Local tests of global entanglement and a counterexample to the   generalized area law
  We introduce a technique for applying quantum expanders in a distributed fashion, and use it to solve two basic questions: testing whether a bipartite quantum state shared by two parties is the maximally entangled state and disproving a generalized area law. In the process these two questions which appear completely unrelated turn out to be two sides of the same coin. Strikingly in both cases a constant amount of resources are used to verify a global property. 
Dorit Aharonov, Aram W. Harrow, Zeph Landau, Daniel Nagaj, Mario   Szegedy, Umesh Vazirani
quant-ph