Biomagnetic Sensing with Nitrogen-Vacancy Centers in Diamonds

The Nitrogen vacancy (NV) center is a novel solid-state sensor for detecting magnetic fields with high sensitivity and high spatial resolution at room temperature. Such a magnetometer has potential applications in a variety of fields, including biomedicine, neuroscience, and nanoscale magnetic resonance microscopy. In this thesis, we demonstrate advances in biomagnetic sensing using an NV magnetometer with sensitivity of 50 pT√Hz in the low frequency range. Our experiments show the first magnetic measurements of optogenetically activated action potential in mammalian muscle tissue. We show that these measurements can be performed in an unshielded laboratory and that the biological signal can be easily recovered by digital signal processing techniques. In addition, we present the development of a miniaturized diamond NV magnetometer with nanotesla sensitivity, suitable for detecting a variety of low-level magnetic fields. Finally, we show the steps towards spatially resolving biomagnetic fields in a proof-of-principle experiment using a camera with an integrated lock-in amplifier.