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Quantum physics

Observing and the observed

Nature volume 443, pages 154–155 (2006)Cite this article

Quantum mechanics states that the measurement process can fundamentally alter what is being measured. This 'back-action' has been observed on the macroscopic scale — in the vibrations of a tiny mechanical device.

In daily life, we continuously observe and then assimilate these observations. The cumulative effect of this process grounds our intuition; our intuition, in turn, governs our next actions. But, oddly, our deep sense of the order of things acquired in this way does not square with fundamental tenets of quantum mechanics. Many people have found this discrepancy profoundly discomforting: Einstein, for instance, famously decried one of the least intuitive consequences of quantum theory as “spooky action at a distance”1,2. In this issue, Naik et al. (page 193)3 provide a beautiful example of how nano-mechanical systems can be used to explore such quandaries. The authors induce cooling of a tiny mechanical resonator just by measuring its vibrations. Closer inspection shows that the phenomenon is a mechanical analogue of the familiar optical cooling of trapped atoms.

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Figure 1: Cooper-pair molasses in action.

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  1. Departments of Physics, Applied Physics and Bioengineering and at the Kavli Nanoscience Institute, California Institute of Technology, Pasadena, 91125, California, USA

    Michael Roukes

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  1. Michael Roukes
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Roukes, M. Observing and the observed. Nature 443, 154–155 (2006). https://doi.org/10.1038/443154a

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