Regularized Counterdiabatic Driving for the Quantum Rabi Model
Pith reviewed 2026-05-20 10:29 UTC · model grok-4.3
The pith
A variational framework with subspace regularization enables counterdiabatic driving in the quantum Rabi model.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
The authors introduce a variational optimization framework equipped with physically motivated renormalization schemes that regularize the trace-based metric by restricting it to relevant displaced and low-energy subspaces. Applied to the quantum Rabi model beyond the dispersive approximation, this yields two distinct counterdiabatic contributions that couple the atomic degree of freedom to the position and momentum quadratures of the field and suppress diabatic excitations across coupling regimes ranging from strong to deep-strong light-matter interaction.
What carries the argument
The renormalized trace-based variational metric restricted to displaced and low-energy subspaces, which produces approximate counterdiabatic Hamiltonians for the Rabi model.
If this is right
- Counterdiabatic driving extends consistently to continuous-variable systems that possess unbounded Hilbert spaces.
- Two specific counterdiabatic contributions can be derived for the Rabi model that remain effective beyond the dispersive approximation.
- A fidelity-based quantum optimal-control strategy provides a practical bypass when trace-based variational methods encounter limitations.
- The resulting control terms can be realized experimentally through Floquet engineering by parametric modulation of the native Hamiltonian.
Where Pith is reading between the lines
- The regularization approach may extend to other bosonic models encountered in quantum optics or superconducting circuits.
- Experimental verification in circuit-QED platforms could test whether the derived terms maintain high fidelity during fast state preparation.
- The subspace-restriction technique offers a route toward scalable control protocols for preparing states in regimes of very strong light-matter coupling.
Load-bearing premise
Restricting the trace-based functional to displaced and low-energy subspaces eliminates divergences while still capturing the essential diabatic suppression dynamics across the full range of coupling strengths.
What would settle it
Numerical simulations of the Rabi model in which the regularized counterdiabatic protocol produces significantly lower state-preparation fidelity than exact methods in the deep-strong coupling limit would show that the subspace restriction fails to capture the required dynamics.
Figures
read the original abstract
Counter-diabatic (CD) driving provides a powerful route to fast and robust state preparation by suppressing diabatic excitations during finite-time evolution. Yet, deriving analytical CD protocols for complex systems remains challenging, motivating the development of variational approaches. These methods typically rely on minimizing trace-based functionals to construct approximate control Hamiltonians. However, in unbounded systems, such functionals can become ill-defined because of the unbounded bosonic Hilbert space, leading to divergent cost functions and unphysical variational coefficients. Here, we introduce a variational optimization framework equipped with physically motivated renormalization schemes that regularize the trace-based metric by restricting it to relevant displaced and low-energy subspaces. As a paradigmatic example, we apply our method to the quantum Rabi model beyond the dispersive approximation and identify two distinct CD contributions that couple the atomic degree of freedom to the position and momentum quadratures of the field. These terms suppress diabatic excitations across coupling regimes ranging from strong to deep-strong light--matter interaction. We further formulate a fidelity-based quantum optimal-control strategy that bypasses the limitations of trace-based variational methods. Finally, we show that the resulting CD terms can be implemented via Floquet engineering through parametric modulation of the native Hamiltonian. Our results demonstrate that CD driving can be consistently extended to continuous-variable systems with unbounded Hilbert spaces, providing a controlled and scalable framework for quantum control in strongly interacting light-matter platforms.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript introduces a variational optimization framework for counterdiabatic (CD) driving in the quantum Rabi model. It regularizes the trace-based metric by restricting it to relevant displaced and low-energy subspaces to handle divergences in the unbounded bosonic Hilbert space. The approach identifies two distinct CD terms that couple the atomic degree of freedom to the position and momentum quadratures of the field, which are claimed to suppress diabatic excitations from strong to deep-strong coupling regimes. The work also formulates a fidelity-based quantum optimal-control strategy and demonstrates implementation of the CD terms via Floquet engineering through parametric modulation of the native Hamiltonian.
Significance. If the subspace regularization is shown to be robust, the results would provide a practical route to extend CD driving to continuous-variable systems with unbounded spectra, which is relevant for fast and robust state preparation in strongly coupled light-matter platforms. The explicit identification of quadrature couplings and the Floquet implementation offer concrete, potentially scalable protocols for quantum control experiments.
major comments (2)
- [Abstract and variational framework section] The central regularization procedure (abstract and the section introducing the variational framework): the claim that restricting the trace-based functional to displaced and low-energy subspaces eliminates divergences while still capturing the essential diabatic suppression dynamics is load-bearing for the main result. In the deep-strong coupling regime the ground-state displacement grows and higher Fock states mix strongly; an explicit convergence test with respect to subspace size or a direct comparison of the resulting variational coefficients against exact time-dependent numerics is required to confirm that the identified position- and momentum-quadrature CD terms do not leave residual excitations outside the chosen subspace.
- [Rabi model application section] Application to the Rabi model (section presenting the identified CD terms): the two quadrature couplings are stated to work across the full range of coupling strengths, yet no quantitative fidelity or excitation-suppression metrics are referenced for the deep-strong limit. Without such data it remains unclear whether the variational solution fully suppresses the relevant transitions or only a subset, which directly affects the claimed generality of the method.
minor comments (2)
- [Abstract] The abstract would benefit from a brief explicit statement of the functional form of the two identified CD terms (e.g., the operators multiplying the atomic Pauli matrices).
- [Method section] Notation for the displaced and low-energy subspaces should be introduced with a clear definition (e.g., a projector or cutoff parameter) at first use to aid readability.
Simulated Author's Rebuttal
We thank the referee for their careful reading and constructive feedback on our manuscript. We address each major comment below and have revised the manuscript to incorporate additional validation and quantitative metrics as requested.
read point-by-point responses
-
Referee: The central regularization procedure (abstract and the section introducing the variational framework): the claim that restricting the trace-based functional to displaced and low-energy subspaces eliminates divergences while still capturing the essential diabatic suppression dynamics is load-bearing for the main result. In the deep-strong coupling regime the ground-state displacement grows and higher Fock states mix strongly; an explicit convergence test with respect to subspace size or a direct comparison of the resulting variational coefficients against exact time-dependent numerics is required to confirm that the identified position- and momentum-quadrature CD terms do not leave residual excitations outside the chosen subspace.
Authors: We agree that explicit convergence validation is essential to substantiate the regularization scheme, especially in the deep-strong regime. In the revised manuscript, we have added a new subsection and figure presenting the variational coefficients as a function of subspace size (both displacement cutoff and Fock-state truncation) for g/ω = 2. We also include a direct comparison of the approximate CD evolution against exact time-dependent numerics for accessible Hilbert-space dimensions, confirming that residual excitations outside the regularized subspace remain negligible and that the quadrature couplings suppress the dominant diabatic transitions. revision: yes
-
Referee: Application to the Rabi model (section presenting the identified CD terms): the two quadrature couplings are stated to work across the full range of coupling strengths, yet no quantitative fidelity or excitation-suppression metrics are referenced for the deep-strong limit. Without such data it remains unclear whether the variational solution fully suppresses the relevant transitions or only a subset, which directly affects the claimed generality of the method.
Authors: We thank the referee for highlighting this point. While the original manuscript emphasized qualitative behavior across regimes, the revised version now includes quantitative fidelity and residual-excitation data specifically for the deep-strong limit (g/ω > 1). These metrics, shown in an updated figure, demonstrate that the two quadrature CD terms achieve high fidelity and strong suppression of excitations relative to the undriven case, supporting the claimed generality. The new results are referenced in the Rabi-model application section. revision: yes
Circularity Check
No significant circularity; regularization framework is independently motivated and applied.
full rationale
The paper proposes a variational framework that regularizes the trace-based metric via explicit restriction to displaced and low-energy subspaces, then applies it to derive two quadrature CD terms for the Rabi model. This restriction is introduced as a physically motivated choice to handle the unbounded bosonic space, not derived from or equivalent to the target CD coefficients by construction. No load-bearing self-citations, uniqueness theorems from prior author work, or fitted inputs renamed as predictions appear in the derivation chain. The fidelity-based optimal control is presented as a separate bypass, and Floquet implementation is a downstream application. The central claims remain independent of the inputs and are externally falsifiable via simulation or experiment.
Axiom & Free-Parameter Ledger
axioms (1)
- domain assumption Restricting the trace-based metric to displaced and low-energy subspaces yields a well-defined and physically relevant cost function for unbounded bosonic systems.
Lean theorems connected to this paper
-
IndisputableMonolith/Cost/FunctionalEquation.leanwashburn_uniqueness_aczel unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
regularize the trace-based metric by restricting it to relevant displaced and low-energy subspaces
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]
I. I. Rabi, On the process of space quantization, Phys. Rev.49, 324 (1936)
work page 1936
-
[2]
E. Jaynes and F. Cummings, Comparison of quantum and semi- classical radiation theories with application to the beam maser, Proc. IEEE51, 89 (1963)
work page 1963
-
[3]
D. C. McKay, R. Naik, P. Reinhold, L. S. Bishop, and D. I. Schuster, High-contrast qubit interactions using multimode cav- ity qed, Phys. Rev. Lett.114, 080501 (2015)
work page 2015
-
[4]
C. Wang, Y . Y . Gao, P. Reinhold, R. W. Heeres, N. Ofek, K. Chou, C. Axline, M. Reagor, J. Blumoff, K. Sliwa,et al., A schr¨odinger cat living in two boxes, Sci.352, 1087 (2016)
work page 2016
-
[5]
F. Yoshihara, T. Fuse, S. Ashhab, K. Kakuyanagi, S. Saito, and K. Semba, Superconducting qubit-oscillator circuit beyond the ultrastrong-coupling regime, Nat. Phys.13, 44 (2017)
work page 2017
-
[6]
X. Zhao, Q. Bin, W. Hou, Y . Li, Y . Li, Y . Lin, X.-Y . L¨u, and J. Du, Experimental observation of parity-symmetry-protected phenomena in the quantum rabi model with a trapped ion, Phys. Rev. Lett.134, 193604 (2025)
work page 2025
-
[7]
Ashhab, Superradiance transition in a system with a single qubit and a single oscillator, Phys
S. Ashhab, Superradiance transition in a system with a single qubit and a single oscillator, Phys. Rev. A87, 013826 (2013)
work page 2013
- [8]
- [9]
- [10]
-
[11]
H. Walther, B. T. Varcoe, B.-G. Englert, and T. Becker, Cavity quantum electrodynamics, Rep. Prog. Phys.69, 1325 (2006)
work page 2006
-
[12]
D. Leibfried, R. Blatt, C. Monroe, and D. Wineland, Quan- tum dynamics of single trapped ions, Rev. Mod. Phys.75, 281 (2003)
work page 2003
- [13]
-
[14]
J. Bourassa, J. M. Gambetta, A. A. Abdumalikov, O. Astafiev, Y . Nakamura, and A. Blais, Ultrastrong coupling regime of cav- ity qed with phase-biased flux qubits, Phys. Rev. A80, 032109 (2009)
work page 2009
-
[15]
P. Forn-D ´ıaz, J. Lisenfeld, D. Marcos, J. J. Garc ´ıa-Ripoll, E. Solano, C. J. P. M. Harmans, and J. E. Mooij, Observation of the bloch-siegert shift in a qubit-oscillator system in the ultra- strong coupling regime, Phys. Rev. Lett.105, 237001 (2010)
work page 2010
-
[16]
I. Chiorescu, P. Bertet, K. Semba, Y . Nakamura, C. Harmans, and J. Mooij, Coherent dynamics of a flux qubit coupled to a harmonic oscillator, Nature431, 159 (2004)
work page 2004
-
[17]
T. Niemczyk, F. Deppe, H. Huebl, E. Menzel, F. Hocke, M. Schwarz, J. Garcia-Ripoll, D. Zueco, T. H¨ummer, E. Solano, et al., Circuit quantum electrodynamics in the ultrastrong- coupling regime, Nat. Phys.6, 772 (2010)
work page 2010
- [18]
-
[19]
P. Forn-D´ıaz, L. Lamata, E. Rico, J. Kono, and E. Solano, Ultra- strong coupling regimes of light-matter interaction, Rev. Mod. Phys.91, 025005 (2019)
work page 2019
-
[20]
A. Frisk Kockum, A. Miranowicz, S. De Liberato, S. Savasta, and F. Nori, Ultrastrong coupling between light and matter, Nat. Rev. Phys.1, 19 (2019)
work page 2019
-
[21]
J. Casanova, G. Romero, I. Lizuain, J. J. Garc ´ıa-Ripoll, and E. Solano, Deep strong coupling regime of the jaynes- cummings model, Phys. Rev. Lett.105, 263603 (2010)
work page 2010
-
[22]
J. Koch, G. R. Hunanyan, T. Ockenfels, E. Rico, E. Solano, and M. Weitz, Quantum rabi dynamics of trapped atoms far in the deep strong coupling regime, Nat. Commun.14, 954 (2023)
work page 2023
-
[23]
D. Lv, S. An, Z. Liu, J.-N. Zhang, J. S. Pedernales, L. Lamata, E. Solano, and K. Kim, Quantum simulation of the quantum rabi model in a trapped ion, Phys. Rev. X8, 021027 (2018)
work page 2018
-
[24]
P. Domokos, J. M. Raimond, M. Brune, and S. Haroche, Simple cavity-qed two-bit universal quantum logic gate: The principle and expected performances, Phys. Rev. A52, 3554 (1995)
work page 1995
-
[25]
A. Rauschenbeutel, G. Nogues, S. Osnaghi, P. Bertet, M. Brune, J. M. Raimond, and S. Haroche, Coherent operation of a tunable quantum phase gate in cavity qed, Phys. Rev. Lett.83, 5166 (1999)
work page 1999
-
[26]
R. Di Candia, F. Minganti, K. Petrovnin, G. S. Paraoanu, and S. Felicetti, Critical parametric quantum sensing, npj Quantum Inf.9, 23 (2023)
work page 2023
- [27]
-
[28]
D. Z. Rossatto, C. J. Villas-B ˆoas, M. Sanz, and E. Solano, Spectral classification of coupling regimes in the quantum rabi model, Phys. Rev. A96, 013849 (2017)
work page 2017
-
[29]
E. Torrontegui, S. Ib ´a˜nez, S. Mart ´ınez-Garaot, M. Modugno, A. del Campo, D. Gu´ery-Odelin, A. Ruschhaupt, X. Chen, and J. G. Muga, Shortcuts to adiabaticity, inAdvances in Atomic, Molecular , and Optical Physics, V ol. 62 (Academic Press,
-
[30]
D. Gu ´ery-Odelin, A. Ruschhaupt, A. Kiely, E. Torrontegui, S. Mart ´ınez-Garaot, and J. G. Muga, Shortcuts to adiabatic- ity: Concepts, methods, and applications, Rev. Mod. Phys.91, 045001 (2019)
work page 2019
-
[31]
M. Demirplak and S. A. Rice, Assisted adiabatic passage revis- ited, J. Phys. Chem. B109, 6838 (2005)
work page 2005
-
[32]
M. V . Berry, Transitionless quantum driving, J. Phys. A: Math. Theor.42, 365303 (2009)
work page 2009
-
[33]
X. Chen, I. Lizuain, A. Ruschhaupt, D. Gu´ery-Odelin, and J. G. Muga, Shortcut to adiabatic passage in two- and three-level 11 atoms, Phys. Rev. Lett.105, 123003 (2010)
work page 2010
-
[34]
del Campo, Shortcuts to adiabaticity by counterdiabatic driv- ing, Phys
A. del Campo, Shortcuts to adiabaticity by counterdiabatic driv- ing, Phys. Rev. Lett.111, 100502 (2013)
work page 2013
-
[35]
Jarzynski, Generating shortcuts to adiabaticity in quantum and classical dynamics, Phys
C. Jarzynski, Generating shortcuts to adiabaticity in quantum and classical dynamics, Phys. Rev. A88, 040101 (2013)
work page 2013
-
[36]
M. Kolodrubetz, D. Sels, P. Mehta, and A. Polkovnikov, Geom- etry and non-adiabatic response in quantum and classical sys- tems, Phys. Rep.697, 1 (2017)
work page 2017
-
[37]
O. Abah, R. Puebla, and M. Paternostro, Quantum state engi- neering by shortcuts to adiabaticity in interacting spin-boson systems, Phys. Rev. Lett.124, 180401 (2020)
work page 2020
-
[38]
Y .-H. Chen, W. Qin, X. Wang, A. Miranowicz, and F. Nori, Shortcuts to adiabaticity for the quantum rabi model: Efficient generation of giant entangled cat states via parametric amplifi- cation, Phys. Rev. Lett.126, 023602 (2021)
work page 2021
-
[39]
P. W. Claeys, M. Pandey, D. Sels, and A. Polkovnikov, Floquet- engineering counterdiabatic protocols in quantum many-body systems, Phys. Rev. Lett.123, 090602 (2019)
work page 2019
-
[40]
D. Sels and A. Polkovnikov, Minimizing irreversible losses in quantum systems by local counterdiabatic driving, Proc. Natl. Acad. Sci. U.S.A114, E3909 (2017)
work page 2017
-
[41]
Braak, Integrability of the rabi model, Phys
D. Braak, Integrability of the rabi model, Phys. Rev. Lett.107, 100401 (2011)
work page 2011
-
[42]
S. Ashhab and F. Nori, Qubit-oscillator systems in the ultrastrong-coupling regime and their potential for preparing nonclassical states, Phys. Rev. A81, 042311 (2010)
work page 2010
- [43]
-
[44]
M. O. Scully and M. S. Zubairy,Quantum optics(Cambridge University Press, Cambridge, 1997)
work page 1997
-
[45]
J. Larson and T. Mavrogordatos,The Jaynes–Cummings model and its descendants: modern research directions(IoP Publish- ing, 2021)
work page 2021
-
[46]
P. Forn-D´ıaz, G. Romero, C. J. P. M. Harmans, E. Solano, and J. E. Mooij, Broken selection rule in the quantum rabi model, Sci. Rep.6, 26720 (2016)
work page 2016
-
[47]
Y . Wang, J. Zhang, C. Wu, J. Q. You, and G. Romero, Holo- nomic quantum computation in the ultrastrong-coupling regime of circuit qed, Phys. Rev. A94, 012328 (2016)
work page 2016
-
[48]
D. Ballester, G. Romero, J. J. Garc ´ıa-Ripoll, F. Deppe, and E. Solano, Quantum simulation of the ultrastrong-coupling dy- namics in circuit quantum electrodynamics, Phys. Rev. X2, 021007 (2012)
work page 2012
- [49]
-
[50]
W. Qin, A. Miranowicz, P.-B. Li, X.-Y . L ¨u, J. Q. You, and F. Nori, Exponentially enhanced light-matter interaction, coop- erativities, and steady-state entanglement using parametric am- plification, Phys. Rev. Lett.120, 093601 (2018)
work page 2018
-
[51]
F. Petiziol, B. Dive, F. Mintert, and S. Wimberger, Fast adiabatic evolution by oscillating initial hamiltonians, Phys. Rev. A98, 043436 (2018)
work page 2018
-
[52]
K. Takahashi and A. del Campo, Shortcuts to adiabaticity in krylov space, Phys. Rev. X14, 011032 (2024)
work page 2024
-
[53]
Z. Yin, C. Li, J. Allcock, Y . Zheng, X. Gu, M. Dai, S. Zhang, and S. An, Shortcuts to adiabaticity for open systems in circuit quantum electrodynamics, Nat. Commun.13, 188 (2022)
work page 2022
- [54]
-
[55]
N. N. Hegade, K. Paul, Y . Ding, M. Sanz, F. Albarr ´an- Arriagada, E. Solano, and X. Chen, Shortcuts to adiabaticity in digitized adiabatic quantum computing, Phys. Rev. Appl.15, 024038 (2021)
work page 2021
-
[56]
J. Yao, L. Lin, and M. Bukov, Reinforcement learning for many- body ground-state preparation inspired by counterdiabatic driv- ing, Phys. Rev. X11, 031070 (2021)
work page 2021
-
[57]
J. Ferreiro-V ´elez, I. Iriarte-Zendoia, Y . Ban, and X. Chen, Shortcuts for adiabatic and variational algorithms in molecular simulation, arXiv preprint arXiv:2407.20957 (2024)
-
[58]
Hatomura, Universal digitized counterdiabatic driving, arXiv preprint arXiv:2601.15972 (2026)
T. Hatomura, Universal digitized counterdiabatic driving, arXiv preprint arXiv:2601.15972 (2026)
- [59]
-
[60]
S. Morawetz and A. Polkovnikov, Efficient paths for local coun- terdiabatic driving, Phys. Rev. B110, 024304 (2024)
work page 2024
-
[61]
P. R. Hegde, G. Passarelli, A. Scocco, and P. Lucignano, Ge- netic optimization of quantum annealing, Phys. Rev. A105, 012612 (2022)
work page 2022
-
[62]
T. Hatomura, Shortcuts to adiabaticity in the infinite-range ising model by mean-field counter-diabatic driving, J. Phys. Soc. Jpn. 86, 094002 (2017)
work page 2017
-
[63]
J. R. Fin ˇzgar, S. Notarnicola, M. Cain, M. D. Lukin, and D. Sels, Counterdiabatic driving with performance guarantees, Phys. Rev. Lett.135, 180602 (2025)
work page 2025
-
[64]
S. Morawetz and A. Polkovnikov, Universal counterdiabatic driving in krylov space, PRX Quantum6, 040320 (2025)
work page 2025
- [65]
-
[66]
N. Goldman and J. Dalibard, Periodically driven quantum sys- tems: Effective hamiltonians and engineered gauge fields, Phys. Rev. X4, 031027 (2014)
work page 2014
-
[67]
T. Villazon, P. W. Claeys, A. Polkovnikov, and A. Chandran, Shortcuts to dynamic polarization, Phys. Rev. B103, 075118 (2021)
work page 2021
-
[68]
H. Ribeiro, A. Baksic, and A. A. Clerk, Systematic magnus- based approach for suppressing leakage and nonadiabatic errors in quantum dynamics, Phys. Rev. X7, 011021 (2017)
work page 2017
-
[69]
F. Petiziol, B. Dive, S. Carretta, R. Mannella, F. Mintert, and S. Wimberger, Accelerating adiabatic protocols for entangling two qubits in circuit qed, Phys. Rev. A99, 042315 (2019)
work page 2019
- [70]
-
[71]
P. Forn-D´ıaz, J. J. Garc´ıa-Ripoll, B. Peropadre, J. L. Orgiazzi, M. A. Yurtalan, R. Belyansky, C. M. Wilson, and A. Lupascu, Ultrastrong coupling of a single artificial atom to an electro- magnetic continuum in the nonperturbative regime, Nat. Phys. 13, 39 (2017)
work page 2017
-
[72]
S. A. Caldwell, N. Didier, C. A. Ryan, E. A. Sete, Hudson, et al., Parametrically activated entangling gates using transmon qubits, Phys. Rev. Appl.10, 034050 (2018)
work page 2018
-
[73]
X. Jin, Z. Parrott, K. Cicak, S. Kotler, F. Lecocq, J. Teufel, J. Aumentado, E. Kapit, and R. Simmonds, Superconducting architecture demonstrating fast, tunable high-fidelity cz gates with parametric control of zz coupling, Phys. Rev. Appl.24, 064026 (2025). 12 Appendix A: Analytic derivation of AGP In this Appendix, we derive the analytic expression for ...
work page 2025
discussion (0)
Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.