# Enhancing the Coherence of a Spin Qubit by Operating it as a Feedback Loop That Controls its Nuclear Spin Bath

 Title: Enhancing the Coherence of a Spin Qubit by Operating it as a Feedback Loop That Controls its Nuclear Spin Bath Author: Bluhm, Hendrik; Foletti, Sandra; Mahalu, Diana; Umansky, Vladimir; Yacoby, Amir Note: Order does not necessarily reflect citation order of authors. Citation: Bluhm, Hendrik, Sandra Foletti, Diana Mahalu, Vladimir Umansky, and Amir Yacoby. 2010. Enhancing the coherence of a spin qubit by operating it as a feedback loop that controls its nuclear spin bath. Physical Review Letters 105(21): 216803. Full Text & Related Files: 1003.4031v2.pdf (211.2Kb; PDF) Abstract: In many realizations of electron spin qubits the dominant source of decoherence is the fluctuating nuclear spin bath of the host material. The slowness of this bath lends itself to a promising mitigation strategy where the nuclear spin bath is prepared in a narrowed state with suppressed fluctuations. Here, this approach is realized for a two-electron spin qubit in a GaAs double quantum dot and a nearly ten-fold increase in the inhomogeneous dephasing time $$T_2^*$$ is demonstrated. Between subsequent measurements, the bath is prepared by using the qubit as a feedback loop that first measures its nuclear environment by coherent precession, and then polarizes it depending on the final state. This procedure results in a stable fixed point at a nonzero polarization gradient between the two dots, which enables fast universal qubit control. Published Version: doi:10.1103/PhysRevLett.105.216803 Other Sources: http://arxiv.org/abs/1003.4031 Terms of Use: This article is made available under the terms and conditions applicable to Open Access Policy Articles, as set forth at http://nrs.harvard.edu/urn-3:HUL.InstRepos:dash.current.terms-of-use#OAP Citable link to this page: http://nrs.harvard.edu/urn-3:HUL.InstRepos:8013323

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Peer reviewed scholarly articles from the Faculty of Arts and Sciences of Harvard University