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arXiv:1706.04779 · Nature Communications

Narrow-bandwidth sensing of high-frequency fields with continuous dynamical decoupling

Alexander Stark, Nati Aharon, Thomas Unden, Daniel Louzon, Alexander Huck, Alex Retzker, Ulrik L. Andersen, Fedor Jelezko

Published Oct 18, 2017• 76 citations
arXivHTMLPDF

Abstract

Abstract State-of-the-art methods for sensing weak AC fields are only efficient in the low frequency domain (<10 MHz). The inefficiency of sensing high-frequency signals is due to the lack of ability to use dynamical decoupling. In this paper we show that dynamical decoupling can be incorporated into high-frequency sensing schemes and by this we demonstrate that the high sensitivity achieved for low frequency can be extended to the whole spectrum. While our scheme is general and suitable to a variety of atomic and solid-state systems, we experimentally demonstrate it with the nitrogen-vacancy center in diamond. For a diamond with natural abundance of 13 C, we achieve coherence times up to 1.43 ms resulting in a smallest detectable magnetic field strength of 4 nT at 1.6 GHz. Attributed to the inherent nature of our scheme, we observe an additional increase in coherence time due to the signal itself.

DOI
10.1038/s41467-017-01159-2

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Abstract Quantum sensors—qubits sensitive to external fields—have become powerful detectors for various small acoustic and electromagnetic fields. A major key to their success have been dynamical decoupling protocols which enhance sensitivity to weak oscillating (AC) signals. Currently, those methods are limited to signal frequencies below a few MHz. Here we harness a quantum-optical effect, the Mollow triplet splitting of a strongly driven two-level system, to overcome this limitation. We microscopically understand this effect as a pulsed dynamical decoupling protocol and find that it enables sensitive detection of fields close to the driven transition. Employing a nitrogen-vacancy center, we detect GHz microwave fields with a signal strength (Rabi frequency) below the current detection limit, which is set by the center’s spectral linewidth 1/T2∗1{\rm{/}}T_2^*1/T2∗​ 1 ∕ T 2 * . Pushing detection sensitivity to the much lower 1/ T 2 limit, this scheme could enable various applications, most prominently coherent coupling to single phonons and microwave photons.