Josephson Junctions

A Josephson junction is a tiny device made of two superconductors separated by a very thin insulating barrier. When cooled below a certain temperature, electrons in the superconductors move without resistance. The junction allows a supercurrent—an electric current with no energy loss—to pass through the insulator via quantum tunneling. This current depends on the phase difference of the electron wavefunctions in the two superconductors and can flow without voltage. Josephson junctions are vital in precision measurement devices like superconducting quantum interference devices (SQUIDs), quantum computers, and sensitive voltage standards due to their unique quantum properties.