Significance of the Compton frequency in atom interferometry
  The recent realization that atom interferometers (AIs) can be used to test the gravitational redshift tests has proven to be controversial in some quarters. Here, we address the issues raised against the interpretation of AIs as redshift tests, reaffirming the fact that Mueller et al. [Nature 463, 926 (2010)] indeed report a gravitational redshift test. 
Michael A. Hohensee and Holger Mueller
gr-qc hep-ph quant-ph