Human cardiac measurements with diamond magnetometers.

The heart produces small magnetic signals, but detecting them without touching the body and without heavy shielding equipment remains a major challenge. In this study, we demonstrate a noninvasive method to measure these signals using compact quantum sensors made from diamond. These sensors operate at room temperature and can detect extremely weak magnetic fields produced by the heart, even outside highly shielded environments. By averaging signals over many heartbeats and using noise suppression techniques, we successfully recorded clear magnetocardiography traces. Although current measurements require averaging, our results show a clear path toward real-time detection. We also explored a gradiometry protocol for unshielded noisy environments, paving the way for contactless cardiac detection in challenging clinical conditions. This work points toward a path for using quantum sensors in practical medical diagnostics of the heart and brain.