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Effects of Dissipation and Temperature on Macroscopic Quantum Tunneling in Josephson Junctions
Author(s) -
WASHBURN SEAN,
WEBB RICHARD A.
Publication year - 1986
Publication title -
annals of the new york academy of sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.712
H-Index - 248
eISSN - 1749-6632
pISSN - 0077-8923
DOI - 10.1111/j.1749-6632.1986.tb12410.x
Subject(s) - watson , ibm , physics , quantum tunnelling , citation , art history , library science , condensed matter physics , history , computer science , optics , natural language processing
In 1978, Leggett’ pointed out that the direct measurement of the lifetime of a macroscopic quantum state was feasible and worthwhile. The large number of degrees of freedom both internal (within the objects considered) and in the coupling to the environment (there are no realizable isolated macroscopic objects) mixes the quantum mechanical states of the macroscopic body so that, in most cases, quantum mechanical behavior is averaged out. The question arose of whether (and under what conditions) the same quantum mechanical behavior would appear a t the macroscopic levels as is familiar in the microscopic world. The answer, according to a series of papers,’ is that the quantum mechanical principles (e.g., superposition) do survive in systems with sufficient internal correlation of the kind called “disconnectivity.” The most thoroughly studied system of this type is the superconducting tunnel junction or Josephson junction.’ In the case of the Josephson junction, as the Cooper pair tunnels through the barrier, the wave function changes its phase by an amount that is equal to the time integral of the voltage across the barrier. The quantum mechanical wave function is linked directly to the macroscopic (experimentally accessible) voltage. Measuring the current-voltage characteristics of the junction will then sample the quantum mechanical behavior of the Cooper pair wave f ~ n c t i o n s . ~ The standard phenomenological model of the Josephson junction is the following equation of motion for the phase difference, 4, across the junction:’