Description:

Abstract:

Noise has been a long-standing issue for further improving the qubit coherence times. It remains an important task to further understand and mitigate the decoherence effect introduced by various noise sources. Usually, such noise is assumed to be Gaussian, while non-Gaussian noise has been frequently detected in superconducting qubits. Understanding the role of realistic non-Gaussian noise is key to accurately predicting and further reducing the errors in realistic qubits. In this talk, I will present our prediction of a symmetry-breaking effect that is unique to the non-Gaussian noise. The breaking introduces a measurable mismatch between the extremum points of the dephasing rates and qubit frequencies in realistic superconducting qubits, which is crosschecked by two independent theoretical methods, the Keldysh expansion and the stochastic Schrodinger equation. This finding sent a warning to the experimental practice for locating the qubit sweet spots, and provides a simple and powerful tool for identifying the non-Gaussian noise experimentally. To mitigate such noise, we propose a triple-protection protocol based on Floquet engineering. By exploring the second-order extremum points in the Floquet spectrum, we find it possible to improve the qubit coherence time by an order of magnitude, which is also confirmed theoretically to be robust to certain drive imperfections.

Speaker: Dr. Ziwan Huang, Fermilab

Host: Jens Koch