Low-frequency spin qubit detuning noise in highly purified $^{28}$Si/SiGe
Tom Struck, Arne Hollmann, Floyd Schauer, Olexiy Fedorets, Andreas Schmidbauer, Kentarou Sawano, Helge Riemann, Nikolay V. Abrosimov, Łukasz Cywiński, Dominique… 展开作者
Tom Struck, Arne Hollmann, Floyd Schauer, Olexiy Fedorets, Andreas Schmidbauer, Kentarou Sawano, Helge Riemann, Nikolay V. Abrosimov, Łukasz Cywiński, Dominique Bougeard, Lars R. Schreiber
The manipulation fidelity of a single electron qubit gate-confined in a $^{28}$Si/SiGe quantum dot has recently been drastically improved by nuclear isotope purification. Here, we identify the dominant source for low-frequency qubit detuning noise in a device with an embedded nanomagnet, a remaining $^{29}$Si concentration of only 60$\,$ppm in the strained $^{28}$Si quantum well layer and a spin echo decay time $T_2^{\text{echo}}=128\,μ$s. The power spectral density (PSD) of the charge noise explains both the observed transition of a $1/f^2$- to a $1/f$-dependence of the detuning noise PSD as well as the observation of a decreasing time-ensemble spin dephasing time from $T_2^* \approx 20\,μ$s with increasing measurement time over several hours. Despite their strong hyperfine contact interaction, the few $^{73}$Ge nuclei overlapping with the quantum dot in the barrier do not limit $T_2^*$, as their dynamics is frozen on a few hours measurement scale. We conclude that charge noise and the design of the gradient magnetic field is the key to further improve the qubit fidelity.
Spectroscopy of low-lying valley states in hot Si/SiGe quantum dots
University of California, Los Angeles（加州大学洛杉矶分校）；Center for Quantum Science and Engineering（量子科学与工程中心）；Department of Physics and Astronomy（物理与天文系）；Department of Electrical and Computer Engineering（电气与计算机工程系）
Beijing Academy of Quantum Information Sciences（北京量子信息科学研究院）；Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所凝聚态物理北京国家实验室）；University of Chinese Academy of Sciences（中国科学院大学）；Department of Physics and Astronomy, University College London（伦敦大学学院物理与天文系）；State Key Laboratory of Semiconductor Physics and Chip Technologies, Institute of Semiconductor, Chinese Academy of Sciences（中国科学院半导体研究所半导体物理与芯片技术国家重点实验室）；School of Electronics, Peking University（北京大学电子学院）
Direct measurement of the energy spectrum of a quantum dot qubit
University of Wisconsin-Madison（威斯康星大学麦迪逊分校）；Q-NEXT, Argonne National Laboratory（Q-NEXT，阿贡国家实验室）；Materials Science Division, Argonne National Laboratory（阿贡国家实验室材料科学部）；Prizker School of Molecular Engineering, University of Chicago（芝加哥大学普里茨克分子工程学院）
