Superconducting Quantum Interference Device

This lecture covers the operation of a DC SQUID, a Superconducting Quantum Interference Device, which consists of a superconducting ring with two Josephson junctions. The critical current determines the voltage across the loop, quantized in units of the flux quantum. The lecture explains how a bias current affects the critical current and the voltage drop across the junction. It also discusses the sensitivity of the critical current to the magnetic flux through the superconducting loop, enabling precise measurements of small variations in the magnetic field. The lecture emphasizes the importance of maintaining the superconducting current in the loop to compensate for externally applied magnetic fields, highlighting the device's extraordinary resolution and measuring range.