Universiteit Leiden

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This Week’s Discoveries | 2 February 2016

2 February 2016
This Week's Discoveries
Oort Building
Niels Bohrweg 2
2333 CA Leiden
De Sitterzaal

First Lecture

Multiparticle entanglement in high dimensions
Wolfgang Löffler (LION)
Wolfgang is a postdoc in the Quantum Matter & Optics group at LION. His research theme is: Spatial entanglement and optical singularities.

We have observed four photons entangled in their orbital angular momentum via splitting UV photons in a nonlinear crystal. The photon orbital angular momentum is the component of angular momentum of light that depends on the spatial field distribution, and not on the polarisation. In contrast to polarization, which can take only two distinct values such as left and right circular polarization, the orbital angular momentum offers an in principle infinite alphabet or quantum space. This is of high interest in a number of fields in quantum information, however, only two photons had been entangled in their orbital angular momentum to date. In fact, never more than two particles had been entangled in more than two discrete degrees of freedom. We have found that, by splitting a UV photon in a nonlinear crystal, we can entangle more photons, and confirm genuine multipartite orbital angular momentum entanglement of four photons. This enables a new route for exploring the complexity of many-particle quantum interference, and novel quantum information applications such as multi-party secret sharing.

Second Lecture, Lorentz Center highlight

Black holes, on the black background of space - so how are you meant to see them?
Speaker: Chris Done (Durham University)
Chris is professor at the Centre for Extragalactic Astronomy in the Physics department of Durham university. She is interested in anything with a decent gravitational field, especially black holes formed from stellar evolution in our Galaxy and the supermassive black holes in the centres of other galaxies which are thought to power the Quasars and Active Galactic Nuclei (AGN).

An enormous amount of gravitational potential energy can be released in the form of high energy X-ray radiation where these capture (accrete) any nearby material. Chris uses the X-ray emission to study the radiation mechanisms and environment of these extreme gravitational objects. She is one of the organizers of the Lorentz Center workshop “The X-ray Spectral-Timing Revolution” that is being held from 1 Feb 2016 through 5 Feb 2016.