Generalization of catability for parity-less cat states
Pith reviewed 2026-06-26 10:00 UTC · model grok-4.3
The pith
Kerr cat states can be certified by replacing parity with a displaced-parity operator in the catability nullifier.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
The displaced-parity operator is inserted in place of the parity component of the original nullifier, yielding a generalized catability that certifies Kerr-cat features from photon-number data alone. Numerical checks confirm faithful certification, accurate approximation of ideal Kerr cats, and improved loss resilience relative to fidelity. An exact anti-linear nullifier based on complex conjugation is also identified as an algebraic description of these states.
What carries the argument
The displaced-parity operator that replaces the parity term inside the nullifier to capture Kerr-cat interference.
If this is right
- Generalized catability certifies Kerr-cat features from photon counts without tomography.
- The measure produces accurate approximations to ideal Kerr cat states.
- Certification remains functional under optical loss where fidelity-based methods degrade.
- An exact anti-linear nullifier supplies an algebraic description of Kerr cat states.
Where Pith is reading between the lines
- The same replacement strategy could be tried on other optical states whose defining symmetry is not parity.
- Photon-number-only certification may lower the resource cost of verifying cat states in lossy channels.
- Direct lab comparison of loss tolerance between the two certification routes would test the numerical resilience claim.
Load-bearing premise
The displaced-parity operator sufficiently captures the interference structure of Kerr cat states for the certification to remain faithful in relevant regimes.
What would settle it
Photon-number statistics from a prepared Kerr cat state that yield low generalized catability while high catability is obtained for clearly non-Kerr states would falsify the method.
Figures
read the original abstract
We extend the nullifier-based certification framework of catability from parity-defined coherent cat states to parity-less Kerr cat states. Since Kerr cats cannot be distinguished by parity alone, we replace the parity component of the original nullifier with a displaced-parity operator that captures their characteristic interference structure. The resulting generalized catability remains directly observable and can be evaluated from a finite number of photon-number measurements without full state tomography. Numerical benchmarks show that the method faithfully certifies Kerr-cat features, produces accurate approximations of ideal Kerr cat states, and is more resilient to optical loss than fidelity-based certification. We also identify an exact anti-linear nullifier based on complex conjugation, providing an ideal algebraic description of Kerr cat states. Our results broaden the scope of catability and provide an experimentally practical approach to the characterization of Kerr cat states.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper extends the nullifier-based catability framework from parity-defined coherent cat states to parity-less Kerr cat states. It replaces the parity component with a displaced-parity operator whose expectation value is claimed to certify the characteristic interference structure from finite photon-number measurements alone, without tomography. Numerical benchmarks are asserted to demonstrate faithful certification of Kerr-cat features, accurate state approximations, and superior loss resilience compared to fidelity. An exact anti-linear nullifier based on complex conjugation is also identified as an algebraic description of Kerr cat states.
Significance. If the displaced-parity construction faithfully isolates Kerr-cat interference across parameter regimes, the result would supply a practical, tomography-free certification tool for states relevant to bosonic quantum error correction and computation. The reported loss resilience relative to fidelity is a concrete experimental advantage. The exact anti-linear nullifier constitutes an algebraic strength that stands independently of the numerics.
major comments (2)
- [§3] §3 (definition of displaced-parity operator): no analytic bound is derived establishing that deviations from the ideal Kerr-cat manifold produce a strictly monotonic increase in the generalized catability; the faithfulness claim therefore rests entirely on unspecified numerical sampling.
- [§4] §4 (numerical benchmarks): the manuscript provides no details on the ranges of Kerr strength and displacement sampled, the number of photon-number measurements used, or the comparison baselines, preventing assessment of whether the operator remains faithful when higher-order terms dominate.
minor comments (2)
- [Abstract] The abstract states that the method 'produces accurate approximations of ideal Kerr cat states,' but the corresponding section does not clarify whether this refers to the catability value itself or to a reconstructed state.
- [§2] Notation for the displaced-parity operator is introduced without an explicit comparison table to the original parity nullifier, which would aid readability.
Simulated Author's Rebuttal
We thank the referee for their thorough review and valuable feedback on our manuscript. We address each of the major comments below and outline the revisions we plan to make.
read point-by-point responses
-
Referee: [§3] §3 (definition of displaced-parity operator): no analytic bound is derived establishing that deviations from the ideal Kerr-cat manifold produce a strictly monotonic increase in the generalized catability; the faithfulness claim therefore rests entirely on unspecified numerical sampling.
Authors: We acknowledge that the manuscript does not provide an analytic bound proving strict monotonicity of the generalized catability with deviations from the ideal Kerr-cat manifold. The claim of faithfulness is indeed based on numerical sampling as presented in §4. In the revised manuscript, we will explicitly state this reliance on numerical evidence and discuss potential limitations. We will also explore adding a brief analytic discussion of the operator's behavior near the ideal manifold if feasible, though a full proof may require further theoretical development. revision: partial
-
Referee: [§4] §4 (numerical benchmarks): the manuscript provides no details on the ranges of Kerr strength and displacement sampled, the number of photon-number measurements used, or the comparison baselines, preventing assessment of whether the operator remains faithful when higher-order terms dominate.
Authors: The referee correctly identifies that specific details regarding the numerical benchmarks were not included in the original submission. We will revise §4 to provide comprehensive information on the sampled ranges of Kerr strength and displacement, the number of photon-number measurements employed for each expectation value, and the specific comparison baselines used (including fidelity and other relevant metrics). This additional information will enable a clearer evaluation of the method's performance, particularly in regimes where higher-order terms may become significant. revision: yes
Circularity Check
No significant circularity detected
full rationale
The paper explicitly constructs a displaced-parity operator to replace the parity nullifier for Kerr-cat states and defines generalized catability from it. This definition is presented as a direct extension rather than derived from the target result. Numerical benchmarks are used to validate faithfulness and resilience, but these are independent evaluations rather than predictions forced by the construction itself. No self-citations are invoked as load-bearing uniqueness theorems, no parameters are fitted and then renamed as predictions, and no ansatz is smuggled via prior work. The derivation chain is self-contained with observable quantities and external numerical checks.
Axiom & Free-Parameter Ledger
axioms (1)
- standard math Standard bosonic mode quantum mechanics and coherent-state formalism
invented entities (1)
-
displaced-parity operator
no independent evidence
Reference graph
Works this paper leans on
-
[1]
the differences between the ideal and approximate Kerr cat states with𝛼=2𝑖, 𝜃= 𝜋/2, the latter obtained as the ground state (20) with𝛽≈0.185
Both states were constructed on a truncated Fock basis with dimension90 andtheirWignerfunctionsevaluatedona473×473phasespacegrid. the differences between the ideal and approximate Kerr cat states with𝛼=2𝑖, 𝜃= 𝜋/2, the latter obtained as the ground state (20) with𝛽≈0.185. Even though their Wigner func- tions𝑊(𝜉),illustratedinFig.2,appeartobevisuallyindisti...
2026
-
[2]
Schrödinger, Die gegenwärtige situation in der quanten- mechanik, Die Naturwissenschaften23, 807 (1935)
E. Schrödinger, Die gegenwärtige situation in der quanten- mechanik, Die Naturwissenschaften23, 807 (1935)
1935
-
[3]
Dodonov, I
V. Dodonov, I. Malkin, and V. Man’ko, Even and odd coherent states and excitations of a singular oscillator, Physica72, 597 (1974)
1974
-
[4]
Yurke and D
B. Yurke and D. Stoler, Generating quantum mechanical super- positions of macroscopically distinguishable states via ampli- tude dispersion, Physical Review Letters57, 13 (1986)
1986
-
[5]
Jeong and M
H. Jeong and M. S. Kim, Efficient quantum computation using coherent states, Physical Review A65, 042305 (2002)
2002
-
[6]
T. C. Ralph, A. Gilchrist, G. J. Milburn, W. J. Munro, and S. Glancy, Quantum computation with optical coherent states, Physical Review A68, 042319 (2003)
2003
-
[7]
A.P.Lund,T.C.Ralph,andH.L.Haselgrove,Fault-tolerantlin- ear optical quantum computing with small-amplitude coherent states, Physical Review Letters100, 030503 (2008)
2008
-
[8]
D. Su, I. Dhand, and T. C. Ralph, Universal quantum computa- tion with optical four-component cat qubits, Physical Review A 106, 042614 (2022)
2022
-
[9]
Hastrup and U
J. Hastrup and U. L. Andersen, All-optical cat-code quantum error correction, Physical Review Research4, 043065 (2022)
2022
-
[10]
J. Lee, N. Kang, S.-H. Lee, H. Jeong, L. Jiang, and S.-W. Lee, Fault-tolerant quantum computation by hybrid qubits with bosonic cat code and single photons, PRX Quantum5, 030322 (2024)
2024
-
[11]
K.Duivenvoorden,B.M.Terhal,andD.Weigand,Single-mode displacement sensor, Physical Review A95, 012305 (2017)
2017
-
[12]
Copetudo, R
X.Pan,T.Krisnanda,A.Duina,K.Park,P.Song,C.Y.Fontaine, A. Copetudo, R. Filip, and Y. Y. Gao, Realization of versatile and effective quantum metrology using a single bosonic mode, PRX Quantum6, 010304 (2025)
2025
-
[13]
A. P. Lund, H. Jeong, T. C. Ralph, and M. S. Kim, Conditional production of superpositions of coherent states with inefficient photon detection, Physical Review A70, 020101 (2004)
2004
-
[14]
D. V. Sychev, A. E. Ulanov, A. A. Pushkina, M. W. Richards, I. A. Fedorov, and A. I. Lvovsky, Enlargement of optical schrödinger’s cat states, Nature Photonics11, 379 (2017)
2017
-
[15]
D. J. Weigand and B. M. Terhal, Generating grid states from schrödinger-catstateswithoutpostselection,PhysicalReviewA 97, 022341 (2018)
2018
-
[16]
Sakaguchi, R
S.Konno,W.Asavanant,F.Hanamura,H.Nagayoshi,K.Fukui, A. Sakaguchi, R. Ide, F. China, M. Yabuno, S. Miki, H. Terai, K.Takase,M.Endo,P.Marek,R.Filip,P.vanLoock,andA.Fu- rusawa, Logical states for fault-tolerant quantum computation with propagating light, Science383, 289 (2024)
2024
-
[17]
Hastrup and U
J. Hastrup and U. L. Andersen, Protocol for generating opti- cal gottesman-kitaev-preskill states with cavity qed, Physical Review Letters128, 170503 (2022)
2022
-
[18]
Banić, V
M. Banić, V. Crescimanna, J. E. Bourassa, C. González- Arciniegas,R.N.Alexander,andK.Heshami,Exactsimulation ofrealisticgottesman-kitaev-preskillclusterstates,PhysicalRe- view A112, 052425 (2025)
2025
-
[19]
Ourjoumtsev, R
A. Ourjoumtsev, R. Tualle-Brouri, J. Laurat, and P. Grangier, Generatingopticalschrödingerkittensforquantuminformation processing, Science312, 83 (2006)
2006
-
[20]
J. S. Neergaard-Nielsen, B. M. Nielsen, C. Hettich, K. Mølmer, and E. S. Polzik, Generation of a superposition of odd pho- ton number states for quantum information networks, Physical Review Letters97, 083604 (2006)
2006
-
[21]
M.Ježek,A.Tipsmark,R.Dong,J.Fiurášek,L.Mišta,R.Filip, and U. L. Andersen, Experimental test of the strongly nonclas- sicalcharacterofanoisysqueezedsingle-photonstate,Physical Review A86, 043813 (2012)
2012
-
[22]
M. Endo, R. He, T. Sonoyama, K. Takahashi, T. Kashiwazaki, T.Umeki,S.Takasu,K.Hattori,D.Fukuda,K.Fukui,K.Takase, W. Asavanant, P. Marek, R. Filip, and A. Furusawa, Non- gaussian quantum state generation by multi-photon subtraction atthetelecommunicationwavelength,OpticsExpress31,12865 (2023)
2023
-
[23]
M. Endo, T. Nomura, T. Sonoyama, K. Takahashi, S. Takasu, D. Fukuda, T. Kashiwazaki, A. Inoue, T. Umeki, R. Nehra, P. Marek, R. Filip, K. Takase, W. Asa- vanant, and A. Furusawa, High-rate four photon subtrac- tion from squeezed vacuum: Preparing cat state for opti- cal quantum computation, arXiv preprint arXiv:2502.08952 10.48550/ARXIV.2502.08952 (2025)
-
[24]
S.Puri,S.Boutin,andA.Blais,Engineeringthequantumstates oflightinakerr-nonlinearresonatorbytwo-photondriving,npj Quantum Information3, 18 (2017)
2017
-
[25]
Grimm, N
A. Grimm, N. E. Frattini, S. Puri, S. O. Mundhada, S. Touzard, M. Mirrahimi, S. M. Girvin, S. Shankar, and M. H. Devoret, Stabilization and operation of a kerr-cat qubit, Nature584, 205 (2020)
2020
-
[26]
Roudsari, P
X.L.He,Y.Lu,D.Q.Bao,H.Xue,W.B.Jiang,Z.Wang,A.F. Roudsari, P. Delsing, J. S. Tsai, and Z. R. Lin, Fast generation of schrödinger cat states using a kerr-tunable superconducting resonator, Nature Communications14, 6358 (2023)
2023
-
[27]
Frattini, R
A.Z.Ding,B.L.Brock,A.Eickbusch,A.Koottandavida,N.E. Frattini, R. G. Cortiñas, V. R. Joshi, S. J. de Graaf, B. J. Chap- man, S. Ganjam, L. Frunzio, R. J. Schoelkopf, and M. H. De- voret, Quantum control of an oscillator with a kerr-cat qubit, Nature Communications16, 5279 (2025)
2025
-
[28]
Omran, H
A. Omran, H. Levine, A. Keesling, G. Semeghini, T. T. Wang, S. Ebadi, H. Bernien, A. S. Zibrov, H. Pichler, S. Choi, J. Cui, M.Rossignolo, P.Rembold, S.Montangero, T.Calarco, M.En- dres, M. Greiner, V. Vuletić, and M. D. Lukin, Generation and manipulation of Schrödinger cat states in Rydberg atom arrays, Science365, 570 (2019)
2019
-
[29]
Schrödinger Cat
C. Monroe, D. M. Meekhof, B. E. King, and D. J. Wineland, A “Schrödinger Cat” Superposition State of an Atom, Science 272, 1131 (1996)
1996
-
[30]
Kienzler, C
D. Kienzler, C. Flühmann, V. Negnevitsky, H.-Y. Lo, M. Marinelli, D. Nadlinger, and J. P. Home, Observation of Quantum Interference between Separated Mechanical Oscilla- tor Wave Packets, Phys. Rev. Lett.116, 140402 (2016)
2016
-
[31]
Shomroni, L
I. Shomroni, L. Qiu, and T. J. Kippenberg, Optomechanical generation of a mechanical catlike state by phonon subtraction, Phys. Rev. A101, 033812 (2020)
2020
-
[32]
B. D. Hauer, J. Combes, and J. D. Teufel, Nonlinear Sideband Cooling to a Cat State of Motion, Phys. Rev. Lett.130, 213604 (2023)
2023
-
[34]
Hacker, S
B. Hacker, S. Welte, S. Daiss, A. Shaukat, S. Ritter, L. Li, and G. Rempe, Deterministic creation of entangled atom–light Schrödinger-cat states, Nat. Photonics13, 110 (2019)
2019
-
[35]
Filip and L
R. Filip and L. Mišta, Detecting quantum states with a positive wigner function beyond mixtures of gaussian states, Physical Review Letters106, 200401 (2011)
2011
-
[36]
Walschaers, Non-gaussian quantum states and where to find them, PRX Quantum2, 030204 (2021)
M. Walschaers, Non-gaussian quantum states and where to find them, PRX Quantum2, 030204 (2021). 9
2021
-
[37]
L.LachmanandR.Filip,Quantumnon-gaussianityoflightand atoms, Progress in Quantum Electronics83, 100395 (2022)
2022
-
[38]
Lee and H
C.-W. Lee and H. Jeong, Quantification of Macroscopic Quan- tum Superpositions within Phase Space, Phys. Rev. Lett.106, 220401 (2011)
2011
-
[39]
J.FiurášekandM.Ježek,Witnessingnegativityofwignerfunc- tion by estimating fidelities of catlike states from homodyne measurements, Physical Review A87, 062115 (2013)
2013
-
[40]
J. Park, J. Zhang, J. Lee, S.-W. Ji, M. Um, D. Lv, K. Kim, and H. Nha, Testing nonclassicality and non-gaussianity in phase space, Physical Review Letters114, 190402 (2015)
2015
-
[41]
Kwon, C.-Y
H. Kwon, C.-Y. Park, K. C. Tan, and H. Jeong, Disturbance- based measure of macroscopic coherence, New J. Phys.19, 043024 (2017)
2017
-
[42]
Chu, Schrödinger cat states of a 16-microgram mechan- ical oscillator, Science380, 274 (2023)
M.Bild,M.Fadel,Y.Yang,U.vonLüpke,P.Martin,A.Bruno, and Y. Chu, Schrödinger cat states of a 16-microgram mechan- ical oscillator, Science380, 274 (2023)
2023
-
[43]
M.G.Genoni,M.L.Palma,T.Tufarelli,S.Olivares,M.S.Kim, and M. G. A. Paris, Detecting quantum non-gaussianity via the wigner function, Physical Review A87, 062104 (2013)
2013
-
[44]
Bräuer, J
Š. Bräuer, J. Provazník, V. Kala, and P. Marek, Catability as a metric for evaluating superposed coherent states, Physical Re- view Letters136, 090205 (2026)
2026
-
[45]
Marek, Ground state nature and nonlinear squeezing of gottesman-kitaev-preskill states, Physical Review Letters132, 210601 (2024)
P. Marek, Ground state nature and nonlinear squeezing of gottesman-kitaev-preskill states, Physical Review Letters132, 210601 (2024)
2024
-
[46]
V. Kala, C. A. Breum, M. V. Larsen, U. L. Ander- sen, J. S. Neergaard-Nielsen, R. Filip, and P. Marek, Nullifiers of non-gaussian cluster states through ho- modyne measurement, arXiv preprint arXiv:2505.21066 10.48550/ARXIV.2505.21066 (2025)
-
[47]
Bräuer, T
Š. Bräuer, T. Opatrný, and P. Marek, Generalized squeezing as a witness of various quantum properties, Physical Review Research7, 033176 (2025)
2025
-
[48]
Hattori, D
T.Sonoyama,K.Takahashi,B.Charoensombutamon,S.Takasu, K. Hattori, D. Fukuda, K. Fukui, K. Takase, W. Asavanant, J.- i. Yoshikawa, M. Endo, and A. Furusawa, Non-gaussian-state generation with time-gated photon detection, Physical Review Research5, 033156 (2023)
2023
-
[49]
M. Endo, T. Sonoyama, M. Matsuyama, F. Okamoto, S. Miki, M. Yabuno, F. China, H. Terai, and A. Furusawa, Quantum detector tomography of a superconducting nanostrip photon- number-resolving detector, Optics Express29, 11728 (2021)
2021
-
[50]
M. A. Nielsen and I. L. Chuang,Quantum Computation and Quantum Information 10th Anniversary Edition(Cambridge University Press, 2011)
2011
-
[51]
Royer, Wigner function as the expectation value of a parity operator, Physical Review A15, 449 (1977)
A. Royer, Wigner function as the expectation value of a parity operator, Physical Review A15, 449 (1977)
1977
-
[52]
Wigner,Group theory and its application(Academic Press, New York, 1959)
E. Wigner,Group theory and its application(Academic Press, New York, 1959)
1959
-
[53]
Cejnar,A Condensed Course of Quantum Mechanics (Karolinum Press, Charles University in Prague, 2013)
P. Cejnar,A Condensed Course of Quantum Mechanics (Karolinum Press, Charles University in Prague, 2013)
2013
-
[54]
J.J.SakuraiandJ.J.Napolitano,Modern Quantum Mechanics, 2nd Edition(Addision Wesley, 2010)
2010
-
[55]
L. E. Ballentine,Quantum Mechanics - Modern Development (World Scientific, 2000)
2000
-
[56]
R. F. Bishop and A. Vourdas, Displaced and squeezed parity operator: Its role in classical mappings of quantum theories, Physical Review A50, 4488 (1994)
1994
-
[57]
Le Jeannic, A
H. Le Jeannic, A. Cavaillès, K. Huang, R. Filip, and J. Laurat, Slowing quantum decoherence by squeezing in phase space, Physical Review Letters120, 073603 (2018)
2018
-
[58]
J. S. Ivan, K. K. Sabapathy, and R. Simon, Operator-sum repre- sentation for bosonic gaussian channels, Physical Review A84, 042311 (2011)
2011
-
[59]
J. D. Hunter, Matplotlib: A 2d graphics environment, Comput- ing in Science & Engineering9, 90 (2007)
2007
-
[60]
S. K. Lam, A. Pitrou, and S. Seibert, Numba (ACM, 2015) pp. 1–6
2015
-
[61]
C. R. Harris, K. J. Millman, S. J. van der Walt, R. Gommers, P. Virtanen, D. Cournapeau, E. Wieser, J. Taylor, S. Berg, N. J. Smith, R. Kern, M. Picus, S. Hoyer, M. H. van Kerkwijk, M. Brett, A. Haldane, J. F. del Río, M. Wiebe, P. Peterson, P. Gérard-Marchant, K. Sheppard, T. Reddy, W. Weckesser, H. Abbasi, C. Gohlke, and T. E. Oliphant, Array programmin...
2020
-
[62]
Virtanen, R
P. Virtanen, R. Gommers, T. E. Oliphant, M. Haber- land, T. Reddy, D. Cournapeau, E. Burovski, P. Peterson, W.Weckesser,J.Bright,S.J.vanderWalt, M.Brett,J.Wilson, K. J. Millman, N. Mayorov, A. R. J. Nelson, E. Jones, R. Kern, E. Larson, C. J. Carey, İ. Polat, Y. Feng, E. W. Moore, J. Van- derPlas, D. Laxalde, J. Perktold, R. Cimrman, I. Henriksen, E. A. Q...
2020
-
[63]
U.Leonhardt,Essential Quantum Optics(CambridgeUniversity Press, 2010)
2010
discussion (0)
Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.