Experimental investigation of dynamical invariants in bipartite   entanglement
  The non-conservation of entanglement, when two or more particles interact, sets it apart from other dynamical quantities like energy and momentum. It does not allow the interpretation of the subtle dynamics of entanglement as a flow of this quantity between the constituents of the system. Here we show that adding a third party to a two-particle system may lead to a conservation law that relates the quantities characterizing the bipartite entanglement between each of the parties and the other two. We provide an experimental demonstration of this idea using entangled photons, and generalize it to N-partite GHZ states. 
O. Jim\'enez Far\'ias, A. Vald\'es Hern\'andez, G. H. Aguilar, P. H.   Souto Ribeiro, S. P. Walborn, L. Davidovich, Xiao-Fen...
quant-ph