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Originally published in Science Express on 20 April 2006
Science 9 June 2006:
Vol. 312. no. 5779, pp. 1495 - 1497
DOI: 10.1126/science.1126041
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Reports

Flip-Flopping Fractional Flux Quanta

T. Ortlepp,1* Ariando,2 O. Mielke,1 C. J. M. Verwijs,2 K. F. K. Foo,2 H. Rogalla,2 F. H. Uhlmann,1 H. Hilgenkamp2

The d-wave pairing symmetry in high–critical temperature superconductors makes it possible to realize superconducting rings with built-in {pi} phase shifts. Such rings have a twofold degenerate ground state that is 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. The integration of p rings 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.

1 Institute of Information Technology, Rapid Single-Flux Quantum (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. E-mail: thomas.ortlepp{at}tu-ilmenau.de

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