# Entanglement-enhanced detection of single-photon scattering events

## Abstract

The ability to detect the interaction of light and matter at the single-particle level is becoming increasingly important for many areas of science and technology. The absorption or emission of a photon on a narrow transition of a trapped ion can be detected with near unit probability1,2, thereby enabling the realization of ultra-precise ion clocks3,4 and quantum information processing applications5. Extending this sensitivity to broad transitions is challenging due to the difficulty of detecting the rapid photon scattering events in this case. Here, we demonstrate a technique to detect the scattering of a single photon on a broad optical transition with high sensitivity. Our approach is to use an entangled state to amplify the tiny momentum kick an ion receives upon scattering a photon. The method should find applications in spectroscopy of atomic and molecular ions6,7,8,9 and quantum information processing.

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Download references ## Acknowledgements This work was supported by the European Commission via the integrated project Atomic QUantum TEchnologies and a Marie Curie International Incoming Fellowship. ## Author information ### Affiliations Authors ### Contributions C.R. conceived and designed the experiments. C.H., B.L., P.J., R.G. and C.R. performed the experiments. C.H., B.L. and C.R. analysed the data. C.H., B.L., R.G., R.B. and C.R. contributed materials and analysis tools. C.H., B.L. and C.R. wrote the paper. ### Corresponding author Correspondence to C. F. Roos. ## Ethics declarations ### Competing interests The authors declare no competing financial interests. ## Supplementary information ### Supplementary information Supplementary information (PDF 521 kb) ## Rights and permissions Reprints and Permissions ## About this article ### Cite this article Hempel, C., Lanyon, B., Jurcevic, P. et al. Entanglement-enhanced detection of single-photon scattering events. Nature Photon 7, 630–633 (2013). https://doi.org/10.1038/nphoton.2013.172 Download citation • Received: • Accepted: • Published: • Issue Date: ## Further reading • ### Protocol for Precise Field Sensing in the Optical Domain with Cold Atoms in a Cavity • Robert J. Lewis-Swan • , Diego Barberena • , Juan A. Muniz • , Julia R. K. Cline • , Dylan Young • , James K. Thompson • & Ana Maria Rey Physical Review Letters (2020) • ### Coherent laser spectroscopy of highly charged ions using quantum logic • P. Micke • , T. Leopold • , S. A. King • , E. Benkler • , L. J. Spieß • , L. Schmöger • , M. Schwarz • , J. R. Crespo López-Urrutia • & P. O. Schmidt Nature (2020) • ### Quantum amplification of mechanical oscillator motion • S. C. Burd • , R. Srinivas • , J. J. Bollinger • , A. C. Wilson • , D. J. Wineland • , D. Leibfried • , D. H. Slichter • & D. T. C. 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