Atom gravimeters and gravitational redshift

Arising from: H. Müller, A. Peters & S. Chu Nature463, 926–929 (2010)10.1038/nature08776 ; Müller & Chu reply In ref. 1 the authors present a re-interpretation of atom interferometry experiments published a decade ago 2 . They now consider the atom interferometry experiments 2 as a measurement of the gravitational redshift on the quantum clock operating at the Compton frequency ω C = mc 2 / ≈ 2π × 3.0 × 10 25 Hz, where m is the caesium (Cs) atom rest mass. They then argue that this redshift measurement compares favourably with existing 3 as well as projected 4 clock tests. Here we show that this interpretation is incorrect.