REVIEW 5 major objections 5 minor 28 references
Quantum Supremacy in Tomographic Imaging: Advances in Quantum Tomography Algorithms
T0 review · 5 major / 5 minor · reviewed 2026-08-08 · deepseek-v4-flash
Pith's one-line read The paper claims that a QUBO-based quantum annealing algorithm reconstructs tomograms exactly, with mean absolute error zero, even when half the sinogram is corrupted or half the projection angles are missing, while classical FFT and…
desk verdict An honest, reproducible extension of the authors' own QUBO tomography framework, but the 'quantum supremacy' conclusion is unsupported because the classical baselines are not run on the same masked problem. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The load-bearing object is the error-excluded QUBO cost function, Eq. (17): $\sum_{(\theta,s)\in D\setminus E} \{(I_P - P)(\theta,s)\}^2 - \sum_{(\theta,s)\in D\setminus E} \{P(\theta,s)\}^2$, where $P$ is the measured sinogram, $I_P$ is the Radon transform of a candidate binary-encoded image, $D$ is the full sinogram domain, and $E$ is the detected error region. Pixel values are expanded as weighted sums of binary qubits, for example $I_{ij} = \alpha_1 + \sum_k (\alpha_k - \alpha_{k-1}) q_k^{ij}$, so the squared mismatch becomes linear and quadratic in the binary variables. The error region $E$ is found by thresholding the mean absolute density difference between adjacent pixels along the position axis, and the reduced QUBO is handed to a hybrid quantum annealer. The exactness claim is carried by the solver reaching a global minimum whose objective value matches the theoretical minimum $-\sum_{D\setminus E} \{P(\theta,s)\}^2$, giving MAE 0.
What would settle it
Run the proposed method on a real sinogram from a CT scan with a known detector defect, keeping clinical image sizes, and compare against a defect-free reference; if the density-variation detector fails to isolate the defective rows or the solver returns MAE greater than zero, the central claim fails. A simpler check is to repeat the 50-percent-missing-angle experiment on the 50 × 50 body image with a new random seed and verify MAE 0; the paper already reports the solver missing the global minimum for the 100 × 100 tooth case, so that experiment directly tests the claimed robustness.
Extended reading notes
Core claim
The central claim is that excluding corrupted regions of a sinogram before building the QUBO objective lets a quantum annealer find a global minimum that classical optimizers miss. The authors encode each pixel of the target image as qubits whose coefficients follow a mass-attenuation representation, define the cost as the sum of squared differences between the measured sinogram and the Radon transform of the candidate image over the uncorrupted domain $D \setminus E$, and solve the resulting binary quadratic model with a hybrid quantum-classical solver. Table I reports MAE 0 for all tested ring-artifact rates (10 to 50 percent) and all tested missing-angle rates (10 to 50 percent) on the 50 × 50 body image, and for the 30 × 30 head image at 10 percent error. The same QUBO given to classical tools either returns nonzero MAE or no solution within the time budget. The authors interpret this as demonstrating quantum supremacy for tomographic reconstruction.
Load-bearing premise
The argument relies on two linked assumptions: that corrupted sinogram rows can be reliably detected by abrupt density changes between neighboring pixels, and that after those rows are removed the remaining QUBO is small enough for the quantum hybrid solver to find the true global minimum.
Editorial extensions
If this is right
- CT scanning could tolerate detector miscalibration without re-scanning, because corrupted projection rows are excluded from the objective rather than corrected.
- Limited-angle reconstruction from half the angular range would shorten scan times, reduce radiation dose, and address the missing-wedge problem in electron tomography.
- The same error-exclusion recipe should transfer to other inverse problems that can be expressed as QUBO cost functions, such as metal-artifact removal by masking high-density pixels.
- The paper's own failure cases show the exactness result is sensitive to problem size and solver behavior, so scaling to clinical images will require larger quantum processors or better solvers.
Reading between the lines
- Beyond the paper, the method suggests a generic recipe for inverse problems: formulate the objective only on the trustworthy subdomain of the data, which could apply to denoising, deconvolution, and sparse-view reconstruction beyond tomography.
- Beyond the paper, the quantum-supremacy claim should be read as benchmark superiority on small constructed instances rather than a complexity-theoretic separation, since the paper compares finite solvers on fixed QUBOs.
- Beyond the paper, a testable extension is to calibrate the error-row detector on real detector defects, because the paper uses artificial errors and notes that real defects are washed out during resizing.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper proposes a QUBO-based formulation for parallel-beam tomographic image reconstruction, solves the resulting binary optimization problems with D-Wave's hybrid solver, and compares against FFT/iradon, Gurobi (presolve only), and D-Wave's simulated-annealing sampler. The central claim is that the quantum/hybrid approach achieves 'quantum supremacy' in tomographic imaging by reconstructing images with MAE 0 from sinograms with up to 50% injected ring-artifact errors and from only 50% of the projection angles. Experiments are reported on Shepp-Logan, tooth, body, and head datasets of sizes 30x30 to 100x100, with pixel value ranges from binary to 0-10.
Significance. If the central claim were supported, exact tomographic reconstruction from half the projection angles and from heavily corrupted sinograms would be a practically interesting result for discrete tomography. The QUBO least-squares expansion in Section II.A is standard and the authors provide a public code repository, which are positive elements. However, the claimed quantum supremacy is not established: the classical baselines are truncated or unrepresentative, the error-detection step is unspecified and likely uses knowledge of the injected artifacts, and the paper itself reports solver suboptimality in key cases. The significance of the work as presented is therefore mostly a proof-of-concept that a commercial hybrid QUBO solver can fit small noiseless masked tomography problems, not a demonstration of quantum advantage.
major comments (5)
- [Section III.B and Table I] The Gurobi baseline is not a real classical optimization baseline: the authors state that they 'focused on the solution obtained from the presolve stage' rather than allowing Gurobi to solve the QUBO. Presolve is a preprocessing step, so the Gurobi MAE values in Table I do not represent the capability of a state-of-the-art classical QUBO/MILP solver. A fair comparison requires a complete Gurobi run (or an equivalently strong classical optimizer) on the same instances; without this, the hybrid solver's success cannot be attributed to quantum advantage.
- [Section III.C, Eq. (17)] The error-region detection procedure is not specified. The text says errors are detected by examining density variations between adjacent pixels and locating positions 'where pixel values differ markedly,' but no threshold, window size, or algorithmic rule is given, and the red regions in Fig. 2a appear to be selected from knowledge of the injected errors. Because the QUBO is constructed on the masked domain D\E, the entire reconstruction depends on this unspecified step. The method is therefore not reproducible, and the MAE-0 results may be an artifact of excluding exactly the corrupted rows.
- [Section IV.B and Section V] The missing control is a competent classical discrete-tomography reconstruction applied to the same masked sinogram. After error exclusion, the task is a noiseless or low-noise integer-valued limited-angle reconstruction, a regime where classical methods such as total-variation-regularized least squares or discrete algebraic reconstruction (DART) are known to be strong. FFT/iradon is a linear filtered-backprojection method, not an optimizer, so its poor performance on masked or limited-angle data is expected and does not demonstrate quantum superiority. A concrete test would be to run a TV-regularized or DART reconstruction on D\E and report the MAE; this is necessary before the Section V claim that the results 'strongly demonstrate the quantum supremacy of our algorithm.'
- [Section IV.A.1 and Section V] The paper's own results contradict the claimed robustness. The authors report that the hybrid solver did not reach the global minimum for the 100x100 tooth case (target -5,393,765.588 vs found -5,373,756.428) and failed at 20% error for the head image (target -4,607,247.045 vs found -4,607,144.207). Thus the MAE-0 entries in Table I are instance-dependent and hold only for specific small images and error levels; they do not support a general claim of accurate reconstruction under 'up to 50% error.'
- [Table I and Eq. (17)] An MAE of 0 on the masked problem is not, by itself, evidence of quantum supremacy. The QUBO in Eq. (17) is a least-squares fit to the remaining sinogram pixels; since the remaining data are noiseless and the pixel values are small integers, any optimizer that reaches the global minimum of the masked QUBO will recover the original image exactly if the remaining projections determine it. These experiments therefore measure whether the hybrid solver can minimize a specific small QUBO, not whether the reconstruction task is classically intractable. The paper provides no complexity argument or scaling analysis showing that the masked QUBO instances are hard for classical algorithms.
minor comments (5)
- [Eq. (17)] The second sum in Eq. (17) appears to be missing the square on P(theta,s); compare with Eq. (10), where the corresponding term is written as {P(theta,s)}^2.
- [Section III.A] The parameters of the injected errors are under-specified: the number of corrupted rows, the scaling-factor ranges, and the random seed (if any) are not reported, which hinders reproduction of the ring-artifact experiments in Table I.
- [Section IV.A.1] The statement that '50% of the original sinogram data was removed' is not clearly connected to the error-rate definition used elsewhere in the paper; the authors should clarify whether the 50% figure refers to removed projection angles, masked rows, or total sinogram pixels.
- [Section II.A, Eq. (4)] With k ranging from 0 to m, the representable integer range is 0 to 2^{m+1}-1, so the phrase 'less than 2^{m+1}' is slightly off; it should be 'at most 2^{m+1}-1.'
- [References] Reference [16] contains the typo 'Hubo formulations' instead of 'QUBO formulations,' and reference [18] lists only K. Jun as author although the text attributes the work to 'Jun and Lee.'
Circularity Check
No significant circularity; the reconstruction claim is a QUBO data-fit rather than a definitional tautology, though the supremacy comparison rests on weak classical baselines.
full rationale
The paper's central derivation is a QUBO least-squares fit of an image to its sinogram: equation (10) minimizes the squared difference between the simulated sinogram IP and the measured sinogram P, and the true image is a global minimizer because P is generated from that image. This is the standard structure of tomographic reconstruction, not a circular derivation: the image is not an input to the objective, only the sinogram is. The new step in Section III.C excludes an estimated error region E from the QUBO domain; this is a preprocessing choice, and the paper explicitly notes that the excluded rows are the ones that cause ring artifacts. Excluding corrupted measurements and then reconstructing from the remainder is a legitimate robust-reconstruction strategy, and the MAE-0 results depend on the D-Wave hybrid solver actually finding the global minimum, which the paper honestly reports it failed to do in the 100x100 tooth case and for the head image at 20% error. The QUBO formulation is attributed to the authors' prior work [17], [18], but the equations are re-derived in Section II, so the argument does not reduce to a self-citation chain. The main weakness is not circularity but experimental design: Gurobi is run only to presolve, SA is an untuned sampler, and FFT is applied to zero-masked sinograms rather than to the same error-excluded objective, so the 'quantum supremacy' claim is not supported against competent classical reconstruction. These are correctness and comparison concerns, not definitional circularity.
Assumptions & free parameters
free parameters (4)
- Error-region detection threshold
- Zero-padding width =
11, 10, 5 pixels depending on dataset
- Pixel value range and qubit encoding =
0-1 tooth, 0-3 body, 0-10 head
- Artificial error scaling factors =
random factors, unspecified
assumptions (6)
- domain assumption The Radon transform model P(theta,s) = integral of MAC along ray (Eq. 3) accurately describes the measured sinogram.
- domain assumption The QUBO formulation from prior work [17,18] correctly encodes tomographic reconstruction as minimization of squared sinogram error.
- domain assumption Error-affected regions in the sinogram are horizontal strips that can be identified by density variation and safely excluded.
- domain assumption The D-Wave hybrid solver returns a solution close enough to the global QUBO minimum to recover the true image.
- domain assumption An image with small integer pixel values and known zero-padding can represent the true object.
- standard math For binary variables q, q^2=q and the QUBO expansion is valid.
Cite this review
Pith. "Pith review of Quantum Supremacy in Tomographic Imaging: Advances in Quantum Tomography Algorithms." pith.science (2026). https://pith.science/paper/I65W7LNW
@misc{pith2026250204830,
author = {Pith},
title = {Pith review of: Quantum Supremacy in Tomographic Imaging: Advances in Quantum Tomography Algorithms},
year = {2026},
howpublished = {\url{https://pith.science/paper/I65W7LNW}},
note = {Machine review of arXiv:2502.04830}
}
read the original abstract
Quantum computing has emerged as a transformative paradigm, capable of tackling complex computational problems that are infeasible for classical methods within a practical timeframe. At the core of this advancement lies the concept of quantum supremacy, which signifies the ability of quantum processors to surpass classical systems in specific tasks. In the context of tomographic image reconstruction, quantum optimization algorithms enable faster processing and clearer imaging than conventional methods. This study further substantiates quantum supremacy by reducing the required projection angles for tomographic reconstruction while enhancing robustness against image artifacts. Notably, our experiments demonstrated that the proposed algorithm accurately reconstructed tomographic images without artifacts, even when up to 50% error was introduced into the sinogram to induce ring artifacts. Furthermore, it achieved precise reconstructions using only 50% of the projection angles from the original sinogram spanning 0{\deg} to 180{\deg}. These findings highlight the potential of quantum algorithms to revolutionize tomographic imaging by enabling efficient and accurate reconstructions under challenging conditions, paving the way for broader applications in medical imaging, material science, and advanced tomography systems as quantum computing technologies continue to advance.
Figures
Figures from the paper (4 more)
Reference graph
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Reviewed August 8, 2026 · model on record in the stance chip above.
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