Berlin 2018 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 80: Graphene

TT 80.3: Talk

Thursday, March 15, 2018, 10:00–10:15, H 3005

Tunable quantum random walks in graphene — •Vanessa Junk, Phillipp Reck, Cosimo Gorini, and Klaus Richter — Institut für Theoretische Physik, Universität Regensburg, Germany

One of the many fascinating aspects connected to quantum computing are quantum random walks [1] which can be used to speed up classical algorithms.

We show that such a quantum walk can be physically implemented in graphene by extending a recently proposed Quantum Time Mirror [2]. The pulse used in Ref. [2] for the time reversal can be tuned such that an initial wave-packet is split into two parts moving in opposed directions. By adjusting the pulse length, the amplitudes of the two resulting packets can be chosen arbitrarily. Hence, applying such a pulse is equivalent to the coin toss in descrete time quantum walks [3] with the advantage of having additional degrees of freedom in the “coin”. Moreover, the system we are dealing with is continuous in space. This allows for arbitrary timing of the pulses which leads to further variety in the probability distribution of the wave-packet in space.

In this talk we will discuss the described system and show the influence of the coin parameters on the resulting quantum walk of charge carriers in graphene.
Y. Aharonov, L. Davidovich, and N. Zagury, Phys. Rev. A 48, 1687-1690 (1993)
P. Reck, C. Gorini, A. Goussev, V. Krueckl, M. Fink, K. Richter, Phys. Rev. B 95, 165421 (2017)
J. Kempe, Contemporary Physics 44, 307-327 (2003)