In the $(x, y, z)$ coordinate system, three point-charges $\text{Q, Q}$, and $\alpha \text{Q}$ are located in free space at $(-1,0,0),(1,0,0)$, and $(0,-1,0)$, respectively. The value of $\alpha$ for the electric field to be zero at $(0,0.5,0)$ is ____________ (rounded off to $1$ decimal place).