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Certified quantum non-demolition measurement of a macroscopic material system

Nature Photonics volume 7, pages 517–520 (2013)Cite this article

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Abstract

Quantum non-demolition (QND) measurements improve sensitivity by evading measurement back-action1. The technique was first proposed to detect mechanical oscillations in gravity-wave detectors2 and demonstrated in the measurement of optical fields3,4, which led to the development of rigorous criteria to distinguish QND from similar non-classical measurements4. Recent QND measurements of macroscopic material systems such as atomic ensembles5,6,7,8,9,10 and mechanical oscillators11,12,13 show some QND features, but not full QND character. Here we demonstrate certified QND measurement of the collective spin of an atomic ensemble. We observed quantum-state preparation (QSP) and information-damage trade-off (IDT) beyond their classical limits by seven and 12 standard deviations, respectively. Our techniques complement recent work with microscopic systems14,15,16 and can be used for quantum metrology6,7,8,9,10,17 and memory18, the preparation19 and detection20 of non-Gaussian states, and proposed quantum simulation21,22,23 and information24,25 protocols. They should enable QND measurements of dynamical quantum variables21,22,26 and the realization of QND-based quantum information protocols19,24,25.

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Figure 1: Experimental set-up and measurement pulse sequence used to verify QND measurement of atomic spins.
Figure 2: Experimental verification of QSP and non-classical IDT in a QND measurement of atomic spins.

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Acknowledgements

This work was supported by the Spanish Ministry of Science and Innovation under the project Magnetometria ultra-precisa basada en optica quantica (MAGO) (Ref. FIS2011-23520), by the European Research Council under the project Atomic Quantum Metrology (AQUMET) and by Fundació Privada CELLEX Barcelona.

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Authors and Affiliations

  1. ICFO-Institut de Ciencies Fotoniques, Av. Carl Friedrich Gauss, 3, Castelldefels, 08860, Barcelona, Spain

    R. J. Sewell, M. Napolitano, N. Behbood, G. Colangelo & M. W. Mitchell

  2. ICREA-Institució Catalana de Recerca i Estudis Avançats, 08015, Barcelona, Spain

    M. W. Mitchell

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Contributions

R.J.S. and M.W.M. conceived and designed the project; R.J.S., M.N., N.B. and G.C. performed the experiment; R.J.S. performed the data analysis; R.J.S. and M.W.M. co-wrote the manuscript with feedback from all the authors.

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Correspondence to R. J. Sewell.

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The authors declare no competing financial interests.

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Sewell, R., Napolitano, M., Behbood, N. et al. Certified quantum non-demolition measurement of a macroscopic material system. Nature Photon 7, 517–520 (2013). https://doi.org/10.1038/nphoton.2013.100

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