Ultrasensitive Magnetometry

We have realized a magnetometer based on a levitated ferromagnet in a superconducting trap, capable of overcoming the so called Energy Resolution Limit, a recently proposed benchmark for magnetometry which turns out to coincide with the standard quantum limit for most classes of magnetometers. Our magnetometer works in classical regime but can outperform most quantum limited sensors. In fact, the quantum limit of a mechanically-detected ferromagnetic sensor is orders of magnitude lower. Interestingly, our sensor can be seen as a modern version of the first magnetometer of history developed by Carl Friedrich Gauss in 1833. Therefore, we have indirectly shown that Gauss magnetometer is still, in some sense, the best on the market. Our paper has been published in Physical Review Letters.