Reacción a "Einstein’s gravity observed in the quantum world"

The press release summarises the study with exquisite precision. However, there are a couple of points that might have warranted greater clarity, given the importance of both the article and the journal in which it appears. In the press release, when it refers to: the pulse splitting into two, with one of the parts being pushed upwards by means of a controlled magnetic pulse, and then converted into a state “almost unaffected by the magnetic field”, so that it can fall freely under the influence of gravity. What is the residual effect here, expressed as a numerical value or a percentage? Does this affect the purported free fall?

Nor have I fully understood the sentence towards the end of the press release (towards the end of the fifth paragraph), which states that ‘this complex experiment provides new clues as to how to achieve the unification [of Einsteinian gravity and quantum physics].’ To the best of my understanding, the work carried out is strictly limited to experimentally confirming that the theoretical calculations made over the last hundred years regarding quantum modifications to the equivalence principle are correct. Perhaps it refers (although this could be explained more clearly in the press release) to the fact that further experiments, to be carried out with larger particles, might be able to explore regimes closer to the classical-quantum transition, which are much more difficult to tackle theoretically. Here, experimentation could get ahead of theory, which would be very positive.

The other point concerns the conclusions of the paper (p. 5, 2nd column, at the beginning), where it is stated that “we have confirmed the predicted phase with a high level of confidence…” One immediately wonders: how high? I believe this question probably slipped past the article’s referees.

The study is of high quality and the writing is excellent, starting with the abstract and the introduction, and ending with the conclusions. In this respect, I believe that drafting the press release must have been a fairly straightforward task. As has it been to write this response to the article. It has been extremely difficult to find any flaws.

The conclusions are supported in the paper by solid data, well established and corroborated for years, as is perfectly reflected in the publication’s bibliography. The paper fits very well with the existing theoretical evidence. This is a positive point. In any case, so as not to leave anything out, it might be worth recalling the well-known saying that, when an experiment is carried out knowing in advance what the outcome should be, it is easier to adjust the result. Let me be clear: this is a purely general observation; it in no way seeks to call into question the rigour of the experimental setup, which I consider, based on the description provided, to be very well controlled.

But it does occur to me to add the following “gedanken” scenario. Let us imagine for a moment that, with the same experimental rigour employed here, the result had diverged from the theoretical one, after having reviewed the experimental setup time and time again. What would have happened in such a case?

Finally, at first glance, it may be difficult to determine the precise real-world implications of the significant result obtained. Although, in fact, it does have implications, if only indirectly: it confirms once again, and brilliantly, that the fundamental theories of physics are firmly established. And we can immediately extend this certainty to the vast number of practical real-world applications these theories have, across a wide range of scales and levels.

The result of this work confirms that we are on solid ground, even if we stand (provided our weight does not exceed certain limits) on the slender bridge that is beginning to connect classical gravity with quantum physics.