Researchers at Delft University of Technology report controlling the magnetism within the nucleus of a single atom using radio waves, a feat previously considered impossible by physicists. The team, led by Hester Vennema, achieved this by simultaneously targeting both the atom’s electron and nucleus with distinct radio signals using a converted scanning tunneling microscope. “According to our simple understanding, this should not really happen,” says lead researcher Sander Otte, describing the unexpected result. This ability to manipulate the well-shielded nuclear spin could offer new avenues for secure quantum information storage and retrieval.

Double Magnetic Resonance Isolates Nuclear and Electron Spins

Two simultaneous radio wave signals enabled researchers to independently control the spin of an atom’s nucleus and its orbiting electron, a feat previously considered impossible given the nucleus’s shielding. Hester Vennema, the main author of the study published in Nature Communications, led the experiment using a converted scanning tunneling microscope to achieve this level of control over the atom’s magnetic properties.

The team refined a technique called double magnetic resonance, adapting it for single-atom manipulation to address the magnetism of both the nucleus and electron independently. This precision allowed them to observe an unexpected interaction, flipping the nuclear spin even when largely disentangled from the electron.

The nucleus’s spin, while significantly weaker than that of the electron, presents a unique advantage in quantum information storage due to its enhanced protection from external interference. “By far the strongest magnetism comes from the electrons,” explained lead researcher Sander Otte, highlighting the conventional focus on electron spin manipulation. “But in some atoms, the nucleus also carries a spin.

That spin is much weaker, but it is also much better shielded from the outside world.” This shielding traditionally made direct manipulation of the nuclear spin seem improbable, as the nucleus was thought to be largely immune to the electrical signals from the scanning tunneling microscope. The team’s success challenges this understanding, prompting a re-evaluation of the underlying mechanisms.

The experimental setup relies on precise frequency targeting, similar to playing specific notes on a guitar to induce vibrations in strings. “You can compare it to the strings of a guitar,” Vennema explained. “Each possible spin rotation is like a string with its own note.

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. The researchers discovered they could independently manipulate these “notes”, flipping the nuclear spin with a targeted radio wave despite the frequency difference and the expected lack of interaction.

The team acknowledges that further investigation into the underlying physics is now necessary. “Back to the drawing board, then,” Otte conceded. “That is really how science works. There is always something new left to figure out.” The unexpected success of manipulating the nuclear spin opens new avenues for research and raises fundamental questions about the interaction between atomic nuclei and external electromagnetic fields.