NPL scientists control collision of electrons to help develop quantum components

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Scientists at the National Physical Laboratory (NPL) have performed a controlled collision of single electrons in a semiconductor chip.

In the process they have revealed the information needed to create single-electron devices for quantum sensing and information processing.

The experiment, described in the journal Nature Nanotechnology, examines the interaction between pairs of flying electrons as they meet in a miniature semiconductor particle collider. Mapping the statistics of electronic collisions is an innovative approach to probing electronics interactions and the quantum properties of electrons in a given environment.

Here, this technique revealed a fleeting electrostatic ‘push’ between electrons large enough to change the electron path. This effect has not been seen in previous experiments, probably because electric field which surrounds each injected electrons is typically ‘neutralised’ by the rearrangement of charges nearby. The Coulomb repulsion was activated here by injecting electrons into unscreened regions far from other conduction electrons.

Commenting Jonathan Fletcher, Senior Scientist at NPL and the lead author said, “The interaction happens on very short time scales, a few picoseconds, so the timing requirements are challenging for this experiment. It was exciting to see such an elementary effect, from both a physics and device engineering perspective.”

While working with theorists on a model, the team realised that more subtle details present in the data can be explained by considering the microscopic behaviour of electron pairs when they are in a strong magnetic field.

Masaya Kataoka, Principal Scientist at NPL who supervised the research, said, “The collision is not so easy to understand when the electron arrival time is slightly mismatched; the electrons repel but still follow similar trajectories. These effects are actually present in our model, which gives us some confidence that we understand these effects.”

Harnessing Coulomb interactions between electrons will be a powerful way to control devices at high speeds and to create the non-linear effects required for quantum circuit elements based on electron quantum optics, a possible platform for quantum sensing or information processing.