Quantum superposition of distinct macroscopic states

In 1935, Schrödinger attempted to demonstrate the limitations of quantum mechanics using a thought experiment in which a cat is put in a quantum superposition of alive and dead states. The idea remained an academic curiosity until the 1980s when it was proposed that, under suitable conditions, a mac...

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Bibliographic Details
Published in:Nature (London) 2000-07, Vol.406 (6791), p.43-46
Main Authors: Friedman, Jonathan R, Patel, Vijay, Chen, W, Tolpygo, S. K, Lukens, J. E
Format: Article
Language:English
Subjects:
Buckminsterfullerene
Classical and quantum physics: mechanics and fields
Exact sciences and technology
Experiments
Foundations, theory of measurement, miscellaneous theories (including aharonov-bohm effect, bell inequalities, berry's phase)
Fullerenes
Humanities and Social Sciences
letter
Microwaves
multidisciplinary
Nanocomposites
Nanostructure
Physics
Quantum mechanics
Quantum theory
Schroedinger equation
Science
Science (multidisciplinary)
SQUIDs
Superconducting quantum interference devices
Superconductivity
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Summary:In 1935, Schrödinger attempted to demonstrate the limitations of quantum mechanics using a thought experiment in which a cat is put in a quantum superposition of alive and dead states. The idea remained an academic curiosity until the 1980s when it was proposed that, under suitable conditions, a macroscopic object with many microscopic degrees of freedom could behave quantum mechanically, provided that it was sufficiently decoupled from its environment. Although much progress has been made in demonstrating the macroscopic quantum behaviour of various systems such as superconductors, nanoscale magnets, laser-cooled trapped ions, photons in a microwave cavity and C60 molecules, there has been no experimental demonstration of a quantum superposition of truly macroscopically distinct states. Here we present experimental evidence that a superconducting quantum interference device (SQUID) can be put into a superposition of two magnetic-flux states: one corresponding to a few microamperes of current flowing clockwise, the other corresponding to the same amount of current flowing anticlockwise.
ISSN:0028-0836
1476-4687
DOI:10.1038/35017505