Quantum Storage in Solid State Atomic Ensembles

Reversible and coherent mapping of quantum information between light and matter is an important experimental challenge in quantum information science. In particular such quantum memories are necessary for the implementation of quantum repeaters that would extend the range of quantum communication. In recent years, atomic ensembles have proven to be a promising system in order to implement such a task. We will describe our efforts towards the realization of a storage device for single photons in a solid state environment. Our approach uses solid state atomic ensembles implemented with rare-earth ions doped into dielectric crystals. Due to the weak interactions with the crystal environment and to the absence of atomic diffusion, the rare-earth ions can be considered as a frozen gas of atoms. Single photons can in principle be stored and recalled with high efficiency in such a media using a modified photon echo approach based on coherent control of the inhomogeneous broadening of the optical transition [1]. This method lends itself naturally to the storage of multiple temporal modes [2]. Different wavelengths of absorption are available using different rare-earth ions. In particular, Erbium doped solids have an optical transition around 1530 nm, which make them an attractive candidate for a quantum memory at telecommunication wavelengths, which is necessary for some quantum repeater protocols [3]. After an introduction to motivate the need for quantum memories in quantum communication, we will present the physical system and the storage protocol, before reviewing first experimental steps towards the practical realization of quantum memories in Erbium doped materials. [1] M. Nilsson and S. Kr\"{o}ll, Opt. Comm. 247, 393 (2005), B. Kraus et al, Phys. Rev. A 73, 020302 (2006), G.H\'{e}tet et al, Phys. Rev. Lett. 100, 023601 (2008) [2] C. Simon et al, Phys. Rev. Lett. 98, 190503 (2007), M.U.Staudt et al, Phys. Rev. Lett. 99, 173602 (2007) [3] N. Sangouard et al, Phys. Rev. A 76, 050301 (2007)