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A Refined Magnetic Sense

By ETH Zurich

July 9, 2018

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An international team has demonstrated that algorithms and hardware developed for quantum computation can be applied to quantum-enhanced sensing of magnetic fields.

The researchers used a single quantum bit (qubit), based on a superconducting circuit, to measure magnetic fields with high sensitivity, using "quantum trickery" to push the limits.

The transmon qubit allows flexibility in engineering circuits to match the problem at hand. Leveraging this flexibility, researchers at Aalto University in Finland developed a transmon qubit in a configuration suited to sensing magnetic fields.

To maximize measurement accuracy, the team, guided by researchers from Switzerland’s ETH Zurich, the Moscow Institute of Physics and Technology, and the Landau Institute for Theoretical Physics in Moscow, implemented two dedicated phase-estimation schemes that exploit the coherent nature of qubit dynamics.

The researchers performed the measurements adaptively, changing sampling parameters depending on previous outcomes. This Bayesian inference enabled the team to reach a sensitivity about six times higher than that achieved with classical phase estimation. That "quantum boost" helped overcome the shot noise, which limits the precision of standard measurement.

Using quantum hardware and quantum algorithms for quantum sensing could lead to new devices that make single- or multi-qubit magnetometers far more sensitive than current magnetic-field sensors.

From ETH Zurich
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