Abstract
We derive spin squeezing inequalities that generalize the concept of the spin squeezing parameter and provide necessary and sufficient conditions for genuine 2-, or 3-qubit entanglement for symmetric states, and sufficient condition for -qubit states. Our inequalities have a clear physical interpretation as entanglement witnesses, can be easily measured, and are given by complex but elementary expressions.
- Received 8 April 2005
DOI:https://doi.org/10.1103/PhysRevLett.95.120502
©2005 American Physical Society