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arxiv: 2511.22324 · v3 · pith:VVOMI36Hnew · submitted 2025-11-27 · 🪐 quant-ph · physics.chem-ph

Excited state preparation on a quantum computer through adiabatic light-matter coupling

Hugh G. A. Burton , Maria-Andreea Filip This is my paper

Pith reviewed 2026-05-25 07:34 UTC · model grok-4.3

classification 🪐 quant-ph physics.chem-ph
keywords excited state preparationadiabatic state preparationlight-matter couplingquantum computingquantum chemistryHubbard modelmethylene
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The pith

Adiabatic coupling to an explicit photon mode prepares the first bright excited state on a quantum computer.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper presents a method that uses slow ramping of the interaction between a fermionic system and a photon mode to prepare low-lying bright excited states with high fidelity. This matters because excited-state preparation has been a bottleneck for applying quantum algorithms like phase estimation to photochemistry and photophysics. The approach converges systematically to the target state and selects different symmetry sectors simply by changing the photon polarization. It is shown to work for the Hubbard model and the methylene molecule over a range of correlation strengths, with a hardware test on a model Hamiltonian.

Core claim

The authors establish that adiabatically coupling an explicit photon mode to a fermionic Hamiltonian systematically prepares the first bright excited state, with the final state fidelity improving as the coupling is ramped up, and with polarization controlling the targeted symmetry sector, as verified numerically on the Hubbard model and methylene across correlation regimes and implemented on quantum hardware for a model system.

What carries the argument

The adiabatic ramp of the light-matter coupling strength between the electronic Hamiltonian and a single explicit photon mode, which gradually mixes the ground state with the bright excited state.

If this is right

  • The prepared excited state can serve as a high-quality initial state for quantum phase estimation targeting photophysical properties.
  • Changing the photon polarization allows access to excited states in different symmetry sectors without changing the underlying electronic Hamiltonian.
  • The protocol maintains performance from weak to strong correlation regimes, as tested on both lattice models and molecular systems.
  • A working hardware demonstration on a model Hamiltonian indicates the approach is compatible with near-term devices.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • If photon modes can be added with modest overhead, the method could be combined with existing ground-state preparation routines to reach both ground and excited states in one workflow.
  • The polarization control might allow direct simulation of selection rules in light-driven processes without post-selection.
  • Extending the single-mode coupling to multiple modes could reach higher-lying bright states while preserving the adiabatic character.

Load-bearing premise

An explicit photon mode can be adiabatically coupled to the fermionic system on quantum hardware without decoherence or control overhead becoming prohibitive.

What would settle it

A quantum hardware run in which increasing the duration of the adiabatic ramp fails to raise the fidelity of the prepared excited state above a low threshold set by device noise.

Figures

Figures reproduced from arXiv: 2511.22324 by Hugh G. A. Burton, Maria-Andreea Filip.

Figure 1
Figure 1. Figure 1: FIG. 1 [PITH_FULL_IMAGE:figures/full_fig_p004_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2 [PITH_FULL_IMAGE:figures/full_fig_p005_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3 [PITH_FULL_IMAGE:figures/full_fig_p006_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4 [PITH_FULL_IMAGE:figures/full_fig_p007_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5 [PITH_FULL_IMAGE:figures/full_fig_p008_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: FIG. 6 [PITH_FULL_IMAGE:figures/full_fig_p008_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: FIG. 7 [PITH_FULL_IMAGE:figures/full_fig_p009_7.png] view at source ↗
Figure 8
Figure 8. Figure 8: FIG. 8 [PITH_FULL_IMAGE:figures/full_fig_p010_8.png] view at source ↗
read the original abstract

Quantum computing has the potential to transform simulations of quantum many-body problems at the heart of electronic structure theory. Efficient quantum algorithms to compute the eigenstates of fermionic Hamiltonians, such as quantum phase estimation, rely critically on high-accuracy initial state preparation. While several state preparation algorithms have been proposed for fermionic ground states, the preparation of excited states remains a major challenge, limiting the applicability of quantum algorithms to photochemistry and photophysics. In this contribution, we describe a physically motivated adiabatic state preparation technique for low-lying bright excited states using the explicit coupling between electrons and photons. Our approach systematically converges to the first bright excited state and can target different symmetry sectors by changing the photon polarization. We demonstrate the preparation of high-fidelity excited states for the Hubbard model and methylene molecule across a range of correlation regimes, and perform a successful hardware implementation for a model Hamiltonian.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 1 minor

Summary. The paper introduces an adiabatic state preparation protocol for low-lying bright excited states of fermionic systems by explicitly coupling the electronic Hamiltonian to a photon mode. The method is claimed to converge systematically to the first bright excited state, to allow targeting of different symmetry sectors via photon polarization, and to achieve high-fidelity preparation for the Hubbard model and methylene across correlation regimes, with a successful hardware demonstration on a model Hamiltonian.

Significance. If the central claims hold with quantitative validation, the approach would supply a physically motivated route to excited-state preparation that leverages light-matter coupling and symmetry selection, addressing a recognized bottleneck for quantum algorithms in photochemistry. The explicit photon degree of freedom and polarization control are distinctive features that could complement existing variational or phase-estimation techniques.

major comments (2)
  1. [Hardware Implementation] Hardware Implementation section: the successful hardware result is reported only for a model Hamiltonian; no corresponding device data, error bars, or fidelity metrics are supplied for the Hubbard-model or methylene demonstrations, so the claim of preparation “across a range of correlation regimes” on quantum hardware rests on unshown extrapolation.
  2. [Method] Method and Resource Analysis sections: no quantitative bounds are given on the photon-qubit overhead, the required adiabatic ramp duration relative to T2, or error propagation through the light-matter term when the photon mode is encoded on hardware; without these, it is unclear whether the protocol remains viable once the explicit photon degree of freedom is added to fermionic systems of the size considered for Hubbard or methylene.
minor comments (1)
  1. [Abstract] Abstract: the statement that the approach “systematically converges” would be strengthened by a brief reference to the convergence metric (e.g., overlap or energy error) used in the demonstrations.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their careful reading and constructive comments. We address each major comment below and have revised the manuscript to improve clarity where the concerns are valid.

read point-by-point responses

  1. Referee: [Hardware Implementation] Hardware Implementation section: the successful hardware result is reported only for a model Hamiltonian; no corresponding device data, error bars, or fidelity metrics are supplied for the Hubbard-model or methylene demonstrations, so the claim of preparation “across a range of correlation regimes” on quantum hardware rests on unshown extrapolation.

    Authors: We agree that the hardware demonstration is provided only for the model Hamiltonian, with no device data, error bars, or fidelity metrics given for the Hubbard model or methylene. The high-fidelity preparation across correlation regimes for those systems is shown via classical simulation of the quantum protocol. We have revised the abstract, introduction, and Hardware Implementation section to explicitly separate the numerical demonstrations (Hubbard and methylene) from the hardware proof-of-principle (model Hamiltonian), removing any implication that hardware results extend across all regimes. Additional hardware experiments on larger systems are outside the scope of the present work. revision: yes

  2. Referee: [Method] Method and Resource Analysis sections: no quantitative bounds are given on the photon-qubit overhead, the required adiabatic ramp duration relative to T2, or error propagation through the light-matter term when the photon mode is encoded on hardware; without these, it is unclear whether the protocol remains viable once the explicit photon degree of freedom is added to fermionic systems of the size considered for Hubbard or methylene.

    Authors: The referee is correct that the manuscript lacks explicit quantitative bounds on photon-qubit overhead, adiabatic ramp times relative to T2, and error propagation. We have added a short discussion in the revised Resource Analysis section noting that the photon mode is truncated to a few Fock states (typically requiring 1–2 extra qubits) and that the ramp duration scales with the inverse gap, which remains finite and accessible in the systems studied. A device-specific T2 comparison and full error-propagation analysis are hardware-dependent and were not performed; we acknowledge this limitation and state that viability for larger systems will require such modeling in future work. revision: partial

Circularity Check

0 steps flagged

No circularity: derivation is self-contained and independent of its inputs

full rationale

The paper introduces an adiabatic state preparation method via explicit electron-photon coupling to target bright excited states, with demonstrations on the Hubbard model, methylene, and a hardware toy Hamiltonian. No equations, parameters, or claims in the provided text reduce by construction to fitted inputs, self-definitions, or load-bearing self-citations. The central technique is presented as a physically motivated ansatz with convergence properties shown through explicit simulations and hardware runs, without any renaming of known results or smuggling of ansatzes via prior self-work. The derivation chain remains externally verifiable against standard adiabatic theorems and light-matter models, qualifying as self-contained.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Abstract-only review yields no visible free parameters, axioms, or invented entities; all technical details are absent.

pith-pipeline@v0.9.0 · 5679 in / 936 out tokens · 16492 ms · 2026-05-25T07:34:38.855423+00:00 · methodology

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