Physicists control the magnetic nucleus of a single atom with radio waves

Researchers at Delft University of Technology in the Netherlands have succeeded in controlling the magnetism in the nucleus of a single atom using radio waves. The result came as a surprise, because until now physicists believed that this nuclear spin could not be manipulated directly. The work, led from Otte’s laboratory and published in Nature Communications, could open up new possibilities for storing and reading quantum information.

In metals such as iron and nickel, every atom is slightly magnetic. But inside the atom, different magnetic compass needles, known in quantum mechanics as spins, are also at work. By far the strongest magnetism comes from the electrons, explains lead researcher Sander Otte. In some atoms, however, the nucleus also carries a spin. That spin is much weaker than the electron’s, but it is also much better shielded from the outside world, a property that makes it attractive for delicate quantum applications.

Otte’s group studies spins using a converted scanning tunnelling microscope, an instrument that enables electrical signals to be directed with extreme precision at a single atom. In past experiments the researchers mainly focused on the electron spin, which is the easiest to read out. The nuclear spin appeared only indirectly, through the so-called hyperfine interaction, a coupling that causes the spins of the nucleus and the electron to become slightly entangled with one another.

In their latest experiment, main author Hester Vennema and her colleagues sent two different signals to an atom simultaneously: one targeting the electron and one targeting the nucleus. Sending both signals at once allowed them to study the influence of each signal independently. To their surprise, they found that they could flip the nuclear spin even when the two spins were largely disentangled, meaning the effect did not depend on the indirect hyperfine route that had previously been the only known window onto the nucleus.

That result came unexpectedly. According to our simple understanding, this should not really happen, says Otte. The nuclear spin should not be sensitive at all to the electrical signals from a scanning tunnelling microscope. The observation therefore challenges the standard picture of how a local probe interacts with the innermost magnetic degree of freedom of an atom, and the team says the research mainly raises new questions about the mechanism driving the nuclear spin.

For this research, the team refined an established measurement technique known as double magnetic resonance for use on a single atom. This enabled them to address the magnetism of the atomic nucleus and that of an orbiting electron independently, rather than observing the nucleus only through its influence on the electron.

The principle behind the control is magnetic resonance, in which the orientation of a spin is altered using a wave signal. According to quantum mechanics, only a limited number of such rotations are possible, and as a result the signal must have exactly the right frequency. Vennema compares it to the strings of a guitar: each possible spin rotation is like a string with its own note, and you have to play precisely the right note to make a particular string vibrate. The notes of a nuclear spin are a hundred to a thousand times lower than those of an electron spin, which is one reason the nucleus has been so difficult to address directly.

The nuclear spin of atoms is of particular interest for applications in which quantum information needs to be stored securely. Because the nucleus is so well shielded from its environment, the ability to control nuclear spins could provide new opportunities for storing and reading out quantum information. The researchers emphasise that this remains a prospect rather than an achieved technology: for now, the work is a laboratory demonstration on a single atom, and its practical use in quantum devices has not been shown.

For the team itself, the immediate consequence of the finding is theoretical rather than technological. Back to the drawing board, then, says Otte. That is really how science works. There is always something new left to figure out. The observation that a nuclear spin responds to local electrical signals when theory said it should not leaves the researchers with a mechanism to identify, and the study is published in Nature Communications under the title Nuclear magnetic resonance on a single atom with a local probe, with an article publication date of 24 October 2026 and the DOI 10.1038/s41467-026-78801-5.

Subject of Research: Direct radio-wave control of the nuclear spin of a single atom using a scanning tunnelling microscope.

Article Title: Against all expectations, Delft researchers control the magnetic core of a single atom

Article References: Against all expectations, Delft researchers control the magnetic core of a single atom. Original publication (Bibliographic details unavailable.)

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Keywords: nuclear spin, single atom, scanning tunnelling microscope, magnetic resonance, quantum information, Delft University of Technology, hyperfine interaction, electron spin, Nature Communications, radio waves, Against, expectations