eprintid: 1474850 rev_number: 29 eprint_status: archive userid: 608 dir: disk0/01/47/48/50 datestamp: 2016-03-23 16:27:11 lastmod: 2021-09-26 22:59:31 status_changed: 2016-03-23 16:27:11 type: article metadata_visibility: show creators_name: Ma, W-L creators_name: Wolfowicz, G creators_name: Li, S-S creators_name: Morton, JJL creators_name: Liu, R-B title: Classical nature of nuclear spin noise near clock transitions of Bi donors in silicon ispublished: pub divisions: UCL divisions: B04 divisions: C06 divisions: F64 note: ©2015 American Physical Society 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. date: 2015-10-08 date_type: published official_url: http://dx.doi.org/10.1103/PhysRevB.92.161403 oa_status: green full_text_type: pub language: eng primo: open primo_central: open_green article_type_text: Journal Article verified: verified_manual elements_id: 1064469 doi: 10.1103/PhysRevB.92.161403 lyricists_name: Morton, John lyricists_name: Wolfowicz, Gary lyricists_id: JJLMO69 lyricists_id: GWOLF53 actors_name: Morton, John actors_name: Smith, Robert actors_id: JJLMO69 actors_id: RSSMI20 actors_role: owner actors_role: impersonator full_text_status: public publication: PHYSICAL REVIEW B volume: 92 article_number: 161403(R) issn: 1098-0121 citation: 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 <https://doi.org/10.1103/PhysRevB.92.161403>. Green open access document_url: https://discovery.ucl.ac.uk/id/eprint/1474850/7/Morton_1474850_paper83.pdf