long coherence time superconducting quantum processors.
@article{arxiv.2306.06258,
title = {Broadband Bandpass Purcell Filter for Circuit Quantum Electrodynamics},
author = {Haoxiong Yan and Xuntao Wu and Andrew Lingenfelter and Yash J. Joshi and Gustav Andersson and Christopher R. Conner and Ming-Han Chou and Joel Grebel and Jacob M. Miller and Rhys G. Povey and Hong Qiao and Aashish A. Clerk and Andrew N. Cleland},
journal= {arXiv preprint arXiv:2306.06258},
year = {2023}
}