Concerning the referee’s other point, about the suitability of this system to measure weak forces, we first note that the use of Bloch oscillations without a cavity is proving to be an excellent way to measure gravity (e.g. the experiments by G.M. Tino’s group). The sensitivity of their measurements, after many years of development, are only one order of magnitude above our estimated sensitivity, and their measurements take one hour whereas ours should take one second which means it might have applications in rather different situations (e.g. local gravity mapping while flying). Our work is very much still in progress and this paper will not, we hope, be our final word on this subject. Indeed, we point out a possible way forward in the last section that builds on the insight gained from the optomechanics analogy. It seems likely that the homodyne phase measurement regime, where backaction can be reduced, will likely be more favourable when it comes to absolute sensitivity than photon counting type measurement we focus on at the moment. For these reasons we would like to keep the measurement aspects of the paper intact: we would like to advertise them and, perhaps, be a little provocative.
The link to the sensing of weak forces (in this case gravity) is interesting, but I am not convinced whether this is a practical approach. The estimated accuracy is $10^6$ that does not sound great.