Abstract:
An intensive research effort has recently been devoted to understanding the properties of general non-signaling theories, which can contain more non-locality than quantum mechanics. Here we argue that in order to form self-consistent theories, sets of non-signaling correlations with limited non-locality must be closed under a natural class of operations called wirings. After introducing useful concepts and tools to address the issue of closure, we present several case studies. Furthermore we discuss the implications of our findings in the broader context of this line of research, in particular concerning the origin of the boundary between quantum and post-quantum correlations, and towards finding constraints on physical theories beyond quantum mechanics.
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Abstract:
Recently, the principle of information causality has appeared as a good candidate for an information-theoretic principle that would single out quantum correlations among more general non-signalling models. Here we present results going in this direction; namely we show that part of the boundary of quantum correlations actually emerges from information causality.
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Abstract:
It has previously been shown that quantum nonlocality offers no benefit over classical correlations for performing a distributed task known as nonlocal computation. This is where separated parties must compute the value of a function without individually learning anything about the inputs. We show that giving the parties some knowledge of the inputs, however small, is sufficient to unlock the power of quantum mechanics to out-perform classical mechanics. This role of information held locally gives new insight into the general question of when quantum nonlocality gives an advantage over classical physics. Our results also reveal a novel feature of the nonlocality embodied in the celebrated task of Clauser, Horne, Shimony and Holt.
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Abstract:
We study the effects of localization on quantum state transfer in spin chains. We show how to use quantum error correction and multiple parallel spin chains to send a qubit with high fidelity over arbitrary distances; in particular distances much greater than the localization length of the chain.
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