We examine the physical significance of fidelity as a measure of similarity for Gaussian states by drawing a comparison with its classical counterpart. We find that the relationship between these classical and quantum fidelities is not straightforward, and in general does not seem to provide insight into the physical significance of quantum fidelity. To avoid this ambiguity we propose that the efficacy of quantum information protocols be characterized by determining their transfer function and then calculating the fidelity achievable for a hypothetical pure reference input state.
© 2007 Optical Society of America
Original Manuscript: May 2, 2006
Revised Manuscript: July 14, 2006
Manuscript Accepted: July 18, 2006
Published: January 26, 2007
Hyunseok Jeong, Timothy C. Ralph, and Warwick P. Bowen, "Quantum and classical fidelities for Gaussian states," J. Opt. Soc. Am. B 24, 355-362 (2007)