Entanglement in highly multipartite systems

Date: 16 February 2017
Time: 12:30 to 13:30
Location: EC Stoner 7.83
Speaker: Jan Sperling (Oxford)

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].