# Stuttgart 2012 – wissenschaftliches Programm

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# Q: Fachverband Quantenoptik und Photonik

## Q 12: Quanteninformation: Photonen und nichtklass. Licht

### Q 12.1: Vortrag

### Montag, 12. März 2012, 14:00–14:15, V7.02

**Continuous-variable cluster state generation with cylindrical vector beams** — •Stefan Berg-Johansen^{1,2}, Ioannes Rigas^{1,2}, Christian Gabriel^{1,2}, Andrea Aiello^{1,2}, Peter van Loock^{1,2}, Christoph Marquardt^{1,2}, and Gerd Leuchs^{1,2} — ^{1}Max Planck Institute for the Science of Light, Erlangen, Germany — ^{2}Institute of Optics, Information and Photonics, University of Erlangen-Nuremberg, Germany

An intriguing property of cylindrically polarized beams of light is that their polarization and spatial degrees of freedom cannot be factorized even in a classical description. In the quantum treatment, this *structural inseparability* leads to spatial and polarization entanglement as well as entanglement between these two degrees of freedom when the beam is quadrature squeezed [1]. In this talk we present several schemes for the generation of four-node cluster states using such beams. A careful analysis of the properties of the resulting clusters reveals that cylindrically polarized modes are indeed well-suited for this purpose. We also report first steps towards the experimental realization of a cluster state. To this end, we generate amplitude squeezed radially and azimuthally polarized beams which form the backbone of our cluster state schemes. In a first implementation of one such scheme we have verified the predicted amplitude quantum correlations between the four resulting nodes.

[1] C. Gabriel et al., Phys. Rev. Lett. **106**, 060502 (2011)