Quantum Metrology: Dynamics vs. Entanglement
  A parameter whose coupling to a quantum probe of $n$ constituents includes all two-body interactions between the constituents can be measured with an uncertainty that scales as $1/n^{3/2}$, even when the constituents are initially unentangled. We devise a protocol that achieves the $1/n^{3/2}$ scaling without generating any entanglement among the constituents, and we suggest that the protocol might be implemented in a two-component Bose-Einstein condensate. 
Sergio Boixo, Animesh Datta, Matthew J. Davis, Steven T. Flammia, Anil   Shaji, Carlton M. Caves