Optical storage of orbital angular momentum via Rydberg electromagnetically induced transparency
Kai Wang, Wei Zhang Wei Zhang, Zhiyuan Zhou Zhiyuan Zhou, Mingxing Dong Mingxing Dong, Shuai Shi Shuai Shi, Shi-Long Liu, 丁冬生, and Baosen Shi and Baosen Shi
In this Letter, we report on the successful optical storage of orbital angular momentum (OAM) using Rydberg electromagnetically induced transparency (EIT) in cold rubidium atoms. With a storage time of 1.4 μs, the retrieved structure is highly similar, showing the ability of storing light’s OAM at a principal quantum number of 20. The results at higher principal quantum numbers (n=25,30) are also measured. These results show the promise of image processing based on a Rydberg atomic system.
In this Letter, we report on the successful optical storage of orbital angular momentum (OAM) using Rydberg electromagnetically induced transparency (EIT) in cold rubidium atoms. With a storage time of 1.4 μs, the retrieved structure is highly similar, showing the ability of storing light’s OAM at a principal quantum number of 20. The results at higher principal quantum numbers (n=25,30) are also measured. These results show the promise of image processing based on a Rydberg atomic system.
A quantum memory is a key component for quantum networks, which will enable the distribution of quantum information. Its successful development requires storage of single-photon light. Encoding photons with spatial shape through higher-dimensional states significantly increases their information-carrying capability and network capacity. However, constructing such quantum memories is challenging. Here we report the first experimental realization of a true single-photon-carrying orbital angular momentum stored via electromagnetically induced transparency in a cold atomic ensemble. Our experiments show that the non-classical pair correlation between trigger photon and retrieved photon is retained, and the spatial structure of input and retrieved photons exhibits strong similarity. More importantly, we demonstrate that single-photon coherence is preserved during storage. The ability to store spatial structure at the single-photon level opens the possibility for high-dimensional quantum memories. Photonic quantum memories are necessary for quantum information networks and can be built using cold atomic gases. In this work, Ding et al. show the first storage and retrieval of single photons carrying orbital angular momentum using electromagnetically induced transparency in a cold rubidium ensemble.
We experimentally investigate the transfer of orbital angular momentum (OAM) of light in a solid driven by electromagnetically induced transparency (EIT). Under the condition of dynamical EIT, the OAM of the probe pulse is stored and retrieved in the experimental medium. By using a four-level double-lambda system to control the retrieval process of EIT storage, we show that OAM can be transferred from the probe field or the second control field to the newly generated signal field, which has a new spatial-frequency mode compared with the input mode. Furthermore, we use EIT-based four-wave mixing to investigate the direct OAM transfer without experiencing the storage, where we do not need to switch off and back on the control field.
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 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.
Summary form only given. The orbital angular momentum (OAM) of light has raised a great deal of applications [1], ranging from the trapping of particles, the driving of optical micromachines to applications in astrophysics studies. In quantum optics, twisted single-photons have also been identified as promising carriers for the implementation of various quantum information protocols. They indeed offer the possibility to encode and process information in high-dimensional Hilbert spaces and could enable to reach higher efficiencies and enhanced information capacity. For further applications in quantum networks involving light-matter interfaces, a critical capability is the ability to reversibly map OAM into and out of atomic memories. While the storage of bright beams of light in Laguerre-Gaussian modes has been reported in the past few years [2, 3], we report here the first demonstration of storage in the single-photon regime [4]. The experimental realization proceeds in the following way. First, LG modes are generated using a spatial light modulator. These modes, which are weak coherent states at the single-photon level, are then mapped into an ensemble of cold cesium atoms in a magneto-optical trap using the dynamic electromagnetically-induced transparency (EIT) protocol. The signal quantum properties, including its OAM, are expected to be transferred to the atomic medium and can be stored for a programmable time, limited by the lifetime of the atomic coherence. After this reversible storage, unlike for bright beams, the detection of twisted single-photons cannot be performed by imaging on a CCD camera. Here we have chosen to work with a combination of a computergenerated hologram, which adds or subtracts one unity of OAM, and a single-mode fiber to implement a mode discriminator. In our experiment, the output mode is actually split on a 50/50 beam splitter and one discriminator is installed in each of the two output paths so that we can quantify both the LG+1 and LG-1 components of the retrieved light. We stored and retrieved LG+1 and LG-1 modes. As can be seen in fig. 1, detection events in the detection path with l opposite to the one of the incoming mode are negligible, within the distinction ratio. For both modes, the overall storage and retrieval efficiency is (16 ± 2%). We thus demonstrated that such pulses carrying OAM can be stored in the single-photon regime into and out the ensemble with preserved handedness of the helical phase structure. Mapping of a TEM10 mode, i.e. an equal-weight superposition of LG+1 and LG-1 modes was also performed. Within our experimental precision, the achieved storage and retrieval efficiency is the same here each LG components than for the individual storage presented previously. Further works should include reconstruction of a full density matrix, including coherences not measured here, and the calculation of process fidelity. We implemented a sophisticated detection technique based on a Mach-Zehnder interferometer. Preliminary results will be reported. Extensions to higher alphabets for the realization of high-dimensional quantum information networks is also work for future.
Abstract The spatial modes of light, carrying a quantized amount of orbital angular momentum (OAM), is one of the excellent candidates that provides access to high-dimensional quantum states, which essentially makes it promising towards building high-dimensional quantum networks. Quantum memory with efficiency above 50% is an essential condition for beating the no-cloning limit or in the one-way quantum computation. However, up till now, the highest storage efficiencies achieved for OAM states are below 30%, which is an obstacle towards practical applications. In this paper, we report the storage and retrieval of photonic qubits encoded with OAM state in an elongated cold rubidium atomic ensemble, achieving a storage efficiency around 65% with an average conditional fidelity above 98%. Our work constitutes an efficient node that is needed towards high dimensional and large scale quantum networks.
Realizing single light bullets and vortices that are stable in high dimensions is a long-standing goal in the study of nonlinear optical physics. On the other hand, the storage and retrieval of such stable high dimensional optical pulses may offer a variety of applications. Here we present a scheme to generate such optical pulses in a cold Rydberg atomic gas. By virtue of electromagnetically induced transparency, strong, long-range atom-atom interaction in Rydberg states is mapped to light fields, resulting in a giant, fast-responding nonlocal Kerr nonlinearity and the formation of light bullets and vortices carrying orbital angular momenta, which have extremely low generation power, very slow propagation velocity, and can stably propagate, with the stability provided by the combination of local and the nonlocal Kerr nonlinearities. We demonstrate that the light bullets and vortices obtained can be stored and retrieved in the system with high efficiency and fidelity. Our study provides a new route for manipulating high-dimensional nonlinear optical processes via the controlled optical nonlinearities in cold Rydberg gases.