Solution to the Landau-Zener problem via Susskind-Glogower operators
  We show that, by means of a right-unitary transformation, the fully quantized Landau-Zener Hamiltonian in the weak-coupling regime may be solved by using known solutions from the standard Landau-Zener problem. In the strong-coupling regime, where the rotating wave approximation is not valid, we show that the quantized Landau-Zener Hamiltonian may be diagonalized in the atomic basis by means of a unitary transformation; hence allowing numerical solutions for the few photons regime via truncation. 
B.M. Rodr\'iguez-Lara, D. Rodr\'iguez-M\'endez and H. Moya-Cessa
quant-ph