Broadband bandpass Purcell filter for circuit quantum electrodynamics

Abstract

In circuit quantum electrodynamics, 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.

Optimize Purcell filter design for reducing influence of fabrication variation

“…In recent years, researchers have explored various bandpass or band-stop filters to inhibit the Purcell effect. [10][11][12][13][14][15][16][17] Purcell filters include the widely used λ /4 resonant filters, [13] the λ /2 CPW resonator, [18] and filters explored by Bronn et al, [19] Reed et al [7] and Heinsoo et al [20] These filters differ in their coupling characteristics, bandwidth, footprint structure, and performance stability. Heinsoo et al [20] implemented a λ /4 filter with the same resonant frequency as the readout resonator to achieve improved suppression while maintaining good readout efficiency.…”