New quantum codes constructed from some self-dual additive ${\mathbb{F}}_4$-codes

For $(n,d)=(66,17),(78,19)$ and $(94,21)$, we construct quantum $[[n,0,d]]$ codes which improve the previously known lower bounds on the largest minimum weights among quantum codes with these parameters. These codes are constructed from self-dual additive ${\mathbb{F}}_4$-codes based on pairs of circulant matrices.