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# A photon–photon quantum gate based on Rydberg interactions

## Abstract

The interaction between Rydberg states of neutral atoms is strong and long-range, making it appealing to put it to use in the context of quantum technologies. Recently, first applications of this idea have been reported in the fields of quantum computation1 and quantum simulation2,3,4. Furthermore, electromagnetically induced transparency allows one to map these Rydberg interactions to light5,6,7,8,9,10,11,12,13,14,15. Here we exploit this mapping and the resulting interaction between photons to realize a photon–photon quantum gate16,17, demonstrating the potential of Rydberg systems as a platform also for quantum communication and quantum networking18. We measure a controlled-NOT truth table with a fidelity of 70(8)% and an entangling-gate fidelity of 63.7(4.5)%, both post-selected upon detection of a control and a target photon. The level of control reached here is an encouraging step towards exploring novel many-body states of photons or for future applications in quantum communication and quantum networking18.

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## Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.

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## Acknowledgements

This work was supported by Deutsche Forschungsgemeinschaft through Nanosystems Initiative Munich.

## Author information

Authors

### Contributions

All authors contributed extensively to the work presented here.

### Corresponding author

Correspondence to Stephan Dürr.

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### Competing interests

The authors declare no competing interests.

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## Supplementary information

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Reprints and Permissions

Tiarks, D., Schmidt-Eberle, S., Stolz, T. et al. A photon–photon quantum gate based on Rydberg interactions. Nature Phys 15, 124–126 (2019). https://doi.org/10.1038/s41567-018-0313-7

• Accepted:

• Published:

• Issue Date:

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