New self-dual additive ${\mathbb{F}}_4$-codes constructed from circulant graphs

In order to construct quantum $[[n,0,d]]$ codes for $(n,d)=(56,15)$, $(57,15)$, $(58,16)$, $(63,16)$, $(67,17)$, $(70,18)$, $(71,18)$, $(79,19)$, $(83,20)$, $(87,20)$, $(89,21)$, $(95,20)$, we construct self-dual additive ${\mathbb{F}}_4$-codes of length $n$ and minimum weight $d$ from circulant graphs. The quantum codes with these parameters are constructed for the first time.