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Entanglement-enhanced detection of single-photon scattering events



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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Figure 1: Cat-state spectroscopy in phase space.
Figure 2: Experimental details.
Figure 3: Cat-state spectroscopy results.


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This work was supported by the European Commission via the integrated project Atomic QUantum TEchnologies and a Marie Curie International Incoming Fellowship.

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Authors and Affiliations



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.

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The authors declare no competing financial interests.

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Hempel, C., Lanyon, B., Jurcevic, P. et al. Entanglement-enhanced detection of single-photon scattering events. Nature Photon 7, 630–633 (2013).

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