We study Landau-Zener-Stuckelberg (LZS) interferometry in multilevel systems
coupled to an Ohmic quantum bath. We consider the case of superconducting flux
qubits driven by a dc+ac magnetic fields, but our results can apply to other
similar systems. We find a dynamic transition manifested by a symmetry change
in the structure of the LZS interference pattern, plotted as a function of ac
amplitude and dc detuning. The dynamic transition is from a LZS pattern with
nearly symmetric multiphoton resonances to antisymmetric multiphoton resonances
at long times (above the relaxation time). We also show that the presence of a
resonant mode in the quantum bath can impede the dynamic transition when the
resonant frequency is of the order of the qubit gap. Our results are obtained
by a numerical calculation of the finite time and the asymptotic stationary
population of the qubit states, using the Floquet-Markov approach to solve a
realistic model of the flux qubit considering up to 10 energy levels.Comment: One new figure added. Final version to be published in PR
