  An $s$-pair state in a graph is a quantum state of the form
$\mathbf{e}_u+s\mathbf{e}_v$, where $u$ and $v$ are vertices in the graph and
$s$ is a non-zero complex number. If $s=-1$ (resp., $s=1$), then such a state
is called a pair state (resp. plus state). In this paper, we develop the theory
of perfect $s$-pair state transfer in continuous quantum walks, where the
Hamiltonian is taken to be the adjacency, Laplacian or signless Laplacian
matrix of the graph. We characterize perfect $s$-pair state transfer in
complete graphs, cycles and antipodal distance-regular graphs admitting vertex
perfect state transfer. We construct infinite families of graphs with perfect
$s$-pair state transfer using quotient graphs and graphs that admit fractional
revival. We provide necessary and sufficient conditions such that perfect state
transfer between vertices in the line graph relative to the adjacency matrix is
equivalent to perfect state transfer between the plus states formed by
corresponding edges in the graph relative to the signless Laplacian matrix.
Finally, we characterize perfect state transfer between vertices in the line
graphs of Cartesian products relative to the adjacency matrix.
