REVIEW 3 major objections 5 minor 41 references
Applications of maximum likelihood estimations for analyzing photon counts in few atom experiments
T0 review · 3 major / 5 minor · reviewed 2026-08-11 · deepseek-v4-flash
Pith's one-line read Maximum likelihood fits of model fluorescence distributions that account for light-assisted collision loss recover atom-number proportions in a tight optical tweezer to few-percent accuracy from about 600 test events where thresholds fail.
desk verdict Useful model-based MLE recipe for tight-tweezer atom counting, with an in-sample validation that deserves an external test before you trust the numbers elsewhere. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The central object is the recursion relation for the model photon-count distributions $b_{i,k}(T)$: a piecewise-Poisson description in which counts at fixed atom number $i$ are Poisson with rate $\eta_i$, and loss events occur as a memoryless Markov process with constant rates $\gamma_{ij}$ from $i$ to $j$ atoms. Its work is to turn control histograms from known atom numbers into an analytic basis that can be evaluated at any exposure time and atom number, and to provide a closed-form two-atom distribution that separates the collision-loss channels. The fitting machinery is the Poisson log-likelihood maximized by a grid search over the proportions, and, for the event-based variant, an effective likelihood that averages over Poisson fluctuations in the control histograms. Bootstrap resampling supplies the confidence intervals on the fitted proportions. This combination is what allows accurate atom-number extraction from datasets as small as about 600 test events.
What would settle it
Take two-atom control histograms at two different detection-light detunings, fit the model parameters ($\{\eta_j\}$, $\{\gamma_{2j}\}$) to each, then fit a known two-atom mixture recorded at the first detuning using the parameters obtained from the second; a systematic offset beyond the bootstrap confidence intervals would falsify the constant-rate assumption and the claimed few-percent accuracy.
Extended reading notes
Core claim
The paper's central claim is that the photon-count distribution for a known initial number of atoms in a tight tweezer can be modeled sufficiently well for fitting by assuming Poisson emission between loss events and memoryless loss at constant rates $\gamma_{ij}$. For an $i$-atom sample, the distribution $b_{i,k}(T)$ obeys a recursion relation whose first term is the no-loss Poisson contribution and whose second term integrates over the time of the first loss event; for up to two atoms this recursion closes into an explicit formula with detection rates $\eta_0,\eta_1,\eta_2$ and loss rates $\gamma_{20},\gamma_{21}$. Fitting these parameters to control histograms from known atom numbers, then fitting a mixture $f_k(\theta)=N_d\sum_i a_i b_{i,k}$ to a test histogram with the Poisson log-likelihood, determines the atom-number proportions $(a_0,a_1,a_2)$ with errors at the few-percent level from about 600 test and 1400 control events. The same procedure using measured instead of modeled basis distributions works when no model is available, at the cost of requiring better statistics, and the effective likelihood improves event-based fits in that regime.
Load-bearing premise
The method relies on the model in which a fixed number of atoms produces photons at a steady average rate and loses atoms at constant, memory-free rates set by the control data; if the real loss rates depend on conditions the controls do not match, the resulting atom-number proportions will be biased.
Editorial extensions
If this is right
- With roughly 600 test and 1400 control events, atom-number proportions are recovered to within a few percent, a level that threshold and Poisson fits do not reach in the loss-dominated regime.
- The recursion relation extends to three or more atoms, so the method promises to replace rudimentary counting in multi-atom tweezer experiments.
- When no analytic model for the photon-count distributions exists, event-based fitting with the effective likelihood remains usable, at the price of requiring larger datasets.
- The observed insensitivity of the photon-count distributions to atom temperature between 27 and 68 µK supports the use of control data taken under slightly different conditions, as long as the detection light rethermalizes the atoms.
- Maximum likelihood outperforms least-squares for these count histograms, because the Poisson likelihood respects the discrete, non-negative nature of the data.
Reading between the lines
- The fitted loss rates $\gamma_{ij}$ are measurable outputs, so the method could double as a probe of light-assisted-collision dynamics rather than only a counting correction.
- The Poisson assumption per atom-number segment may fail if saturation or high collection efficiency changes the count statistics; the event-based effective-likelihood route would be the fallback in that regime.
- Splitting the exposure into time bins and fitting the recursion jointly would yield time-resolved loss curves, a natural extension that the paper does not discuss.
- A direct stress test would be to vary the detection-beam power after calibration and check whether a single set of loss rates reproduces the observed histograms; if not, the fitted proportions will be biased.
Signed reviews
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper presents a maximum-likelihood method to infer the atom-number distribution of zero, one, or two atoms in a tightly focused optical tweezer from the photon-number distribution measured during fluorescence imaging. The method models the photon-count distribution for a fixed atom number as Poisson, and accounts for light-assisted-collision loss during the exposure via a Markov recursion (Eq. 2), yielding a closed form for up to two atoms (Eq. 3). Model parameters are calibrated on control histograms of known atom numbers, and the unknown proportions are found by maximizing a Poisson log-likelihood over a grid. The paper also studies an event-based variant that uses recorded histograms and an effective likelihood, and it tests the method's accuracy by resampling from experimental test and control pools. The main claims are that the model-based fit achieves few-percent accuracy with about 600 test and 1400 control events, outperforms least-squares fitting, and can be extended to situations without a model.
Significance. If the accuracy claim can be fully supported, this is a useful and practical tool for the cold-atom and quantum-information community. The explicit modeling of light-assisted loss during detection, the comparison of Poisson and effective likelihoods, and the bootstrap error estimates are valuable contributions. The paper is honest about the assumptions made in the model, and the model fits the control histograms well. However, the validation strategy is entirely in-sample, and the treatment of pre-detection loss is inconsistent between the model-based and event-based analyses, so the quantitative few-percent accuracy claim is not yet fully established.
major comments (3)
- [Sec. V A and Sec. VIII B] The accuracy claim is validated only by resampling from the same experimental pool that is used for calibration. Section V A randomly assigns blocks from a single pool to test and control, so both the fitted b_i and the test histograms are drawn from the same underlying conditional distributions. As a result, the reported few-percent RMSE in Figs. 4–6 measures sampling fluctuations under the empirically measured distributions, not the correctness of the model in Sec. III. If Eq. (2) is misspecified—for example, if the light-assisted-collision loss rate is not constant during the exposure or depends on the instantaneous two-atom separation—the calibration in Sec. IV B will absorb the misspecification into effective values of eta_i and gamma_ij, and the test will still appear unbiased. The only external check, Sec. VIII B, varies the initial temperature, but the authors state that the detection light rethermalizes the atoms, so it does not test a different physical regime. I recommend adding an out-of-sample validation, for example simulated data generated from a different (e.g., time-dependent-loss) model, or an independent atom-number measurement, and reporting how the method performs under those conditions.
- [Sec. IV C, Sec. V A, and Appendix A] The treatment of the pre-detection loss probability ell is inconsistent between the model-based and event-based fits. The model-based fit in Sec. IV C uses pure distributions b_i,k, i.e., the photon-count distributions conditional on i atoms being present at the start of the detection exposure. Consequently, the fitted proportions a_i are the actual atom-number distribution at that moment. In contrast, the validation ground truth in Sec. V A is the distribution of the preparation-stage labels (the number of atoms loaded into the tweezers), which is related to the actual distribution by binomial thinning with survival probability 1 - ell. The paper corrects the event-based fits for ell in Appendix A (Eqs. A1–A3) but applies no corresponding correction to the model-based fits before comparing them to the known input proportions. For ell ~ 0.03, this introduces a systematic offset of order 1–5 percentage points in the reported errors, which is not separated from the statistical scatter in Figs. 4–6 and could be mistaken for the distribution-overlap effects discussed in Fig. 5. The authors should state explicitly which quantity (pre-detection label distribution or post-detection actual-atom-number distribution) is being estimated, and apply the appropriate transformation consistently for both model-based and event-based fits in the performance comparison.
- [Sec. VII] The bootstrap error estimation in Sec. VII resamples only the test data and keeps the model distributions b_i,k fixed. The uncertainty in the model parameters (eta_i and gamma_ij), which are themselves estimated from a finite control sample, is therefore not propagated into the reported confidence intervals. The sensitivity to N_c seen in Figs. 4 and 6 shows that this uncertainty is non-negligible for small control sets, and the effective likelihood method of Sec. VI A explicitly attempts to account for it only in the event-based case. To make the bootstrap CIs reliable in general, the authors should either resample the control histograms as well (e.g., a nested bootstrap) or provide an estimate of the additional uncertainty and state the range of N_c over which the fixed-b_i approximation is valid.
minor comments (5)
- [Eq. (6)] The inequality '1 < r < 100' in the definition of the averaging over resamples should read '1 <= r <= 100'.
- [Sec. IV B] The sentence 'This parameter gathers single atom losses...' is grammatically incomplete and would read better as 'This parameter accounts for single-atom losses proceeding from collisions with background gas, from the merge process, and from false 1-atom detection with the EMCCD camera.'
- [Fig. 4] The labels in the inset of Fig. 4 are very small; please enlarge the inset or describe the color scale in the caption so the reader can follow the dependence of Delta on both N_d and N_c.
- [Sec. III A] The symbol T in Eq. (2) is used before it is defined; the general model would benefit from an explicit statement at the start of Sec. III A that T denotes the exposure duration, with T = T_exp later in Sec. III B.
- [Sec. VIII A] The phrase 'the F = 3 -> F' = 3 component was turned off' is ambiguous; more precisely, the frequency component resonant with that transition was turned off, not the transition itself.
Circularity Check
No significant circularity: calibration and inference are separate, and the derivation is self-contained.
full rationale
The paper's central inference is a standard two-stage procedure. Section III derives the model distributions b_{i,k} from two stated assumptions (Poisson photon statistics during loss-free intervals and fixed-rate Markov loss events), giving recursion Eq. (2) and the closed form Eq. (3). The parameters {eta_j} and {gamma_ij} are calibrated in Sec. IV B by maximum-likelihood fits to control histograms with known atom numbers. The unknown atom-number proportions are then inferred by fitting Eq. (5) to a separate test histogram; the fitted parameters a_i are not used in the calibration, so the inference is not defined in terms of its target. The performance test in Sec. V uses a random train/test split of the experimental pool: control histograms determine b_{i,k}, and independent test histograms with known mixture proportions are fit to recover a_i. This measures end-to-end accuracy under the actual data-generating process. The self-citations (e.g., Refs. [12,18,21-24] for experimental procedures) are not load-bearing for the derivation; they describe the apparatus rather than justify the statistical method. The in-sample limitation noted by the skeptic—that control and test data share the same experimental conditions—is a generalizability caveat, not a circular step, and the paper explicitly acknowledges the temperature-insensitivity is design-dependent. No equation or fitted parameter is renamed as a prediction, and no uniqueness claim is imported from prior work by the authors. The validation would detect systematic model bias because the test histograms are drawn from the true distributions with known atom-number labels, independent of the control fits. Overall, the derivation chain is self-contained and non-circular.
Assumptions & free parameters
free parameters (6)
- eta_0 =
not reported in text
- eta_1 =
not reported in text
- eta_2 =
not reported in text
- gamma_20 =
not reported in text
- gamma_21 =
not reported in text
- ell =
0.8% to 2.9% in examples
assumptions (6)
- domain assumption Photon counts for a fixed atom number are Poisson distributed.
- domain assumption Loss events occur at fixed rates gamma_ij, independent of history.
- domain assumption Single-atom loss during the 3.5 ms exposure is negligible (gamma_10 = 0).
- domain assumption No additional two-body loss beyond the modeled gamma_20 and gamma_21 channels.
- domain assumption Control histograms are representative of the conditions in the unknown experiment.
- standard math Standard maximum likelihood and bootstrap theory.
Cite this review
Pith. "Pith review of Applications of maximum likelihood estimations for analyzing photon counts in few atom experiments." pith.science (2026). https://pith.science/paper/BDYNWR55
@misc{pith2026241217434,
author = {Pith},
title = {Pith review of: Applications of maximum likelihood estimations for analyzing photon counts in few atom experiments},
year = {2026},
howpublished = {\url{https://pith.science/paper/BDYNWR55}},
note = {Machine review of arXiv:2412.17434}
}
read the original abstract
We present a method for determining the atom number distribution of few atoms in a tight optical tweezer from their fluorescence distributions. In the tight tweezer regime, the detection light causes rapid atom loss due to light-assisted collisions. This in turn leads to non-Poissonian and overlapping fluorescence distributions for different initial atom numbers, and commonly used threshold techniques fail. We use maximum likelihood estimation algorithms to fit model distributions that account for the atom loss. This gives accurate atom number distributions for relatively few experimental runs (about 600 is sufficient) to sample a photon number distribution. We show that the method can be extended to situations when the photon number distributions for known initial atom numbers cannot be modeled, at the cost of requiring a higher number of experimental runs.
Figures
Figures from the paper (5 more)
Reference graph
Works this paper leans on
-
[1]
T. Grünzweig, A. Hillard, M. McGovern, and M. F. An- dersen, Nat. Phys.6, 951 (2010)
work page 2010
-
[2]
L. R. Liu, J. D. Hood, Y. Yu, J. T. Zhang, N. R. Hutzler, 11 T. Rosenband, and K.-K. Ni, Science360, 900 (2018)
work page 2018
-
[3]
M. Weyland, S. S. Szigeti, R. A. B. Hobbs, P. Ruk- sasakchai, L. Sanchez, and M. F. Andersen, Phys. Rev. Lett. 126, 083401 (2021)
work page 2021
-
[4]
M. F. Andersen, Advances in Physics: X 7, 2064231 (2022)
work page 2022
-
[5]
C. Weitenberg, S. Kuhr, K. Mølmer, and J. F. Sherson, Phys. Rev. A84, 032322 (2011)
work page 2011
-
[6]
T. Graham, Y. Song, J. Scott, C. Poole, L. Phuttitarn, K. Jooya, P. Eichler, X. Jiang, A. Marra, B. Grinke- meyer, M. Kwon, M. Ebert, J. Cherek, M. T. Licht- man, M. Gillette, J. Gilbert, D. Bowman, T. Ballance, C. Campbell, E. D. Dahl, O. Crawford, N. S. Blunt, B. Rogers, T. Noel, and M. Saffman, Nature604, 457 (2022)
work page 2022
-
[7]
Bernien, S
H. Bernien, S. Schwartz, A. Keesling, H. Levine, A. Om- ran, H. Pichler, S. Choi, A. S. Zibrov, M. Endres, M. Greiner, V. Vuletić, and M. D. Lukin, Nature551, 579 (2017)
2017
-
[8]
Browaeys and T
A. Browaeys and T. Lahaye, Nature Physics 16, 132 (2020)
2020
Show all 41 references
-
[9]
Ðorđević, P
T. Ðorđević, P. Samutpraphoot, P. L. Ocola, H. Bernien, B. Grinkemeyer, I. Dimitrova, V. Vuletić, and M. D. Lukin, Science373, 1511 (2021)
2021
-
[10]
T. Wilk, A. Gaëtan, C. Evellin, J. Wolters, Y. Miroshny- chenko, P. Grangier, and A. Browaeys, Phys. Rev. Lett. 104, 010502 (2010)
2010
-
[11]
Fuhrmanek, Y
A. Fuhrmanek, Y. R. P. Sortais, P. Grangier, and A. Browaeys, Phys. Rev. A82, 023623 (2010)
2010
-
[12]
L. A. Reynolds, E. Schwartz, U. Ebling, M. Weyland, J. Brand, and M. F. Andersen, Phys. Rev. Lett.124, 073401 (2020)
2020
-
[13]
D. S. Grün, S. J. M. White, A. Ortu, A. Di Carli, H. Edri, M. Lepers, M. J. Mark, and F. Ferlaino, Phys. Rev. Lett. 133, 223402 (2024)
2024
-
[14]
J. T. Zhang, Y. Yu, W. B. Cairncross, K. Wang, L. R. B. Picard, J. D. Hood, Y.-W. Lin, J. M. Hutson, and K.-K. Ni, Phys. Rev. Lett.124, 253401 (2020)
2020
-
[15]
S. Kuhr, W. Alt, D. Schrader, I. Dotsenko, Y. Mirosh- nychenko, A. Rauschenbeutel, and D. Meschede, Phys. Rev. A72, 023406 (2005)
2005
-
[16]
W. Xu, A. V. Venkatramani, S. H. Cantu, T. Šumarac, V. Klüsener, M. D. Lukin, and V. Vuletić, Phys. Rev. Lett. 127, 050501 (2021)
2021
-
[17]
Bloch, B
D. Bloch, B. Hofer, S. R. Cohen, A. Browaeys, and I. Ferrier-Barbut, Phys. Rev. Lett.131, 203401 (2023)
2023
-
[18]
McGovern, A
M. McGovern, A. J. Hilliard, T. Grünzweig, and M. F. Andersen, Opt. Lett.36, 1041 (2011)
2011
-
[19]
Y. Meng, C. Liedl, S. Pucher, A. Rauschenbeutel, and P. Schneeweiss, Phys. Rev. Lett.125, 053603 (2020)
2020
-
[20]
Sompet, S
P. Sompet, S. S. Szigeti, E. Schwartz, A. S. Bradley, and M. F. Andersen, Nature communications10, 1 (2019)
2019
-
[21]
A. V. Carpentier, Y. H. Fung, P. Sompet, A. J. Hilliard, T. G. Walker, and M. F. Andersen, Laser Phys. Lett. 10, 125501 (2013)
2013
-
[22]
A. J. Hilliard, Y. H. Fung, P. Sompet, A. V. Carpentier, and M. F. Andersen, Phys. Rev. A91, 053414 (2015)
2015
-
[23]
Y. H. Fung, P. Sompet, and M. F. Andersen, Technolo- gies 4 (2016)
2016
-
[24]
Y. H. Fung and M. F. Andersen, New J. Phys.17, 073011 (2015)
2015
-
[25]
J. W. Goodman,Statistical Optics (John Wiley & Sons Inc., 2015)
2015
-
[26]
Grünzweig, M
T. Grünzweig, M. McGovern, A. J. Hillard, and M. F. Andersen, Quantum Inf. Process.10, 925 (2011)
2011
-
[27]
S. G. W. Stefany Coxe and L. S. Aiken, Journal of Per- sonality Assessment91, 121 (2009)
2009
-
[28]
We use the MLE function of MATLAB for this
-
[29]
Raikov, Comptes Rendus de l’Academie des Sciences de l’URSS14, 9 (1937)
D. Raikov, Comptes Rendus de l’Academie des Sciences de l’URSS14, 9 (1937)
1937
-
[30]
Barlow,Statistics: A Guide to the Use of Statistical Methods in the Physical Sciences (John Wiley & Sons Inc., 1989)
R. Barlow,Statistics: A Guide to the Use of Statistical Methods in the Physical Sciences (John Wiley & Sons Inc., 1989)
1989
-
[31]
J. R. Taylor,An Introduction to Error Analysis, 2nd ed. (University Science Books, 1997)
1997
-
[32]
While more sophisticated fitting algorithms would be able to perform this fit, we chose this simple approach as it can also serve as a robust method when directly fitting to experimentally measured control distributions with no functional model, as described in Sec. VI
-
[33]
Sompet, A
P. Sompet, A. V. Carpentier, Y. H. Fung, M. McGovern, and M. F. Andersen, Phys. Rev. A88, 051401 (2013)
2013
-
[34]
Glüsenkamp, Journal of Instrumentation15, P01035 (2020)
T. Glüsenkamp, Journal of Instrumentation15, P01035 (2020)
2020
-
[35]
Bohm and G
G. Bohm and G. Zech, Nucl. Instrum. Methods Phys. Res. A: Accel. Spectrom. Detect. Assoc. Equip.691, 171 (2012)
2012
-
[36]
Bohm and G
G. Bohm and G. Zech, Nucl. Instrum. Methods Phys. Res. A: Accel. Spectrom. Detect. Assoc. Equip.748, 1 (2014), arXiv:1309.1287
2014 arXiv
- [37]
-
[38]
Glüsenkamp, Eur
T. Glüsenkamp, Eur. Phys. J. Plus133, 218 (2018)
2018
-
[39]
C. A. Argüelles, A. Schneider, and T. Yuan, Journal of High Energy Physics2019, 30 (2019)
2019
-
[40]
As a result the average error starts being located towards the upped edge or even outside of the confidence interval
When the fit fails in a small region ofθ-space, the average error increases without a significant impact on the 1σ confidence interval. As a result the average error starts being located towards the upped edge or even outside of the confidence interval
-
[41]
M. R. Chernick,Bootstrap Methods: A Guide for Practi- tioners and Researchers(John Wiley & Sons Inc., 2007)
2007
Reviewed August 11, 2026 · model on record in the stance chip above.
Discussion (0). Continue with ORCID to comment.