Quantum noise tamed in the tunnel effect

When disruptions become useful

What is usually considered a disturbance can be surprisingly useful under certain conditions: noise. Researchers at the University of Duisburg-Essen have shown how the random noise caused by the quantum mechanical tunnel effect - a phenomenon that is also the focus of this year's Nobel Prize in Physics - can be specifically influenced. The results, which have now been published in Communications Physics, open up new perspectives for future quantum devices.

Hi-fi enthusiasts hate it, electronics engineers find it difficult to work with: noise - unwanted, random interference from the environment that overlays and distorts the actual signal. However, noise can also be useful and amplify various processes. The mechanism behind this is "stochastic resonance". In this phenomenon, small random fluctuations amplify a weak signal so that it can be perceived more clearly and regularly.

In a collaboration of experiment and theory, the research groups led by Materials Chain members Prof. Dr. Axel Lorke and Prof. Dr. Jürgen König at the University of Duisburg-Essen (UDE) have now succeeded in observing stochastic resonance in a quantum phenomenon. Using high-resolution laser spectroscopy, the research groups have tracked the movement of a single electron, which can either be located in a tiny nanostructure (a "quantum dot") or outside in an electron reservoir. There is a barrier between the reservoir and the quantum dot, which the electron can penetrate due to the quantum mechanical tunnel effect. "If you throw a ball against a barrier, it will bounce back. In the quantum world, however, an electron can penetrate the barrier with a certain probability and reach the other side. This is possible because particles also behave like waves. This is the tunnel effect," explains Lorke.

The tunneling process, research into which was awarded this year's Nobel Prize, is completely random and therefore represents a source of noise for the movement of electrons. By applying a small alternating voltage, however, this random movement could be tamed so that the electron oscillated back and forth between the quantum dot and the electron reservoir in a much more regular manner.

To demonstrate this, millions of tunnel processes were analyzed over time using highly developed statistical methods. Surprisingly, the best suppression of the random motion did not occur at the frequency that would have been expected according to the usual explanations of stochastic resonance. Depending on the strength of the alternating voltage, it was sometimes even significantly lower. A phenomenon that is not yet fully understood and opens the door to further investigations.

The work of the Duisburg physicists is relevant for visionary quantum devices, for example for tap-proof communication channels in which the individual bits are to be sent as regularly as possible.

To the publication:

Mannel, H., Zöllner, J., Kleinherbers, E. et al. Quantum stochastic resonance in a single-photon emitter. Commun Phys 8, 404 (2025). doi: 10.1038/s42005-025-02334-4

https://www.uni-due.de/cenide/en/news-detail.php?id=quantum-noise-tamed-in-the-tunnel-effect