Researchers in the Netherlands have demonstrated that radio waves can control the nuclear spin of a single atom even when it is largely disentangled from the spin of its electrons, challenging existing expectations about how atomic nuclei respond to electrical signals.The experiment, conducted at Delft University of Technology, revealed an unexpected way to manipulate the weak magnetism inside an atomic nucleus. The researchers say the finding could eventually support new approaches to storing and retrieving quantum information.Using a modified scanning tunneling microscope, the team directed precisely controlled electrical signals at an individual atom. They found that a signal targeting the nucleus could flip its spin without relying on the strong coupling between nuclear and electron spins previously thought necessary for this type of manipulation.The result surprised the researchers because nuclear spins are generally much less responsive to external electrical signals than electron spins. Their relative isolation makes them attractive for quantum information storage, but also presents challenges when scientists attempt to control them.Separating two magnetic signalsAtoms contain several sources of magnetism, including the spins of their electrons and, in some cases, their nuclei.Electron spins produce much stronger magnetic effects and are comparatively easy to manipulate. Nuclear spins are weaker and better shielded from their surroundings, making them harder to access directly.Previous experiments at Delft primarily focused on controlling electron spins and observing their influence on nuclear spins through an interaction known as hyperfine coupling.This interaction links the magnetic behavior of electrons and nuclei, allowing changes in one spin to influence the other.In the latest experiment, researchers led by Hester Vennema refined a technique called double magnetic resonance to investigate the two spins separately.They applied two signals simultaneously, with one targeting the electron spin and the other targeting the nuclear spin.By independently adjusting the signals, the team could examine how each component responded.The researchers discovered that the nuclear spin could be flipped even when the electron and nuclear spins were largely disentangled.“According to our simple understanding, this should not really happen,” said Sander Otte, who leads the research group.“The nuclear spin should not be sensitive at all to the electrical signals from a scanning tunnelling microscope.”The finding suggests that the mechanism responsible for the observed nuclear-spin transitions is not fully explained by the researchers’ existing model.Tuning individual quantum statesThe experiment relied on magnetic resonance, a technique that uses signals at specific frequencies to change the orientation of magnetic spins.Because quantum spins can occupy only certain states, researchers must apply a signal at the appropriate frequency to induce a transition.Vennema compared the process to playing a guitar string, where each string responds to a particular note.The researchers noted that the frequencies associated with nuclear-spin transitions are typically 100 to 1,000 times lower than those associated with electron spins.By refining double magnetic resonance for a single atom, the team demonstrated a way to address these different magnetic components independently.The ability to manipulate nuclear spins is particularly relevant to quantum information research.Because nuclear spins are relatively isolated from environmental disturbances, they are promising candidates for storing quantum states. However, reliable control and readout remain essential requirements for practical applications.The new experiment demonstrates an additional control mechanism, but it does not establish a working quantum memory or explain precisely how the nuclear spin responds to the applied signal.Further research will be needed to identify the underlying physical mechanism and determine whether the technique can be used reliably in quantum devices.The findings were published in Nature Communications.