PerspectiveQuantum Measurement

Classical-quantum sensors keep better time

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Science  26 May 2017:
Vol. 356, Issue 6340, pp. 802-803
DOI: 10.1126/science.aan1112

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The key task in metrology is to determine physical parameters as precisely as possible given certain resources, and few problems are as important as keeping time. The history of science is closely connected with the development of the accuracy of our clocks, right up to our current standards of time: The second is defined by the frequency of an electronic transition of a cesium atom. On pages 837 and 832 of this issue, Boss et al. (1) and Schmitt et al. (2) report the independent development of nearly identical methods to greatly improve existing frequency measurements. They measured oscillating magnetic fields driven by a clock by using repeated measurements of the spin state of a nitrogen-vacancy center in diamond. It is one of those surprisingly common events in science when different research groups hit on the same idea at nearly the same time, sometimes called “multiple independent discovery.”