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Ab initio quantum-enhanced optical phase estimation using real-time feedback control

Nature Photonics volume 9, pages 577–581 (2015)Cite this article

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Abstract

Optical phase estimation is a vital measurement strategy that is used to perform accurate measurements of various physical quantities including length, velocity and displacements1,2. The precision of such measurements can be greatly enhanced by the use of entangled or squeezed states of light as demonstrated in a variety of different optical systems3,4,5,6,7,8. Most of these accounts, however, deal with the measurement of a very small shift of an already known phase, which is in stark contrast to ab initio phase estimation where the initial phase is unknown9,10,11,12. Here, we report on the realization of a quantum-enhanced and fully deterministic ab initio phase estimation protocol based on real-time feedback control. Using robust squeezed states of light combined with a real-time Bayesian adaptive estimation algorithm, we demonstrate deterministic phase estimation with a precision beyond the quantum shot noise limit. The demonstrated protocol opens up new opportunities for quantum microscopy, quantum metrology and quantum information processing.

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Figure 1: Principle of squeezing-enhanced phase estimation.
Figure 2: Working principle of the Bayesian feedback scheme.
Figure 3: Simplified experimental layout.
Figure 4: Illustration of a single measurement sequence.
Figure 5: Estimation variance results.

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Acknowledgements

The authors acknowledge financial support from the Danish Agency for Science, Technology and Innovation (Sapere Aude grant from FTP: 10-081599) and the Lundbeck Foundation. T.G. was supported by the HC Ørsted Postdoc programme. The authors would like to thank Roman Schnabel from the Albert Einstein Institute in Hannover for the support in using the squeezing source.

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Authors and Affiliations

  1. Department of Physics, Technical University of Denmark, Fysikvej, 2800 Kgs, Lyngby, Denmark

    Adriano A. Berni, Tobias Gehring, Bo M. Nielsen & Ulrik L. Andersen

  2. Max-Planck-Institut für Gravitationsphysik (Albert-Einstein-Institut) and Institut für Gravitationsphysik, Leibniz Universität Hannover, Callinstraße 38, Hannover, 30167, Germany

    Vitus Händchen

  3. Department of Physics, Università degli Studi di Milano, Milano, I-20133, Italy

    Matteo G. A. Paris

Authors
  1. Adriano A. Berni
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  6. Ulrik L. Andersen
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Contributions

A.A.B. and T.G. performed the main experiment and analysed the data. A.A.B., T.G. and B.M.N. developed the feedback protocol. T.G. and V.H. built the squeezed light source. A.A.B., T.G., M.G.A.P. and U.L.A. discussed the results. A.A.B and U.L.A wrote the paper with support from T.G. and M.G.A.P. U.L.A. conceived and supervised the project.

Corresponding author

Correspondence to Ulrik L. Andersen.

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The authors declare no competing financial interests.

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Berni, A., Gehring, T., Nielsen, B. et al. Ab initio quantum-enhanced optical phase estimation using real-time feedback control. Nature Photon 9, 577–581 (2015). https://doi.org/10.1038/nphoton.2015.139

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