Laboratoire de Physique Théorique
Toulouse - UMR 5152

The rapid development of quantum control makes it now possible to create large scale quantum entanglement in various physical systems such as trapped ions or cold atoms. Since full tomography in these cases is not possible, for the detection of entanglement one has to find methods that need few measurements. Moreover, in many-particle systems typically the particles cannot be accessed individually thus these methods can only use collective measurements.

In the talk methods are presented that can be used for entanglement detection under these circumstances in a system of many spin-1/2 particles. We describe the complete set of generalized spin squeezing inequalities that detect entanglement with the first and second moments of the collective angular momentum components. These entanglement criteria can be used to show the presence of bound entanglement in the thermal states of several spin models.

[1] G. Toth, C. Knapp, O. Guhne, and H.J. Briegel, Phys. Rev. Lett., in press ; quant-ph/0702219