Dear Dr. Kurtsiefer, The above manuscript has been reviewed by our referees. Acceptance of your paper for publication is likely, but we first ask you to consider carefully the appended comments. With your resubmittal, please include a summary of changes made and a brief response to all recommendations and criticisms. Yours sincerely, Thomas Pattard Managing Editor Physical Review A Email: pra@aps.org http://journals.aps.org/pra/ APS Partners with ORCID Link your identifier via https://authors.aps.org/Profile P.S. We regret the delay in obtaining these reports. PROBLEMS WITH MANUSCRIPT: In reviewing the figures of your paper, we note that the following changes would be needed in order for your figures to conform to the style of the Physical Review. Please check all figures for the following problems and make appropriate changes in the text of the paper itself wherever needed for consistency. * Captions to color PostScript figures should begin with "(Color online)", unless they are to be published in color in print, in which case they should begin "(Color)". ---------------------------------------------------------------------- Second Report of Referee A -- LP14346A/Gulati ---------------------------------------------------------------------- *The authors have made several changes to the manuscript since submission to PRL. One of the changes concerns the title with now reads "Direct generation of an exponentially rising single photon field from parametric conversion in atoms". I think this title is misleading because the initial phrase "direct generation" gives the impression that the single photons are emitted directly, i.e. on the push of a button. However, this is not the case because in the experiment the photon generation is totally probabilistic, although heralded, but with a herald that by necessity comes after the emission of the photon. Therefore I strongly recommend to change the title to something like "Observation of an exponentially rising single-photon field parametrically emitted by an atomic ensemble"*. Such title would more clearly describe the experiment. I recommend publication of the manuscript after the authors have made the necessary change of the title. ---------------------------------------------------------------------- Report of the Third Referee -- LP14346A/Gulati ---------------------------------------------------------------------- I found the manuscript to be an interesting complement to the group’s earlier work, showing important new physics, specifically a photon in an exponentially rising temporal mode in the signal channel. I believe the new version adequately addresses the referees’ concerns, and I recommend it for publication in Physical Review. There are a couple of issues, though, that I would like the authors to think about when working on the revision. The authors say that the timing of the process is that the signal photon populates the intermediate level, which subsequently decays exponentially to the ground level. First of all, I am not sure this is true: both transitions, especially if they are collectively enhanced, may occur in a coherent, simultaneous fashion – see e.g. PRL 75, 3265 (1995). Second, if it is true, a question arises how coherent the rising exponential mode of the photon is. This question is important: only if the mode is coherent is the authors’ claim regarding the light-atom interfacing applicability valid. If the timing is sequential, it may happen that the atom in the intermediate level decoheres before decaying further. In this case, one would still observe exponentially rising timing, but the mode would not be coherent. The coherence of the photon mode can be verified by calculating the autocorrelation of the homodyne photocurrent data – see PRL 109, 033601 (2012) and arXiv:1405.6251 for details. This test (which, I believe, would not require acquisition of any new data) would be helpful in clarifying the underlying physics. As an additional minor issue, I found it difficult to understand the author’s explanation how the exponentially rising mode obtains. To this effect, I found Referee B’s argument much clearer. The authors may think about incorporating it into their paper. I do not insist on the above recommendations.