REVIEW 1 major objections 1 cited by
Temporal modes of quantum states of light scattered by a two-level system
T0 review · 1 major / 0 minor · reviewed 2026-06-30 · grok-4.3
Pith's one-line read Scattering single-mode two-photon light off a two-level system produces approximate two-mode NOON states.
desk verdict Analytic input-output map for temporal modes is the clear new piece; NOON approximation claim lacks any reported fidelity or error numbers. 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
Analytic mapping of input temporal modes to output light via unidirectional scattering on a two-level system, followed by principal-mode decomposition of the two-photon output state.
What would settle it
Compute the overlap or fidelity of the decomposed output state with an ideal two-photon NOON state, or measure the Wigner function of the output to verify whether negativity exceeds that of the single-mode input.
Extended reading notes
Core claim
By numerically decomposing the output state in terms of its principal modes, we find that it is possible to map single-mode two-photon inputs into two-mode entangled output states, i.e., two-photon NOON states, to very good approximation. The latter states, in turn, are known to have more Wigner negativity compared to the associated input, which ultimately suggests a potential application of our considered setup in the deterministic generation of non-Gaussian states.
Load-bearing premise
The numerical principal-mode decomposition yields a sufficiently accurate approximation to ideal NOON states for the claimed increase in Wigner negativity to be practically useful.
Editorial extensions
If this is right
- The output approximates ideal NOON states, which carry more Wigner negativity than the single-mode input.
- This scattering setup offers a deterministic method to generate non-Gaussian quantum states of light without relying on probabilistic sources.
- The closed-form description in input modes enables direct computation of output properties for arbitrary multimode multiphoton inputs.
- Temporal mode structure transforms under the scattering in a way that entangles previously unentangled photons across two modes.
Reading between the lines
- The same scattering process might convert other specific input mode combinations into higher-order entangled or non-Gaussian states for larger photon numbers.
- Experimental tests could focus on preparing well-defined temporal modes and projecting the output onto the identified principal modes to confirm the predicted entanglement.
- This deterministic mapping could complement existing methods for non-Gaussian state preparation in continuous-variable quantum information processing.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript derives an analytic input-output map for the temporal modes of multimode, multiphoton light scattered unidirectionally by a two-level system, expressed explicitly in terms of the input modes. For the special case of two photons in one input mode, numerical principal-mode decomposition of the output is used to argue that the state approximates a two-photon NOON state, which in turn exhibits increased Wigner negativity relative to the input and therefore offers a route to deterministic non-Gaussian state generation.
Significance. The explicit temporal-mode description is a clear technical contribution that improves both interpretability and computational efficiency over purely numerical treatments of the same scattering problem. The numerical observation that a single-mode two-photon input can be mapped to an approximate NOON output would, if properly quantified, constitute a concrete deterministic protocol for enhancing non-Gaussianity; the current lack of fidelity metrics prevents that claim from being evaluated at the level required for practical impact.
major comments (1)
- [Abstract] Abstract (and the corresponding numerical results on the two-photon case): the central claim that the output approximates 'two-photon NOON states, to very good approximation' is unsupported by any reported overlap integral, fidelity, trace distance, or other quantitative distance to the ideal state (|2,0⟩ + |0,2⟩)/√2. Because Wigner negativity is a continuous functional, an unquantified approximation leaves open whether the reported negativity increase is large enough to be useful or merely marginal.
Simulated Author's Rebuttal
We thank the referee for their careful reading and constructive comments. We appreciate the acknowledgment of the analytic temporal-mode description as a technical contribution. We address the single major comment below.
read point-by-point responses
-
Referee: [Abstract] Abstract (and the corresponding numerical results on the two-photon case): the central claim that the output approximates 'two-photon NOON states, to very good approximation' is unsupported by any reported overlap integral, fidelity, trace distance, or other quantitative distance to the ideal state (|2,0⟩ + |0,2⟩)/√2. Because Wigner negativity is a continuous functional, an unquantified approximation leaves open whether the reported negativity increase is large enough to be useful or merely marginal.
Authors: We agree that a quantitative metric is required to substantiate the claim of a 'very good approximation' and to evaluate whether the increase in Wigner negativity is practically meaningful. In the revised manuscript we will report the fidelity (overlap) between the numerically reconstructed output state and the ideal NOON state (|2,0⟩ + |0,2⟩)/√2, computed directly from the principal temporal modes obtained in the decomposition. This addition will allow readers to assess the approximation rigorously. revision: yes
Circularity Check
No circularity detected; analytic scattering map and numerical decomposition are independent
full rationale
The paper derives an explicit analytic input-output map for the scattered light solely in terms of input temporal modes from the two-level system interaction. The two-photon NOON-state approximation is obtained via separate numerical principal-mode decomposition of that output state, without any reduction of the claimed mapping to a fitted parameter, self-definition, or self-citation chain. No equations equate a derived quantity to its own inputs by construction, and the central claim rests on the scattering dynamics rather than renaming or smuggling prior results. This is the normal case of a self-contained derivation.
Assumptions & free parameters
Cite this review
Pith. "Pith review of Temporal modes of quantum states of light scattered by a two-level system." pith.science (2026). https://pith.science/paper/VRKF6HY7
@misc{pith2026260629974,
author = {Pith},
title = {Pith review of: Temporal modes of quantum states of light scattered by a two-level system},
year = {2026},
howpublished = {\url{https://pith.science/paper/VRKF6HY7}},
note = {Machine review of arXiv:2606.29974}
}
read the original abstract
Non-Gaussian quantum states of light are of paramount importance to quantum computing. Nevertheless, their deterministic generation is challenging problem due to the difficulty to control nonlinearities in physical systems. In this work, we characterize the light stemming from one of the most fundamental quantum optics configurations: the unidirectional scattering of multimode and multiphoton light by a two-level system. We provide an analytic and explicit description of the output light solely in terms of the corresponding input temporal modes which allows a straightforward physical interpretation and is computationally more effective compared to numerical methods. Then, we focus on the specific case of the scattering of two photons in a single mode. By numerically decomposing the output state in terms of its principal modes, we find that it is possible to map single-mode two-photon inputs to be into two-mode entangled output states, i.e., two-photon NOON states, to very good approximation. The latter states, in turn, are known to have more Wigner negativity compared to the associated input, which ultimately suggests a potential application of our considered setup in the deterministic generation of non-Gaussian states.
Figures
Forward citations
Cited by 1 Pith paper
-
Bimodal non-Gaussian photonic states from a single quantum emitter in a waveguide
A waveguide-coupled two-level emitter driven by pulsed squeezed vacuum can produce two-mode non-Gaussian states from which high-fidelity squeezed cat states are obtained by temporal-mode selection and single-photon heralding.
Reference graph
Works this paper leans on
-
[1]
Hamiltonian and temporal modes The setup of interest consists in a single two-level sys- tem (TLS) coupled to a one-dimensional continuum of photonic modes. The dynamics of the whole system is governed by the HamiltonianHtot =H ph +H at +H int, where Hph = Z ∞ −∞ dk ω ka†(k)a(k),(1) Hat =ω geσee,(2) Hint = r Γ 4π Z ∞ −∞ dk a(k)σ eg +h.c.,(3) are, respecti...
-
[2]
time- localized
are written in units such thatℏ=c= 1, and we as- sume the dispersion relation to beωk =|k|for the photon frequency associated with momentumk. Furthermore, ωge denotes the atomic transition frequency between the excited (|e⟩) and ground (|g⟩) states,σ ee =|e⟩ ⟨e|, σeg =|e⟩ ⟨g|andΓis the spontaneous emission rate of the TLS. The ladder operatorsa†(k),a(k), ...
-
[3]
This state is scattered by the TLS, whose initial and final states are both assumed to be the ground state
Input and output states We consider an incidentn-photon, multimode, pure state of the (free) field, which propagates unidirection- ally. This state is scattered by the TLS, whose initial and final states are both assumed to be the ground state. This setup is illustrated in Fig. 1 and can be thought of as describing, for example, an atom coupled to a chira...
-
[4]
(9) and (10), re- spectively
Definition and relation to the output state The scattering matrix (orS-matrix) is an operatorS that maps an input state to a scattered output state, which, in our case, are given by Eqs. (9) and (10), re- spectively. Mathematically, this relation reads [25] |ψout⟩=S |ψ in⟩,(12) and we define the corresponding matrix elements associ- ated with the scatteri...
-
[5]
(13), in time (and frequency) domain
Analytical expression ofS (n) In [24], the authors derive an analytical expression of theS-matrix coefficients, as defined in Eq. (13), in time (and frequency) domain. We reproduce here the basic idea of this derivation. To that end, we observe that Eq. (13) implies the symmetry ofS(n) (t1,...,tn),(u1,...,un) under any permutation of the indices(t 1, . . ...
-
[6]
(29) is valid only whent≥t′, which was so far left implicit
Input mode In the momentum domain, the Lorentzian mode reads ˜fL(p) = r γ π γ/2 (γ/2)2 +p 2 ,(30) 6 We recall that Eq. (29) is valid only whent≥t′, which was so far left implicit. To recover the wavefunction in the case when t′ ≥t, one then has to swap the time arguments in the equation. whereγis the Lorentzian’s full width at half maximum. The mode corre...
-
[7]
(31) into Eq
Output mode analysis By plugging Eq. (31) into Eq. (29), we obtain the out- put state’s wavefunction for the Lorentzian input. In this case, the computation can even be performed an- alytically; the explicit expression for the output state wavefunction is given in Appendix C. Then, with the full expression of the output state’s wavefunction, we nu- merica...
-
[8]
mode op- timization
We recognize inΨout the wavefunction of a Hang-Ou-Mandel state, also known as two-photon NOON state. The principal modesψ1 andψ 2 are plotted in Fig. 3. TheformofEq.(32)furtherimpliesthatonecandefine a rotated basis of modes, as ϕ1(t) = 1√ 2(ψ1(t) +ψ 2(t))(33) ϕ2(t) = 1√ 2(ψ1(t)−ψ 2(t)),(34) such thatϕ1(t)andϕ 2(t)decompose the wavefunction as Ψout(t, t′)...
Show all 54 references
-
[9]
(9) by imposing the input state|ψ in⟩to be normalized
Normalization of the input state We determine the factorNin Eq. (9) by imposing the input state|ψ in⟩to be normalized. That is, we compute 9 ⟨ψin|ψin⟩=N 2 Z Rn dnt Z Rn dnu nY j=1 fj(uj)f ∗ j (tj)⟨0|a(t 1). . . a(t n)a†(u1). . . a †(un)|0⟩= 1.(A1) One can then simplify the abo...
-
[10]
(12) in the main text
Output state wavefunction Theoutputstateisobtainedbyapplyingthescattering matrix to the input state, as given by Eq. (12) in the main text. Using the definition of our input state, given by Eq. (9), we have that |ψout⟩=S |ψ in⟩ =N Z Rn dnu nY j=1 fj(uj) Sa †(u1). . . a...
-
[11]
Quantum-to-classical transition with single-photon- added coherent states of light.Science, 306(5696):660– 662, 2004
Alessandro Zavatta, Silvia Viciani, and Marco Bellini. Quantum-to-classical transition with single-photon- added coherent states of light.Science, 306(5696):660– 662, 2004
2004
-
[12]
Generating optical schrödinger kittens for quantum information processing.Science, 312(5770):83–86, 2006
Alexei Ourjoumtsev, Rosa Tualle-Brouri, Julien Laurat, and Philippe Grangier. Generating optical schrödinger kittens for quantum information processing.Science, 312(5770):83–86, 2006
2006
-
[13]
Probing quantum commutation rules by addition and subtraction of single photons to/from a light field.Science, 317(5846):1890–1893, 2007
Valentina Parigi, Alessandro Zavatta, Myungshik Kim, and Marco Bellini. Probing quantum commutation rules by addition and subtraction of single photons to/from a light field.Science, 317(5846):1890–1893, 2007
2007
-
[14]
Experimental generation of squeezed cat states with an operation allowing iterative growth
Jean Etesse, Martin Bouillard, Bhaskar Kanseri, and Rosa Tualle-Brouri. Experimental generation of squeezed cat states with an operation allowing iterative growth. Phys. Rev. Lett., 114:193602, May 2015
2015
-
[15]
A. I. Lvovsky and J. Mlynek. Quantum-optical catalysis: generating nonclassical states of light by means of linear optics.Phys. Rev, Lett., 88(25):250401, 2002
2002
-
[16]
Non- gaussian and gottesman–kitaev–preskill state prepara- tion by photon catalysis.New Journal of Physics, 21(11):113034, nov 2019
Miller Eaton, Rajveer Nehra, and Olivier Pfister. Non- gaussian and gottesman–kitaev–preskill state prepara- tion by photon catalysis.New Journal of Physics, 21(11):113034, nov 2019
2019
-
[17]
Photon catalysis for general multimode multi-photon quantum state preparation.PRX Quantum, 7:020323, May 2026
Andrei Aralov, Émilie Gillet, Viet Nguyen, Andrea Cosentino, Mattia Walschaers, and Massimo Frigerio. Photon catalysis for general multimode multi-photon quantum state preparation.PRX Quantum, 7:020323, May 2026
2026
-
[18]
Non-gaussian quantum states and where to find them.PRX Quantum, 2:030204, Sep 2021
Mattia Walschaers. Non-gaussian quantum states and where to find them.PRX Quantum, 2:030204, Sep 2021. 13
2021
-
[19]
D. E. Chang, V. Vuletić, and M. D. Lukin. Quantum nonlinear optics—photon by photon.Nature Photonics, 8(9):685–694, 2014
2014
-
[20]
Deterministic creation of entangled atom–light schrödinger-cat states.Nature Photonics, 13(2):110–115, 2019
Bastian Hacker, Stephan Welte, Severin Daiss, Armin Shaukat, Stephan Ritter, Lin Li, and Gerhard Rempe. Deterministic creation of entangled atom–light schrödinger-cat states.Nature Photonics, 13(2):110–115, 2019
2019
-
[21]
Deterministic freely propagating photonic qubits with negative wigner functions.Nature Photonics, 17(8):688–693, 2023
Valentin Magro, Julien Vaneecloo, Sébastien Garcia, and Alexei Ourjoumtsev. Deterministic freely propagating photonic qubits with negative wigner functions.Nature Photonics, 17(8):688–693, 2023
2023
-
[22]
A.Goban, C.-L.Hung, S.-P.Yu, J.D.Hood, J.A.Muniz, J. H. Lee, M. J. Martin, A. C. McClung, K. S. Choi, D. E. Chang, O. Painter, and H. J. Kimble. Atom–light inter- actions in photonic crystals.Nat. Commun., 5(1):3808, 2014
2014
-
[23]
Corzo, Baptiste Gouraud, Aveek Chandra, Akihisa Goban, Alexandra S
Neil V. Corzo, Baptiste Gouraud, Aveek Chandra, Akihisa Goban, Alexandra S. Sheremet, Dmitriy V. Kupriyanov, and Julien Laurat. Large bragg reflection from one-dimensional chains of trapped atoms near a nanoscale waveguide.Phys. Rev. Lett., 117:133603, Sep 2016
2016
-
[24]
E. T. Jaynes and F. W. Cummings. Comparison of quan- tum and semiclassical radiation theories with application to the beam maser.Proceedings of the IEEE, 51(1):89– 109, 1963
1963
-
[25]
A. H. Kiilerich and K. Mølmer. Input-output theory with quantum pulses.Physical review letters, 123(12):123604, 2019
2019
-
[26]
A. H. Kiilerich and K. Mølmer. Quantum interac- tions with pulses of radiation.Physical Review A, 102(2):023717, 2020
2020
-
[27]
J. Yang, I. Strandberg, A. Vivas-Viaña, A. Gaikwad, C. Castillo-Moreno, A. F. Kockum, M. A. Ullah, C. S. Muñoz, A. M. Eriksson, and S. Gasparinetti. Entan- glement of photonic modes from a continuously driven two-level system.npj Quantum Information, 11(1):69, 2025
2025
-
[28]
Elliott and S
A. Elliott and S. Parkins. Cavity qed systems for steady- state sources of wigner-negative light.Journal of the Op- tical Society of America B, 41(8):C53–C67, 2024
2024
-
[29]
Maffei, P
M. Maffei, P. A. Camati, and A. Auffèves. Closed-system solution of the 1d atom from collision model.Entropy, 24(2):151, 2022
2022
-
[30]
Fabre and N
C. Fabre and N. Treps. Modes and states in quantum op- tics.Reviews of Modern Physics, 92(3):035005, Septem- ber 2020
2020
-
[31]
F. D. M. Haldane and S. Raghu. Possible realization of directional optical waveguides in photonic crystals with broken time-reversal symmetry.Phys. Rev. Lett., 100:013904, Jan 2008
2008
-
[32]
Wang, Y.D
Z. Wang, Y.D. Chong, J. D. Joannopoulos, and M. Sol- jačić. Reflection-free one-way edge modes in a gy- romagnetic photonic crystal.Physical review letters, 100(1):013905, 2008
2008
-
[33]
Shen and J.-T
Y. Shen and J.-T. Shen. Photonic-fock-state scattering in a waveguide-qed system and their correlation functions. Physical Review A, 92(3):033803, 2015
2015
-
[34]
Caneva, M
T. Caneva, M. T. Manzoni, T. Shi, J. S. Douglas, J. I. Cirac, and D. E. Chang. Quantum dynamics of prop- agating photons with strong interactions: a general- ized input–output formalism.New Journal of Physics, 17(11):113001, 2015
2015
-
[35]
J. R. Taylor.Scattering theory: the quantum theory of nonrelativistic collisions. Courier Corporation, 2012
2012
-
[36]
C. W. Gardiner and M. J. Collett. Input and output in damped quantum systems: Quantum stochastic differen- tial equations and the master equation.Physical Review A, 31(6):3761, 1985
1985
-
[37]
Wallis and G
D. Wallis and G. Milburn.Quantum optics. Springer, 1995
1995
-
[38]
S. Fan, Ş. E. Kocabaş, and J.-T. Shen. Input-output formalism for few-photon transport in one-dimensional nanophotonic waveguides coupled to a qubit.Physi- cal Review A—Atomic, Molecular, and Optical Physics, 82(6):063821, 2010
2010
-
[39]
Xu and S
S. Xu and S. Fan. Input-output formalism for few-photon transport: A systematic treatment beyond two photons. Physical Review A, 91(4):043845, 2015
2015
-
[40]
Shi and C
T. Shi and C. P. Sun. Lehmann-symanzik-zimmermann reduction approach to multiphoton scattering in coupled- resonator arrays.Physical Review B—Condensed Matter and Materials Physics, 79(20):205111, 2009
2009
-
[41]
Domokos, P
P. Domokos, P. Horak, and H. Ritsch. Quantum descrip- tion of light-pulse scattering on a single atom in waveg- uides.Physical Review A, 65(3):033832, 2002
2002
-
[42]
Roulet and V
A. Roulet and V. Scarani. Solving the scattering of n photons on a two-level atom without computation.New Journal of Physics, 18(9):093035, 2016
2016
-
[43]
Dąbrowska, D
A. Dąbrowska, D. Chruściński, S. Chakraborty, and G. Sarbicki. Eternally non-markovian dynamics of a qubit interacting with a single-photon wavepacket.New Journal of Physics, 23(12):123019, 2021
2021
-
[44]
Dalibard and S
J. Dalibard and S. Reynaud. Correlation signals in res- onance fluorescence: interpretation via photon scatter- ing amplitudes.Journal de Physique, 44(12):1337–1343, 1983
1983
-
[45]
On the simultaneous scattering of two photons by a single two-level atom.Nature Photon- ics, 17(11):972–976, 2023
Luke Masters, Xin-Xin Hu, Martin Cordier, Gabriele Maron, Lucas Pache, Arno Rauschenbeutel, Max Schem- mer, and Jürgen Volz. On the simultaneous scattering of two photons by a single two-level atom.Nature Photon- ics, 17(11):972–976, 2023
2023
-
[46]
D. Stoler. Photon antibunching and possible ways to observe it.Physical Review Letters, 33(23):1397, 1974
1974
-
[47]
H. J. Carmichael and D. F. Walls. Proposal for the mea- surement of the resonant stark effect by photon correla- tiontechniques.Journal of Physics B: Atomic and Molec- ular Physics, 9(4):L43–L46, 1976
1976
-
[48]
H. J. Kimble, M. Dagenais, and L. Mandel. Photon an- tibunching in resonance fluorescence.Physical Review Letters, 39(11):691, 1977
1977
-
[49]
Lopetegui-Gonzalez, Massimo Frigerio, and Mattia Walschaers
Carlos E. Lopetegui-Gonzalez, Massimo Frigerio, and Mattia Walschaers. Geometric characterization of non- gaussian entanglement for finite stellar rank states, 2025
2025
-
[50]
Singular value decomposition for the takagi factorization of symmetric matrices.Applied Mathematics and Com- putation, 234:380–384, 2014
Alexander M Chebotarev and Alexander E Teretenkov. Singular value decomposition for the takagi factorization of symmetric matrices.Applied Mathematics and Com- putation, 234:380–384, 2014
2014
-
[51]
Single-photon-state generation from a continuous-wave nondegenerate opti- cal parametric oscillator.Physical Review A—Atomic, Molecular, and Optical Physics, 75(2):023806, 2007
Anne EB Nielsen and Klaus Mølmer. Single-photon-state generation from a continuous-wave nondegenerate opti- cal parametric oscillator.Physical Review A—Atomic, Molecular, and Optical Physics, 75(2):023806, 2007
2007
-
[52]
Ex- perimentally accessing the optimal temporal mode of traveling quantum light states.Physical review letters, 111(21):213602, 2013
Olivier Morin, Claude Fabre, and Julien Laurat. Ex- perimentally accessing the optimal temporal mode of traveling quantum light states.Physical review letters, 111(21):213602, 2013
2013
-
[53]
M. M. Lund, F. Yang, and K. Mølmer. Perfect splitting 14 of a two-photon pulse.Physical Review A, 107(2):023715, 2023
2023
-
[54]
Weinberg.The quantum theory of fields, volume 2
S. Weinberg.The quantum theory of fields, volume 2. Cambridge university press, 1995
1995
Reviewed June 30, 2026 · model on record in the stance chip above.
Discussion (0). Continue with ORCID to comment.