The most sensitive devices available for magnetometry. The detector consists of a superconducting loop and one or two Josephson junctions.

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Devices formed of superconducting loops containing Josephson junctions used to measure magnetic fields

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Detecting ultra-small changes in magnetic fields. A SQUID is built up from one or more Josephson junctions using a subtle quantum mechanical effect on the supercurrent or the tunneling current running between the two superconductors in the presence of an external magnetic field. A SQUID is able to detect a change in the magnetic field in the order of ft (femtotesla) which is much smaller than the magnetic field of the earth. SQUID's are in use to measure the magnetic fields of mammalian brains for example. See also "Josephson effect".

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