Scientific Results

Noise spectroscopy of a quantum-classical environment with a diamond qubit

Year: 2018

Authors: Hernandez Gomez S., Poggiali F., Cappellaro P., Fabbri N.

Autors Affiliation: LENS European Laboratory for Non linear Spectroscopy, Università di Firenze, I-50019 Sesto Fiorentino, Italy;
CNR-INO Istituto Nazionale di Ottica del Consiglio Nazionale delle Ricerche, I-50019 Sesto Fiorentino, Italy;
Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.

Abstract: Knowing a quantum system’s environment is critical for its practical use as a quantum device. Qubit sensors can reconstruct the noise spectral density of a classical bath, provided long enough coherence time. Here, we present a protocol that can unravel the characteristics of a more complex environment, comprising both unknown coherently coupled quantum systems, and a larger quantum bath that can be modeled as a classical stochastic field. We exploit the rich environment of a nitrogen-vacancy center in diamond, tuning the environment behavior with a bias magnetic field, to experimentally demonstrate our method. We show how to reconstruct the noise spectral density even when limited by relatively short coherence times, and identify the local spin environment. Importantly, we demonstrate that the reconstructed model can have predictive power, describing the spin qubit dynamics under control sequences not used for noise spectroscopy, a feature critical for building robust quantum devices. At lower bias fields, where the effects of the quantum nature of the bath are more pronounced, we find that more than a single classical noise model are needed to properly describe the spin coherence under different controls, due to the back action of the qubit onto the bath.

Journal/Review: PHYSICAL REVIEW B

Volume: 98 (21)      Pages from: 214307-1  to: 214307-6

More Information: The authors thank F. S. Cataliotti for critical reading of the manuscript and M. Inguscio for supporting the project. This work was supported by EU-FP7 ERC Starting Q-SEnS2 (Grant No. 337135) and by NSF Grant No. EECS1702716.
KeyWords: Open quantum systems and decoherence; Quantum control; Quantum sensing; Nitrogen-vacancy centers in diamond;
DOI: 10.1103/PhysRevB.98.214307

Citations: 12
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