@article {1377,
title = {Fast quantum algorithm for numerical gradient estimation},
journal = {Physical Review Letters},
volume = {95},
year = {2005},
month = {2005/7/28},
abstract = { Given a blackbox for f, a smooth real scalar function of d real variables,
one wants to estimate the gradient of f at a given point with n bits of
precision. On a classical computer this requires a minimum of d+1 blackbox
queries, whereas on a quantum computer it requires only one query regardless of
d. The number of bits of precision to which f must be evaluated matches the
classical requirement in the limit of large n.
},
doi = {10.1103/PhysRevLett.95.050501},
url = {http://arxiv.org/abs/quant-ph/0405146v2},
author = {Stephen P. Jordan}
}