Noise effects on Landau-Zener-Stuckelberg interferometry in multilevel artificial atoms

We have developed a comprehensive theory of Landau-Zener-Stuckelberg interferometry in a strongly driven multilevel superconducting flux qubit interacting with the environment bath. It is found that not only the dephasing but also the intrawell relaxation make important contribution to the interference fringes. We propose that Fourier-transform-based phase tomography can be used to determine the intrawell relaxation rate as well as the type of the low-frequency noise, besides dephasing rate. The quantitative agreement between our theory and the experimental results indicates that Landau-Zener-Stuckelberg interferometry provides a useful tool to analyze the noise source of solid-state qubits.