Spatially entangled twin photons allow the study of high-dimensional entanglement, and the Laguerre-Gauss modes are the most commonly used basis to discretize the single-photon mode spaces. In this basis, to date only the azimuthal degree of freedom has been investigated experimentally due to its fundamental and experimental simplicity. We show that the full spatial entanglement is indeed accessible experimentally; i.e., we have found practicable radial detection modes with negligible cross correlations. This allows us to demonstrate hybrid azimuthal-radial quantum correlations in a Hilbert space with more than 100 dimensions per photon.

Optical dipole-traps are used in various scientific fields, including classical optics, quantum optics and biophysics. Here, we propose and implement a dipole-trap for nanoparticles that is based on focusing from the full solid angle with a deep parabolic mirror. The key aspect is the generation of a linear-dipole mode which is predicted to provide a tight trapping potential. We demonstrate the trapping of rod-shaped nanoparticles and validate the trapping frequencies to be on the order of the expected ones. The described realization of an optical trap is applicable for various other kinds of solid-state targets. The obtained results demonstrate the feasibility of optical dipole-traps which simultaneously provide high trap stiffness and allow for efficient interaction of light and matter in free space.

Polarization properties of photon echo generated at the inter-combination transition (6s 2 ) 1 S0 ↔ (6s6p) 3 P1 of 174 Yb (transition of type 0 ↔ 1) are for the first time investigated experimentally for a complete set of polarizations of two exciting pulses of resonant radiation (linear-linear, circularlinear, linear-circular, and circular-circular) in a pure ytterbium vapor. In all cases the photon echo polarization coincides with polarization of the second exciting pulse. Photon echo in a pure gas does not appear neither for exciting pulses of mutually orthogonal linear polarizations, nor for the pulses of opposite circular polarizations. Experimental results are in agreement with theoretical predictions. Polarization diagrams for the exciting pulses (left) and photon echo (right). Echo polarization coincides with the polarization of the second exciting pulse

We investigate the emission of single photons from CdSe/CdS dot-in-rods which are optically trapped in the focus of a deep parabolic mirror. Thanks to this mirror, we are able to image almost the full 4π emission pattern of nanometer-sized elementary dipoles and verify the alignment of the rods within the optical trap. From the motional dynamics of the emitters in the trap we infer that the single-photon emission occurs from clusters comprising several emitters. We demonstrate the optical trapping of rod-shaped quantum emitters in a configuration suitable for efficiently coupling an ensemble of linear dipoles with the electromagnetic field in free space. arXiv:1905.09108v1 [quant-ph]