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.
Cite
@article{arxiv.quant-ph/0005020,
title = {Singlet aided infinite resource reduction in the comparison of distant fields},
author = {S. Bose and S. F. Huelga and M. B. Plenio},
journal= {arXiv preprint arXiv:quant-ph/0005020},
year = {2009}
}