Quantum Superposition of Macroscopic Persistent-Current States

Microwave spectroscopy experiments have been performed on two quantum levels of a macroscopic superconducting loop with three Josephson junctions. Level repulsion of the ground state and first excited state is found where two classical persistent-current states with opposite polarity are degenerate,...

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Bibliographic Details
Published inScience (American Association for the Advancement of Science) Vol. 290; no. 5492; pp. 773 - 777
Main Authors van der Wal, Caspar H., A. C. J. ter Haar, Wilhelm, F. K., Schouten, R. N., C. J. P. M. Harmans, Orlando, T. P., Lloyd, Seth, Mooij, J. E.
Format Journal Article
LanguageEnglish
Published Washington, DC American Society for the Advancement of Science 27.10.2000
American Association for the Advancement of Science
The American Association for the Advancement of Science
Subjects
Amplitude
Analysis
Condensed matter: electronic structure, electrical, magnetic, and optical properties
Electric current
Electric currents
Electromagnetism
Energy
Exact sciences and technology
Ground state
Josephson junction
Josephson junctions
Mechanics (Physics)
Microwaves
Numbers
Physics
Proximity effects, weak links, tunneling phenomena, and Josephson effects
Proximity effects, weak links, tunneling phenomena, and josephson effects, adreev effect, sn and sns junctions
Quantum Mechanics
Quantum theory
Scientific imaging
Solid state physics
Spectroscopy
Superconductivity
Tunnels
Vortex rings
Persistent current
Electrical switching
Two-level systems
Theoretical study
Quantum effect
Excited states
Superconductors
Cooper pairs
Double well model
Josephson junctions
Transport processes
Microwave spectra
Superposition
Mesoscopic systems
IV characteristic
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Summary:Microwave spectroscopy experiments have been performed on two quantum levels of a macroscopic superconducting loop with three Josephson junctions. Level repulsion of the ground state and first excited state is found where two classical persistent-current states with opposite polarity are degenerate, indicating symmetric and antisymmetric quantum superpositions of macroscopic states. The two classical states have persistent currents of 0.5 microampere and correspond to the center-of-mass motion of millions of Cooper pairs.
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ISSN:0036-8075
1095-9203
DOI:10.1126/science.290.5492.773