Decoherence models for discrete-time quantum walks and their application to neutral atom experiments

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Alberti, Andrea; Alt, Wolfgang; Werner, Reinhard; Meschede, Dieter: Decoherence models for discrete-time quantum walks and their application to neutral atom experiments. In: New Journal of Physics 16 (2014), 123052. DOI:

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Sum total of downloads: 357

We discuss decoherence in discrete-time quantum walks in terms of a phenomenological model that distinguishes spin and spatial decoherence. We identify the dominating mechanisms that affect quantum-walk experiments realized with neutral atoms walking in an optical lattice. From the measured spatial distributions, we determine with good precision the amount of decoherence per step, which provides a quantitative indication of the quality of our quantum walks. In particular, we find that spin decoherence is the main mechanism responsible for the loss of coherence in our experiment. We also find that the sole observation of ballistic-instead of diffusive-expansion in position space is not a good indicator of the range of coherent delocalization. We provide further physical insight by distinguishing the effects of short- and long-time spin dephasing mechanisms. We introduce the concept of coherence length in the discrete-time quantum walk, which quantifies the range of spatial coherences. Unexpectedly, we find that quasi-stationary dephasing does not modify the local properties of the quantum walk, but instead affects spatial coherences. For a visual representation of decoherence phenomena in phase space, we have developed a formalism based on a discrete analogue of the Wigner function. We show that the effects of spin and spatial decoherence differ dramatically in momentum space.
License of this version: CC BY 3.0 Unported
Document Type: Article
Publishing status: publishedVersion
Issue Date: 2014-12-19
Appears in Collections:Fakultät für Mathematik und Physik

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1 image of flag of Germany Germany 296 82.91%
2 image of flag of United States United States 28 7.84%
3 image of flag of China China 16 4.48%
4 image of flag of Japan Japan 3 0.84%
5 image of flag of Ireland Ireland 2 0.56%
6 image of flag of France France 2 0.56%
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10 image of flag of Hungary Hungary 1 0.28%
    other countries 5 1.40%

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