Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Leggett-Garg Inequalities and No-Signalling in Time: A
  Quasi-Probability Approach   The Leggett-Garg (LG) inequalities were proposed in order to assess whether
sets of pairs of sequential measurements on a single quantum system can be
consistent with an underlying notion of macrorealism. Here, the LG inequalities
are explored using a simple quasi-probability linear in the projection
operators to describe the properties of the system at two times. We show that
this quasi-probability is measurable, has the same correlation function as the
usual two-time measurement probability (for the bivalent variables considered
here) and has the key property that the probabilities for the later time are
independent of whether an earlier measurement was made, a generalization of the
no-signalling in time condition of Kofler and Brukner. We argue that this
quasi-probability, appropriately measured, provides a non-invasive measure of
macrorealism per se at the two time level. This measure, when combined with the
LG inequalities, provides a characterization of macrorealism more detailed than
that provided by the LG inequalities alone. When the quasi-probability is
non-negative, the LG system has a natural parallel with the EPRB system and
Fine's theorem. A simple spin model illustrating key features of the approach
is exhibited.

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The categories of this paper are: nucl-ex
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The categories of this paper are: funct-an
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The categories of this paper are: hep-lat
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The categories of this paper are: acc-phys
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The categories of this paper are: eess
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The categories of this paper are: cond-mat
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The categories of this paper are: cmp-lg
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The categories of this paper are: bayes-an
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The categories of this paper are: cs
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The categories of this paper are: stat
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The categories of this paper are: econ
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The categories of this paper are: ao-sci
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The categories of this paper are: chao-dyn
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The categories of this paper are: comp-gas
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The categories of this paper are: nlin
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The categories of this paper are: supr-con