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NONLINEAR INTERFEROMETRY

Measure in circles

Nature Physics volume 18, pages 124–125 (2022)Cite this article

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Entanglement can provide an extra boost in precision, but entangled states are hard to detect. A recent experiment solves this problem by letting the entangling dynamics come full circle — or not, depending on the subtle perturbation to be sensed.

The sensitivity of devices such as atomic clocks, magnetometers and gravimeters is limited by statistical fluctuations inherent in the probabilistic nature of quantum measurements. The fluctuations can be reduced by first allowing the constituent atoms to interact and thereby acquire quantum correlations. Typically, longer interaction times lead to stronger entanglement and thus, in principle, to higher sensitivity. This makes entanglement a critical resource for advancing precision measurements, but the most highly entangled states are often the most difficult to detect. Now, writing in Nature Physics, Qi Liu and colleagues report that they have solved this problem through a clever design of interactions that give rise to a cyclic time evolution — the same interactions that initially entangle the atoms ultimately also disentangle them1.

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Fig. 1: Linear and SU(1,1) interferometry.

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Authors and Affiliations

  1. Department of Physics, Stanford University, Stanford, CA, USA

    Philipp Kunkel & Monika Schleier-Smith

  2. SLAC National Accelerator Laboratory, Menlo Park, CA, USA

    Philipp Kunkel

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  1. Philipp Kunkel
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  2. Monika Schleier-Smith
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Correspondence to Monika Schleier-Smith.

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Kunkel, P., Schleier-Smith, M. Measure in circles. Nat. Phys. 18, 124–125 (2022). https://doi.org/10.1038/s41567-021-01500-z

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