How scientists discover a strange way to control atoms despite what should happen

A weaker kind of magnetism

Magnetism in an atom is most strongly associated with electrons. Some atomic nuclei also carry spin, but this magnetism is much weaker and more shielded from the outside world.

Lead researcher Sander Otte said the contrast makes nuclear spin difficult to influence. He described the nuclear magnetism as both weaker and better protected than electron magnetism.

Signals reach the nucleus

Otte’s team studied magnetism at the atomic scale with a modified scanning tunneling microscope that can direct electrical signals at individual atoms. Earlier experiments mainly examined electron spin, which is easier to detect and manipulate.

Researchers had observed nuclear spin indirectly through the hyperfine interaction, a quantum coupling between an electron’s and nucleus’s magnetic properties. Otte said the team’s result ran against their simple understanding: nuclear spin was not expected to respond to the microscope’s electrical signals.

Adapting magnetic resonance

The team adapted double magnetic resonance, an established technique, for use with a single atom. It let researchers address the electron and nucleus independently with signals tuned to their respective magnetic resonances.

Spin can shift between specific allowed states in quantum mechanics, with each transition requiring a signal at the appropriate frequency. The adapted method gave the researchers a way to control an individual nuclear spin.

Possible quantum information uses

The researchers said practical applications remain a future possibility. Otte described the unexpected result as a reminder that science often requires revisiting assumptions and continuing to investigate.