# Picosecond coherent electron motion in a silicon single-electron source

## TL;DR

This paper demonstrates both theoretically and experimentally that ultrafast, coherent electron dynamics inside a silicon single-electron source can be detected, revealing quantum oscillations at approximately 200 GHz, which is crucial for quantum technologies.

## Contribution

The study introduces a method to observe internal electron dynamics within a single-electron source using a resonant level, enabling detection of GHz-scale quantum oscillations.

## Key findings

- Electron wave packets oscillate coherently at ~200 GHz inside the source.
- The method combines experimental measurements with realistic simulations.
- Potential applications include high-precision current sources and quantum sensing.

## Abstract

Understanding ultrafast coherent electron dynamics is necessary for application of a single-electron source to metrological standards, quantum information processing, including electron quantum optics, and quantum sensing. While the dynamics of an electron emitted from the source has been extensively studied, there is as yet no study of the dynamics inside the source. This is because the speed of the internal dynamics is typically higher than 100 GHz, beyond state-of-the-art experimental bandwidth. Here, we theoretically and experimentally demonstrate that the internal dynamics in a silicon singleelectron source comprising a dynamic quantum dot can be detected, utilising a resonant level with which the dynamics is read out as gate-dependent current oscillations. Our experimental observation and simulation with realistic parameters show that an electron wave packet spatially oscillates quantum-coherently at $\sim$ 200 GHz inside the source. Our results will lead to a protocol for detecting such fast dynamics in a cavity and offer a means of engineering electron wave packets. This could allow high-accuracy current sources, high-resolution and high-speed electromagnetic-field sensing, and high-fidelity initialisation of flying qubits.