Physics – Quantum Physics
Scientific paper
2004-03-26
Phys. A, vol 347C, pp. 137-152 (2005)
Physics
Quantum Physics
Elsevier style, 18 pages. New enhanced version with more material: new title, a new section was added and the discussion was u
Scientific paper
10.1016/j.physa.2004.08.070
We investigate the quantum walk on the line when decoherences are introduced either through simultaneous measurements of the chirality and particle position, or as a result of broken links. Both mechanisms drive the system to a classical diffusive behavior. In the case of measurements, we show that the diffusion coefficient is proportional to the variance of the initially localized quantum random walker just before the first measurement. When links between neighboring sites are randomly broken with probability $p$ per unit time, the evolution becomes decoherent after a characteristic time that scales as $1/p$. The fact that the quadratic increase of the variance is eventually lost even for very small frequencies of disrupting events, suggests that the implementation of a quantum walk on a real physical system may be severely limited by thermal noise and lattice imperfections.
Abal Gonzalo
Auyuanet Adriana
Donangelo Raul
Romanelli Alejandro
Siri R.
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