The target-adapted contract

Fix $x_0,x_1\in U$, $x_0\ne x_1$, with

Fix a departure time $T_{\mathrm{d}}$. The prescribed target pair is

The developed straight segment is future null.

Choose any integer $m\ge 1$. Install the $m+1$ sites

where the notation $x_m=x_1$ is understood. Each site has a register $A_j\cong {\mathbb{C}}^d$, with $d=2^p\ge 2$. Set

At tick $j=1,\dots ,m$, apply SWAP to $A_{j-1}\otimes A_j$ and identities to all other sites.

The station locations and tick duration are task data. They are not selected by the unknown payload or inferred from its entanglement.