  Consider the Dirichlet-type space on the bidisk consisting of holomorphic
functions $f(z_1,z_2):=\sum_{k,l\geq 0}a_{kl}z_1^kz_2^l$ such that
$\sum_{k,l\geq 0}(k+1)^{\alpha_1} (l+1)^{\alpha_2}|a_{kl}|^2 <\infty.$ Here the
parameters $\alpha_1,\alpha_2$ are arbitrary real numbers. We characterize the
polynomials that are cyclic for the shift operators on this space. More
precisely, we show that, given an irreducible polynomial $p(z_1,z_2)$ depending
on both $z_1$ and $z_2$ and having no zeros in the bidisk: if
$\alpha_1+\alpha_2\leq 1$, then $p$ is cyclic; if $\alpha_1+\alpha_2>1$ and
$\min\{\alpha_1,\alpha_2\}\leq 1$, then $p$ is cyclic if and only if it has
finitely many zeros in the two-torus $\mathbb T^2$; if
$\min\{\alpha_1,\alpha_2\}>1$, then $p$ is cyclic if and only if it has no
zeros in $\mathbb T^2$.
