We report an experimental demonstration of optimal measurements of small displacement and tilt of a Gaussian beam - two conjugate variables - involving a homodyne detection with a TEM10 local oscillator. We verify that the standard split detection is only 64% efficient. We also show a displacement measurement beyond the quantum noise limit, using a squeezed vacuum TEM10 mode within the input beam.
@article{arxiv.quant-ph/0607142,
title = {TEM10 homodyne detection as an optimal small displacement and tilt measurements scheme},
author = {Vincent Delaubert and Nicolas Treps and Mikael Lassen and Charles C. Harb and Claude Fabre and Ping Koy Lam and Hans A. Bachor},
journal= {arXiv preprint arXiv:quant-ph/0607142},
year = {2009}
}