Macroscopic Quantum Superposition in a Three-Josephson-Junction Loop

Caspar H. van der Wal (), A. C. J. ter Haar, F. K. Wilhelm, R. N. Schouten, C. J. P. M. Harmans, T. P. Orlando, Seth Lloyd and J. E. Mooij
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Caspar H. van der Wal: Delft University of Technology, Department of Applied Physics and Delft Institute for Micro Electronics and Submicron Technology (DIMES)
A. C. J. ter Haar: Delft University of Technology, Department of Applied Physics and Delft Institute for Micro Electronics and Submicron Technology (DIMES)
F. K. Wilhelm: Delft University of Technology, Department of Applied Physics and Delft Institute for Micro Electronics and Submicron Technology (DIMES)
R. N. Schouten: Delft University of Technology, Department of Applied Physics and Delft Institute for Micro Electronics and Submicron Technology (DIMES)
C. J. P. M. Harmans: Delft University of Technology, Department of Applied Physics and Delft Institute for Micro Electronics and Submicron Technology (DIMES)
T. P. Orlando: MIT, Department of Electrical Engineering and Computer Science
Seth Lloyd: MIT, Department of Mechanical Engineering
J. E. Mooij: Delft University of Technology, Department of Applied Physics and Delft Institute for Micro Electronics and Submicron Technology (DIMES)

A chapter in Macroscopic Quantum Coherence and Quantum Computing, 2001, pp 25-34 from Springer

Abstract: Abstract We present microwave-spectroscopy experiments on two quantum levels of a superconducting loop with three Josephson junctions. The level separation between the ground state and first excited state shows an anti-crossing where two classical persistent-current states with opposite polarity are degenerate. This is evidence for symmetric and antisymmetric quantum superpositions of two macroscopic states; the classical states have persistent currents of 0.5 µA and correspond to the center-of-mass motion of millions of Cooper pairs. A study of the thermal occupancies of the two quantum levels shows that the loop is at low temperatures in a non-equilibrium state.

Keywords: Macroscopic quantum mechanics; Josephson effect; SQUIDs; microwave spectroscopy (search for similar items in EconPapers)
Date: 2001
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DOI: 10.1007/978-1-4615-1245-5_4

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