  Magnetic field sensors that exploit quantum effects have shown that they can
outperform classical sensors in terms of sensitivity enabling a range of novel
applications in future, such as a brain machine interface. Negatively charged
nitrogen-vacancy (NV) centers in diamond have emerged as a promising high
sensitivity platform for measuring magnetic fields at room temperature.
Transferring this technology from laboratory setups into products and
applications, the total size of the sensor, the overall power consumption, and
the costs need to be reduced and optimized. Here, we demonstrate a fiber-based
NV magnetometer featuring a complete integration of all functional components
without using any bulky laboratory equipment. This integrated prototype allows
portable measurement of magnetic fields with a sensitivity of 344 pT/ SqrtHz.
