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TT: Tiefe Temperaturen

TT 6: Josephson-Kontakte und SQUIDs I

TT 6.4: Vortrag

Montag, 27. März 2000, 17:00–17:15, H19

Thermal Activation of a Josephson Vortex from a Magnetic Field-Induced Potential Well — •A. Wallraff¹, M. V. Fistul¹, A. Kemp¹, Y. Koval¹, M. Levitchev², and A. V. Ustinov¹ — ¹Physikalisches Institut III, Universität Erlangen-Nürnberg, D-91058 Erlangen — ²ISI, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany

Long Josephson junctions are known as the most clean systems to experimentally study basic properties of Josephson vortices [1]. A Josephson vortex trapped in an annular junction does interact with pinning potentials of different physical origins. We study the pinning induced by the magnetic dipole interaction of the vortex with an external magnetic field. Measurements of the thermal activation of the vortex from the magnetic field-induced potential well are presented and the effect of an external rf-field on the activation of the vortex is investigated. Moreover, we discuss the possibility to experimentally observe quantum tunneling of the vortex as predicted by theory [2,3]. Our interest in these systems is related to the possibility of using macroscopic quantum states of a Josephson vortex for quantum computation [4]. We suggest that a fluxon trapped in a double-well potential inside a narrow long junction can be used as a qubit.

[1] A. V. Ustinov, Physica D 123, 315 (1998)

[2] T. Kato and M. Imada, J. Phys. Soc. Japan 65, 2963 (1996).

[3] A. Shnirman, E. Ben-Jacob, and B. Malomed, Phys. Rev. B 56, 14677 (1997).

[4] A. Wallraff et al. , J. Low Temp. Phys. (in print).