Characterization of noise correlations in superconducting quantum circuits

Superconducting quantum circuits have been an important platform to realize a scalable quantum computing system. Qubit decoherence, which is caused by the fluctuations of its environment, remains a main obstacle to realize fault-tolerant quantum computing. To reduce decoherence, it is important to identify the source of fluctuations by precisely characterizing its correlations. Prevalent methods only consider the second order correlation under the Gaussian approximation. However, environment with higher order correlations is not uncommon in mesoscopic quantum systems. Based on a weak measurement scheme ^[1], we present an experiment to detect high-order correlations in a superconducting circuit. We verified the scheme by reconstructing the noise power spectral density and compared the results with that obtained from dynamical decoupling. We also demonstrated the characterization of higher-order correlation of the environment.

Reference:
[1]Wang P, Chen C, Peng X, et al. Characterization of arbitrary-order correlations in quantum baths by weak measurement. arXiv preprint arXiv:1902.03606 (2019).