@article{troyer2003qwl,
  author = {Troyer, M. and Wessel, S. and Alet, F.},
  title = {{Flat-Histogram Methods for Quantum Systems: Algorithms to Overcome Tunneling Problems and Calculate the Free Energy}},
  journal = {Physical Review Letters},
  volume = {90},
  number = {12},
  pages = {120201},
  year = {2003},
  doi = {10.1103/PhysRevLett.90.120201}
}