Superconducting Quantum Interference Device

A Superconducting Quantum Interference Device (SQUID) is a very sensitive device for detection of magnetic flux. At low temperatures (about 4K) the output of the DC SQUID circuit can be about 1 microvolt per flux quantum (fluxon ~ 2x10-15Weber) (if the effective resistance of the circuit is about 1 Ohm and the effective inductance is about 1 nanoHenry.

While it is used in various research applications, it is under consideration as a satellite-based intelligence sensor for such purposes as detecting deeply buried structures.