We comment on a recent paper [Phys. Rev. Lett. 97, 070401 (2006): quant-ph/0603229] concerning rubidium atoms trapped near a superconducting niobium surface at ~4K. This seeks to calculate the rate of atomic spin flips induced by thermal magnetic noise. We point out that the calculation is in error by a large factor because it is based on the two-fluid model of superconductivity. This model gives a poor description of electromagnetic dissipation just below the critical temperature because it cannot incorporate the case II coherences of a fuller quantum theory.
@article{arxiv.quant-ph/0610095,
title = {Comment on `Spin Decoherence in Superconducting Atom Chips'},
author = {Stefan Scheel and E. A. Hinds and P. L. Knight},
journal= {arXiv preprint arXiv:quant-ph/0610095},
year = {2007}
}