Multiple image storage and frequency conversion in a cold atomic ensemble

The strong demand for quantum memory, a key building block of quantum network, has inspired new methodologies and led to experimental progress for quantum storage. The use of quantum memory for spatial multimode or image storage could dramatically increase the channel bit rate. Furthermore, quantum memory that can store multiple optical modes would lead to higher efficiencies in quantum communication and computation. Here, by using resonant tripod electromagnetically induced transparency in a cold atomic ensemble, we experimentally demonstrate the storage of two probes with different frequencies and images in the frequency domain. In addition, by using different read light, we realize the frequency conversion of retrieved images with high efficiency. Besides, our method may be used to create a superposition of the images by realizing the function of a beam splitter. All advantages make our method useful in many fields, including quantum information, detection, imaging, sensing, and so on.