Eur. Phys. J. B (2014) 87: 57
https://doi.org/10.1140/epjb/e2014-40899-4

Regular Article

Quantum computing through electron propagation in edge states of quantum spin Hall systems

¹ National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, P.R. China
² Department of Physics and Center of Theoretical and Computational Physics, The University of Hong Kong, Pokfulam Road, Hong Kong, P.R. China
³ Laboratory of Quantum Engineering and Quantum Materials, and School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510006, P.R. China

^a e-mail: zwang@hku.hk
^b e-mail: shen@nju.edu.cn

Received: 9 October 2013
Received in final form: 15 January 2014
Published online: 5 March 2014

Abstract

We propose to implement quantum computing by the on-demand control of the wave packets propagation in helical edge channels of the quantum spin Hall systems (QSHs). Two non-commutative single-qubit gates are realized by the gate voltages applied on the edge channels. The two-qubit controlled phase gate is implemented by the capacitive Coulomb interaction between two adjacent edge channels from two parallel QSHs. A universal set of quantum gates thus can be realized in an all-electrical way. It is also shown that the fidelity and the purity of the controlled phase gate can reach a high value, with both the time delay and the finite width of the wave packets taken into account.