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Researchers at Delft University of Technology report that they used radio-frequency signals to flip the nuclear spin of a single atom, even when its spin was largely disentangled from the atom’s electron spin. The Nature Communications study could inform ways to store and read quantum information, but the mechanism behind the response remains unexplained.
Researchers at Delft University of Technology say they used radio-frequency signals to control and flip the nuclear spin of a single atom, a result that was not expected under their previous understanding of how the spin responds to electrical signals. The finding, reported in Nature Communications, may help inform future approaches to storing and reading quantum information, although the mechanism behind the effect is still unresolved.
The team used a converted scanning tunnelling microscope to direct electrical signals with high precision at an individual atom. In the latest experiment, researchers sent two signals at the same time: one aimed at the atom’s electron spin and another aimed at its nuclear spin. The setup let them examine the influence of the two signals separately, using a refined form of double magnetic resonance.
The researchers found they could flip the nuclear spin even when it was largely disentangled from the electron spin. Previously, the group had mainly studied the electron spin, which is easier to read out. The nuclear spin had been observed indirectly through the hyperfine interaction, a coupling that can slightly entangle the two spins.
In magnetic resonance, a spin changes orientation in response to a signal at an appropriate frequency. The researchers said nuclear-spin frequencies are roughly 100 to 1,000 times lower than those of electron spins. The experiment’s ability to address each spin independently allowed the team to probe those distinct responses in a single atom.
A Possible Route to Quantum Memory
Nuclear spins attract interest for quantum information because they are more shielded from the outside world than electron spins, according to the researchers. That shielding may make them useful for retaining information, while the ability to manipulate a spin could help with writing or reading it. The Delft result is relevant because it suggests a possible way to control a nuclear spin at the scale of one atom.
The work does not establish a working quantum memory or show that the method can store information reliably over a particular period. Its immediate importance is more basic: the team reports control in a situation where its earlier understanding predicted little or no response. Explaining that response will be necessary before the finding can be assessed as a practical method for quantum technologies.
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From Electron Signals to Nuclear Spins
The Delft group studies atomic spins with a modified scanning tunnelling microscope, which can deliver electrical signals to a selected atom. Earlier work described in the source material focused largely on electron spins, whose magnetic effects are stronger and easier to measure. The nucleus carries a weaker magnetic spin, but its relative shielding is one reason researchers are interested in it for quantum information.
The study builds on double magnetic resonance, a technique refined here for use on a single atom. By applying separate signals to the electron and nucleus at once, the team could test their effects individually rather than relying only on the indirect influence of their coupling. The results were published in Nature Communications; the available report does not provide enough detail to characterize the work beyond the stated experimental findings.
“According to our simple understanding, this should not really happen.”
— Sander Otte, lead researcher
The Spin-Flip Mechanism Remains Unknown
The researchers have not yet explained how the nuclear spin responds to the signals in the reported conditions. Otte said the result conflicts with the team’s simple understanding: the nuclear spin was not expected to be sensitive to electrical signals from the microscope, particularly when the two spins were largely disentangled.
The source material does not specify how consistently the spin could be flipped, how long its state could be maintained, or whether the method has been tested in other atoms or experimental settings. It also provides no demonstration of quantum information being stored or read out using this technique. Those points should not be inferred from the reported control of the spin.
Explaining the Unexpected Response
The immediate next step is for the researchers to investigate the physical mechanism behind the spin flip. The source material gives no timetable for follow-up experiments or a specific next publication. Further work will need to establish how the signal acts on the nuclear spin and whether the effect can be controlled and measured reliably.
For now, the study is an experimental result that raises a question as much as it answers one. Any future use in quantum information storage or readout depends on clarifying the effect and demonstrating performance beyond the single-atom control reported here.
Key Questions
What did the Delft researchers control?
They report flipping the nuclear spin of a single atom using radio-frequency signals, while also addressing the atom’s electron spin separately.
Why was the result unexpected?
The team’s simple understanding suggested that the nuclear spin should not respond to electrical signals from the scanning tunnelling microscope. Yet the researchers observed a flip even when the nuclear and electron spins were largely disentangled.
Does this mean quantum information can now be stored in an atom’s nucleus?
No such demonstration is reported. The finding may inform future methods for storing or reading quantum information, but the study described here reports spin control, not a functioning quantum memory.
What is still unknown?
The mechanism behind the nuclear-spin response remains unresolved. The available report also does not give results on reliability, state-retention time, or performance in other atoms.
Source: thequantuminsider.com
