Quantum spin chains with fractional revival

A systematic study of fractional revival at two sites in XX$XX$ quantum spin chains is presented. Analytic models with this phenomenon are obtained by combining two basic ways of realizing fractional revival in a spin chain. The first proceeds through isospectral deformations of spin chains with perfect state transfer. The second makes use of couplings provided by the recurrence coefficients of polynomials with a bi-lattice orthogonality grid. The latter method leads to analytic models previously identified that can exhibit perfect state transfer in addition to fractional revival.