@misc{W2106725754,
  author = {L.-M. Duan and G. Giedke and J. I. Cirac and P. Zoller},
  title = {Inseparability Criterion for Continuous Variable Systems},
  year = {2000},
  howpublished = {Physical Review Letters},
  doi = {https://doi.org/10.1103/physrevlett.84.2722}
}