Quantum Phase Tomography of a Strongly Driven Qubit
Mark Spencer Rudner, A. V. Shytov, Leonid Levitov, David M. Berns, William D. Oliver, Sergio O. Valenzuela, Terry P. Orlando · Physical Review Letters · 2008
The interference between repeated Landau-Zener transitions in a qubit swept through an avoided level crossing results in Stückelberg oscillations in qubit magnetization, a hallmark of the coherent strongly driven regime in two-level systems. The two-dimensional Fourier transforms of the resulting oscillatory patterns are found to exhibit a family of one-dimensional curves in Fourier space, in agreement with recent observations in a superconducting qubit. We interpret these images in terms of time evolution of the quantum phase of the qubit state and show that they can be used to probe dephasing mechanisms.