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Fundamental limits of electron and nuclear spin qubit lifetimes in an isolated self-assembled quantum dot
npj Quantum Information ( IF 7.6 ) Pub Date : 2021-02-24 , DOI: 10.1038/s41534-021-00378-2
George Gillard , Ian M. Griffiths , Gautham Ragunathan , Ata Ulhaq , Callum McEwan , Edmund Clarke , Evgeny A. Chekhovich

Combining external control with long spin lifetime and coherence is a key challenge for solid state spin qubits. Tunnel coupling with electron Fermi reservoir provides robust charge state control in semiconductor quantum dots, but results in undesired relaxation of electron and nuclear spins through mechanisms that lack complete understanding. Here, we unravel the contributions of tunnelling-assisted and phonon-assisted spin relaxation mechanisms by systematically adjusting the tunnelling coupling in a wide range, including the limit of an isolated quantum dot. These experiments reveal fundamental limits and trade-offs of quantum dot spin dynamics: while reduced tunnelling can be used to achieve electron spin qubit lifetimes exceeding 1 s, the optical spin initialisation fidelity is reduced below 80%, limited by Auger recombination. Comprehensive understanding of electron-nuclear spin relaxation attained here provides a roadmap for design of the optimal operating conditions in quantum dot spin qubits.



中文翻译:

孤立的自组装量子点中电子和核自旋量子位寿命的基本极限

将外部控制与长自旋寿命和相干性相结合是固态自旋量子位的关键挑战。隧道与电子费米储层的耦合在半导体量子点中提供了强大的电荷状态控制,但由于缺乏全面的了解,导致了电子和核自旋的不期望松弛。在这里,我们通过在宽范围内(包括孤立的量子点的限制)系统地调节隧穿耦合,来阐明隧穿辅助和声子辅助自旋弛豫机制的贡献。这些实验揭示了量子点自旋动力学的基本限制和权衡:虽然减少的隧穿可用于实现超过1 s的电子自旋量子位寿命,但由于俄歇重组,光学自旋初始化保真度降低到80%以下。

更新日期:2021-02-24
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