A review of advances in magnetocardiography with second generation quantum sensors

Abstract Magnetocardiography (MCG) offers a non-invasive, contactless, and radiation-free method for detecting the heart’s electrophysiological activity with high spatial and temporal resolution. Despite its diagnostic potential, clinical adoption has been limited by the technological and economic constraints of current sensing platforms. Superconducting quantum interference devices (SQUIDs) remain the gold standard for sensitivity but require cryogenic cooling and costly magnetic shielding, while optically pumped magnetometers (OPMs) provide room-temperature operation but face challenges such as dead zones, thermal management, and limited miniaturization. Recently, nitrogen-vacancy (NV) centers in diamond have emerged as a promising alternative. NV-based magnetometers combine solid-state robustness, miniaturization potential, and scalability, enabling prospects for portable and high-density sensor arrays. Current prototypes, however, remain two orders of magnitude less sensitive than clinical requirements. This paper reviews the state of SQUID, OPM, and NV technologies for MCG and highlights the technical advantages and limitations of each. Strategies for improving NV sensitivity are discussed as pathways toward bridging the sensitivity gap. While NV-based sensors are not yet clinically viable, their combination of robustness, scalability, and cost-reduction potential positions them as a compelling candidate for next-generation MCG systems, with the prospect of expanding cardiac diagnostics.