Arbitrary phase shift of a semiconductor quantum dot charge qubit on a short time scale

Key Laboratory of Quantum Information, CAS, University of Science and Technology of China Hefei, Anhui 230026, China and Synergetic Innovation Center of Quantum Information & Quantum Physics, University of Science and Technology of China - Hefei, Anhui 230026, China

^(a) gpguo@ustc.edu.cn (corresponding author)

Received: 14 August 2015
Accepted: 30 October 2015

Abstract

We present an experimental technique to better control the phase of an electron charge qubit, formed by a GaAs double quantum dot. A standard non-adiabatic gate pulse is used to generate the qubit rotation around the x-axis of the Bloch sphere. To gain good control of the z-rotation (the phase) on a short time scale, a fast 130 ps tipping pulse is superimposed on the non-adiabatic pulse. The two-axis gate operation is exhibited in the composite pulse excited qubit evolution spectrum. We demonstrate that the dynamic phase can be varied continuously from 0 to by varying the amplitude of the tipping pulse. The understanding of the spectrum is validated through simulation of the von Neumann equation.