We present a scalable method for the tomography of large multiqubit quantum registers. It acquires information about the permutationally invariant part of the density operator, which is a good approximation to the true state in many, relevant cases. Our method gives the best measurement strategy to minimize the experimental effort as well as the uncertainties of the reconstructed density matrix. We apply our method to the experimental tomography of a photonic four-qubit symmetric Dicke state.
@article{arxiv.1005.3313,
title = {Permutationally invariant quantum tomography},
author = {Geza Toth and Witlef Wieczorek and David Gross and Roland Krischek and Christian Schwemmer and Harald Weinfurter},
journal= {arXiv preprint arXiv:1005.3313},
year = {2011}
}
Comments
4 pages including 5 figures, 3-page appendix with 2 figures, revtex4; v2: shortened, some references added; v3: Observation 2 improved, extension to many qubits discussed; v4: more details added to the Appendix, published version