Dresden 2003 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 15: Poster der Symposien SYQI und SYQD
TT 15.2: Poster
Mittwoch, 26. März 2003, 14:30–19:00, P2d
Compensation of telegraph noise decoherence by means of bang-bang control — •Henryk Gutmann1, William Kaminsky2, Seth Lloyd2, and Frank Wilhelm1 — 1LS von Delft, LMU München — 2Mechanical Engineering, MIT, Cambridge, Massachusetts 02139
The physics of the bistable fluctuators attracts recent attention concerning modeling decoherence in solid state qubits due to material defects [1,2]. Its special meaning does not only originate in the description of spin-like noise sources but in particular in the generation of 1/f-noise by means of ensembles with appropriate spectral distribution.
We investigate the effect of an easily implemented bang-bang control protocol [3] on a single qubit coupled to a bistable fluctuator as a semiclassical noise source. This correction method is suitably designed for this kind of noise perturbation as it suppresses low frequency fluctuations. We quantitatively analyze this setup and check the obvious assumption, that the factor of reduction of the occuring random walk on the Bloch sphere is controlled by the ratio of the typical fluctuator switching time scale and the applied bang-bang pulse length. Therefore we expect the bang-bang mechanism working like a high-pass filter suppressing the low-frequency parts of any spectral composition of fluctuators. Consequently it appears to be possible to diminish the most harmful fraction of 1/f-noise.
[1] E. Paladino et al., Phys. Rev. Lett. 88, 228304 (2002)
[2] H. Gassmann, F. Marquardt, and C. Bruder, Phys. Rev. E 66, 041111 (2002)
[3] L. Viola, E. Knill, and S. Lloyd, Phys. Rev. Lett. 82, 2417 (1999)