Magnetic tunnel junctions as quantum property sensors*

Sensors based on magnetic tunnel junctions (MTJs), ultra sensitive, low noise devices in which tunneling occurs through a thin insulating layer between spin polarized ferromagnetic electrodes, could effectively be used to quantify magnetic fields to picoTesla sensitivity and with spatial resolution on a relevant mesoscopic length scale. MTJ sensors have recently been pushed to increase their range of operating temperatures and broaden their frequency response, possibly into the GHz range. Measurement techniques used to detect thermal and shot noise of the MTJs must evolve alongside to match the operating ranges of these devices. In this talk, we will discuss ways in which we have made measuring these versatile, low noise devices possible.