Local quantum protocols for separable measurements with many parties

Purity estimation with separable measurements.

Given a large number N of copies of a qubit state of which we wish to estimate its purity, we prove that separable-measurement protocols can be as efficient as the optimal joint-measurement one if classical communication is used. This shows that the optimal estimation of the entanglement of a two-qubit state can also be achieved asymptotically with fully separable measurements. Thus, quantum me...

How Many Quantum Correlations Are Not Local?

We study how generic is the property of nonlocality among the set of quantum correlations for bipartite dichotomic measurements. To do so, we consider the characterization of these quantum correlations as those of the form γ = (〈ui, vj〉)i,j=1, where the vectors ui and vj are in the unit sphere of a real Hilbert space. The important parameters in this description are the number of vectors n and ...

Necessary Condition for Local Quantum Operations and Classical Communication with Extensive Violation by Separable Operations

Endogenous platforms: the case of many parties

We analyze existence of equilibrium in a one-dimensional model of endogenous party platforms andmore than two parties. The platforms proposed by parties depend on their membership composition. The policy implemented is a function of the different proposals and the vote distribution among such proposals. It is shown that if voters are sincere there is always an equilibrium regardless of the numb...

Stability of quantum statistical ensembles with respect to local measurements.

We introduce a stability criterion for quantum statistical ensembles describing macroscopic systems. An ensemble is called "stable" when a small number of local measurements cannot significantly modify the probability distribution of the total energy of the system. We apply this criterion to lattices of spins-1/2, thereby showing that the canonical ensemble is nearly stable, whereas statistical...