Hamburg 2001 – scientific programme

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TT: Tiefe Temperaturen

TT 6: Postersitzung I: Josephsonkontakte und SQUIDs, Supraleitung: Theorie, Korrelierte Elektronen, Niederdimensionale Systeme, Magnetotransport, Quantenhalleffekt, Kohlenstoff-Nanoröhrchen, Quantenflüssigkeiten

TT 6.7: Poster

Monday, March 26, 2001, 14:30–17:00, Rang S\ 3

Josephson Vortex Dynamics at Millikelvin Temperatures — •A. Wallraff, A. Kemp, and A. V. Ustinov — Physikalisches Institut III, Friedrich-Alexander-Universität Erlangen-Nürnberg, D-91058 Erlangen

We experimentally study the dynamics of a single Josephson vortex in a tilted periodic potential. Applying a bias current uniformly to a shaped long Josephson junction subject to an in-plane external magnetic field, metastable vortex-states are created. The escape of the vortex from these states is experimentally investigated by measuring the statistical distribution of the junction critical current, i.e. the vortex depinning current. At high temperatures, the thermal activation of the vortex is observed. As temperature and damping is reduced, the macroscopic quantum properties of Josephson vortices, such as energy level quantization and quantum tunneling, are predicted to appear [2,3]. Here we report on our current experimental work to observe these effects at millikelvin temperatures. Our interest in this macroscopic quantum system is related to the possibility of using quantum states of Josephson vortices for performing quantum computation. We have suggested that a vortex trapped in a double-well potential in a narrow long junction can be used as a scalable and well-controllable qubit [3].

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

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

[3] A. Wallraff et al. , J. Low Temp. Phys. 188, 543 (2000).