We propose a scheme for creating quantum superposition states involving of order 1014 atoms via the interaction of a single photon with a tiny mirror. This mirror, mounted on a high-quality mechanical oscillator, is part of a high-finesse optical cavity which forms one arm of a Michelson interferometer. By observing the interference of the photon only, one can study the creation and decoherence of superpositions involving the mirror. All experimental requirements appear to be within reach of current technology.
@article{arxiv.quant-ph/0210001,
title = {Towards quantum superpositions of a mirror},
author = {William Marshall and Christoph Simon and Roger Penrose and Dik Bouwmeester},
journal= {arXiv preprint arXiv:quant-ph/0210001},
year = {2009}
}