| The Landau-Zener transition, one of central dynamic problems of quantum mechanics, is the quantum tunneling at the avoided crossing of two levels varying in time. The noisy environment substantially changes the tunneling probability. The diagonal noise leads to the loss of coherence, whereas the non-diagonal noise enhances or suppresses the transitions. The classical noise in adiabatic limit leads to equipopulation of the two levels and supports the time-reversal symmetry for the transition probabilility. The quantum noise violates both these symmetries. The Landau-Zener transitions in many body-system is analyzed specifically for the molecular production at the Feshbach resonance in the Fermi-gas of cooled alkali atoms. The perturbation analysis based on Keldysh-Schwinger technics demonstrates that the Landau-Zener formula is invalid as a consequence of many-body effects. |
|