Spin manipulation and spin dephasing in quantum dot integrated with a slanting magnetic field

TL;DR

This paper investigates how a slanting magnetic field affects spin manipulation and dephasing in a quantum dot, revealing modulation effects, dephasing mechanisms, and strategies to improve qubit coherence times.

Contribution

It demonstrates the role of longitudinal slanting magnetic fields in mediating spin control and dephasing, and proposes methods to mitigate dephasing in silicon quantum dots.

Findings

Spin population inversion shows modulated Rabi oscillation.

Dephasing time T*_2 is about 20 microseconds.

Echo time T_2^echo is about 100 microseconds.

Abstract

A slanting magnetic field is usually used to realize a slight hybridization between the spin and orbital degrees of freedom in a semiconductor quantum dot, such that the spin is manipulable by an external oscillating electric field. Here we show that, the longitudinal slanting field mediates a longitudinal driving term in the electric-dipole spin resonance, such that the spin population inversion exhibits a modulated Rabi oscillation. Fortunately, we can reduce this modulation by increasing the static magnetic field. The longitudinal slanting field also mediates a spin-1/f-charge noise interaction, which causes the pure dephasing of the spin qubit. Choosing proper spectrum function strength, we find the spin dephasing time is about $T^{*}_{2}=20$ $\mu$s and the spin echo time is about $T^{\rm echo}_{2}=100$ $\mu$s in a Si quantum dot. We also propose several strategies to alleviate the spin dephasing, such as lowering the experimental temperature, reducing the quantum dot size, engineering the slanting field, or using the dynamical decoupling scheme.