REVIEW 3 major objections 3 minor 41 references
From classical probability densities to quantum states: quantization of Gaussians for arbitrary orderings
T0 review · 3 major / 3 minor · reviewed 2026-08-12 · deepseek-v4-flash
Pith's one-line read By quantizing a Gaussian phase-space density with $s$-ordered creation-annihilation operator orderings, the paper shows a valid quantum state results exactly when the inverse variance $\lambda \le (1+s)^{-1}$, and for antinormal ordering…
desk verdict The s-ordered Gaussian critical line is real and clean; the paper overreaches when it extends the result to arbitrary distributions on a false Fock-diagonality premise. 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 engine is the $s$-ordered Cahill-Glauber quantizer $\hat{\Omega}_s(f)=\int d^2\xi\,\tilde f(\xi)\,e^{\xi a^\dagger}e^{-\bar\xi a}e^{-\frac{1-s}{2}|\xi|^2}$, which realizes normal ($s=1$), symmetric ($s=0$), and antinormal ($s=-1$) ordering of annihilation and creation operators. Applied to the Gaussian, its Fourier transform $\tilde\rho_\lambda(\xi)=\pi^{-1}e^{-|\xi|^2/2\lambda}$ combines with the quantizer's Gaussian kernel; the angular integral enforces $n=m$, so the Fock-basis matrix is diagonal, and the remaining radial integrals sum to the geometric formula for $\rho_{nn}$. The critical line $\lambda_c(s)=(1+s)^{-1}$ is where the base of the geometric series changes sign, separating positive from non-positive spectra.
What would settle it
Take a Gaussian with nonzero mean or unequal variances, for example $\rho(q,p)\propto\exp[-q^2/(2\sigma_q^2)-p^2/(2\sigma_p^2)]$ with $\sigma_q^2+\sigma_p^2<1+s$ or a nonzero mean, compute its $s$-ordered quantization in the Fock basis, and check whether off-diagonal matrix elements vanish and whether positivity fails exactly at the claimed bound. Any non-vanishing off-diagonal element, or a positive operator outside the bound, would refute the general criterion; the centered radial Gaussian formula would remain unaffected.
Extended reading notes
Core claim
The paper's central result is that the $s$-ordered Cahill-Glauber quantization of the Gaussian $\rho_\lambda(z)=\frac{\lambda}{\pi}e^{-2\lambda|z|^2}$ is diagonal in the Fock basis, with entries $\rho_{nn}=\frac{2\lambda}{1+(1-s)\lambda}\left(\frac{1-(1+s)\lambda}{1+(1-s)\lambda}\right)^n$ and $\rho_{nm}=0$ for $n\neq m$. This operator is a valid density matrix, positive and of trace one, if and only if $\lambda\le(1+s)^{-1}$ for $s>-1$; for $s=-1$ every $\lambda$, including the $\lambda\to\infty$ delta limit, gives a valid state, with $\hat{\Omega}_{-1}(\delta)=|0\rangle\langle0|$. The Weyl symmetric case is recovered at $s=0$, with critical value $\lambda_c=1$, matching the Heisenberg uncertainty principle; the paper further derives ordering-dependent necessary conditions $\Delta_q^2+\Delta_p^2\ge 1+s$ for arbitrary phase-space densities under the assumption that the quantized operator is diagonal in the Fock basis.
Load-bearing premise
The appendices assume that every classical probability density turns into an operator that is diagonal in the harmonic-oscillator basis after quantization; this is true for the centered radial Gaussian, but not for shifted or squeezed densities, so the paper's general variance-sum criterion for arbitrary densities rests on that assumption.
Editorial extensions
If this is right
- For symmetric Weyl ordering ($s=0$), a Gaussian maps to a valid state only for $\lambda\le1$, i.e. phase-space variance $(2\lambda)^{-1}\ge1/2$; at $\lambda=1$ it becomes the coherent-state projector $|0\rangle\langle0|$, and sharper Gaussians are unphysical.
- For every $s>-1$ there is a sharpness ceiling: inverse variances above $(1+s)^{-1}$ produce a Hermitian, normalized but non-positive operator, so the classical density has no quantum counterpart.
- For antinormal ordering ($s=-1$) no such ceiling exists: the $\delta$-function is mapped to the vacuum state, so perfectly localized classical data remain quantizable.
- The temperature mapping shifts with $s$: a thermal Wigner function with inverse temperature $\beta=(1+s)^{-1}$ corresponds exactly to the critical density, so negative-temperature classical Gaussians are precisely those with $\lambda>\lambda_c(s)$.
- For arbitrary densities the paper argues $\Delta_q^2+\Delta_p^2\ge1+s$ is necessary for positivity, reducing to $\Delta q\,\Delta p\ge(1+s)/2$ when the position and momentum variances are equal.
Reading between the lines
- This suggests a practical probe: prepare a classical phase-space distribution with controlled variance and measure whether the quantized state has negative eigenvalues; the boundary should move with the ordering parameter $s$ according to $\lambda_c(s)=(1+s)^{-1}$.
- Because the Fock-diagonal proof exploits the radial symmetry of the Gaussian, anisotropic or displaced Gaussians may develop off-diagonal Fock elements; an immediate extension would check whether the same threshold or a modified variance inequality governs those cases.
- The antinormal map sends the delta function to the vacuum state, indicating that the correspondence cannot preserve all classical information at extreme localization; multiple classical densities must collapse onto the same low-rank quantum image.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper studies the s-ordered Cahill-Glauber quantization of the centered Gaussian ρ_λ(z) = (λ/π)exp(-2λ|z|²), together with the γ-ordered Weyl quantization of the same family. The explicit Fock-basis calculation yields ρ_nn = (2λ)/(1+(1-s)λ) [(1-(1+s)λ)/(1+(1-s)λ)]^n, from which the authors derive the critical line λ_c(s) = (1+s)^{-1}; for s = -1 the critical value diverges and the δ-function maps to |0⟩⟨0|. The paper further claims general necessary conditions for arbitrary probability densities, Δ_q²+Δ_p² ≥ 1 for Weyl quantization and Δ_q²+Δ_p² ≥ 1+s for s-ordering, based on Appendices B.2 and C.4.
Significance. The Gaussian-specific result is correct, and the computations in Appendices B.1 and C.2 are explicit and checkable. The identification of the antinormal ordering as the one for which every classical distribution, including a delta, has a quantum image is a useful and concrete observation, and it can be supported independently by the antinormal P-representation. The general uncertainty-type statements, however, are not established by the arguments given: they rest on a false Fock-diagonality assumption for non-radial distributions. The paper's value therefore lies in the Gaussian critical line, not in the claimed general theorems, and the latter need to be either proved by covariance-matrix methods or removed/restricted.
major comments (3)
- [Appendices B.2 and C.4; main text after Eq. (13) and after Eq. (22)] The blanket assertion in Appendix B.2 (repeated in C.4) that the Weyl or s-ordered quantization of an arbitrary probability density is diagonal in the Fock basis is false. The argument in Appendix C.2 works because the Gaussian (19) is radial: the angular integral forces k = 0. For a displaced Gaussian, or for a centered anisotropic Gaussian, the quantized operator has off-diagonal Fock elements (the latter is a squeezed state). Consequently the vanishing conditions (33), the covariance matrix (37), and the main-text statements "if Δ_q²+Δ_p² < 1 then Ω̂(ρ) is not positive" and its s-ordered analogue are not proven for general densities. These claims should be proved by a covariance-matrix/Gaussification argument that does not presuppose Fock diagonality, or explicitly restricted to centered radially symmetric distributions.
- [Appendix C.4, Eqs. (53)-(62)] The derivation of the s-dependent uncertainty condition contains a factor-1/2 error: q̂² = (a² + a†² + 2N + 1)/2, so Δ = tr(q̂²Ω_s(f)) equals (1/2)tr({a,a†}Ω_s(f)), not tr({a,a†}Ω_s(f)) as written in Eq. (53). Using the corrected expression together with Ω^{-1}_{-s}({a,a†}) = 2z\bar z - s reproduces the final inequality Δ_q²+Δ_p² ≥ 1+s, but the intermediate displayed inequality (61) with 1/2+s is not consistent with Eq. (62). Please correct the intermediate step so that the displayed derivation is coherent.
- [Main text after Eq. (21)] Because the general condition in Appendix C.4 is not established, the sentence claiming that for the antinormal ordering any classical probability distribution can have a quantum analogue does not follow from the preceding derivation. The statement is nevertheless true: for s = -1 the quantizer (17) gives Ω_{-1}(f) = ∫ d²z f(z)|z⟩⟨z|, which is positive for every nonnegative f. The paper should present this direct argument rather than deriving the statement from the faulty general condition.
minor comments (3)
- [Summary and conclusions] The final paragraph says "only for λ ≥ λc we get a quantum state", which contradicts Eq. (20), Fig. 1, and the earlier correct statement λ ≤ λ_c(s). Please correct the inequality direction in the conclusions.
- [Throughout] The manuscript contains numerous typos and grammatical slips ('Guassian', 'Summry', 'annihalation', 'perfomed', 'alings', 'eiegenvalues', 'for the reminder', missing spaces in expressions such as 'values ofλ < λc'); a careful proofreading pass is needed.
- [Appendix C.4] The notation Ω^{-1}_{-s} is confusing because the dequantizer is not the inverse operator in the usual sense but the quantizer with s replaced by -s; please clarify this notation at first use.
Circularity Check
No significant circularity: the Gaussian critical line λ_c(s)=(1+s)^{-1} follows from explicit Fock-basis integrals with no fitted parameters; the flagged weakness is a false general-diagonality premise in Apps. B.2/C.4, which is a correctness issue, not circularity.
full rationale
The central claim, Eq. (20), is derived self-containedly: the Gaussian's Fourier transform Eq. (43) is inserted into the Cahill-Glauber map Eq. (42), the angular integral forces the Fock matrix to be diagonal for the radial Gaussian, and the radial integral yields ρ_nn. Positivity of these eigenvalues gives λ ≤ λ_c(s)=(1+s)^{-1}, and the δ→|0⟩⟨0| limit for s=-1 is the direct λ→∞ limit of the same formula. No parameter is fitted to data and no 'prediction' is a renamed input. The Weyl case is the same calculation at s=0. The temperature-shift remark in App. C.3 is a direct comparison of Fourier transforms, not a fit or a self-citation. The only self-citation, Ref. [38] (Lizzi & Vitale), is background on star-product bases and is not load-bearing. The manuscript's general variance conditions in Apps. B.2 and C.4 rely on the premise that the quantization of an arbitrary probability density is diagonal in the Fock basis ('Let us start with a probability distribution ρ(q,p). Its Weyl-symmetric quantization, i.e. Ω(f), is diagonal in the Fock basis'), which is unproven and in fact false for non-radial or displaced distributions; this is a missing-support/correctness flaw in the general statement, but it is not circular because the Gaussian theorem does not depend on that premise. No equation reduces to its own input by construction.
Assumptions & free parameters
assumptions (5)
- standard math Standard single-mode continuous-variable quantum mechanics: Hilbert space L2(R), canonical commutation relations [q,p]=i, Fock basis |n> with N |n> = n |n>.
- domain assumption Weyl quantization map Eq. (10) and Cahill-Glauber s-ordered map Eq. (17) are valid quantizers/dequantizers satisfying the trace orthogonality Eq. (8).
- standard math Baker-Campbell-Hausdorff formula e^{A+B} = e^{-[A,B]/2} e^A e^B for operators with c-number commutator.
- standard math Covariance matrix positivity criterion V + iOmega >= 0 characterizes valid Gaussian states (Eq. (23)).
- ad hoc to paper The quantization of an arbitrary probability density is diagonal in the Fock basis.
Cite this review
Pith. "Pith review of From classical probability densities to quantum states: quantization of Gaussians for arbitrary orderings." pith.science (2026). https://pith.science/paper/6VHFEOA3
@misc{pith2026241114043,
author = {Pith},
title = {Pith review of: From classical probability densities to quantum states: quantization of Gaussians for arbitrary orderings},
year = {2026},
howpublished = {\url{https://pith.science/paper/6VHFEOA3}},
note = {Machine review of arXiv:2411.14043}
}
abstract
The primary focus of this work is to investigate how the most emblematic classical probability density, namely a Gaussian, can be mapped to a valid quantum states. To explore this issue, we consider a Gaussian whose squared variance depends on a parameter $\lambda$. Specifically, depending on the value of $\lambda$, we study what happens in the classical-quantum correspondence as we change the indeterminacy of the classical particle. Furthermore, finding a correspondence between a classical state and a quantum state is not a trivial task. Quantum observables, described by Hermitian operators, do not generally commute, so a precise ordering must be introduced to resolve this ambiguity. In this work, we study two different arbitrary orderings: the first is an arbitrary ordering of the position and momentum observables; the second, which is the main focus of the present work, is an arbitrary ordering of the annihilation and creation operators. In this latter case, we find the interesting result that even a $\delta$-function, which in general has no quantum correspondence, can be mapped into a valid quantum state for a particular ordering, specifically the antinormal one (all creation operators are to the right of all annihilation operators in the product). This means that the Gaussian probability density corresponds to a valid quantum state, regardless of how localized classical particles are in phase space.
Figures
Reference graph
Works this paper leans on
-
[1]
Weyl, The Theory of Groups and Quantum Mechanics
H. Weyl, The Theory of Groups and Quantum Mechanics . Dover, New York, 1931
work page 1931
-
[2]
M. Suleymanov and M. Zubkov, “Wigner–Weyl formalism and the propagator of Wilson fermions in the presence of varying external electromagnetic field,” Nuclear Physics B 938 (2019) 171–199
work page 2019
-
[3]
Applications of the Weyl-Wigner formalism to noncommutative geometry,
A. Zampini, “Applications of the Weyl-Wigner formalism to noncommutative geometry,” other thesis, Universit` a di NapoliFederico II, 5, 2005
work page 2005
-
[4]
The Wigner representation of quantum mechanics,
V. Tatarski ˘ ı, “The Wigner representation of quantum mechanics,”Soviet Physics Uspekhi 26 no. 4, (1983) 311
work page 1983
-
[5]
On the Quantum Correction For Thermodynamic Equilibrium,
E. P. Wigner, “On the Quantum Correction For Thermodynamic Equilibrium,” Phys. Rev. 40 (1932) 749
work page 1932
-
[6]
C. Ferrie and J. Emerson, “Frame representations of quantum mechanics and the necessity of negativity in quasi-probability representations,” Journal of Physics A: Mathematical and Theoretical 41 no. 35, (July, 2008) 352001. http://dx.doi.org/10.1088/1751-8113/41/35/352001
-
[7]
C. Ferrie, “Quasi-probability representations of quantum theory with applications to quantum information science,” Reports on Progress in Physics 74 no. 11, (Oct., 2011) 116001. http://dx.doi.org/10.1088/0034-4885/74/11/116001
-
[8]
Negative quasi-probability as a resource for quantum computation,
V. Veitch, C. Ferrie, D. Gross, and J. Emerson, “Negative quasi-probability as a resource for quantum computation,” New Journal of Physics 14 no. 11, (Nov., 2012) 113011. http://dx.doi.org/10.1088/1367-2630/14/11/113011
Show all 41 references
-
[9]
Positive Wigner Functions Render Classical Simulation of Quantum Computation Efficient,
A. Mari and J. Eisert, “Positive Wigner Functions Render Classical Simulation of Quantum Computation Efficient,” Physical Review Letters 109 no. 23, (Dec., 2012) 230503. http://dx.doi.org/10.1103/PhysRevLett.109.230503
2012 doi
-
[10]
B. T. Gard, K. R. Motes, J. P. Olson, P. P. Rohde, and J. P. Dowling, An Introduction to Boson-Sampling, p. 167–192. WORLD SCIENTIFIC, June, 2015. http://dx.doi.org/10.1142/9789814678704_0008
2015 doi
-
[11]
Quantum computational advantage using photons,
H.-S. Zhong, H. Wang, Y.-H. Deng, M.-C. Chen, L.-C. Peng, Y.-H. Luo, J. Qin, D. Wu, X. Ding, Y. Hu, P. Hu, X.-Y. Yang, W.-J. Zhang, H. Li, Y. Li, X. Jiang, L. Gan, G. Yang, L. You, Z. Wang, L. Li, N.-L. Liu, C.-Y. Lu, and J.-W. Pan, “Quantum computational advantage using photo...
2020 doi
-
[12]
Quantum sampling problems, BosonSampling and quantum supremacy,
A. P. Lund, M. J. Bremner, and T. C. Ralph, “Quantum sampling problems, BosonSampling and quantum supremacy,” npj Quantum Information 3 no. 1, (Apr., 2017)
2017
-
[13]
Ordered expansions in boson amplitude operators,
K. E. Cahill and R. J. Glauber, “Ordered expansions in boson amplitude operators,” Phys. Rev. 177 (1969) 1857–1881
1969
-
[14]
Quantum non-Gaussianity witnesses in phase space,
C. Hughes, M. G. Genoni, T. Tufarelli, M. G. A. Paris, and M. S. Kim, “Quantum non-Gaussianity witnesses in phase space,” Phys. Rev. A 90 (Jul, 2014) 013810. https://link.aps.org/doi/10.1103/PhysRevA.90.013810. 14
2014 doi
-
[15]
http://dx.doi.org/10.1038/s41534-017-0018-2
-
[16]
A measure of non-Gaussianity for quantum states,
J. S. Ivan, M. S. Kumar, and R. Simon, “A measure of non-Gaussianity for quantum states,” Quantum information processing 11 no. 3, (2012) 853–872
2012
-
[17]
Negativity of quasiprobability distributions as a measure of nonclassicality,
K. C. Tan, S. Choi, and H. Jeong, “Negativity of quasiprobability distributions as a measure of nonclassicality,” Physical review letters 124 no. 11, (2020) 110404
2020
-
[18]
Measuring nonclassicality of bosonic field quantum states via operator ordering sensitivity,
S. De Bievre, D. B. Horoshko, G. Patera, and M. I. Kolobov, “Measuring nonclassicality of bosonic field quantum states via operator ordering sensitivity,” Physical Review Letters 122 no. 8, (2019) 080402
2019
-
[19]
Coherent representation of fields and deformation quantization,
J. Berra-Montiel and A. Molgado, “Coherent representation of fields and deformation quantization,” International Journal of Geometric Methods in Modern Physics 17 no. 11, (2020) 2050166
2020
-
[20]
Star product representation of coherent state path integrals,
J. Berra-Montiel, “Star product representation of coherent state path integrals,” The European Physical Journal Plus 135 no. 11, (2020) 906
2020
-
[21]
Theory and application of the quantum phase-space distribution functions,
H.-W. Lee, “Theory and application of the quantum phase-space distribution functions,” Physics Reports 259 no. 3, (1995) 147–211. https://doi.org/10.1016/0370-1573(95)00007-4
1995 doi
-
[22]
Hilbert space representation of the minimal length uncertainty relation,
A. Kempf, G. Mangano, and R. B. Mann, “Hilbert space representation of the minimal length uncertainty relation,” Phys. Rev. D 52 (1995) 1108–1118, arXiv:hep-th/9412167
1995 arXiv
-
[23]
Noncommutative space-time, stringy space-time uncertainty principle, and density fluctuations,
R. Brandenberger and P.-M. Ho, “Noncommutative space-time, stringy space-time uncertainty principle, and density fluctuations,” Phys. Rev. D 66 (2002) 023517, arXiv:hep-th/0203119
2002 arXiv
-
[24]
Noncommutative geometry as a framework for unification of all fundamental interactions including gravity. Part I.,
A. Chamseddine and A. Connes, “Noncommutative geometry as a framework for unification of all fundamental interactions including gravity. Part I.,” Fortschritte der Physik 58 no. 6, (May, 2010) 553–600. http://dx.doi.org/10.1002/prop.201000069
2010 doi
-
[25]
Spectral Noncommutative Geometry, Standard Model and all that,
A. Devastato, M. Kurkov, and F. Lizzi, “Spectral Noncommutative Geometry, Standard Model and all that,” Int. J. Mod. Phys. A 34 no. 19, (2019) 1930010, arXiv:1906.09583 [hep-th]
2019 arXiv
-
[26]
Missing the point in noncommutative geometry,
N. Huggett, F. Lizzi, and T. Menon, “Missing the point in noncommutative geometry,” Synthese 199 no. 1-2, (2021) 4695–4728, arXiv:2006.13035 [physics.hist-ph]
2021 arXiv
-
[27]
Quantum information with Gaussian states,
X. Wang, T. Hiroshima, A. Tomita, and M. Hayashi, “Quantum information with Gaussian states,” Physics Reports 448 no. 1–4, (Aug., 2007) 1–111. http://dx.doi.org/10.1016/j.physrep.2007.04.005
2007 doi
-
[28]
Gaussian quantum information,
C. Weedbrook, S. Pirandola, R. Garc ´ ıa-Patr´ on, N. J. Cerf, T. C. Ralph, J. H. Shapiro, and S. Lloyd, “Gaussian quantum information,” Reviews of Modern Physics 84 no. 2, (May,
-
[29]
Conditional and unconditional Gaussian quantum dynamics,
M. G. Genoni, L. Lami, and A. Serafini, “Conditional and unconditional Gaussian quantum dynamics,” Contemporary Physics 57 no. 3, (2016) 331–349
2016
-
[30]
Continuous variable quantum information: Gaussian states and beyond,
G. Adesso, S. Ragy, and A. R. Lee, “Continuous variable quantum information: Gaussian states and beyond,” Open Systems & Information Dynamics 21 no. 01n02, (2014) 1440001
2014
-
[31]
Quantum mechanics as a statistical theory,
J. E. Moyal, “Quantum mechanics as a statistical theory,” Proc. Cambr. Phil. Soc. 45 (1949) 99
1949
-
[32]
Learning quantum states of continuous variable systems,
F. A. Mele, A. A. Mele, L. Bittel, J. Eisert, V. Giovannetti, L. Lami, L. Leone, and S. F. E. Oliviero, “Learning quantum states of continuous variable systems,” 2024. https://arxiv.org/abs/2405.01431. 15
2024
-
[33]
Quantum Mechanics in Phase Space,
T. L. Curtright and C. K. Zachos, “Quantum Mechanics in Phase Space,” Asia Pac. Phys. Newslett. 1 (2012) 37–46, arXiv:1104.5269 [physics.hist-ph]
2012 arXiv
-
[34]
On the Principles of elementary quantum mechanics,
H. J. Groenewold, “On the Principles of elementary quantum mechanics,” Physica 12 (1946) 405–460
1946
-
[35]
Complex Weyl symbols of metaplectic operators: an elementary approach,
B. Cahen, “Complex Weyl symbols of metaplectic operators: an elementary approach,”
-
[36]
Quantization of gaussians,
J. Derezi´ nski and M. Karczmarczyk, “Quantization of gaussians,” Analysis as a Tool in Mathematical Physics: In Memory of Boris Pavlov (2020) 277–304, arXiv:1701.07297 [math-ph]. https://arxiv.org/abs/1701.07297
2020 arXiv
-
[37]
Phase space distributions and a duality symmetry for star products,
V. I. Man’ko, G. Marmo, and P. Vitale, “Phase space distributions and a duality symmetry for star products,” Phys. Lett. A 334 (2005) 1, arXiv:hep-th/0407131
2005 arXiv
-
[38]
Matrix Bases for Star Products: a Review,
F. Lizzi and P. Vitale, “Matrix Bases for Star Products: a Review,” SIGMA 10 (2014) 086, arXiv:1403.0808 [hep-th]. 16
2014 arXiv
-
[39]
Serafini, Quantum continuous variables: A primer of theoretical methods
A. Serafini, Quantum continuous variables: A primer of theoretical methods . CRC Press, Taylor & Francis Group, Boca Raton, USA, 2017
2017
-
[2012]
http://dx.doi.org/10.1103/RevModPhys.84.621
621–669. http://dx.doi.org/10.1103/RevModPhys.84.621
-
[2023]
https://arxiv.org/abs/2306.12947
Reviewed August 12, 2026 · model on record in the stance chip above.
Discussion (0). Continue with ORCID to comment.