Optical memory for arbitrary perfect Poincaré states in an atomic ensemble.

Inherent spin angular momentum (SAM) and orbital angular momentum (OAM), which manifest as polarization and spatial degrees of freedom (DOFs) of photons, hold a promise of large capability for applications in classical and quantum information processing. To enable these photonic spin and orbital dynamic properties strongly coupled with each other, Poincaré states have been proposed and offer advantages in data multiplexing, information encryption, precision metrology, and quantum memory. However, since the transverse size of Laguerre-Gaussian beams strongly depends on their topological charge numbers | l |, it is difficult to store asymmetric Poincaré states due to the significantly different light-matter interaction for distinct spatial modes. Here, we experimentally realize the storage of perfect Poincaré states with arbitrary OAM quanta using the perfect optical vortex, in which 121 arbitrarily selected perfect Poincaré states have been stored with high fidelity. The reported work has great prospects in optical communication and quantum networks for dramatically increased encoding flexibility of information.