Scientists Achieve 89% Coherent Nuclear Spin Control Without RF Fields

Why It Matters

Removing bulky RF hardware lowers power budgets and simplifies quantum system design, while the extended nuclear coherence enhances memory and sensing capabilities.

Key Takeaways

• RF‑free nuclear control uses microwave pulses only
• 89% tomography fidelity achieved at room temperature
• Nuclear T2* exceeds 100 µs, far surpassing electron T2
• Tilted magnetic field activates hyperfine‑enhanced spin coupling
• Silicon carbide platform compatible with CMOS manufacturing

Pulse Analysis

The reliance on radio‑frequency (RF) fields has long been a bottleneck for solid‑state quantum platforms, demanding high‑power amplifiers and complex wiring that hinder miniaturisation. By harnessing only microwave (MW) pulses to drive the electron spin of a PL6 divacancy in silicon carbide, researchers have sidestepped this limitation entirely. The method leverages a precisely tilted magnetic field to invoke hyper‑fine‑enhanced interactions, delivering nuclear‑spin manipulation with a single MW source. This simplification not only cuts power consumption but also reduces the footprint of control electronics, a critical step toward portable quantum devices.

The PL6 centre in 4H‑SiC proves especially suited for this RF‑free scheme. It exhibits a bright optical response—about 200 kcps photon count rate—and a 30 % spin‑readout contrast at ambient conditions. Coherence measurements reveal an electron spin T₁ of ~243 µs, T₂ of 25 µs, and a Ramsey dephasing time T₂* of 2.7 µs, while the coupled nuclear spin reaches T₂* beyond 100 µs and a Hahn‑echo T₂ of 151 µs, more than six times the electron’s T₂. Hyperfine couplings of A_z ≈ 6.7 MHz and A_⊥ ≈ 5.5 MHz, together with a mere 2° magnetic tilt, create a “sweet spot” that maximises nuclear‑spin contrast without sacrificing oscillation speed.

From an industry perspective, the breakthrough aligns perfectly with the push for CMOS‑compatible quantum hardware. Silicon carbide can be processed using standard wafer‑scale fabrication, enabling integration of millions of colour‑centre qubits on a single chip. The extended nuclear coherence times promise longer quantum‑memory lifetimes and heightened magnetic‑field sensitivity for sensing applications in biology, materials science, and geophysics. Future work will likely focus on coupling multiple nuclear spins and improving defect uniformity, paving the way for robust, room‑temperature quantum processors and sensors that can be manufactured at scale.