18 research outputs found
On optimal entanglement assisted one-shot classical communication
The one-shot success probability of a noisy classical channel for
transmitting one classical bit is the optimal probability with which the bit
can be sent via a single use of the channel. Prevedel et al. (PRL 106, 110505
(2011)) recently showed that for a specific channel, this quantity can be
increased if the parties using the channel share an entangled quantum state. We
completely characterize the optimal entanglement-assisted protocols in terms of
the radius of a set of operators associated with the channel. This
characterization can be used to construct optimal entanglement-assisted
protocols from the given classical channel and to prove the limit of such
protocols. As an example, we show that the Prevedel et al. protocol is optimal
for two-qubit entanglement. We also prove some simple upper bounds on the
improvement that can be obtained from quantum and no-signaling correlations.Comment: 5 pages, plus 7 pages of supplementary material. v2 is significantly
expanded and contains a new result (Theorem 2
Generalizing Tsirelson's bound on Bell inequalities using a min-max principle
Bounds on the norm of quantum operators associated with classical Bell-type
inequalities can be derived from their maximal eigenvalues. This quantitative
method enables detailed predictions of the maximal violations of Bell-type
inequalities.Comment: 4 pages, 2 figures, RevTeX4, replaced with published versio