ABSTRACT Neuronal cells communicate through tiny electrical pulses called action potentials. Measuring these signals is key to understanding brain function and diagnosing diseases like Parkinson's and Alzheimer's. Yet, non‐invasive detection at large scale with single‐cell resolution remains a major challenge. We propose a method based on nitrogen‐vacancy centers in diamond, a leading quantum sensing platform capable of detecting extremely small magnetic fields from electrical activity. Our approach uses bias‐field‐free, single‐frequency continuous‐wave optically detected magnetic resonance (CW‐ODMR). Unlike conventional methods, it requires no external magnetic field—avoiding interference with neuronal behavior and simplifying experiments. By probing at a single microwave frequency, we also significantly reduce acquisition time while achieving sensitivity for electric pulses as short as 0.2 ms. We validate the technique using 2 ms electrical pulses in a biomimetic gold wire (25–2.5 mA), observing clear CW‐ODMR responses that correlate with the input signals. Our results demonstrate a fast and minimally invasive approach for detecting transient electrical activity, through the induced magnetic field, achieving microtesla sensitivity to millisecond signals. However, the current magnetic field sensitivity remains above the nanotesla regime required for direct neuronal detection. While inspired by biological systems, the presented technique is immediately applicable to material and device characterization, as well as information and communication technologies, where the detection of leakage currents and short electrical transients—relevant to emerging neuromorphic architectures—represents a compelling application domain.
Silva et al. (2026) studied this question.