10/01/2013, 15:00 — 16:00 — Room P3.10, Mathematics Building
Mafalda Almeida, Physics of Information Group, Instituto de Telecomunicações
"Guess your neighbour's input" - a game to distinguish
classical/quantum correlations from supra-quantum ones in a world
with more than two observers.
One manifestation of the exotic nature of quantum theory is the
existence of correlations between systems that would be impossible
within any classical theory. Quantum correlations, for instance in
the form of quantum entanglement or quantum nonlocality, are
considered a key ingredient for the overachieving performance of
quantum systems at information processing tasks. Despite their
importance, the set of quantum correlations is only known in very
simple situations. We can impose a bound on the strength of quantum
correlations by assuming that they obey the "no-signalling
principle", i.e., they are compatible with restrict relativity by
not allowing information to be sent instantaneously. But this
principle alone is not enough: some no-signalling correlations are
not possible in a quantum world.
In this talk I will present a very simple (almost naive!)
multi-party game, "Guess your neighbour's input", where the best
performance of the players is a signature of the kind of physical
resources they use (classical, quantum or no-signalling). I show
that we can distinguish classical/quantum theories from
no-signalling ones, but only in the case we have more than two
players. This indicates the existence of a generalized
no-signalling principle for the multipartite setting.