Noise and Configuration Recovery Impact on Quantum Selected Configuration Interaction
Pith reviewed 2026-05-25 04:06 UTC · model grok-4.3
The pith
Sampling noise in QSCI with LUCJ, when combined with configuration recovery, improves energies by exploring configurations beyond the ideal ansatz support.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
Noiseless LUCJ sampling in QSCI produces compact and biased configurational spaces that limit the accuracy of the resulting CI energies, particularly in strongly correlated regimes. Introducing a simple noise model shows that sampling noise enhances Hilbert-space exploration by generating additional configurations beyond those supported by the ideal ansatz. When combined with configuration recovery, this leads to systematically improved energies. Recovery alone, starting from randomly generated configurations, can efficiently construct accurate CI spaces.
What carries the argument
The simple noise model applied during LUCJ sampling in QSCI together with the configuration recovery procedure that augments the set of configurations before classical diagonalization.
If this is right
- Noiseless LUCJ sampling restricts accuracy through biased configuration spaces.
- Sampling noise adds configurations outside the ansatz support.
- Noise combined with recovery yields systematically better CI energies.
- Recovery from random configurations alone builds accurate CI spaces efficiently.
Where Pith is reading between the lines
- Inherent hardware noise could provide a practical advantage in QSCI rather than a drawback.
- The recovery step may be more decisive for overall performance than the quantum sampling quality.
- The observed noise benefit might extend to other sampling-based hybrid quantum-classical algorithms.
Load-bearing premise
The simple noise model produces sampling statistics representative of actual quantum hardware errors on the LUCJ ansatz for the chosen N2 active space.
What would settle it
Executing the LUCJ ansatz on real quantum hardware for the N2 system, collecting the sampled configurations, applying recovery, and checking whether the energy improvements match those from the simulated noise model would test the claim.
Figures
read the original abstract
Quantum-selected configuration interaction (QSCI) is a promising hybrid quantum-classical approach in which a quantum device generates configurations for subsequent classical diagonalization. Here, we analyze the performance of QSCI combined with the local unitary cluster Jastrow (LUCJ) ansatz, focusing on the interplay between ansatz expressivity, sampling, noise, and configuration recovery. Using the dissociation of N2 in a large active space as a benchmark, we show that noiseless LUCJ sampling produces compact and biased configurational spaces, limiting the accuracy of the resulting CI energies, particularly in strongly correlated regimes. By introducing a simple noise model, we demonstrate that sampling noise can enhance Hilbert-space exploration by generating additional configurations beyond those supported by the ideal ansatz. When combined with configuration recovery, this leads to systematically improved energies. Moreover, recovery alone (starting from randomly generated configurations) can efficiently construct accurate CI spaces, highlighting its central role in QSCI.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript examines Quantum Selected Configuration Interaction (QSCI) with the local unitary cluster Jastrow (LUCJ) ansatz applied to the N2 dissociation in a large active space. It demonstrates that noiseless LUCJ sampling yields compact and biased configuration spaces that limit CI accuracy in strongly correlated regimes. A simple noise model is introduced to show that sampling noise can generate additional configurations, improving Hilbert-space exploration, and when paired with configuration recovery, leads to better energies. Recovery from random configurations is also shown to efficiently build accurate CI spaces.
Significance. If the results hold under hardware-realistic conditions, the work provides concrete numerical evidence on the N2 benchmark that sampling noise can constructively expand the sampled configuration space beyond the ideal LUCJ ansatz expressivity, while highlighting the central role of classical configuration recovery. This offers a potentially useful perspective for near-term hybrid quantum-classical algorithms in quantum chemistry that treat noise as a resource rather than solely a liability.
major comments (2)
- [Methods section introducing the simple noise model] The central claim that sampling noise enhances Hilbert-space exploration (and yields improved energies with recovery) rests on the simple noise model generating configuration distributions representative of real-device behavior on the LUCJ ansatz. The manuscript provides no validation or comparison of this model against hardware error characteristics (e.g., correlated gate errors, readout noise, or ansatz-specific decoherence) for the chosen N2 active space; this assumption is load-bearing for transferability of the reported energy gains.
- [Results section on N2 benchmark] Table or figure reporting the N2 energies with/without noise and recovery: the quantitative improvement attributed to noise is presented without error bars or statistical analysis over multiple noise realizations, making it difficult to assess whether the observed gains exceed sampling variance in the CI diagonalization step.
minor comments (2)
- [Methods] Notation for the LUCJ parameters and the precise definition of the configuration recovery procedure could be clarified with an explicit equation or pseudocode in the methods.
- [Abstract] The abstract states outcomes on the N2 benchmark but does not specify the active-space size or the exact form of the noise model; adding these details would improve readability.
Simulated Author's Rebuttal
We thank the referee for their thoughtful review and constructive feedback on our manuscript. We address each major comment below, proposing revisions where the points identify areas for improvement while defending the core contributions on their merits.
read point-by-point responses
-
Referee: [Methods section introducing the simple noise model] The central claim that sampling noise enhances Hilbert-space exploration (and yields improved energies with recovery) rests on the simple noise model generating configuration distributions representative of real-device behavior on the LUCJ ansatz. The manuscript provides no validation or comparison of this model against hardware error characteristics (e.g., correlated gate errors, readout noise, or ansatz-specific decoherence) for the chosen N2 active space; this assumption is load-bearing for transferability of the reported energy gains.
Authors: We agree that the simple noise model is an idealized approximation and does not incorporate device-specific error channels such as correlated gate errors or readout noise. Its purpose in the manuscript is to isolate and illustrate the mechanism by which even minimal sampling perturbations can expand the configuration space beyond the ideal LUCJ support, rather than to claim quantitative fidelity to any particular hardware. We will revise the Methods section to explicitly state the model's assumptions and limitations, add a brief discussion of why a minimal model suffices for the conceptual demonstration, and note that hardware validation remains an important direction for future work. This addresses the concern without altering the reported numerical results. revision: partial
-
Referee: [Results section on N2 benchmark] Table or figure reporting the N2 energies with/without noise and recovery: the quantitative improvement attributed to noise is presented without error bars or statistical analysis over multiple noise realizations, making it difficult to assess whether the observed gains exceed sampling variance in the CI diagonalization step.
Authors: We acknowledge that the absence of error bars or multi-realization statistics makes it harder to quantify the robustness of the observed energy improvements. We will perform additional independent noise realizations for the reported N2 points, compute standard deviations, and include error bars (or shaded regions) in the revised figures and tables. This will allow readers to assess whether the gains from noise plus recovery exceed the variance arising from both sampling and the subsequent classical CI step. revision: yes
Circularity Check
No circularity: numerical benchmark study with independent experimental claims
full rationale
The paper is a numerical benchmark on QSCI + LUCJ for N2 dissociation. It reports simulation outcomes under ideal sampling, a simple noise model, and recovery procedures. No derivation chain, first-principles prediction, or fitted parameter is presented as a result; all claims are direct outputs of the described Monte Carlo sampling and diagonalization experiments. No self-citation is used to justify uniqueness or to close a logical loop. The noise-model assumption is an external modeling choice whose validity can be tested against hardware, not a self-referential definition.
Axiom & Free-Parameter Ledger
Reference graph
Works this paper leans on
-
[1]
Noisy intermediate-scale quantum algorithms , author =. 2022 , publisher =
work page 2022
- [2]
-
[3]
C. J. Cramer , publisher =. Essentials of Computational Chemistry:
-
[4]
Nobel lecture: Quantum chemical models , author=. 1999 , publisher=
work page 1999
-
[5]
Grimsley, Harper R and Barron, George S and Barnes, Edwin and Economou, Sophia E and Mayhall, Nicholas J , doi =
-
[6]
An adaptive variational algorithm for exact molecular simulations on a quantum computer , volume =
Grimsley, Harper R and Economou, Sophia E and Barnes, Edwin and Mayhall, Nicholas J , doi =. An adaptive variational algorithm for exact molecular simulations on a quantum computer , volume =
-
[7]
Nature Communications , author =
Peruzzo, Alberto and McClean, Jarrod and Shadbolt, Peter and Yung, Man-Hong and Zhou, Xiao-Qi and Love, Peter J. and Aspuru-Guzik, Al. A variational eigenvalue solver on a photonic quantum processor , volume =. doi:10.1038/ncomms5213 , isbn =
-
[8]
Alves, Mafalda Franciso Ramôa da Costa , title =
-
[9]
and Claudino, Daniel and Economou, Sophia E
Grimsley, Harper R. and Claudino, Daniel and Economou, Sophia E. and Barnes, Edwin and Mayhall, Nicholas J. , title =. 2020 , doi =
work page 2020
-
[10]
Variational Quantum Simulation: A Case Study for Understanding Warm Starts , author =. PRX Quantum , volume =. 2025 , month =. doi:10.1103/PRXQuantum.6.010317 , url =
-
[11]
Quantum Algorithm Providing Exponential Speed Increase for Finding Eigenvalues and Eigenvectors , author =. Phys. Rev. Lett. , volume =. 1999 , month =. doi:10.1103/PhysRevLett.83.5162 , url =
-
[12]
Al\'an Aspuru-Guzik and Anthony D. Dutoi and Peter J. Love and Martin Head-Gordon , title =. Science , volume =. 2005 , doi =
work page 2005
-
[13]
Efficient quantum circuits for quantum computational chemistry , author =. Phys. Rev. A , volume =. 2020 , month =. doi:10.1103/PhysRevA.102.062612 , url =
-
[14]
ffsim: Faster simulations of fermionic quantum circuits , howpublished =
-
[15]
Lee, Joonho and Huggins, William J and Head-Gordon, Martin and Whaley, K Birgitta , doi =
-
[16]
Tang, Ho Lun and Shkolnikov, V.O. and Barron, George S and Grimsley, Harper R and Mayhall, Nicholas J and Barnes, Edwin and Economou, Sophia E , doi =. PRX Quantum , number =
-
[17]
Yordanov, Yordan S and Armaos, V and Barnes, Crispin H. W. and Arvidsson-Shukur, David R. M. , doi =
-
[18]
Natural Orbitals , editor =. 1972 , issn =. doi:https://doi.org/10.1016/S0065-3276(08)60547-X , url =
-
[19]
Pulay, Peter and Hamilton, Tracy P. , title = ". 1988 , issn =. doi:10.1063/1.454704 , url =
-
[21]
Sun, Qiming and Berkelbach, Timothy C. and Blunt, Nick S. and Booth, George H. and Guo, Sheng and Li, Zhendong and Liu, Junzi and McClain, James D. and Sayfutyarova, Elvira R. and Sharma, Sandeep and Wouters, Sebastian and Chan, Garnet Kin-Lic , doi =. PySCF: the Python-based simulations of chemistry framework , volume =
-
[22]
Powell, M. J. D. A Direct Search Optimization Method That Models the Objective and Constraint Functions by Linear Interpolation. Advances in Optimization and Numerical Analysis. 1994. doi:10.1007/978-94-015-8330-5_4
-
[23]
Nocedal, Jorge and Wright, Stephen J. Numerical Optimization. 1994. doi:10.1007/978-0-387-40065-5
-
[24]
Charles R. Harris and K. Jarrod Millman and St. Array programming with. 2020 , month=sep, journal=nature, volume=. doi:10.1038/s41586-020-2649-2 , publisher=
-
[25]
Virtanen, Pauli and Gommers, Ralf and Oliphant, Travis E. and Haberland, Matt and Reddy, Tyler and Cournapeau, David and Burovski, Evgeni and Peterson, Pearu and Weckesser, Warren and Bright, Jonathan and. 2020 , volume =
work page 2020
-
[26]
OpenFermion: The Electronic Structure Package for Quantum Computers , author=. 2019 , eprint=
work page 2019
-
[27]
Fink, William H. , title =. doi:https://doi.org/10.1002/qua.560070602 , year =
-
[29]
and Degroote, Matthias and Johnson, Peter D
Cao, Yudong and Romero, Jonathan and Olson, Jonathan P. and Degroote, Matthias and Johnson, Peter D. and Kieferová, Mária and Kivlichan, Ian D. and Menke, Tim and Peropadre, Borja and Sawaya, Nicolas P. D. and Sim, Sukin and Veis, Libor and Aspuru-Guzik, Alán , title =. 2019 , doi =
work page 2019
-
[30]
Preskill, John , journal =. Quantum. doi:10.22331/q-2018-08-06-79 , url =
work page internal anchor Pith review doi:10.22331/q-2018-08-06-79 2018
- [31]
-
[32]
New Journal of Physics , author =
Jarrod R McClean and Jonathan Romero and Ryan Babbush and Al\'an Aspuru-Guzik , title =. doi:10.1088/1367-2630/18/2/023023 , year =
-
[33]
The unitary coupled-cluster method , journal = cpl, volume =
Alternative coupled-cluster ansätze II. The unitary coupled-cluster method , journal = cpl, volume =. 1989 , issn =. doi:https://doi.org/10.1016/S0009-2614(89)87372-5 , author =
-
[34]
Taube, Andrew G. and Bartlett, Rodney J. , title =. doi:https://doi.org/10.1002/qua.21198 , year =
-
[35]
doi:10.1038/s42005-023-01312-y , journal = comphys, month =
Feniou, C. doi:10.1038/s42005-023-01312-y , journal = comphys, month =
-
[36]
Tang, Ho Lun and Shkolnikov, V.O. and Barron, George S and Grimsley, Harper R and Mayhall, Nicholas J and Barnes, Edwin and Economou, Sophia E , doi =. PRX Quantum , keywords =
-
[37]
and Tennyson, Jonathan , doi =
Tilly, Jules and Chen, Hongxiang and Cao, Shuxiang and Picozzi, Dario and Setia, Kanav and Li, Ying and Grant, Edward and Wossnig, Leonard and Rungger, Ivan and Booth, George H. and Tennyson, Jonathan , doi =
-
[38]
Bertels, Luke W. and Grimsley, Harper R. and Economou, Sophia E. and Barnes, Edwin and Mayhall, Nicholas J. , title =. 2022 , doi =
work page 2022
-
[39]
and Perdomo-Ortiz, Alejandro and Yung, Man-Hong and Aspuru-Guzik, Al\'
Kassal, Ivan and Whitfield, James D. and Perdomo-Ortiz, Alejandro and Yung, Man-Hong and Aspuru-Guzik, Al\'. Simulating Chemistry Using Quantum Computers , journal = arpc, volume =. 2011 , doi =
work page 2011
-
[40]
Scalable Quantum Simulation of Molecular Energies , author =. 2016 , month =. doi:10.1103/PhysRevX.6.031007 , url =
-
[41]
Powell, M. J. D. , editor=. A Direct Search Optimization Method That Models the Objective and Constraint Functions by Linear Interpolation , bookTitle=. 1994 , publisher=
work page 1994
-
[42]
Giesbertz, K. J. H. and Baerends, E. J. , title = ". 2010 , month =. doi:10.1063/1.3426319 , url =
- [43]
- [44]
- [45]
-
[46]
A precise solution of the rotation bending Schrödinger equation for a triatomic molecule with application to the water molecule , journal = jms, volume =. 1979 , issn =. doi:https://doi.org/10.1016/0022-2852(79)90019-5 , author =
-
[47]
PennyLane: Automatic differentiation of hybrid quantum-classical computations , author=. 2022 , eprint=
work page 2022
-
[48]
Qiskit: An Open-source Framework for Quantum Computing , year =
-
[49]
A self-consistent field approach for the variational quantum eigensolver: orbital optimization goes adaptive , author=. 2022 , eprint=
work page 2022
-
[50]
TETRIS-ADAPT-VQE: An adaptive algorithm that yields shallower, denser circuit Ans\"atze , author =. Phys. Rev. Res. , volume =. 2024 , publisher =
work page 2024
-
[51]
Quantum computation and quantum information , author=. 2010 , publisher=
work page 2010
-
[52]
Barren plateaus in quantum neural network training landscapes , author =. 2018 , month =. doi:10.1038/s41467-018-07090-4 , url =
-
[53]
Quantum computational chemistry , author =. 2020 , month =. doi:10.1103/RevModPhys.92.015003 , url =
-
[54]
Quantum variational algorithms are swamped with traps , author =. 2022 , month =. doi:10.1038/s41467-022-35364-5 , url =
-
[55]
Training Variational Quantum Algorithms Is NP-Hard , author =. Phys. Rev. Lett. , volume =. 2021 , month =. doi:10.1103/PhysRevLett.127.120502 , url =
-
[56]
Arrasmith, Andrew and Holmes, Zoë and Cerezo, M and Coles, Patrick J , title =. 2022 , month =. doi:10.1088/2058-9565/ac7d06 , url =
-
[57]
Strategies for quantum computing molecular energies using the unitary coupled cluster ansatz
Romero, Jonathan and Babbush, Ryan and McClean, Jarrod R and Hempel, Cornelius and Love, Peter J and Aspuru-Guzik, Al \'a n. Strategies for quantum computing molecular energies using the unitary coupled cluster ansatz. Quantum Sci. Technol. 2018 , doi =
work page 2018
-
[58]
Quantum supremacy using a programmable superconducting processor , volume=. Nature , author=. 2019 , month=. doi:10.1038/s41586-019-1666-5 , number=
-
[59]
Dalton, Kieran and Long, Christopher K. and Yordanov, Yordan S. and Smith, Charles G. and Barnes, Crispin H. and Mertig, Normann and Arvidsson-Shukur, David R. , year=. Quantifying the effect of gate errors on variational quantum eigensolvers for Quantum Chemistry , volume=. doi:10.1038/s41534-024-00808-x , number=
-
[60]
Evidence for the utility of quantum computing before Fault Tolerance , volume=. Nature , author=. 2023 , month=. doi:10.1038/s41586-023-06096-3 , number=
-
[61]
Vaquero-Sabater, Nonia and Carreras, Abel and Or\'us, Rom\'an and Mayhall, Nicholas J. and Casanova, David , year=. Physically motivated improvements of variational quantum eigensolvers , volume=. doi:10.1021/acs.jctc.4c00329 , number=
-
[62]
and Peng, Bo and Govind, Niranjan and Alexeev, Yuri , year=
Fedorov, Dmitry A. and Peng, Bo and Govind, Niranjan and Alexeev, Yuri , year=. VQE method: A short survey and recent developments , volume=. doi:10.1186/s41313-021-00032-6 , number=
- [63]
-
[65]
Limitations of quantum hardware for molecular energy estimation using VQE , volume =
Carreras, Abel and Or. Limitations of quantum hardware for molecular energy estimation using VQE , volume =. doi:10.1039/D5CP03907J , issue =
-
[66]
Gao, Hong and Imamura, Satoshi and Kasagi, Akihiko and Yoshida, Eiji , doi =. Distributed Implementation of Full Configuration Interaction for One Trillion Determinants , volume =
- [67]
-
[68]
Adam A. Holmes and Hitesh J. Changlani and C. J. Umrigar , title =. 2016 , doi =
work page 2016
-
[69]
Adam A. Holmes and Norm M. Tubman and C. J. Umrigar , title =. 2016 , doi =
work page 2016
-
[70]
Holmes and Guillaume Jeanmairet and Ali Alavi and C
Sandeep Sharma and Adam A. Holmes and Guillaume Jeanmairet and Ali Alavi and C. J. Umrigar , title =. 2017 , doi =
work page 2017
-
[71]
Hastings and Dave Wecker and Bela Bauer and Matthias Troyer , title =
Matthew B. Hastings and Dave Wecker and Bela Bauer and Matthias Troyer , title =. Quantum Inf. Comput. , volume =. 2015 , doi =
work page 2015
-
[72]
Chong and Charles Chung and Christopher Codella and Antonio D
Yuri Alexeev and Maximilian Amsler and Paul Baity and Marco Antonio Barroca and Sanzio Bassini and Torey Battelle and Daan Camps and David Casanova and Young Jai Choi and Frederic T. Chong and Charles Chung and Christopher Codella and Antonio D. C\'orcoles and James Cruise and Alberto Di Meglio and Jonathan Dubois and Ivan Duran and Thomas Eckl and Sophia...
work page 2024
-
[74]
Sung and Maika Takita and Minh C
Javier Robledo-Moreno and Mario Motta and Holger Haas and Ali Javadi-Abhari and Petar Jurcevic and William Kirby and Simon Martiel and Kunal Sharma and Sandeep Sharma and Tomonori Shirakawa and Iskandar Sitdikov and Rong-Yang Sun and Kevin J. Sung and Maika Takita and Minh C. Tran and Seiji Yunoki and Antonio Mezzacapo , title =. 2025 , doi =
work page 2025
-
[76]
Peter Reinholdt and Karl Michael Ziems and Erik Rosendahl Kjellgren and Sonia Coriani and Stephan P. A. Sauer and Jacob Kongsted , title =. 2025 , doi =
work page 2025
-
[77]
Mario Motta and Kevin J. Sung and K. Birgitta Whaley and Martin Head-Gordon and James Shee , title =. 2023 , doi =
work page 2023
- [78]
-
[79]
Abhinav Anand and Philipp Schleich and Sumner Alperin-Lea and Phillip W. K. Jensen and Sukin Sim and Manuel Díaz-Tinoco and Jakob S. Kottmann and Matthias Degroote and Artur F. Izmaylov and Alán Aspuru-Guzik , title =. 2022 , doi =
work page 2022
-
[81]
Exclusive-or encoded algebraic structure for efficient quantum dynamics , url =
Broers, Lukas and Mathey, Ludwig , date =. Exclusive-or encoded algebraic structure for efficient quantum dynamics , url =. doi:10.1088/1367-2630/ae5c2c , journal = njp, number =
-
[82]
Broers, Lukas and Sun, Rong-Yang and Yunoki, Seiji , month =. 2025 , url =
work page 2025
-
[83]
Robledo-Moreno, J.; Motta, M.; Haas, H.; Javadi-Abhari, A.; Jurcevic, P.; Kirby, W.; Martiel, S.; Sharma, K.; Sharma, S.; Shirakawa, T.; Sitdikov, I.; Sun, R.-Y.; Sung, K. J.; Takita, M.; Tran, M. C.; Yunoki, S.; Mezzacapo, A. Chemistry beyond the scale of exact diagonalization on a quantum-centric supercomputer. Sci. Adv. 2025, 11, eadu9991 mcitethebibliography
work page 2025
-
[84]
Molecular electronic structure theory; Wiley & Sons: New York, 2000
Helgaker, T.; J rgensen, P.; Olsen, J. Molecular electronic structure theory; Wiley & Sons: New York, 2000
work page 2000
-
[85]
Cramer, C. J. Essentials of Computational Chemistry: T heories and models ; Wiley & Sons: New York, 2002
work page 2002
-
[86]
McArdle, S.; Endo, S.; Aspuru-Guzik, A.; Benjamin, S. C.; Yuan, X. Quantum computational chemistry. Rev. Mod. Phys. 2020, 92, 015003
work page 2020
discussion (0)
Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.