Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Laser cooling of a nanomechanical oscillator into its quantum ground state


The simple mechanical oscillator, canonically consisting of a coupled mass–spring system, is used in a wide variety of sensitive measurements, including the detection of weak forces1 and small masses2. On the one hand, a classical oscillator has a well-defined amplitude of motion; a quantum oscillator, on the other hand, has a lowest-energy state, or ground state, with a finite-amplitude uncertainty corresponding to zero-point motion. On the macroscopic scale of our everyday experience, owing to interactions with its highly fluctuating thermal environment a mechanical oscillator is filled with many energy quanta and its quantum nature is all but hidden. Recently, in experiments performed at temperatures of a few hundredths of a kelvin, engineered nanomechanical resonators coupled to electrical circuits have been measured to be oscillating in their quantum ground state3,4. These experiments, in addition to providing a glimpse into the underlying quantum behaviour of mesoscopic systems consisting of billions of atoms, represent the initial steps towards the use of mechanical devices as tools for quantum metrology5,6 or as a means of coupling hybrid quantum systems7,8,9. Here we report the development of a coupled, nanoscale optical and mechanical resonator10 formed in a silicon microchip, in which radiation pressure from a laser is used to cool the mechanical motion down to its quantum ground state (reaching an average phonon occupancy number of ). This cooling is realized at an environmental temperature of 20 K, roughly one thousand times larger than in previous experiments and paves the way for optical control of mesoscale mechanical oscillators in the quantum regime.

This is a preview of subscription content, access via your institution

Relevant articles

Open Access articles citing this article.

Access options

Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Optomechanical resonator with phononic shield.
Figure 2: Experimental set-up.
Figure 3: Mechanical and optical response.
Figure 4: Optical cooling results.


  1. Braginsky, V. & Manukin, A. Measurement of Weak Forces in Physics Experiments (Univ. Chicago Press, 1977)

    Google Scholar 

  2. Jensen, K., Kim, K. & Zettl, A. An atomic-resolution nanomechanical mass sensor. Nature Nanotechnol. 3, 533–537 (2008)

    Article  CAS  ADS  Google Scholar 

  3. O’Connell, A. D. et al. Quantum ground state and single-phonon control of a mechanical resonator. Nature 464, 697–703 (2010)

    Article  ADS  CAS  PubMed  Google Scholar 

  4. Teufel, J. D. et al. Sideband cooling of micromechanical motion to the quantum ground state. Nature 475, 359–363 (2011)

    Article  CAS  ADS  PubMed  Google Scholar 

  5. Caves, C., Thorne, K., Drever, R., Sandberg, V. D. & Zimmermann, M. On the measurement of a weak classical force coupled to a quantum-mechanical oscillator. Rev. Mod. Phys. 52, 341–392 (1980)

    Article  ADS  Google Scholar 

  6. Regal, C. A., Teufel, J. D. & Lehnert, K. W. Measuring nanomechanical motion with a microwave cavity interferometer. Nature Phys. 4, 555–560 (2008)

    Article  CAS  Google Scholar 

  7. Wallquist, M., Hammerer, K., Rabl, P., Lukin, M. & Zoller, P. Hybrid quantum devices and quantum engineering. Phys. Scr. 2009, 014001 (2009)

    Article  Google Scholar 

  8. Stannigel, K., Rabl, P., Sørensen, A. S., Zoller, P. & Lukin, M. D. Optomechanical transducers for long-distance quantum communication. Phys. Rev. Lett. 105, 220501 (2010)

    Article  CAS  ADS  PubMed  Google Scholar 

  9. Safavi-Naeini, A. H. & Painter, O. Proposal for an optomechanical traveling wave phonon-photon translator. N. J. Phys. 13, 013017 (2011)

    Article  Google Scholar 

  10. Eichenfield, M., Chan, J., Camacho, R. M., Vahala, K. J. & Painter, O. Optomechanical crystals. Nature 462, 78–82 (2009)

    Article  CAS  ADS  PubMed  Google Scholar 

  11. Cohen-Tannoudji, C. N. & Phillips, W. D. New mechanisms for laser cooling. Phys. Today 43, 33–40 (1990)

    Article  CAS  Google Scholar 

  12. Diedrich, F., Bergquist, J. C., Itano, W. M. & Wineland, D. J. Laser cooling to the zero-point energy of motion. Phys. Rev. Lett. 62, 403–406 (1989)

    Article  CAS  ADS  PubMed  Google Scholar 

  13. Kippenberg, T. J. & Vahala, K. J. Cavity optomechanics: back-action at the mesoscale. Science 321, 1172–1176 (2008)

    Article  CAS  ADS  PubMed  Google Scholar 

  14. Cohadon, P.-F., Heidmann, A. & Pinard, M. Cooling of a mirror by radiation pressure. Phys. Rev. Lett. 83, 3174–3177 (1999)

    Article  CAS  ADS  Google Scholar 

  15. Metzger, C. H. & Karrai, K. Cavity cooling of a microlever. Nature 432, 1002–1005 (2004)

    Article  CAS  ADS  PubMed  Google Scholar 

  16. Gigan, S. et al. Self-cooling of a micromirror by radiation pressure. Nature 444, 67–70 (2006)

    Article  CAS  ADS  PubMed  Google Scholar 

  17. Arcizet, O., Cohadon, P.-F., Briant, T., Pinard, M. & Heidmann, A. Radiation-pressure cooling and optomechanical instability of a micromirror. Nature 444, 71–74 (2006)

    Article  CAS  ADS  PubMed  Google Scholar 

  18. Gröblacher, S. et al. Demonstration of an ultracold micro-optomechanical oscillator in a cryogenic cavity. Nature Phys. 5, 485–488 (2009)

    Article  ADS  CAS  Google Scholar 

  19. Thompson, J. D. et al. Strong dispersive coupling of a high-finesse cavity to a micromechanical membrane. Nature 452, 72–75 (2008)

    Article  CAS  ADS  PubMed  Google Scholar 

  20. Rivière, R. et al. Optomechanical sideband cooling of a micromechanical oscillator close to the quantum ground state. Phys. Rev. A 83, 063835 (2011)

    Article  ADS  CAS  Google Scholar 

  21. Rocheleau, T. et al. Preparation and detection of a mechanical resonator near the ground state of motion. Nature 463, 72–75 (2010)

    Article  CAS  ADS  PubMed  Google Scholar 

  22. Teufel, J. D. et al. Circuit cavity electromechanics in the strong-coupling regime. Nature 471, 204–208 (2011)

    Article  CAS  ADS  PubMed  Google Scholar 

  23. Wiseman, H. M. & Milburn, G. J. Quantum Measurement and Control (Cambridge Univ. Press, 2010)

    MATH  Google Scholar 

  24. Alegre, T. P. M., Safavi-Naeini, A., Winger, M. & Painter, O. Quasi-two-dimensional optomechanical crystals with a complete phononic bandgap. Opt. Express 19, 5658–5669 (2011)

    Article  CAS  ADS  PubMed  Google Scholar 

  25. Marquardt, F., Chen, J. P., Clerk, A. A. & Girvin, S. M. Quantum theory of cavity-assisted sideband cooling of mechanical motion. Phys. Rev. Lett. 99, 093902 (2007)

    Article  ADS  CAS  PubMed  Google Scholar 

  26. Safavi-Naeini, A. H. et al. Electromagnetically induced transparency and slow light with optomechanics. Nature 472, 69–73 (2011)

    Article  CAS  ADS  PubMed  Google Scholar 

  27. Vitali, D. et al. Optomechanical entanglement between a movable mirror and a cavity field. Phys. Rev. Lett. 98, 030405 (2007)

    Article  CAS  ADS  PubMed  Google Scholar 

  28. Akram, U., Kiesel, N., Aspelmeyer, M. & Milburn, G. J. Single-photon optomechanics in the strong coupling regime. N. J. Phys. 12, 083030 (2010)

    Article  CAS  Google Scholar 

  29. Chang, D., Safavi-Naeini, A. H., Hafezi, M. & Painter, O. Slowing and stopping light using an optomechanical crystal array. N. J. Phys. 13, 023003 (2011)

    Article  CAS  Google Scholar 

  30. Rabl, P. Photon blockade effect in optomechanical systems. Phys. Rev. Lett. 107, 063601 (2011)

    Article  CAS  ADS  PubMed  Google Scholar 

Download references


This work was supported by the DARPA/MTO ORCHID program through a grant from the AFOSR, the European Commission (MINOS, QUESSENCE), the European Research Council (ERC QOM), the Austrian Science Fund (CoQuS, FOQUS, START) and the Kavli Nanoscience Institute at the California Institute of Technology. The authors thank B. Baker for help with the cryostat set-up, J.C. thanks R. Li, and J.C. and A.H.S.-N. acknowledge support from NSERC.

Author information

Authors and Affiliations



J.C., T.P.M.A. and A.H.S.-N. designed the device, and J.C. fabricated it with support from J.T.H. J.C., T.P.M.A., A.H.S.-N., J.T.H., A.K. and S.G. performed the measurements and analysed the measured data. O.P. and M.A. supervised the measurements and the data analysis. All authors contributed to the writing of the manuscript.

Corresponding author

Correspondence to Oskar Painter.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

The file contains Supplementary Text, Supplementary Figures 1-7 with legends and additional references. (PDF 744 kb)

PowerPoint slides

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Chan, J., Alegre, T., Safavi-Naeini, A. et al. Laser cooling of a nanomechanical oscillator into its quantum ground state. Nature 478, 89–92 (2011).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

This article is cited by


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing