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Micrographs showing a loop of superconducting material used to demonstrate coherent quantum phase slip. The image on the left shows the loop of superconductor and the image on the right is a magnified section showing how the superconductor narrows to a nanowire. The magnetic field is applied perpendicular to the loop. (Courtesy: RIKEN)
'Magnetic Josephson Effect' Seen for the First Time
Apr 19, 2012



A fundamental prediction of superconductivity theory has been demonstrated in the lab for the first time. An international team of physicists has observed coherent quantum phase slip, a phenomenon similar to the well-known Josephson effect in which magnetic flux takes the place of electric charge. Its discovery has fundamental implications for our understanding of macroscopic quantum systems and could also lead to intriguing applications, including a possible way to produce a qubit in a quantum computer.

In 1962 the British physicist Brian Josephson developed a theory of how superconducting electrons tunnel across a thin insulating layer between two superconductors – a structure now called a Josephson junction. This was quickly verified in the lab and Josephson was awarded the 1973 Nobel Prize for Physics. The Josephson junction has become an important technology in its own right. For example, superconducting quantum interference devices (SQUIDs) that, depending on their design, use either one or two Josephson junctions are among the most sensitive magnetometers to have been invented. The devices have also shown promise as possible quantum bits (qubits) in quantum computers.
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