Post-fabrication frequency trimming of coplanar-waveguide resonators in circuit QED quantum processors

TL;DR

This paper introduces a post-fabrication frequency trimming technique for microwave resonators in circuit QED, improving device yield and enabling precise frequency adjustments for better qubit readout performance.

Contribution

The authors develop a grounding airbridge array method compatible with existing fabrication processes, allowing 100 MHz range and 10 MHz resolution frequency trimming of CPW resonators post fabrication.

Findings

Enables elimination of frequency crowding in multiplexed readout

Achieves frequency matching of resonator pairs

Improves readout speed and fidelity in multi-transmon processors

Abstract

We present the use of grounding airbridge arrays to trim the frequency of microwave coplanar-waveguide (CPW) resonators post fabrication. This method is compatible with the fabrication steps of conventional CPW airbridges and crossovers and increases device yield by allowing compensation of design and fabrication uncertainty with $100~\mathrm{MHz}$ range and $10~\mathrm{MHz}$ resolution. We showcase two applications in circuit QED. The first is elimination of frequency crowding between resonators intended to readout different transmons by frequency-division multiplexing. The second is frequency matching of readout and Purcell-filter resonator pairs. Combining this matching with transmon frequency trimming by laser annealing reliably achieves fast and high-fidelity readout across 17-transmon quantum processors.