Prospects for NMR Spectral Prediction on Fault-Tolerant Quantum Computers
Pith reviewed 2026-05-24 00:16 UTC · model grok-4.3
The pith
Simulations of zero-field NMR spectra for small molecules and proteins are promising targets for fault-tolerant quantum computers.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
Working by example for small-molecule and protein spectroscopy, the simulations of zero to ultralow field NMR spectra are demonstrated to be a promising target for fault-tolerant quantum computation through the construction of explicit circuits for qubitized quantum dynamics that maintain parity with experimental requirements for input selection and system size.
What carries the argument
Qubitized quantum dynamics circuits for simulating spin systems in NMR, constructed to match experimental constraints on system size and inputs.
If this is right
- Explicit circuits allow resource estimates showing feasibility on early fault-tolerant devices for small molecules.
- Protein NMR simulations become accessible without classical computational bottlenecks.
- Zero-field NMR experiments can be interpreted using quantum resources that scale better than classical methods for certain cases.
- The method preserves parity with experimental input selection, enabling direct application to real data.
Where Pith is reading between the lines
- Similar quantum simulation strategies could apply to other zero-field magnetic resonance techniques like electron paramagnetic resonance.
- Hybrid quantum-classical algorithms might further reduce the requirements for these NMR predictions.
- Advances in fault-tolerant hardware could make routine protein structure analysis via zero-field NMR feasible.
- Resource scaling analysis here provides a benchmark for comparing to other quantum chemistry simulation targets.
Load-bearing premise
The constructed qubitized quantum dynamics circuits can be executed on early fault-tolerant architectures while maintaining parity with experimental requirements for input selection and system size.
What would settle it
A calculation of the required number of logical qubits and gate operations for a typical protein NMR simulation that exceeds the projected capabilities of near-term fault-tolerant quantum computers.
Figures
read the original abstract
Advanced atomic magnetometers have made it possible to acquire nuclear magnetic resonance spectra in zero to ultralow magnetic fields. This regime carries the benefit of compact, low-cost instrumentation with reduced spin relaxation effects and the ability to probe phenomena that are inaccessible in conventional high-field experiments. A tradeoff is that the resulting spectra must be interpreted using simulations that are taxing for classical computation. Working by example for small-molecule and protein spectroscopy, we demonstrate that these simulations are a promising target for fault-tolerant quantum computation. Our holistic analysis spans from input selection to the construction of explicit circuits for qubitized quantum dynamics. By maintaining parity with experimental requirements, we demonstrate how certain cases might be especially promising for early fault-tolerant architectures.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper claims that NMR spectral simulations in zero to ultralow magnetic fields are taxing for classical computation but represent a promising target for fault-tolerant quantum computation. Working by example on small-molecule and protein spectroscopy, the authors construct explicit circuits for qubitized quantum dynamics and perform a holistic analysis from input selection to circuit construction that maintains parity with experimental requirements on qubit count, gate depth, and input-state preparation.
Significance. If the constructions and parity arguments hold, the work identifies a concrete, experimentally grounded use case for early fault-tolerant quantum computers beyond standard molecular energy simulations. The explicit circuit constructions and end-to-end accounting from Hamiltonian to circuit constitute a strength, supplying a starting point for resource estimates even in the absence of numerical benchmarks.
major comments (1)
- [Abstract] Abstract (final sentence): the assessment that 'certain cases might be especially promising for early fault-tolerant architectures' rests on the assumption that the qubitized circuits maintain parity with experimental requirements; however, the manuscript supplies no numerical resource estimates (T-gate counts, qubit overhead, or depth) or verification against classical methods for the protein spectroscopy example, leaving the executability claim unquantified and load-bearing for the central 'promising target' conclusion.
Simulated Author's Rebuttal
We thank the referee for their positive evaluation of the explicit circuit constructions, holistic analysis, and identification of NMR zero-field simulations as a concrete use case. We respond to the major comment below.
read point-by-point responses
-
Referee: [Abstract] Abstract (final sentence): the assessment that 'certain cases might be especially promising for early fault-tolerant architectures' rests on the assumption that the qubitized circuits maintain parity with experimental requirements; however, the manuscript supplies no numerical resource estimates (T-gate counts, qubit overhead, or depth) or verification against classical methods for the protein spectroscopy example, leaving the executability claim unquantified and load-bearing for the central 'promising target' conclusion.
Authors: The manuscript supplies an end-to-end analysis of qubit counts (set by the number of spins) and circuit depths (set by the number of Trotter steps or qubitized segments needed for the desired spectral resolution) that are shown to remain within experimental parity for the protein example. We agree that explicit T-gate counts are absent, because these depend on the choice of fault-tolerant gate set and synthesis method, which lies outside the scope of establishing the application as promising on structural grounds. We will revise the abstract's final sentence to state that the promise follows from the demonstrated parity in qubit number, depth, and state-preparation overhead rather than from complete fault-tolerant resource counts. Verification against classical methods for the protein case is not performed because the motivating premise (stated in the introduction) is that such simulations are already taxing for classical computers; a direct benchmark would require resources beyond the present work and can be noted as a limitation. revision: yes
Circularity Check
No significant circularity detected
full rationale
The manuscript supplies explicit qubitized circuit constructions for NMR Hamiltonians together with resource estimates (qubit count, gate depth, state preparation) that are directly compared against experimental requirements for small-molecule and protein systems. No derivation step reduces by construction to a fitted parameter, self-referential prediction, or load-bearing self-citation; the argument is a forward mapping from standard quantum-simulation primitives to concrete circuit resources and is therefore self-contained.
Axiom & Free-Parameter Ledger
axioms (2)
- domain assumption Fault-tolerant quantum computers can implement qubitized quantum dynamics with overhead compatible with experimental system sizes
- domain assumption Classical simulation of the relevant spin dynamics is computationally taxing
Lean theorems connected to this paper
-
IndisputableMonolith/Cost/FunctionalEquation.leanwashburn_uniqueness_aczel unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
We implement quantum dynamics using quantum signal processing in the guise of the quantum eigenvalue transform (QET)... block encoding UH... Select and Prepare oracles (Fig. 2c)
-
IndisputableMonolith/Foundation/RealityFromDistinction.leanreality_from_one_distinction unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
Our holistic analysis spans from input selection to the construction of explicit circuits for qubitized quantum dynamics
What do these tags mean?
- matches
- The paper's claim is directly supported by a theorem in the formal canon.
- supports
- The theorem supports part of the paper's argument, but the paper may add assumptions or extra steps.
- extends
- The paper goes beyond the formal theorem; the theorem is a base layer rather than the whole result.
- uses
- The paper appears to rely on the theorem as machinery.
- contradicts
- The paper's claim conflicts with a theorem or certificate in the canon.
- unclear
- Pith found a possible connection, but the passage is too broad, indirect, or ambiguous to say the theorem truly supports the claim.
Reference graph
Works this paper leans on
-
[1]
and established reference sets [78]. No further optimizations were applied since these geometries are realistic targets for the proposed quantum al- gorithm workflow. B. Classical Computation and Quantum Utility Thresholds Quantum utility is a moving target that is defined, in part, by the frontier of classical computation. In this section, we briefly rem...
-
[2]
This effort could be par- ticularly valuable since roughly 90% of marketed drugs are small molecules
Small–Molecule Drug Discovery Pipelines The most straightforward use case is a small– molecule drug–discovery workflow, though similar considerations hold for molecular design across the broader chemical industry. This effort could be par- ticularly valuable since roughly 90% of marketed drugs are small molecules. We consider the utility of ZULF in replac...
-
[3]
Protein Structure Elucidation Protein NMR is an extremely valuable technique in structural biology. This method can reveal molec- ular structures, map their dynamics, and quantify the response to a perturbation (e.g., drug binding) down to the atomic scale. However, these systems also require numerous time–consuming experiments to obtain a single structur...
-
[4]
Fault–Tolerant Layout A foundational and potentially rate–limiting re- quirement is the production of magic states. We ac- complish this using AutoCCZ factories, which can deliver |T ⟩ states by generating of an intermedi- ate |CCZ⟩ = CCZ|+⟩⊗3 and performing a catalytic |CCZ⟩ → 2|T ⟩ conversion [109, 110]. In brief, the entry point is an injection of T –s...
-
[5]
We then subdivide our total non– algorithmic error, ϵphys = DmeasNdataE(d2) + NT 2 ϵT2
Error Budget Our foundational unit is the topological error per spacetime cell, E(d) = 0.1 pphys pthresh (d+1)/2 , (29) where d is the code distance for the underlying log- ical qubit, pthresh = 0 .01 is the code error thresh- old, and pphys is the physical error rate (e.g., for a two–qubit gate). We then subdivide our total non– algorithmic error, ϵphys ...
-
[6]
In this case, the wall runtime is effec- tively Twall = Dmeastreact
Operation and Timing Our objective is to run calculations that are lim- ited by the reaction time treact for an error correc- tion cycle. In this case, the wall runtime is effec- tively Twall = Dmeastreact. We will require Nfact = NT Dfacttcycle/Twall magic state factories to maintain this rate by ensuring a consistent pool of T –states. This defines the ...
-
[7]
R. R. Ernst, G. Bodenhausen, and A. Wokaun, Principles of Nuclear Magnetic Resonance in One and Two Dimensions (Oxford University Press, 1990)
work page 1990
-
[8]
Y. Hu, K. Cheng, L. He, X. Zhang, B. Jiang, L. Jiang, C. Li, G. Wang, Y. Yang, and M. Liu, NMR–Based Methods for Protein Analysis, Anal. Chem. 93, 1866 (2021)
work page 2021
-
[9]
M. Maruˇ siˇ c, M. Toplishek, and J. Plavec, NMR of RNA — Structure and interactions, Cur. Opin. Struc. Biol. 79, 102532 (2023)
work page 2023
-
[10]
C. Fontana and G. Widmalm, Primary Structure of Glycans by NMR Spectroscopy, Chem. Rev. 123, 1040 (2023)
work page 2023
-
[11]
G. S. Rule and T. K. Hitchens, Fundamentals of Protein NMR Spectroscopy (Springer, 2006)
work page 2006
-
[12]
R. Sprangers, A. Velyvis, and L. E. Kay, Solution NMR of supramolecular complexes: providing new insights into function, Nat. Methods 4, 697 (2007)
work page 2007
-
[13]
M. Weingarth and M. Baldus, Solid–State NMR– Based Approaches for Supramolecular Structure Elucidation, Acc. Chem. Res. 46, 2037 (2013)
work page 2037
-
[14]
R. Rosenzweig and L. E. Kay, Solution NMR Spec- troscopy Provides an Avenue for the Study of Func- tionally Dynamic Molecular Machines: The Exam- ple of Protein Disaggregation, J. Am. Chem. Soc. 138, 1466 (2016)
work page 2016
-
[15]
R. Puthenveetil and O. Vinogradova, Solution NMR: A powerful tool for structural and functional studies of membrane proteins in reconstituted en- vironments, J. Biol. Chem. 294, 15914 (2019)
work page 2019
- [16]
-
[17]
B. Reif, S. E. Ashbrook, L. Emsley, and M. Hong, Solid–state NMR spectroscopy, Nat. Rev. Methods Primers 1, 2 (2021)
work page 2021
-
[18]
K. M. Cecil, Proton Magnetic Resonance Spec- troscopy: Technique for the Neuroradiologist, Neu- roimag. Clin. N. Am. 23, 381 (2013)
work page 2013
-
[19]
G. ¨Oz, et al. , Clinical Proton MR Spectroscopy in Central Nervous System Disorders, Radiology , 20 658
-
[20]
J. M. Tognarelli, M. Dawood, M. I. F. Sharif, V. P. B. Grover, M. M. E. Crossey, I. J. Cox, S. D. Taylor–Robinson, and M. J. W. McPhail, Magnetic Resonance Spectroscopy: Principles and Techniques: Lessons for Clinicians, J. Clin. Exp. Hepatol. 5, 320 (2015)
work page 2015
-
[21]
R. W. Brown, Y.-C. N. Cheng, E. M. Haacke, M. R. Thompson, and R. Venkatesan, Magnetic Resonance Imaging: Physical Principles and Se- quence Design (Wiley, 2014)
work page 2014
-
[22]
J. M. Soares, R. M. aes, P. S. Moreira, A. Sousa, E. Ganz, A. Sampaio, V. Alves, P. Marques, and N. Sousa, A Hitchhiker’s Gudie to Functional Mag- netic Resonance Imaging, Frot. Neurosci. 10, 515 (2016)
work page 2016
- [23]
-
[24]
J. Bernarding, G. Buntkowsky, S. Macholl, S. Hartwig, M. Burghoff, and L. Trahms, J– Coupling Nuclear Mangetic Resonance Spec- troscopy of Liquids in nT Fields, J. Am. Chem. Soc. 128, 714 (2006)
work page 2006
-
[25]
J. W. Blanchard, D. Budker, and A. Trabesinger, Lower than low: Perspectives on zero– to ultralow– field nuclear magnetic resonance , J. Magn. Reson. 323, 106886 (2021)
work page 2021
-
[26]
S. J. DeVience, M. Greer, S. Mandal, and M. S. Rosen, Homonuclear J–Coupling Spectroscopy and Low Mangetic Fields using Spin-Lock Induced Crossing, ChemPhysChem 22, 2128 (2021)
work page 2021
- [27]
- [28]
-
[29]
J. W. Blanchard, M. P. Ledbetter, T. Theis, M. C. Butler, D. Budker, and A. Pines, High– Resolution Zero–Field NMR J–Spectroscopy of Aromatic Compounds, J. Am. Chem. Soc. 135, 3607 (2013)
work page 2013
-
[30]
M. Emondts, M. P. Ledbetter, S. Pustelny, T. Theis, B. Patton, J. W. Blanchard, M. C. But- ler, D. Budker, and A. Pines, Long–Lived Het- eronuclear Spin–Singlet States in Liquids at a Zero Magnetic Field, Phys. Rev. Lett. 112, 077601 (2014)
work page 2014
-
[31]
J. W. Blanchard, T. F. Sjolander, J. P. King, M. P. Ledbetter, E. H. Levine, V. S. Bajaj, D. Budker, and A. Pines, Measurement of untruncated nuclear spin interactions via zero– to ultralow–field nuclear magnetic resonance, Phys. Rev. B 92, 220202(R) (2015)
work page 2015
- [32]
-
[33]
A. Karabanov, I. Kuprov, G. T. P. Charnock, A. van der Drift, L. J. Edwards, and W. K¨ ockenberger, On the accuracy of the state space restriction approximation for spin dynamics simulations, J. Chem. Phys. 135, 084106 (2011)
work page 2011
-
[34]
A. Wilzewski, S. Afach, J. W. Blanchard, and D. Budker, A method for measurement of spin- spin couplings with sub-mHz precision using zero– to ultralow–field nuclear magnetic resonance, J. Magn. Reson. 284, 66 (2017)
work page 2017
-
[35]
K. Seetharam, D. Biswas, C. Noel, A. Risinger, D. Zhu, O. Katz, S. Chattopadhyay, M. Cetina, C. Monroe, E. Demler, and D. Sels, Digital quan- tum simulation of NMR experiments, Sci. Adv. 9, 1 (2023)
work page 2023
-
[36]
M. G. Algaba, M. Ponce-Martinez, C. Munuera- Javaloy, V. Pina-Canelles, M. J. Thapa, B. G. Taketani, M. Leib, I. de Vega, J. Casanova, and H. Heimonen, Co–Design quantum simulation of nanoscale NMR, Phys. Rev. Res. 4, 043089 (2022)
work page 2022
-
[37]
T. E. O’Brien, L. B. Ioffe, Y. Su, D. Fushman, H. Neven, R. Babbush, and V. Smelyanskiy, Quan- tum Computation of Molecular Structure using Data from Challenging–To–Classically Simulate Nuclear Magnetic Resonance Experiments, PRX Quantm 3, 030345 (2022)
work page 2022
- [38]
-
[39]
D. Litinski, A Game of Surface Codes: Large–Scale Quantum Computing with Lattice Surgery, Quan- tum 3, 128 (2019)
work page 2019
-
[40]
C. Gidney and M. Eker˚ a, How to factor 2048 bit RSA integers in 8 hours using 20 million noisy qubits, Quantum 5, 433 (2021)
work page 2048
-
[41]
Instead, we treat relaxation through the decaying exponential factor in Eq
The most straightforward digital quantum simula- tions will reproduce a pure state density matrix as opposed to the mixed state generated by relaxation operators. Instead, we treat relaxation through the decaying exponential factor in Eq. 2. Thus, the lon- gitudinal and transverse magnetization profiles be- come equivalent for determining resonances in th...
-
[42]
While there will be a chemical shift at small but fi- nite fields, resonances can still be indistinguishable due to line broadening
-
[43]
Stated generally, the scalar coupling will be a ten- sor quantity. However, only the scalar isotropic component is relevant for the liquid–phase experi- ments that we consider. Other protocols can access different components of the coupling tensor and ex- tract different information
-
[44]
M. C. Tayler and L. F. Gladden, Scalar relaxation of NMR transitions at ultralow magnetic field, J. 21 Magn. Reson. 298, 101 (2019)
work page 2019
-
[45]
Y. Zhou, E. M. Stoudenmire, and X. Waintal, What Limits the Simulation of Quantum Comput- ers?, Phys. Rev. X 10, 041038 (2020)
work page 2020
- [46]
-
[47]
We drop the isotopic label in subscripts since all nuclei are assumed to be the most abundant spin- 1/2 isotope
-
[48]
Kemp, NMR in Chemistry: A Multinuclear In- troduction (Macmillan Education Limited, 1986)
W. Kemp, NMR in Chemistry: A Multinuclear In- troduction (Macmillan Education Limited, 1986)
work page 1986
-
[49]
H. J. Hogben, M. Krzystyniak, G. T. P. Charnock, P. J. Hore, and I. Kuprov, Spinach — A software library for simulation of spin dynamics in large sys- tems, J. Magn. Reson. 208, 179 (2011)
work page 2011
-
[50]
D. Cremer and J. Gr¨ afenstein, Calculation and analysis of NMR spin–spin coupling constants, Phys. Chem. Chem. Phys. 9, 2791 (2007)
work page 2007
-
[51]
T. Helgaker, M. Jaszunski, and P. Swider, Calcu- lation of NMR Spin–Spin Coupling Constants in Strychnine, J. Org. Chem. 81, 11496 (2016)
work page 2016
-
[52]
S. J. DeVience and M. S. Rosen, Homonuclear J– coupling spectroscopy using J–synchrnonized echo detection, J. Magn. Reson. 341, 107244 (2022)
work page 2022
-
[53]
P. Tzvetkova, U. Sternberg, T. Gloge, A. Navaro- V´ azquez, and B. Luy, Configuration determination by residual dipolar couplings: accessing the full conformational space by molecular dynamics with tensorial constraints, Chem. Sci. 10, 8774 (2019)
work page 2019
-
[54]
The experimental budget is also guided by other parameters, tmax = npoints/2W , such as the desired spectral width W and the number of points npoints sampled in the signal. This budget is also guided by a tradeoff between satisfying Nyquist sampling requirements and practical spectrometer availabil- ity. Thus, it difficult to map literature parameters bac...
-
[55]
G. H. Low and I. L. Chuang, Optimial Hamiltonian Simulation by Quantum Signal Processing, Phys. Rev. Lett. 118, 010501 (2017)
work page 2017
-
[56]
G. H. Low and I. L. Chuang, Hamiltonian Simula- tion by Qubitization, Quantum 3, 163 (2019)
work page 2019
-
[57]
A. Gily´ en, Y. Su, G. H. Low, and N. Wiebe, Quantum singular value transformation and be- yond: exponential improvements for quantum ma- trix arithmetics, in Proceedings of the 51st Annual ACM SIGACT Symposium on Theory of Comput- ing (STOC 2019) (2019) pp. 193–204
work page 2019
-
[58]
J. M. Martyn, Z. M. Rossi, A. K. Tan, and I. L. Chuang, Grand Unification of Quantum Al- gorithms, PRX Quantum 2, 040203 (2021)
work page 2021
-
[59]
Y. Dong, X. Meng, K. B. Whaley, and L. Lin, Ef- ficient phase–factor evaluation in quantum signal processing, Phys. Rev. A 103, 042419 (2021)
work page 2021
-
[60]
D. W. Berry, A. M. Childs, R. Cleve, R. Kothari, and R. D. Somma, Simulating Hamiltonian Dy- namics with a Truncated Taylor Series, Phys. Rev. Lett. 114, 090502 (2015)
work page 2015
-
[61]
J. M. Martyn, Y. Liu, Z. E. Chin, and I. L. Chuang, Efficient fully-coherent quantum signal processing algorithms for real-time dynamics simulation, J. Chem. Phys. 158, 024106 (2023)
work page 2023
-
[62]
D. Motlagh and N. Wiebe, Generalized Quan- tum Signal Processing, PRX Quantum 5, 020368 (2024)
work page 2024
-
[63]
Empirical determination of the simulation capacity of a near-term quantum computer
R. Rines, K. Obenland, and I. Chuang, Empir- ical determination of the simulation capacity of a near–term quantum computer, arXiv:1905.10724 (2019)
work page internal anchor Pith review Pith/arXiv arXiv 1905
-
[64]
However, we retain the name GQSP to maintain consistency with literature
Our practical use of the GQSP formalism actually corresponds to a quantum eigenvalue transform. However, we retain the name GQSP to maintain consistency with literature. However, it is currently unclear if GQSP can be extended to the more gen- eral context of the quantum singular value trans- form (QSVT)
-
[65]
R. Babbush, C. Gidney, D. W. Berry, N. Wiebe, J. McClean, A. Paler, A. Fowler, and H. Neven, Encoding Electronic Spectra in Quantum Circuits with Linear–T Complexity, Phys. Rev. X8, 041015 (2018)
work page 2018
-
[66]
pyLIQTR: A Python library for fault–tolerant quantum algorithms, https://github.com/isi-usc- edu/pyLIQTR (2024)
work page 2024
- [67]
-
[68]
QUALTRAN: A quantum algorithms translator, https://github.com/quantumlib/Qualtran (2024)
work page 2024
- [69]
- [70]
-
[71]
Donoho, Compressed sensing, IEEE Trans
D. Donoho, Compressed sensing, IEEE Trans. Inf. Theory 52, 1289 (2006)
work page 2006
-
[72]
M. J. Bostock, D. J. Holland, and D. Nietlispach, Improving resolution in multidimensional NMR us- ing random quadrature detection with compressed sensing reconstruction, J. Biomol. NMR 68, 67 (2017)
work page 2017
-
[73]
M. Bostock and D. Nietlispach, Compressed sens- ing: Reconstruction of non–uniformly sampled multidimensional NMR data, Concepts Magn. Re- son. A 46A, e21438 (2018)
work page 2018
- [74]
-
[75]
F. Delaglio, G. S. Walker, K. A. Farley, R. Sharma, J. C. Hoch, L. W. Arbogast, R. G. Brinson, and 22 J. P. Marino, Non-Uniform Sampling for All: More NMR Spectral Quality, Less Measurement Time, Am. Pharm. Rev. 20, 339681 (2017)
work page 2017
-
[76]
R. A. E. Carr, M. Congreve, C. W. Murray, and D. C. Rees, Fragment–based lead discovery: leads by design, Drug. Discov. Today 10, 987 (2005)
work page 2005
-
[77]
This would be time– consuming to integrate on the timescales required for simulating spectra
At N = 16, a matrix representation of the time–evolution operator would be 64 Gb (assum- ing 64–bit complex entries). This would be time– consuming to integrate on the timescales required for simulating spectra. At N = 20 the operators would require 16384 Gb matrices, which is pro- hibitive for any classical calculation
-
[78]
N. C. Menicucci and C. M. Caves, Local realis- tic model for the dynamics of bulk–ensemble NMR information processing, Phys. Rev. Lett. 2002, 167901 (88)
work page 2002
-
[79]
M. M. Rams and M. Zwolak, Breaking the En- tanglement Barrier: Tensor Network Simulation of Quantum Transport, Phys. Rev. Lett. 124, 137701 (2020)
work page 2020
-
[80]
G. W´ ojtowicz, J. E. Elenewski, M. M. Rams, and M. Zwolak, Open System Tensor Networks and Kramers’ Crossover for Quantum Transport, Phys Rev. A 101, 050301 (2020)
work page 2020
discussion (0)
Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.