Quantum memories have been realized in different physical systems, such as atomic ensembles or solid systems. To date, all quantum memories have realized the storage and retrieval of photons encoded using only a two-dimensional space spanned, for example, by the orthogonal polarization states, and hence can only store a quantum bit. Using electromagnetically induced transparency in a cold atomic ensemble, we report the experimental realization of a quantum memory storing a photon encoded in a three-dimensional space spanned by orbital angular momentum (OAM) states. We experimentally reconstruct the storage process density matrix with a fidelity of $85.3%\ifmmode\pm\else\textpm\fi{}1.8%$ using a 4-f imaging system. We also realize storage of two special photonic qutrit states as examples. Toward storing a higher-dimensional state encoded in OAM space, the efficiency difference between different OAM states should be considered according to the experimental results. The capability to store high-dimensional quantum states with high fidelity is a key step towards building high-dimensional quantum networks.Quantum memories have been realized in different physical systems, such as atomic ensembles or solid systems. To date, all quantum memories have realized the storage and retrieval of photons encoded using only a two-dimensional space spanned, for example, by the orthogonal polarization states, and hence can only store a quantum bit. Using electromagnetically induced transparency in a cold atomic ensemble, we report the experimental realization of a quantum memory storing a photon encoded in a three-dimensional space spanned by orbital angular momentum (OAM) states. We experimentally reconstruct the storage process density matrix with a fidelity of $85.3%\ifmmode\pm\else\textpm\fi{}1.8%$ using a 4-f imaging system. We also realize storage of two special photonic qutrit states as examples. Toward storing a higher-dimensional state encoded in OAM space, the efficiency difference between different OAM states should be considered according to the experimental results. The capability to store high-dimensional quantum states with high fidelity is a key step towards building high-dimensional quantum networks.

arXiv:1310.3092Physical Review AOct 1, 201432 citations

Quantum Memory in Atomic Ensembles

Joshua Nunn

Jan 1, 200810 citations

Multimode image memory based on a cold atomic ensemble

Dong-Sheng Ding, Jinghui Wu, Zhi‐Yuan Zhou +4 more

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.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.

arXiv:1204.1130Physical Review AJan 28, 201327 citations

Coherent Coupling between Microwave and Optical Fields via Cold Atoms*

Zhen-Tao Liang, Qing-Xian Lv, Shanchao Zhang +4 more

We demonstrate a long-coherent-time coupling between microwave and optical fields through cold atomic ensembles. The phase information of the microwave field is stored in a coherent superposition state of a cold atomic ensemble and is then read out by two optical fields after 12 ms. A similar operation of mapping the phase of optical fields into a cold atomic ensemble and then retrieving by microwave is also demonstrated. These studies demonstrate that long-coherent-time cold atomic ensembles could resonantly couple with microwave and optical fields simultaneously, which paves the way for realizing high-efficiency, high-bandwidth, and noiseless atomic quantum converters.We demonstrate a long-coherent-time coupling between microwave and optical fields through cold atomic ensembles. The phase information of the microwave field is stored in a coherent superposition state of a cold atomic ensemble and is then read out by two optical fields after 12 ms. A similar operation of mapping the phase of optical fields into a cold atomic ensemble and then retrieving by microwave is also demonstrated. These studies demonstrate that long-coherent-time cold atomic ensembles could resonantly couple with microwave and optical fields simultaneously, which paves the way for realizing high-efficiency, high-bandwidth, and noiseless atomic quantum converters.

Chinese Physics LettersAug 1, 20195 citations

Toward Manipulating Quantum Information Using Atomic Ensembles

Mikhail D. Lukin, Axel André, M. A. Eisaman +5 more

icapAug 1, 20020 citations

85.3%\ifmmode\pm\else\textpm\fi{}1.8%

using a 4-f imaging system. We also realize storage of two special photonic qutrit states as examples. Toward storing a higher-dimensional state encoded in OAM space, the efficiency difference between different OAM states should be considered according to the experimental results. The capability to store high-dimensional quantum states with high fidelity is a key step towards building high-dimensional quantum networks.

{}^{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.