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Published Online April 20, 2006
Science DOI: 10.1126/science.1126041

Reports

Submitted on February 9, 2006
Accepted on April 6, 2006

Flip-Flopping Fractional Flux Quanta

Thomas Ortlepp 1*, Ariando Ariando 2, O. Mielke 1, C. J. M. Verwijs 2, K. F. K. Foo 2, H. Rogalla 2, F. H. Uhlmann 1, H. Hilgenkamp 2

1 Institute of Information Technology, RSFQ Design Group, University of Technology Ilmenau, Post Office Box 100565, D-98684 Ilmenau, Germany.
2 Faculty of Science and Technology and MESA+ Institute for Nanotechnology, University of Twente, Post Office Box 217, 7500 AE Enschede, Netherlands.

* To whom correspondence should be addressed.
Thomas Ortlepp , E-mail: thomas.ortlepp{at}tu-ilmenau.de

The d-wave pairing symmetry in high-Tc superconductors provides the possibility to realize superconducting rings with built-in {pi}-phase shifts. Such rings have a two-fold degenerate ground state characterized by the spontaneous generation of fractional magnetic flux quanta with either up- or down-polarity. We have incorporated {pi}-phase biased superconducting rings in a logic circuit, a Flip-Flop, in which the fractional flux polarity is controllably toggled by applying single flux quantum pulses at the input channel. Integration into conventional rapid single flux quantum-logic as natural two-state devices should alleviate the need for bias current lines, improve device symmetry, and enhance the operation margins.




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Science. ISSN 0036-8075 (print), 1095-9203 (online)