Singlet aided infinite resource reduction in the comparison of distant   fields
  We present a task which can be faithfully solved with finite resources only when aided by particles prepared in a particular entangled state: the singlet state. The task consists of identifying the mutual parallelity or orthogonality of weak distant magnetic fields whose absolute directions are completely unknown. 
S. Bose, S.F. Huelga, M.B. Plenio