Abstract
Several experiments and experimental proposals for the production of macroscopic superpositions naturally lead to states of the general form , where the number of subsystems is very large, but the states of the individual subsystems have large overlap, . We propose two different methods for assigning an effective particle number to such states, using ideal Greenberger-Horne-Zeilinger states of the form as a standard of comparison. The two methods are based on decoherence and on a distillation protocol, respectively. Both lead to an effective size of the order of .
- Received 16 May 2002
DOI:https://doi.org/10.1103/PhysRevLett.89.210402
©2002 American Physical Society