Nanophysics and nanotechnology applied to sensors Part 2: Part 26 in a series of tutorials on instrumentation and measurement

In this paper, the author discusses quantum sensor devices of magnetic flux; properties of superfluids; the magnetic flux quantum; the superconducting quantum interference detector (SQUID); the scanning tunneling microscope (STM); cuprate superconductors; the working principles of magnetic resonance imaging (MRI); compare MRI with SQUID and STM; and explain how tunneling spectroscopy works in superconductors. A SQUID application is presented that has the potential to lower the cost of MRI. The scanning tunneling microscope (STM) affords the highest spatial resolution of any scanning sensor combined with a powerful spectroscopic capability, and its utility is illustrated in this tutorial with examples from the study of high temperature cuprate superconductors.