Quantum fluctuations in superconducting point contacts

Quantum fluctuations of the phase difference of the order parameter of superconductors in pure S-c-S point contacts are investigated. Expressions for the effective action describing the quantum behavior of the phase difference are derived within the framework of the microscopic theory. The mean-square deviation of the magnetic flux from the classical mean value is determined for a superconducting ring containing a point Josephson junction, and the probability of quantum tunneling decay of a metastable current state is calculated.

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