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Entanglement-enhanced probing of a delicate material system

Nature Photonics volume 7, pages 28–32 (2013)Cite this article

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Abstract

Quantum metrology1 uses entanglement2,3,4,5 and other quantum effects6 to improve the sensitivity of demanding measurements7,8,9. Probing of delicate systems demands high sensitivity from limited probe energy and has motivated the field's key benchmark—the standard quantum limit10. Here we report the first entanglement-enhanced measurement of a delicate material system. We non-destructively probe an atomic spin ensemble by means of near-resonant Faraday rotation, a measurement that is limited by probe-induced scattering in quantum-memory and spin-squeezing applications6,11,12,13. We use narrowband, atom-resonant NOON states to beat the standard quantum limit of sensitivity by more than five standard deviations, both on a per-photon and per-damage basis. This demonstrates quantum enhancement with fully realistic loss and noise, including variable-loss effects14,15,16. The experiment opens the way to ultra-gentle probing of single atoms17, single molecules18, quantum gases19 and living cells20.

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Figure 1: NOON state probing of an atomic ensemble by Faraday rotation.
Figure 2: High-visibility super-resolving Faraday rotation probing using optical NOON states.
Figure 3: NOON state characterization.
Figure 4: Quantum enhancement in probing of a delicate system, quantified by FI per mean scattering (S) from the 85Rb atomic ensemble.
Figure 5: Spectroscopic characterization of the rubidium atomic ensemble.

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Acknowledgements

The authors thank A. Cerè, Y.A. de Icaza Astiz, M. Napolitano, N. Behbood, R.J. Sewell and M. Hendrych for useful discussions. This work was supported by the Spanish Ministerio de Economia y Competitividad under the project Magnetometria Optica (no. FIS2011-23520), by the European Research Council starting grant ‘AQuMet’, by Fundació Privada Cellex and by an Institute of Photonic Sciences – Ontario Centres of Excellence collaborative research programme. F.W. is supported by the Commission for Universities and Research of the Department of Innovation, Universities and Enterprises of the Catalan Government and the European Social Fund. N.G. acknowledges support from the National Sciences and Engineering Research Council of Canada.

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Author notes

  1. Florian Wolfgramm

    Present address: Present address: innoFSPEC, Physical Chemistry, Institute of Chemistry, University of Potsdam, Am Mühlenberg 3, 14476 Potsdam, Germany,

Authors and Affiliations

  1. ICFO – Institut de Ciencies Fotoniques, Mediterranean Technology Park, Castelldefels (Barcelona), 08860, Spain

    Florian Wolfgramm, Federica A. Beduini & Morgan W. Mitchell

  2. Center of Life Nanoscience at La Sapienza, Istituto Italiano di Tecnologia, Viale Regina Elena 255, Rome, 00181, Italy

    Chiara Vitelli

  3. Département de Génie Physique, COPL, École Polytechnique de Montréal, C.P. 6079, Succ. Centre-ville, H3C 3A7, Montréal (Québec), Canada

    Nicolas Godbout

  4. ICREA – Institució Catalana de Recerca i Estudis Avançats, Barcelona, 08015, Spain

    Morgan W. Mitchell

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Contributions

F.W. and M.W.M. conceived and designed the project. F.W., C.V. and F.A.B. designed, constructed and tested the apparatus. F.W. acquired the data and performed the analysis. M.W.M. and N.G. performed the modelling and simulation. All authors contributed to the preparation of the manuscript.

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Correspondence to Morgan W. Mitchell.

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Wolfgramm, F., Vitelli, C., Beduini, F. et al. Entanglement-enhanced probing of a delicate material system. Nature Photon 7, 28–32 (2013). https://doi.org/10.1038/nphoton.2012.300

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