In a pair of related papers, Wang et al. [Phys. Rev. A 75, 013813 (2007); 75, 042105 (2007)] claim to present evidence, based on quantum field theory, for the superluminality of evanescent modes in undersized waveguides. Here we show that the conclusion of the authors is false and is based on an error: they mistake a nonzero propagator for a nonzero commutator. The commutator of the field operator at two points separated by a spacelike interval is strictly zero, which makes true superluminality impossible.

• Received 16 May 2007

DOI:https://doi.org/10.1103/PhysRevA.76.057803