Multi-moded CPW resonators for the investigation of two-level systems in quantum circuits

Two-level systems (TLS) are identified to be the dominant source of dissipation and decoherence in superconducting qubits. Accurate measurement of two-level system (TLS) induced loss in superconducting resonators and quantum circuits is a challenging task due to the low signal-to-noise ratio (SNR) and the inherent fluctuations of the TLS. These effects can lead to uncertainties as large as 30% in the estimated loss tangent. To address this challenge, we developed a multi-wave resonator architecture which extends the standard quarter-wave resonator length of λ/4 to Nλ/4 where N≈30 at 5GHz. We present experimental results on Al resonators showing that this extension reduces TLS induced fluctuations by a factor of N while improving the SNR by a factor of N as compared to standard λ/4 resonators. Lastly, we show that this new design reduces the uncertainties in the estimated loss by a factor of sqrt(N)​.