Scientists watched the nuclear spin of a single titanium atom switch in real time. They saw its state changes as a step-like jump in current and found that this tiny magnet can stay stable for around five seconds.

The team also read the state faster than it changed, which is known as single-shot readout. That kind of speed is crucial if you want to control a quantum system instead of averaging over it.

Why stability matters

The work comes from Delft University of Technology in the Netherlands (DUT). Evert W. Stolte is co-first author of the paper.

Nuclear spins tend to keep their state longer than electron spins, which makes them appealing for information storage in quantum devices.

A seconds-long lifetime in a single atom on a surface gives engineers time to set, read, and reset a state without hurrying or losing track.

Electron spins in similar systems typically relax in roughly 100 nanoseconds, so this result opens a much wider timing window for experiments.

Longer lifetimes reduce errors and make feedback and calibration loops far more practical.

The group also reports high-fidelity state identification in single shots. That kind of reliability keeps experiments from getting swamped by noise and false positives.

What the team measured

The atom they studied was a titanium atom placed on a thin layer of magnesium oxide sitting on silver, kept at very cold temperatures.

Its nucleus can take on several different magnetic states, and the researchers focused on detecting just one of them.

When the nucleus occupied that target state, the tunneling current jumped to a higher level. When it occupied any other state, the current returned to a lower level.

The researchers then used a pulse-and-wait routine to find the intrinsic lifetime of the nuclear state. The result was 5.3 plus or minus 0.5 seconds, and it did not require continuous driving during the waiting time.

“We were able to show that this switching corresponds to the nuclear spin flipping from one quantum state to another, and back again,” said Stolte. That direct confirmation anchors the interpretation of the two-level signal.

How nuclear spin was detected

A scanning tunneling microscope (STM) approaches a conductive tip to within a few angstroms of the surface and measures current as electrons tunnel between tip and sample. The current depends on atomic-scale details and can be used as a very sensitive probe.

STM cannot feel a nucleus directly. The team leveraged the hyperfine interaction that links electron and nuclear spins, which shifts the electron’s energy depending on the nuclear state, as shown in prior hyperfine measurements on single atoms.

They drove the electron with electron spin resonance (ESR) at a fixed frequency, chosen so that the electron responded only when the nucleus sat in one particular state.

The ESR response raised the tunneling current, so a live current trace turned into a live nuclear-state readout.

Because the readout was faster than the nuclear flipping, the team achieved true single-shot readout with reported fidelities up to 98 percent.

The pulsed protocol also showed that continuous driving speeds up relaxation, so the intrinsic lifetime had to be measured with the drive off between probes.

How it compares to past work

In 2015, scientists first managed to use STM together with ESR to study a single atom of iron placed on magnesium oxide.

This was a turning point, because it allowed them to measure the energy of single spins with enough precision to tell them apart clearly.

On-surface access to the nucleus followed when teams resolved hyperfine shifts for individual atoms. That work proved that nuclear degrees of freedom were not out of reach on surfaces.

Last year, the same community tracked electron, nucleus, and their mutual coupling evolving together in a single atom, mapping coherent dynamics in time.

The present study advances this line by timing how long an on-surface nuclear state persists without constant driving.

Other platforms have reported single-shot nuclear readout under different conditions and materials.

For instance, silicon carbide defects reached millisecond-scale single-shot performance with high fidelity in a report, showing the broader relevance of nuclear spins across solid-state systems.

Seconds matter for quantum sensing

Seconds-long stability means a sensor made from a single nuclear spin can integrate weak signals without losing its state mid-measurement.

That makes detecting tiny magnetic fields or tracking slow dynamics more realistic at the atomic scale.

More time also gives experimenters room to run sequences that prepare, control, and verify the state. That reduces the need for complicated error-correction schemes at this early stage of atomic-scale device building.

Long-lived nuclei can serve as memory while a faster electron acts as the actuator. Separating roles like that can simplify architectures for atomic assemblies and enable more complex experiments on surfaces.

“The first step in any new experimental frontier is being able to measure it, and that is what we were able to do for nuclear spins at the atomic scale,” said Stolte.

Clear measurement opens the door to control, coupling, and eventually small arrays.

Next steps for nuclear spin research

The STM tip does more than measure. Its position and magnetization tune local fields and couplings, so future work can likely lengthen lifetimes further by careful placement and field control.

Driving conditions can be optimized to reduce unwanted relaxation paths. The pulsed method already shows which parts of the protocol disturb the nucleus and which do not, which helps set safe operating points.

Building pairs or chains of nuclei on surfaces is now a credible target.

With single-shot readout and seconds-long lifetimes, these atoms become candidates for testbed qubits and nanoscale sensors that can be arranged with atomic precision.

The study is published in Nature Communications.

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