Multimode image memory based on a cold atomic ensemble

Abstract

Quantum memory is one of the key components constituting a quantum network. An important step towards the successful development of such a network is the storage of single photons. Encoding photons in high-dimensional photonic states can significantly increase the network's information-carrying capacity. Furthermore, quantum memories that are able to store multiple optical modes offer advantages over single-mode memories, in terms of both speed and capacity. However, a practical implementation of such a scheme for storing and retrieving multiple images at the single-photon level has not yet been achieved. Here, we provide experimental evidence that two spatial probe fields imprinted with a real image each can be stored and retrieved with good visibility and similarity at the single-photon level in a ${}^{85}$Rb cold atomic ensemble, making use of electromagnetically induced transparency. Our results are very promising for the realization of a high-dimensional quantum network in the future.