Silicon–germanium heterostructures are a promising quantum circuit platform, but crucial aspects, such as the long-term charge dynamics and cooldown-to-cooldown variations, are still widely unexplored quantitatively. In this Letter, we present the results of an extensive bias cooling study performed on gated silicon–germanium quantum dots with an Al2O3 dielectric. Over 80 cooldowns were performed in the course of our investigations. The performance of the devices is assessed by low-frequency charge noise measurements in the band of 200 μHz to 10 mHz. We measure the total noise power as a function of the applied voltage during cooldown in four different devices and find a minimum in noise at 0.7 V bias cooling voltage for all observed samples. We manage to decrease the total noise power median by a factor of 6 and compute a reduced tunneling current density using Schrödinger–Poisson simulations. Furthermore, we show the variation in noise from the same device in the course of eleven different cooldowns performed under the nominally same conditions.

中文翻译：

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通过门控 Si/6 Ge1−x 量子点中的偏置冷却降低噪声


硅-锗异质结构是一种有前途的量子电路平台，但关键方面，例如长期电荷动力学和冷却到冷却变化，仍未得到广泛的定量探索。在这封信中，我们介绍了对具有 Al2O3 电介质的门控硅-锗量子点进行的广泛偏压冷却研究的结果。在我们的调查过程中，进行了超过 80 次冷却。通过 200 μHz 至 10 mHz 频段的低频电荷噪声测量来评估器件的性能。我们测量了四个不同器件冷却期间总噪声功率与所施加电压的函数关系，并发现所有观察到的样品在 0.7 V 偏置冷却电压下噪声最小。我们设法将总噪声功率中值降低 6 倍，并使用薛定谔-泊松模拟计算降低的隧道电流密度。此外，我们还展示了在名义上相同的条件下执行的十一次不同冷却过程中同一设备的噪声变化。