  We theoretically study tunneling of Cooper pairs from a superconductor
spanning a two-dimensional topological insulator strip into its helical edge
states. The coherent low-energy electron-pair tunneling sets off positive
current cross correlations along the edges, which reflect an interplay of two
quantumentanglement processes. Most importantly, superconducting spin pairing
dictates a Cooper pair partitioning into the helical edge liquids, which
transport electrons in opposite directions for opposite spin orientations. At
the same time, Luttinger-liquid correlations fractionalize electrons injected
at a given edge into counterpropagating charge pulses carrying definite
fractions of the elementary electron charge.
