  We stand by our result [H. Mueller et al., Nature 463, 926-929 (2010)]. The
comment [P. Wolf et al., Nature 467, E1 (2010)] revisits an interesting issue
that has been known for decades, the relationship between test of the
universality of free fall and redshift experiments. However, it arrives at its
conclusions by applying the laws of physics that are questioned by redshift
experiments; this precludes the existence of measurable signals. Since this
issue applies to all classical redshift tests as well as atom interferometry
redshift tests, these experiments are equivalent in all aspects in question.
