Abstract
Steering criteria are conditions whose violation excludes the possibility of describing the observed measurement statistics with local hidden state (LHS) models. When the available data do not allow to exclude arbitrary LHS models, it may still be possible to exclude LHS models with a specific separability structure. Here, we derive experimentally feasible criteria that put quantitative bounds on the multipartite entanglement of LHS. Our results reveal that separable states may contain hidden entanglement that can be unlocked by measurements on another system, even if no steering between the two systems is possible.
Highlights
The classification of quantum correlations is crucial for our understanding of the resources that enable quantum information tasks [1, 2, 3, 4, 5, 6, 7]
We focus on multipartite settings with one untrusted party (A) that may share quantum correlations with another multipartite quantum system (B), on which local hidden state (LHS) models can be classified according to their multipartite entanglement
A violation of condition (3) implies that the observed sensitivity and fluctuations cannot be described in terms of a Λseparable LHS model, either because steering from A to B is possible, or because only entangled LHS models are able to account for the correlations
Summary
The classification of quantum correlations is crucial for our understanding of the resources that enable quantum information tasks [1, 2, 3, 4, 5, 6, 7]. Steering criteria rule out LHS descriptions by verifying a local complementarity principle in form of an uncertainty relation [17] or a metrological bound [18]. In the limit when even genuine multipartite entangled LHS are excluded these criteria converge to metrological steering criteria that can be approximated to yield uncertainty-based bounds. We show that if a LHS model for B exists, this model cannot always be constructed from separable LHS, even if B is separable This implies that quantum information processing assisted by measurements on A can unlock hidden entanglement of B even in the absence of steering. Our criteria can be tested with state-of-the-art experimental setups and provide quantitative bounds on the multipartite entanglement of LHS models
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