Experimental principle and clock state preparation diagram. Image source: Ye Yinghao et al. Recently, a team led by Professor Guo Guangcan used guided magnetic fields combined with clock state preparation to achieve long-life storage of photon high-dimensional orbital angular mom

Experimental principle and clock status preparation diagram. Image source: Ye Yinghao et al.

Recently, a team led by Professor Guo Guangcan used guiding magnetic field combined with clock state preparation to achieve long-life storage of photon high-dimensional orbital angular momentum (OAM) quantum state based on cold atom ensemble. Their work was published on " Physical Review Express " .

Previous work shows that integrating multimode memory into quantum network can greatly improve channel capacity , which is crucial for long-distance quantum communication . The collective enhancement effect of cold atom ensemble makes it an effective medium for storing photons and information. Despite significant progress, there are still many problems to be solved in long-life space multimode memory based on cold atomic ensembles, one of which is how to achieve high fidelity of multimode memory after long-term storage because multiple spatial modes are more susceptible to the surrounding environment.

Based on the degree of freedom of OAM, the team used the cold 85Rb system to study the long-life storage of high-dimensional multi-modulus quantum states. In this work, to overcome the effects of inhomogeneous evolution due to the spatial complexity of the storage OAM, the team used a guided magnetic field to dominate the atom evolution, and then adopted a pair of magnetically insensitive states to suppress lateral decoherence. After adopting the clock state, destructive interference between different Zeeman sub-levels is eliminated, thus extending the service life of faithful storage.

The team expanded the dimensions of stored OAM superposition states to three in the experiment, and achieved fidelity beyond the quantum classical standard after 400μs of storage time, which was two orders of magnitude longer than previous work. When the storage time was extended from 10μs to 400μs, the retrieval efficiency dropped from 10.7% to 4.7%, showing a significant downward trend, with almost no attenuation of fidelity.

More information: Ye Yinghao et al., longevity memory of orbital angular momentum quantum states, "Physical Review Express " (2022). DOI: 10.1103/PhysRevLett.129.193601

Journal information: Physical comments Express