ELFT HÍRADÓ

[Bálint Kollár <kollar.balint AT wigner.mta.hu>]

MEGHÍVÓ

Wigner FK SZFI Kvantumoptika és Kvantuminformatika Csoport szemináriuma
2015. január 19. hétfő, 10:00

Asbóth János (Wigner FK SZFI)
"Localization, Diffusion, Topological Phases in 2-D quantum walks"

The hallmark property of Quantum Walks is that they spread
ballistically, <x^2> \propto t^2, faster than the diffusive, <x^2>
\propto t spreading of random walks. This gives them a "quantum
speedup", which can be exploited in quantum algorithms. In the
presence of time-independent disorder, however, 1- and 2-dimensional
(1D and 2D) quantum walks are expected to suffer Anderson
localization, whereby their spread stops completely, <x^2> \to \const,
except for a few exceptions. This has recently been seen in
simulations of a simple quantum walk, the 2D split-step Hadamard walk
[1].

We have shown [2] that the conclusions drawn about the 2D split-step
Hadamard walk are in fact incorrect: over longer timescales, instead
of localization, it spreads diffusively. The reason is that this
quantum walk is an iterative dynamical system tuned to a critical
point at a topological phase transition. In the talk, I will explain
what we mean by that.

[1]: J. Svozilik, R. D. J. Leon-Montiel, and J. P. Torres, PRA 86,
052327 (2012).
[2]: J. M. Edge and J. K. Asboth, submitted to PRB,
http://arxiv.org/abs/1411.7691

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Az előadás helye és ideje:
Wigner FK SZFI
Konkoly-Thege M. út 29-33., 1-es épület Tanácsterem
2015. január 19. hétfő, 10:00.

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