We propose a scheme utilising a quantum interference phenomenon to switch the transport of atoms in a 1D optical lattice through a site containing an impurity atom. The impurity represents a qubit which in one spin state is transparent to the probe atoms, but in the other acts as a single atom mirror. This allows a single-shot quantum non-demolition measurement of the qubit spin.
@article{arxiv.quant-ph/0406020,
title = {A Single Atom Transistor in a 1D Optical Lattice},
author = {A. Micheli and A. J. Daley and D. Jaksch and P. Zoller},
journal= {arXiv preprint arXiv:quant-ph/0406020},
year = {2009}
}