Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Relativistic quantum information and time machines   Relativistic quantum information combines the informational approach to
understanding and using quantum mechanics systems - quantum information - with
the relativistic view of the universe. In this introductory review we examine
key results to emerge from this new field of research in physics and discuss
future directions. A particularly active area recently has been the question of
what happens when quantum systems interact with general relativistic closed
timelike curves - effectively time machines. We discuss two different
approaches that have been suggested for modelling such situations. It is argued
that the approach based on matching the density operator of the quantum state
between the future and past most consistently avoids the paradoxes usually
associated with time travel.

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The categories of this paper are: gr-qc
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The categories of this paper are: acc-phys
25
The categories of this paper are: patt-sol
36
The categories of this paper are: cmp-lg
8
The categories of this paper are: hep-ex
3
The categories of this paper are: physics
26
The categories of this paper are: bayes-an
17
The categories of this paper are: q-fin
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The categories of this paper are: chao-dyn
29
The categories of this paper are: funct-an
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The categories of this paper are: astro-ph
2
The categories of this paper are: math
27
The categories of this paper are: comp-gas
32
The categories of this paper are: atom-ph
37
The categories of this paper are: supr-con
11
The categories of this paper are: hep-lat