Wednesday, February 8, 2012

1111.1864 (Joel J. Wallman et al.)

Observers can always generate nonlocal correlations without aligning
measurements by covering all their bases
   [PDF]

Joel J. Wallman, Stephen D. Bartlett
Quantum theory allows for correlations between the outcomes of distant
measurements that are inconsistent with any locally causal theory, as
demonstrated by the violation of a Bell inequality. Typical demonstrations of
these correlations require careful alignment between the measurements, which
requires distant parties to share a reference frame. Here, we prove, following
a numerical observation by Shadbolt et al., that if two parties share a Bell
state and each party randomly chooses three orthogonal measurements, then the
parties will always violate a Bell inequality. Furthermore, we prove that this
probability is highly robust against local depolarizing noise, in that small
levels of noise only decrease the probability of violating a Bell inequality by
a small amount. We also show that generalizing to N parties increases the
robustness against noise. These results improve on previous ones that only
allowed a high probability of violating a Bell inequality for large numbers of
parties.
View original: http://arxiv.org/abs/1111.1864

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