The twisted XXZ-chain 2-sum conjecture

Let $L=2n$ and consider the twisted XXZ chain at $\Delta=-\frac{1}{2}$, with the groundstate wavefunction normalised as in the source. Let $S_{2n}^{(2)}$ be the sum of the squares of its components, and let $A_n$ be the number of $n\times n$ alternating sign matrices. The twisted-chain 2-sum conjecture.

$$S_{2n}^{(2)}=A_n^2.$$

This predicts that the squared norm of the complex twisted-chain groundstate is the square of an alternating-sign-matrix enumeration. It is supported by finite-size calculations but remains conjectural in the source.