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Classical nature of nuclear spin noise near clock transitions of Bi donors in silicon

Ma, W-L; Wolfowicz, G; Li, S-S; Morton, JJL; Liu, R-B; (2015) Classical nature of nuclear spin noise near clock transitions of Bi donors in silicon. PHYSICAL REVIEW B , 92 , Article 161403(R). 10.1103/PhysRevB.92.161403. Green open access

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Abstract

Whether a quantum bath can be approximated as classical Gaussian noise is a fundamental issue in central spin decoherence and also of practical importance in designing noise-resilient quantum control. Spin qubits based on bismuth donors in silicon have tunable interactions with nuclear spin baths and are first-order insensitive to magnetic noise at so-called clock transitions (CTs). This system is therefore ideal for studying the quantum/classical Gaussian nature of nuclear spin baths since the qubit-bath interaction strength determines the back-action on the baths and hence the adequacy of a Gaussian noise model. We develop a Gaussian noise model with noise correlations determined by quantum calculations and compare the classical noise approximation to the full quantum bath theory. We experimentally test our model through a dynamical decoupling sequence of up to 128 pulses, finding good agreement with simulations and measuring electron spin coherence times approaching 1 s—notably using natural silicon. Our theoretical and experimental study demonstrates that the noise from a nuclear spin bath is analogous to classical Gaussian noise if the back-action of the qubit on the bath is small compared to the internal bath dynamics, as is the case close to CTs. However, far from the CTs, the back-action of the central spin on the bath is such that the quantum model is required to accurately model spin decoherence.

Type: Article
Title: Classical nature of nuclear spin noise near clock transitions of Bi donors in silicon
Open access status: An open access version is available from UCL Discovery
DOI: 10.1103/PhysRevB.92.161403
Publisher version: http://dx.doi.org/10.1103/PhysRevB.92.161403
Language: English
Additional information: ©2015 American Physical Society
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > London Centre for Nanotechnology
URI: https://discovery.ucl.ac.uk/id/eprint/1474850
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