Theoretical Physics

16 February 2017
Time: 12:30 to 13:30
Location: EC Stoner 7.83

Theoretical Physics Seminar: Jan Sperling (Oxford)

Entanglement in highly multipartite systems

Nonlocal quantum correlations had been at the center of the early debates about the validity
of quantum physics. Nowadays, quantum entanglement is believed to be one of the main resources
for applications using quantum technologies and robust schemes to produce inseparable states have
been proposes [1]. Still, the characterization of multipartite entanglement is a challenging problem,
especially, due to the richness of possible correlations between a manifold of subsystems [2].
In this talk, we study different notions of entanglement in systems that consist of many subsystems.
In particular, the detection of such forms of correlations is established using the unique
tool of separability eigenvalue equations [3]. We discuss two experimental implementation of
this technique. In the first experiment, every single partitioning out of 115 974 possible forms
of mode decompositions is demonstrated to be entangled for an experimentally generated, tenmode
frequency-comb state [4]. In the second experiment, a six-mode state of light was prepared
which is biseparable and, at the same time, exhibits entanglement for any other higher-order partitioning.
Finally, we outline the generalization of our approach to infer many-particle entanglement
in compound systems with a non-deterministic, i.e., fluctuating, number of particles [6].


[1] J. Metz, M. Trupke, and A. Beige, Phys. Rev. Lett. 97, 040503 (2006).
[2] R. Horodecki, et al., Rev. Mod. Phys. 81, 865 (2009).
[3] J. Sperling and W. Vogel, Phys. Rev. Lett. 111, 110503 (2013).
[4] S. Gerke, et al., Phys. Rev. Lett. 114, 050501 (2015).
[5] S. Gerke, et al., Phys. Rev. Lett. 117, 110502 (2016).
[6] J. Sperling and I. A. Walmsley, arXiv:1611.06028 [quant-ph].



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