Geometric phase in open systems: beyond the Markov approximation and   weak coupling limit
  Beyond the quantum Markov approximation and the weak coupling limit, we present a general theory to calculate the geometric phase for open systems with and without conserved energy. As an example, the geometric phase for a two-level system coupling both dephasingly and dissipatively to its environment is calculated. Comparison with the results from quantum trajectory analysis is presented and discussed. 
X. X. Yi, D. M. Tong, L. C. Wang, L. C. Kwek, C. H. OH