# Questions tagged [werner-states]

For questions regarding well-known Werner States, which are states that are entangled but are still incapable of violating any Bell nonlocality inequality. This means that those states have an explicit local hidden variable model construction.

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### Are there separable states $\rho$ with separable pure decompositions requiring $\operatorname{rank}(\rho)^2$ components?

In What separable $\rho$ only admit separable pure decompositions with more than $\mathrm{rank}(\rho)$ terms?, examples were given of separable states $\rho$ with separable decompositions requiring ...
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### Is there a way to compute how many hidden variables are needed to describe a given local state?

Consider a bipartite state $\rho$ that is local. By local I mean here that there is a local hidden variable model explaining the correlations resulting from measuring $\rho$. In other words, $\rho$ ...
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### How to show that Werner states produce correlations explainable via local hidden variable models?

Werner states can be written as $$\rho_W= p\frac{\Pi_+}{\binom{n+1}{2}} +(1-p)\frac{\Pi_-}{\binom{n}{2}},$$ with $\Pi_\pm\equiv\frac12(I\pm\mathrm{SWAP})$ projectors onto the $\pm1$ eigenspaces of ...
Consider the two-qubit Werner state, defined as $$\rho_z = z |\Psi_-\rangle\!\langle \Psi_-| + \frac{1-z}{4}I, \quad |\Psi_-\rangle\equiv\frac{1}{\sqrt2}(|00\rangle-|11\rangle),$$ for $z\ge0$. Using ...