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arXiv · 1603.08944

Quantum metrology with full and fast quantum control

Pavel Sekatski·Michalis Skotiniotis·Janek Kołodyński·Wolfgang Dür
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Abstract

We establish general limits on how precise a parameter, e.g. frequency or the strength of a magnetic field, can be estimated with the aid of full and fast quantum control. We consider uncorrelated noisy evolutions of N qubits and show that fast control allows to fully restore the Heisenberg scaling (~1/N^2) for all rank-one Pauli noise except dephasing. For all other types of noise the asymptotic quantum enhancement is unavoidably limited to a constant-factor improvement over the standard quantum limit (~1/N) even when allowing for the full power of fast control. The latter holds both in the single-shot and infinitely-many repetitions scenarios. However, even in this case allowing for fast quantum control helps to increase the improvement factor. Furthermore, for frequency estimation with finite resource we show how a parallel scheme utilizing any fixed number of entangled qubits but no fast quantum control can be outperformed by a simple, easily implementable, sequential scheme which only requires entanglement between one sensing and one auxiliary qubit.

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Pavel Sekatski, Michalis Skotiniotis, Janek Kołodyński, Wolfgang Dür. 2017-09-05. Quantum metrology with full and fast quantum control. https://doi.org/10.22331/q-2017-09-06-27

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