A superconducting quantum interference device (SQUID) is a highly sensitive magnetometer used to measure extremely weak magnetic fields. It operates based on the principles of quantum mechanics and superconductivity, utilizing Josephson junctions to detect changes in magnetic flux. SQUIDs can achieve sensitivity levels that are orders of magnitude greater than traditional magnetometers. These devices are widely used in various fields, including medical imaging through magnetoencephalography (MEG), geophysics for mineral exploration, and fundamental physics research. Their ability to measure tiny magnetic fields makes them valuable tools for studying phenomena such as brain activity and particle physics.