Re: LD14306 Excitation of a single atom with exponentially rising light pulses by Syed Abdullah Aljunid, Gleb Maslennikov, Yimin Wang, et al. Dear Dr. Kurtsiefer, The above manuscript has been reviewed by our referees. We ask you to consider the appended comments from the reports. While we cannot make a definite commitment, the probable course of action if you choose to resubmit is indicated below. ( ) Acceptance, if the editors can judge that all or most of the criticism has been met. (x) Return to the previous Referees A and B for review if available. ( ) Submittal to new referee(s) for review. With any resubmittal, please include a summary of changes made and a brief response to all recommendations and criticisms. Yours sincerely, Frank Narducci Adjunct Associate Editor Physical Review Letters Email: prl@aps.org http://prl.aps.org/ APS Partners with ORCID Link your identifier via https://authors.aps.org/Profile EDITORIAL EVENTS 2013 DAMOP Meeting (Quebec City, Quebec, Canada) SYMPOSIUM TO RECOGNIZE GEORGE BASBAS' 33 YEARS AS A PRL EDITOR Tuesday, June 4, 2013, 7:30-9:30PM Light refreshments and cocktails to follow Room 301AB, Quebec Convention Centre TUTORIAL FOR AUTHORS AND REFEREES (Session K3) Wednesday, June 5, 2013, 4:00-5:30PM Room 205AB, Quebec Convention Centre MEET THE APS JOURNAL EDITORS Thursday, June 6, 2013, 4:00-5:30PM Reception Refreshments Foyer 206, Quebec Convention Centre P.S. Referee A is incorrect about the length of your manuscript. According to our length count, your manuscript currently fits within the length limit of PRL. ---------------------------------------------------------------------- Report of Referee A -- LD14306/Aljunid ---------------------------------------------------------------------- The report by the group of Kurtsiefer reports on studies of single atoms with various excitation beams. they successfully observe Rabi oscillations and fit their results with the Weisskopf-Wigner model. The work is very complete and I have no questions about the experimental results. small errors (missing definition of symbols in Fig 5) should be fixed. also the paper is very long - much longer than PRL limit. Fig 2 and 3 could be combined and Fig 1 can be moved to supplementary material. Saying that, the work is very "narrow-fielded". though interesting to the researchers from the trapped atoms/ions community, it has little appeal to the broader field of QED or atomic physics. If the authors can explain why their experiments are significant, I would recommend this work to be published in PRL. ---------------------------------------------------------------------- Report of Referee B -- LD14306/Aljunid ---------------------------------------------------------------------- In their manuscript "Excitation of a single atom with exponentially rising light pulses," Aljunid et. al describe measurements of the excitation probability of a single, trapped Rb atom when subjected to square and exponentially rising optical pulses. The pulses are in a coherent state and are characterized by small average photon numbers. The work is interesting in that it provides direct experimental evidence that for small photon number, excitation probability is enhanced when the excitation temporal profile is the time-reversed Weisskopf-Wigner profile of spontaneous emission. With this work, the authors take a significant step towards efficient excitation of an atom in free space by a small photon number light field. The work is well-done and the most of the main claims are well-supported. However, the authors' claim that they "clearly observe Rabi oscillations" is not supported for an exponentially rising pulse shape. In Figure 4, Rabi oscillations are clear for a square pulse, although the data is close to undersampled. The reasonably good agreement between the theory curve and data for the exponential pulse is suggestive; however, the magnitude of the error bars relative to the amplitude of a supposed oscillation makes it impossible to claim that they are observing Rabi oscillations. Additionally, the authors state: "The observation of Rabi oscillations demonstrates a possibility of using a single atom for low photon number optical switching [17¡V19]." Even if the error bars were small enough to conclude that Rabi oscillations were seen in this data (which I don't think they are), I don't believe a 60% maximum excitation probability at the peak would be sufficient perform low photon number optical switching. Additionally photon numbers of 1300 per pulse are not extremely low. I think the claim in this sentence is stronger than the data can support. Finally, for the square pulse curve, why does the model deviate so noticeably from the data for t>0, but not t<0? A few more minor points must also be addressed: 1) How "square" are the square pulses? A discussion of the risetime of the square pulses relative to their duration would elucidate exactly how different the square pulse is from the exponentially rising pulse. 2) Figure 6 demonstrates convincingly that for average photon numbers of about 2-3, exponentially rising pulses give higher excitation probability than square pulses. However, the agreement with theory is poor and the authors suggest this is due to residual motion of the atom. After looking at reference 21, I find this explanation plausible; however, I think a bit more explanation is in order (i.e. what difference would one expect based on the parameters of the system?). 3) How were the average photon numbers for the data displayed in Fig. 6 chosen? Are these the average numbers which give rise to the maximum difference between the square and exponential pulse excitation probabilities? By looking at the upper two panels of Fig 5, it seems that a larger average photon number would enhance this difference. Is this true? This should be made clearer in the text.