Comment on "Rovibrational quantum interferometers and gravitational waves"

In a recent paper, Wicht, L\"ammerzahl, Lorek, and Dittus [Phys. Rev. {\bf A 78}, 013610 (2008)] come to the conclusion that a molecular rotational-vibrational quantum interferometer may possess the sensitivity necessary to detect gravitational waves. We do not agree with their results and demonstrate here that the true sensitivity of such interferometer is many orders of magnitude worse than that claimed in the mentioned paper. In the present comment we estimate the expected energy shifts and derive equations of motion for a quantum symmetric top (diatomic molecule or deformed nucleus) in the field of gravitational wave, and then estimate the sensitivity of possible experiments.