quant-ph digest — 2026-04-29
Scored against Yuan's research programme (Y1–Y6):
- Y1 — arXiv:2502.09704 — iterative warm-started QAOA
- Y2 — arXiv:2304.06915 — quasi-binary portfolio QAOA
- Y3 — arXiv:2410.16265 — QAOA DGMVP portfolio (QST 2026)
- Y4 — arXiv:2603.14744 — Grover + ADMM cardinality-constrained BO
- Y5 — arXiv:2510.08292 — GW speed-ups via Gibbs states + Pauli sparsity
- Y6 — arXiv:2510.11213 — PBR test on IBM Heron2
Source
arXiv listing: https://arxiv.org/list/quant-ph/new (95 new + 23 cross = 118 entries; announce cycle for Tuesday, 28 April 2026)
Coverage: all 118 entries scored. 25 relevant (score ≥ 1); 93 SKIP (score 0, omitted).
Scoring rubric
0–10 on method/scope/conclusion overlap — max wins. HIGH 8–10 · MED 5–7 · LOW 1–4 · SKIP 0.
Highly relevant (score 8–10) — 5 papers
A Spectral Gap Informed Parameter Schedule for QAOA
- Authors: Kieran McDowall, Konstantinos Georgopoulos, Petros Wallden
- arXiv: 2604.24580
- Category: new submission — quant-ph
- Score: 9/10 (HIGH)
- Overlaps with: Y1, Y2, Y3 (method: QAOA parameter scheduling, mixer-Hamiltonian-based adiabatic schedules, scalability via gap extrapolation; scope: MIS, QUBO penalties, depolarising noise on QAOA)
- Why it matters: SGIR-QAOA is a non-variational schedule that directly competes with the layerwise/dual-annealing pipeline of Y3, and the gap-extrapolation trick lets it scale beyond classically simulable sizes. Empirical exponent improvement on degree-3 MIS (2−0.41 n vs. 2−0.56 n) and survival under mild depolarising noise are directly comparable to Y3's hardware-noise crossover analyses.
A challenge with the Quantum Approximate Optimisation Algorithm (QAOA), and variational algorithms in general, is finding good variational parameters, a task which in itself can be NP-hard. Recent work has sought to de-variationalise QAOA by picking well-informed guesses for the variational parameters. The Linear Ramp QAOA (LR-QAOA) achieves this by using parameter schedules inspired by the quantum adiabatic algorithm. We go a step further and use spectral gap information from an adiabatic Hamiltonian, with the QAOA mixer Hamiltonian as our initial Hamiltonian, to make smooth ramps which we call Spectral Gap Informed Ramps (SGIR-QAOA). SGIR-QAOA schedules perform slow evolution where the spectral gap of the adiabatic Hamiltonian is small. We show that SGIR-QAOA has performance improvements over LR-QAOA on Grover's problem at constant depth and that SGIR-QAOA requires shorter depths to achieve the same optimal solution probability. We then show that these performance benefits extend to a problem with potential practical applications — the Maximum Independent Set (MIS) problem. Finally, we demonstrate the scalability of the SGIR-QAOA method using extrapolated spectral gap information for scales that the spectral gap cannot be exactly evaluated, and show that the advantage appears to persist under mild depolarising noise.
Exhaustive and feasible parametrisation with applications to the travelling salesperson problem
- Authors: Marvin Schwiering, Timo Ziegler, Lennart Binkowski, Benjamin Sambale
- arXiv: 2604.24297
- Category: new submission — quant-ph
- Score: 9/10 (HIGH)
- Overlaps with: Y2, Y4 (method: feasibility-respecting parametrised circuits with finite-parameter exact reachability, generalising Hadfield-style hard mixers; scope: hard-constrained combinatorial optimisation including TSP and, by analogy, fixed-cardinality binary optimisation)
- Why it matters: Defines exhaustively parametrised circuits that reach every feasible state exactly with O(n log n) parameters via a group-theoretic recipe (transitive group action + generating sequence of involutions). Beats QAOA-AO on a 9-city TSP by reaching approximation ratio 0.91 vs. ~0.60. The same construction, with Sn replaced by the symmetric group on fixed-cardinality strings, gives an exact-reachability ansatz for Y2's quasi-binary portfolio mixer and Y3's DGMVP feasibility set.
This paper introduces the concept of exhaustively parametrised, feasibility-respecting quantum circuits for constrained combinatorial optimisation problems. Such circuits can reach, given the right parameter values, every feasible solution with certainty — including the optimum — with a fixed number of parameters, while avoiding infeasible solutions altogether. This is in sharp contrast to conventional quantum alternating operator ansatz schemes, which are merely guaranteed to reach the optimum asymptotically. We introduce an abstract pipeline for constructing exhaustively parametrised, feasibility-respecting circuits from a transitive group action on a problem's feasible set. Our constructions rely on the simple combination of the group action with group representation and the novel notion of generating sequences: group elements in fixed order, possibly with repetitions, that generate the entire group.
Improvement of performance of Grover's algorithm on three generations of Heron family IBM QPUs without and with topological dynamical decoupling
- Authors: Tihomir G. Tenev, Nayden P. Nedev, Nikolay V. Vitanov
- arXiv: 2604.23228
- Category: new submission — quant-ph
- Score: 8/10 (HIGH)
- Overlaps with: Y4, Y6 (method: Grover's algorithm; scope: superconducting hardware experiments on IBM Heron r1/r2/r3, dynamical decoupling under realistic noise; conclusion: hardware-regime feasibility for quantum-search algorithms)
- Why it matters: First clean 6-qubit Grover demonstration on IBM Heron r3 (Pittsburgh) with topological DD. Provides the most current 2Q-gate counts and noise overheads on the same Heron platform Y6 used for the PBR test, and is the natural empirical baseline for Y4's hardware-feasibility claims for the Grover step.
We investigate the performance of Grover's algorithm on three different generations of IBM Heron QPUs. On Heron family of IBM QPUs the success probabilities for three, four and five qubits without dynamical decoupling is better than results reported for previous generations of QPUs. The success probability as function of number of iterations of Grover operator is considered. A study of the improvement of results of Grover's algorithm for five qubit case with the help of topological dynamical decoupling is considered. For a six qubit case on Heron r3 QPU a clear result for finding the sought-after bitstring is reported for theoretically suboptimal number of iterations of Grover operator with the help of dynamical decoupling.
Constrained Quantum Optimization meets Model Reduction
- Authors: Max Tschaikowski, Andrea Vandin
- arXiv: 2604.23317
- Category: new submission — quant-ph
- Score: 8/10 (HIGH)
- Overlaps with: Y2, Y3 (method: exact dimensionality reduction of constrained QAOA via Quantum Zeno projector lifting; scope: classical simulation of hard-constrained quantum optimisation; conclusion: enables much larger feasible-subspace classical simulations)
- Why it matters: Shows constrained QAOA dynamics can be simulated exactly in the d-dimensional feasible subspace rather than the full 2n Hilbert space, with cost O((ν+s) d2). For Y3's DGMVP setting, d = C(N, K) can be far smaller than 2N, immediately extending the classically simulable size. Plug-in compatible with Y3's existing dual-annealing/layerwise pipeline.
Quantum optimization algorithms promise advantages for difficult problems but are costly to simulate and analyze on classical machines. Recently, constrained quantum optimization has been investigated through the lens of Quantum Zeno dynamics, an approach which constrains the search to a subspace by means of quantum measurements. Exploiting that quantum measurements are projections, we propose a model reduction approach and show that simulations can be conducted in a lower-dimensional space. As possible applications, we demonstrate exponential state-space reduction of constrained quantum optimization in case of random 3-SAT and an agent coordination problem over graphs.
Optimization Using Locally-Quantum Decoders
- Authors: Noah Shutty, Avijit Mandal, Seyoon Ragavan, Quentin Buzet, André Chailloux, Nicholas C. Rubin, Abid Khan, Sami Boulebnane, Ruslan Shaydulin, John Azariah, Stephen P. Jordan
- arXiv: 2604.24633
- Category: new submission — quant-ph
- Score: 8/10 (HIGH)
- Overlaps with: Y4, Y5 (method: Regev's reduction with fine-grained unambiguous-measurement decoders, head-to-head against QAOA at depth p=14, p=16; conclusion: maps the boundary of quantum advantage on max-k-XORSAT, including a Turbo-Prange classical algorithm matching the FGUM scores)
- Why it matters: The most quantitatively complete head-to-head between structured-quantum-search algorithms (Y4 territory) and QAOA (Y1–Y3 territory) on a clean Gallager-ensemble benchmark, including explicit asymptotic behaviour. The "locally-quantum-but-matched-by-classical" pattern is a cautionary template for any structured-search advantage claim, including Y4's. The QAOA-asymptotically-dominates-FGUM result at p ≥ 14 is a useful talking point for Yuan's QAOA-favoring narrative.
It was pointed out in [JSW+25] that widely-studied optimization problems such as D-regular max-k-XORSAT can be reduced to decoding of LDPC codes, using quantum algorithms related to Regev's reduction. LDPC codes have very good decoders, such as Belief Propagation (BP), and this therefore makes D-regular max-k-XORSAT an enticing target for this class of quantum algorithms. However, BP was found insufficient to achieve quantum advantage. Here, we develop an intrinsically quantum decoding technique, which decodes classical LDPC codes subject to coherent superpositions of bit flip errors. For average-case instances of D-regular max-k-XORSAT drawn from Gallager's ensemble, this quantum decoder strongly outperforms classical belief propagation at many values of k and D. For some (k,D) the approximate optima achievable using this decoder surpass both Prange's algorithm and simulated annealing. However, we stop short of achieving quantum advantage because we identify an enhancement to Prange's algorithm that recovers a precise tie.
Moderately relevant (score 5–7) — 7 papers
Accelerating quantum Gibbs sampling without quantum walks
- arXiv: 2604.22996
- Category: new submission — quant-ph; math-ph; math.NA
- Score: 7/10 (MED)
- Overlaps with: Y5 (method: quantum Gibbs sampling, KMS detailed balance, quantum singular-value transformation with quadratic spectral-gap improvement)
- Why it matters: Provides a walk-free quantum algorithm for purified Gibbs-state preparation with quadratic gap-dependence improvement, relevant to Y5's GW-via-Gibbs-state framework. Y5's quantum-inspired regime relies on Pauli-sparse Gibbs preparation; this paper offers a cleaner construction for the parent-Hamiltonian factorisation.
Szegedy's quantum walk gives a generic quadratic speedup for reversible classical Markov chains, but extending this mechanism to quantum Gibbs sampling has remained challenging beyond special cases. We present a walk-free quantum algorithm for preparing purified Gibbs states with a quadratic improvement in spectral-gap dependence for a broad class of quantum Gibbs samplers that satisfy exact Kubo-Martin-Schwinger detailed balance. Our main structural result is an explicit factorization of the corresponding parent Hamiltonian into noncommutative first-order operators. This turns purified Gibbs-state preparation into a singular-value filtering problem and enables a quantum singular value transformation algorithm with quadratically improved gap dependence under standard coherent-access assumptions.
Experimental high-dimensional multi-qubit Bell non-locality on a superconducting quantum processor
- arXiv: 2604.24740
- Category: new submission — quant-ph; cond-mat.stat-mech; physics.comp-ph
- Score: 7/10 (MED)
- Overlaps with: Y6 (scope: foundations test on a superconducting quantum processor; conclusion: high-dimensional Bell violations between two d=64 systems on 12 qubits)
- Why it matters: Same scope class as Y6's PBR test on Heron2 — foundations experiments on contemporary superconducting hardware. The simultaneous high-dimensional and many-body violation regime is novel and complements Y6's epistemic-vs-ontic narrative.
Combining recent advances in superconducting quantum hardware, we explore quantum correlations in a previously inaccessible regime by observing simultaneously high-dimensional and many-body Bell non-locality. We report a high-confidence Bell violation in the correlations between two d=64-dimensional systems encoded in twelve qubits. For system sizes up to d=32, the strength of the observed nonlocal correlations exceeds the quantum upper bound for d=2 systems, providing direct evidence of high-dimensional nonlocality. Furthermore, we demonstrate that the observed violation is genuinely collective: all qubits contribute to the nonlocal correlations, while most pairwise correlations across the bipartition remain Bell-local.
AutoQResearch: LLM-Guided Closed-Loop Policy Search for Adaptive Variational Quantum Optimization
- arXiv: 2604.24283
- Category: new submission — quant-ph
- Score: 6/10 (MED)
- Overlaps with: Y1, Y3 (method: adaptive solver-control policies for variational quantum optimisation, with diagnostics-driven decisions; scope: combinatorial optimisation)
- Why it matters: An LLM-driven sequential-policy framework for QAOA solver/ansatz/optimiser selection. Adjacent to Y1's iterative warm-starting and Y3's robust-optimiser study. Worth reading to compare adaptive-vs-fixed pipelines.
Configuring variational quantum algorithms for combinatorial optimization remains a difficult, expert-driven process requiring coordinated choices over solver family, ansatz, objective, and optimizer. We present AutoQResearch, an LLM-guided closed-loop experimentation framework that casts this task as sequential policy search over a curated design space. Instead of a single static configuration, the framework searches for adaptive solver-control policies that condition future decisions on diagnostics such as feasibility, optimality gap, and convergence stagnation.
Practical lower bounds for hybrid quantum interior point methods in linear programming
- arXiv: 2604.24362
- Category: new submission — quant-ph
- Score: 6/10 (MED)
- Overlaps with: Y4 (method: hybrid quantum-classical optimisation; conclusion: rigorous lower bounds on quantum runtime against open-source classical solvers)
- Why it matters: Methodologically very close to Y4's ADMM hybrid analysis — instead of asserting asymptotic speed-ups, the paper rigorously rules out practical advantage on real LP instances against HiGHS. Y4's epsilon-approximation guarantees should be re-examined in the same hybrid-benchmarking framework.
Quantum interior point methods (QIPMs) promise polynomial speed-ups over classical solvers for linear programming by outsourcing the solution of Newton linear systems to quantum linear solvers (QLSAs). However, asymptotic speed-ups do not necessarily translate to practical advantages on realistic problem instances. In this work, I evaluate whether practical advantage of a standard hybrid QIPM pipeline can already be excluded relative to the classical open-source solver HiGHS on a broad and diverse collection of LP instances spanning eight problem families.
Non-unitary extension of Grover's search algorithm
- arXiv: 2604.23382
- Category: new submission — quant-ph; math-ph
- Score: 6/10 (MED)
- Overlaps with: Y4 (method: Grover-style amplitude redistribution with non-unitary diffusion plus QSVT/block-encoding; conclusion: complexity analysis of single-rotation search)
- Why it matters: A Grover variant that performs a single big rotation rather than O(√N) small rotations, made coherent via QSVT + Chebyshev approximation. Same operator-class as Y4's structured-feasible-set search.
We have developed a non-unitary extension of Grover's search algorithm by changing the hidden geometry of Hilbert space carried by diffusion operator. Our algorithm finds the solution for search problem by performing a unique bigger rotation rather than small rotations in order polynomial times in the size N of search space. We analyze the complexity of implementing the non-unitary operation and we observed that the price paid by performing this rotation is due the normalization. In Kraus operator approach we need O(N) repetition of the algorithm to have a chance of measuring a solution in a post-selection, this is no better than the classical solution. However, the quantum singular value transform in addition with block encoding and Chebyshev polynomial approximation, we got complexity O(log N).
Calibrating the Role of Entanglement in Variational Quantum Algorithms from a Geometric Perspective
- arXiv: 2604.23555
- Category: new submission — quant-ph
- Score: 5/10 (MED)
- Overlaps with: Y1, Y3 (method: VQA / QAOA dynamics, geometric phase analysis on hardware-efficient ansatz)
- Why it matters: Argues that VQA evolution in problem-agnostic ansatzes is governed by the geometric phase rather than dynamical phase, with the trajectory shaped by parameter-dependent Hilbert-space geometry. Useful framing for thinking about Y1's warm-start trajectories.
Calibrating the role of entanglement in quantum algorithms is a crucial task in the development of quantum computing. Most existing studies have primarily focused on how the static properties of entanglement-such as its magnitude and phase-affect key performance metrics. In this work, we instead explore the relationship between the dynamical behaviors of entanglement and the execution of variational quantum algorithms from a geometric perspective. We find that, in contrast to conventional Hamiltonian dynamics where the evolution process is dominated by the dynamical phase, quantum state evolution in quantum algorithms is primarily governed by the geometric phase with the trajectory determined by the parameter-dependent Hilbert space geometry.
Explore Simpler Eigenmarking: Quantum Entailment Model Checking
- arXiv: 2604.23531
- Category: new submission — quant-ph; cs.ET
- Score: 5/10 (MED)
- Overlaps with: Y4 (method: Grover-search variant with extra qubits enforcing minority criteria via complementary states)
- Why it matters: A simpler version of Eigenmarking-style Grover search applied to entailment model checking. Indirect relevance to Y4's structured-search framework.
Targeting entailment model checking, a recent study has pioneered an idea of Eigenmarking search, an improvement over Grover search using extra qubits. The extra qubits condition the quantum state evolution such that the answer states (if exist) are always in the minority. The minority criteria is essential to Grover probability-amplitude amplification and consequently the effectiveness of Grover search.
Tangential (score 1–4) — 13 papers
- 2604.24475 · score 3/10 · Improving Zero-Noise Extrapolation via Physically Bounded Models — ZNE noise mitigation on IBM backends; relevant to Y3's hardware-noise crossover analysis.
- 2604.24397 · score 3/10 · Few-Shot Cross-Device Transfer for Quantum Noise Modeling on Real Hardware — transfer-learning noise models across IBM Fez/Marrakesh; same Heron family as Y6.
- 2604.22859 · score 3/10 · Bell Inequalities from Polyhedral Sampling — Bell-polytope facet enumeration; foundations adjacency to Y6.
- 2604.23898 · score 3/10 · Contextuality from the Projector Overlap Matrix — unifies Kochen-Specker indicators in a projector-geometric framework; foundations adjacency to Y6.
- 2604.24735 · score 3/10 · How Quantum Contextuality disappears in the Classical Limit — decoherence-driven suppression of state-dependent and state-independent contextuality; Y6 adjacent.
- 2604.23700 · score 2/10 · Quantum Circuit Cutting: Complexity and Optimization — circuit cutting for NISQ; tangential to Y3's hardware-feasibility analyses.
- 2604.23777 · score 2/10 · Architecture-aware Unitary Synthesis — superconducting hardware compilation; relevant only as compilation infrastructure.
- 2604.24467 · score 2/10 · Adaptive Tensor Network Sampling for Quantum Optimal Control — gradient-free MPS-based control; tangential to QAOA optimisation.
- 2604.24551 · score 2/10 · GSC-QEMit: A Telemetry-Driven Hierarchical Forecast-and-Bandit Framework for Adaptive Quantum Error Mitigation — QEM scheduling on noisy hardware; Y3 adjacency.
- 2604.24422 · score 2/10 · Noise-aware selection of circuit cutting strategies under hardware noise non-uniformity — circuit cutting in non-uniform noise topologies.
- 2604.24727 · score 2/10 · Operating a contextual Stern-Gerlach apparatus — cQED contextuality experiment; foundations adjacency.
- 2604.24760 · score 2/10 · Contracting Tensor Networks with Generalized Belief Propagation — GBP for tensor-network contraction; tangential to BP-related decoders in Y4.
- 2604.23304 · score 2/10 · Intrinsic Pointer Basis and Irreversible Classicality from Coherence Contraction — classicality emergence; Y6-adjacent foundations.
Summary table
| Score | arXiv ID | Short title | Overlaps | arXiv |
|---|---|---|---|---|
| 9 | 2604.24580 | Spectral Gap Informed Parameter Schedule for QAOA | Y1, Y2, Y3 | link |
| 9 | 2604.24297 | Exhaustive feasible parametrisation, TSP | Y2, Y4 | link |
| 8 | 2604.23228 | Grover on three Heron QPUs with topological DD | Y4, Y6 | link |
| 8 | 2604.23317 | Constrained Quantum Optimization meets Model Reduction | Y2, Y3 | link |
| 8 | 2604.24633 | Optimization Using Locally-Quantum Decoders | Y4, Y5 | link |
| 7 | 2604.22996 | Accelerating quantum Gibbs sampling without quantum walks | Y5 | link |
| 7 | 2604.24740 | High-dimensional multi-qubit Bell non-locality on superconducting QPU | Y6 | link |
| 6 | 2604.24283 | AutoQResearch (LLM-guided VQO policy search) | Y1, Y3 | link |
| 6 | 2604.24362 | Practical lower bounds for hybrid QIPM in LP | Y4 | link |
| 6 | 2604.23382 | Non-unitary extension of Grover's search | Y4 | link |
| 5 | 2604.23555 | Calibrating Entanglement in VQA (geometric) | Y1, Y3 | link |
| 5 | 2604.23531 | Eigenmarking: Quantum Entailment Model Checking | Y4 | link |
| 3 | 2604.24475 | Improving ZNE via Physically Bounded Models | Y3 | link |
| 3 | 2604.24397 | Few-Shot Cross-Device Quantum Noise Modeling | Y3, Y6 | link |
| 3 | 2604.22859 | Bell Inequalities from Polyhedral Sampling | Y6 | link |
| 3 | 2604.23898 | Contextuality from the Projector Overlap Matrix | Y6 | link |
| 3 | 2604.24735 | How Quantum Contextuality disappears in Classical Limit | Y6 | link |
| 2 | 2604.23700 | Quantum Circuit Cutting: Complexity and Optimization | Y3 | link |
| 2 | 2604.23777 | Architecture-aware Unitary Synthesis | Y3 | link |
| 2 | 2604.24467 | Adaptive Tensor Network Sampling for QOC | Y1, Y3 | link |
| 2 | 2604.24551 | GSC-QEMit (telemetry-driven QEM) | Y3 | link |
| 2 | 2604.24422 | Noise-aware circuit cutting under non-uniform noise | Y3 | link |
| 2 | 2604.24727 | Operating a contextual Stern-Gerlach apparatus | Y6 | link |
| 2 | 2604.24760 | Contracting Tensor Networks with Generalized BP | Y4 | link |
| 2 | 2604.23304 | Intrinsic Pointer Basis and Irreversible Classicality | Y6 | link |