Controlling Nuclear Spin Without Radio Waves express
A quantum computer is like an orchestra where electrons and nuclei play different instruments. Usually, the conductor needs two batons: microwaves for electrons and radio waves for nuclei. Scientists from Japan found a way to get by with just one baton: they made microwave pulses control both the nucleus and the electron simultaneously.
In a silicon carbide crystal, they created a defect — a spot where atoms are arranged differently than in the rest of the crystal. Such a defect acts as a trap for an electron, and next to it sits a silicon nucleus. The electron spin (its intrinsic rotation, like a spinning top) usually responds to microwaves, while the nuclear spin responds only to radio waves. But if you tilt the external magnetic field at a precise angle, the coupling between them sharply increases. Now, when a microwave pulse flips the electron spin, it also nudges the nucleus.
This trick saves energy and simplifies the quantum device's architecture. No more separate wires for radio signals or bulky amplifiers. Quantum memory based on nuclear spins lasts almost as long as the material itself allows — the time it takes for the nuclear spin to lose its orientation approaches the theoretical limit. This matters for quantum sensors that already measure magnetic fields in living cells or search for minerals underground. Instead of complex equipment, just one microwave source and a precisely tilted magnet.
Original abstract
as written by the authors arXiv:2601.21499
Color centers that enable nuclear-spin control without RF fields offer a powerful route towards simplified and scalable quantum devices. Such capabilities are especially valuable for quantum sensing and computing platforms that already find applications in biology, materials science, and geophysics. A key challenge is the coherent manipulation of nearby nuclear spins, which serve as quantum memories and auxiliary qubits but conventionally require additional high-power RF fields which increase the experimental complexity and overall power consumption. Finding systems where both electron and nuclear spins can be controlled using a single MW source is therefore highly desirable. Here, using a modified divacancy center in silicon carbide, we show that coherent control of a coupled nuclear spin is possible without any RF fields. Instead, MW pulses driving the electron spin also manipulate the nuclear spin through hyperfineenhanced effects, activated by a precisely tilted external magnetic field. We demonstrate high-fidelity nuclear-spin control, achieving 89% two-qubit tomography fidelity and nearly T1-limited nuclear coherence times. This approach offers a simplified and scalable route for future quantum applications.
Nuclear spin can store quantum information thousands of times longer than electron spin, because the nucleus is less affected by environmental noise.
In the series 'Devs,' a quantum computer is controlled by microwaves, but to work with nuclei, the characters would have had to add radio transmitters — here, that problem is solved.