While there are many ways to build a quantum computer, one popular platform that features superconducting qubits can leverage existing semiconductor fabrication processes and has demonstrated potential for scalability. Most commonly used is the transmon qubit, a micron-sized, nonlinear resonator made from superconducting films typically fabricated on silicon wafers. But because of defects in the fabrication process, unintentional quantum states called “two-level systems” (TLS) can appear on the qubit surfaces, seriously hindering computing performance and information storage capacity. One way to study them is to examine their effects on superconducting micro-resonators, which are parameterized by an internal quality factor (Qi) to quantify the parasitic loss from TLS. Measuring the Qi value is difficult, however, as it must be done in the single-photon limit to reflect the same regime in which the qubit operates. Chen at al. addressed this challenge by presenting new strategies to mitigate the influence of the measurement noise on extracting the Qi value of a resonator. “We introduce a hybrid approach that extracts certain resonator parameters from high-power measurements and re-applies them to analyze low-power data,” said author Cliff Chen.

Full analysis : Ironing out kinks in quantum computing.