Experimental criteria for steering and the EPR paradox

Giuseppe Faraci, D. Gutkowski, S. Notarrigo +1 more

Eric G. Cavalcanti, S. J. Jones, Howard M. Wiseman +1 more

We formally link the concept of steering (a concept created by Schr\"odinger but only recently formalized by Wiseman, Jones, and Doherty [Phys. Rev. Lett. 98, 140402 (2007)]) and the criteria for demonstrations of Einstein-Podolsky-Rosen (EPR) paradox introduced by Reid [Phys. Rev. A 40, 913 (1989)]. We develop a general theory of experimental EPR-steering criteria, derive a number of criteria applicable to discrete as well as continuous-variable observables, and study their efficacy in detecting that form of nonlocality in some classes of quantum states. We show that previous versions of EPR-type criteria can be rederived within this formalism, thus unifying these efforts from a modern quantum-information perspective and clarifying their conceptual and formal origin. The theory follows in close analogy with criteria for other forms of quantum nonlocality (Bell nonlocality and entanglement), and because it is a hybrid of those two, it may lead to insights into the relationship between the different forms of nonlocality and the criteria that are able to detect them.

Ziwei Li, Zhihua Guo, Huaixin Cao

Qiongyi He, M. D. Reid

We propose criteria and experimental strategies to realise the Einstein-Podolsky-Rosen (EPR) steering nonlocality. One-way steering can be obtained where there is asymmetry of thermal noise on each system. We also present EPR steering inequalities that act as signatures and suggest how to optimise EPR correlations in specific schemes so that the genuine multipartite EPR steering nonlocality (EPR paradox) can also possibly be realised. The results presented here also apply to the spatially separated macroscopic atomic ensembles.

Tapan Kumar Ghosh

Eric G. Cavalcanti, C. J. Foster, M. D. Reid +2 more

We show that the correct formulation of the premises behind the EPR argument [1] is that of a Local Hidden State model, recently introduced as a formalisation of Steering by Wiseman and co-authors [2] This unifies the two concepts and allows one to define the problem of characterising the set of correlations that demonstrate the EPR paradox, providing a solid basis and extending the area of investigation introduced by M.D. Reid in 1989 [3]. In the setup of two settings and two outcomes we derive a necessary and sufficient criteria, and show that the CHSH-Bell inequality [4] is violated only if this inequality is.