@misc{cryptoeprint:2015:551,
author = {Anne Broadbent and Stacey Jeffery},
title = {Quantum homomorphic encryption for circuits of low $T$-gate complexity},
howpublished = {Cryptology ePrint Archive, Report 2015/551},
year = {2015},
note = {\url{http://eprint.iacr.org/}},
}
You will need the url.sty package (comes with most LaTeX installations) for the last line. Otherwise, remove the \url command.