[quantum-info] Reminder: Q+ Hangout, tomorrow 9am , Speaker: Francesco Buscemi (Nagoya University)

[Aharon Brodutch]

Hi all
 Just a reminder, we will be connecting to the Q+ hangout tomorrow
morning (28/08).  RAC1, 1101 at 9am.
Cheers
 Aharon


On Tue, Aug 21, 2012 at 2:20 PM, Aharon Brodutch <cap.fwiffo at gmail.com> wrote:
> Hi all
>
> We will be joining the Q+ hangout via video conference in RAC1 1101 at
> 9am on Tuesday 28/08, see details below
>
> Cheers
> Aharon Brodutch
>
>
> ====
> Q+ Hangout 28/08 9am (14:00 British Summer Time)
> Speaker: Francesco Buscemi (Nagoya University)
> Title: All entangled quantum states are nonlocal: equivalence between
> locality and separability in quantum theory
>
> Abstract:
> In this talk I will show how, by slightly modifying the rules of
> nonlocal games, one can prove that all entangled states violate local
> realism.
>
> As it is well known, Bell inequalities, which are used to test the
> violation of local realism, can be equivalently reformulated in terms
> of nonlocal games (namely, cooperative games with incomplete
> information) played between one referee and two (or more) players,
> these latter being separated so to make any form of communication
> between them impossible during the game. Quantum nonlocality is that
> property of quantum states that allows players sharing them to win
> nonlocal games more frequently than the assumption of local realism
> would imply.
>
> However, as Werner proved in 1989, not all quantum states enable such
> a violation of local realism. In particular, Werner showed the
> existence of quantum states that cannot be created locally (the
> so-called "entangled" states) and, yet, do not allow any violation of
> local realism in nonlocal games. This fact has been since then
> considered an unsatisfactory gap in the theory, attracting a
> considerable amount of attentions in the literature.
>
> In this talk I will present a simple proof of the fact that all
> entangled states indeed violate local realism. This will be done by
> considering a new larger class of nonlocal games, which I call
> "semiquantum," differing from the old ones merely in that the referee
> can now communicate with the players through quantum channels, rather
> than being restricted to use classical ones, as it was tacitly assumed
> before. I will then prove that one quantum state always provides
> better payoffs than another quantum state, in semiquantum nonlocal
> games, if and only if the latter can be obtained from the former, by
> local operations and shared randomness (LOSR). The main claim will
> then follow as a corollary.
>
> The new approach not only provides a clear theoretical picture of the
> relation between locality and separability, but also suggests, thanks
> to its simplicity, new experimental tests able in principle to verify
> the violation of local realism in situations where previous
> experiments would fail.
>
> Based on http://arxiv.org/abs/1106.6095