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Quantum metrology with full and fast quantum control

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Author Sekatski Pavel, Skotiniotis Michalis, Kołodyński Janek, Dür Wolfgang,
Project Quantum metrology and macroscopic quantum states
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Original article (peer-reviewed)

Journal Quantum
Volume (Issue) 1
Page(s) 27
Title of proceedings Quantum
DOI 10.22331/q-2017-09-06-27

Open Access

URL https://quantum-journal.org/papers/q-2017-09-06-27/
Type of Open Access Publisher (Gold Open Access)

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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