An advanced understanding of ultrafast coherent electron dynamics is necessary for the application of submicrometre devices under a non-equilibrium drive to quantum technology, including on-demand single-electron sources1, electron quantum optics2-4, qubit control5-7, quantum sensing8,9 and quantum metrology10. Although electron dynamics along an extended channel has been studied extensively2-4,11, it is hard to capture the electron motion inside submicrometre devices. The frequency of the internal, coherent dynamics is typically higher than 100 GHz, beyond the state-of-the-art experimental bandwidth of less than 10 GHz (refs. 6,12,13). Although the dynamics can be detected by means of a surface-acoustic-wave quantum dot14, this method does not allow for a time-resolved detection. Here we theoretically and experimentally demonstrate how we can observe the internal dynamics in a silicon single-electron source that comprises a dynamic quantum dot in an effective time-resolved fashion with picosecond resolution using a resonant level as a detector. The experimental observations and the simulations with realistic parameters show that a non-adiabatically excited electron wave packet15 spatially oscillates quantum coherently at ~250 GHz inside the source at 4.2 K. The developed technique may, in future, enable the detection of fast dynamics in cavities, the control of non-adiabatic excitations15 or a single-electron source that emits engineered wave packets16. With such achievements, high-fidelity initialization of flying qubits5, high-resolution and high-speed electromagnetic-field sensing8 and high-accuracy current sources17 may become possible.

中文翻译：

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硅单电子源中的皮秒相干电子运动。

对于亚微米设备在量子技术的非平衡驱动下的应用，需要超速相干电子动力学的高级理解，包括按需单电子源1，电子量子光学器件2-4，量子位控制5-7，量子感测8,9和量子计量10。尽管已经广泛研究了沿扩展通道的电子动力学[2-4,11]，但很难捕获亚微米器件内部的电子运动。内部相干动态的频率通常高于100 GHz，超出了低于10 GHz的最新实验带宽（参考文献6,12,13）。尽管可以通过表面声波量子点14来检测动力学，但是此方法不允许进行时间分辨检测。在这里，我们在理论上和实验上演示了如何在有效的时间分辨方式下以皮秒分辨率使用共振能级作为检测器，观察包含动态量子点的硅单电子源的内部动力学。实验观察和具有实际参数的模拟表明，非绝热激发的电子波包15在4.2 K的源内在〜250 GHz处空间上量子相干振荡。未来，这种发达的技术可能能够检测腔中的快速动力学。 ，控制非绝热激发15或发出工程波包16的单电子源。有了这样的成就，飞行量子比特的高保真初始化5，