Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: One-way quantum key distribution: Simple upper bound on the secret key
  rate   We present a simple method to obtain an upper bound on the achievable secret
key rate in quantum key distribution (QKD) protocols that use only
unidirectional classical communication during the public-discussion phase. This
method is based on a necessary precondition for one-way secret key
distillation; the legitimate users need to prove that there exists no quantum
state having a symmetric extension that is compatible with the available
measurements results. The main advantage of the obtained upper bound is that it
can be formulated as a semidefinite program, which can be efficiently solved.
We illustrate our results by analysing two well-known qubit-based QKD
protocols: the four-state protocol and the six-state protocol. Recent results
by Renner et al., Phys. Rev. A 72, 012332 (2005), also show that the given
precondition is only necessary but not sufficient for unidirectional secret key
distillation.

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The categories of this paper are: hep-ex
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The categories of this paper are: nlin
12
The categories of this paper are: nucl-th
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The categories of this paper are: physics
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The categories of this paper are: chao-dyn
2
The categories of this paper are: math
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The categories of this paper are: alg-geom
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The categories of this paper are: ao-sci
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The categories of this paper are: cs
15
The categories of this paper are: nucl-ex
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The categories of this paper are: comp-gas
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The categories of this paper are: hep-lat
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The categories of this paper are: q-fin
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The categories of this paper are: bayes-an
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The categories of this paper are: math-ph
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The categories of this paper are: chem-ph