Quantum technologies promise transformative advances in computing, sensing, and secure information processing. Yet one stubborn bottleneck remains: steering the quantum state of a single qubit at atomic scales. Traditional control relies on magnetic fields, but precisely confining those fields to an individual molecule is exceptionally difficult—especially when neighboring spins must remain unaffected.
Now, an international team led by the Center for Quantum Nanoscience (QNS) at the Institute for Basic Science (IBS) has demonstrated electrical control of an individual magnetic molecule. Collaborators at Karlsruhe Institute of Technology (KIT) used electron spin resonance in combination with scanning tunnelling microscopy (ESR-STM) to probe how a voltage applied at the nanoscale can reshape a molecule’s spin behavior.
The researchers focused on iron phthalocyanine (FePc) and closely related spin-carrying complexes on a surface. By sweeping the voltage with fine precision, they observed that the spin response was not weak and linear—as earlier electric-field approaches often were—but instead became strongly nonlinear near specific molecular electronic energy levels.
At the heart of the effect is an exchange-mediated interaction between the molecular spin and the magnetic STM tip. As the voltage tunes the system toward an electronic resonance, this exchange coupling boosts the effective spin splitting, producing resonance-frequency shifts approaching 30%. That magnitude is roughly an order of magnitude larger than most prior electrically induced tuning effects in molecular spin systems.
Crucially, the data also supports a theoretical framework advanced at QNS: voltage-controlled exchange interactions can generate a highly localized effective magnetic field without physically deforming the molecule. Because the interaction is mediated through a nearby electrode, the control region stays confined to the target spin.
Beyond shifting energy levels, the team performed coherent control. Using Rabi-oscillation measurements, they showed that individual molecular spins can be selectively driven by electrical voltages rather than by changing external magnetic fields. They further tuned coupled spins without significantly disturbing a neighboring molecule, a key requirement for scalable quantum architectures.
Unlike strategies that depend on manipulating the molecule’s geometry, this exchange-driven method offers a practical route toward nanoscale quantum circuitry. Electrical signals are naturally easier to route and integrate than localized magnetic fields, opening a path for dense device layouts.
The work appears in Nature Physics, providing a new mechanism for spin–electric control at the single-molecule level and strengthening the roadmap toward atom- and molecule-based quantum computing, quantum sensing, and quantum information processing.
Subject of Research: Not applicable
Article Title: Exchange-mediated spin–electric control of single molecules on surfaces
News Publication Date: 29-Jul-2026
Web References: http://dx.doi.org/10.1038/s41567-026-03353-w
References: https://doi.org/10.1038/s41567-026-03353-w
Image Credits: Institute for Basic Science
Keywords: qubits, quantum computing, quantum information processing, quantum information science, spin manipulation, scanning tunneling microscopy, exchange-mediated control, single-molecule quantum control
