In briefSymanzik effective Hamiltonian for lattice quantum field theories
SummaryThis paper proposes a framework for constructing the Symanzik effective Hamiltonian of lattice quantum field theories directly from dimensional analysis and symmetries in the Hamiltonian formulation. It enables classification of all operators that can contribute at a given order in the spatial lattice spacing, and this list can be reduced using equations of motion and other identities. The framework is demonstrated for φ⁴ theory and pure gauge theory, with results consistent with earlier work for classical improvement. It is intended as a basis for a future non-perturbative improvement programme in the Hamiltonian formulation.
In briefHolonomy, spectral topology and detailed balance in classical and open quantum systems
SummaryThis tutorial paper organizes band topology and non-Hermitian spectral theory around holonomy and applies them to mechanical metamaterials, chiral active fluids, stochastic networks and open quantum systems. Its central claim is that the spectrum of a linear generator can rule out detailed balance, forcing positive entropy production, but cannot determine how large dissipation is. The authors also propose benchtop tests for their statements.
In briefA proposed alternative framework to quantum theory
SummaryThis paper proposes an alternative framework that seeks to recover the empirical results of quantum theory from a holistic, scale-invariant ontology. It assumes only point particles in Euclidean space, described by ratios of masses, charges, and mutual separations, with shapes captured by a single scale-invariant function and no dynamical evolution. The author suggests the framework could in principle describe finite subsystems within an infinite configuration of particles.
In briefUniversal two-qubit control across fridges over a 10 km optical link
SummaryThis paper introduces a coherent optical link that transmits microwave control signals and phase references between two dilution refrigerators. Using a laser, a microwave-to-optical transducer, and an optical-to-microwave photodiode, the link carries control signals over 10 km of fiber. Through this link, the authors apply a universal gate set to a transmon qubit and a cavity qubit in another refrigerator and entangle them, reporting a Bell-state fidelity of 80.6%.
In briefReachable and unreachable quantum precision limits in ultrastrong light-matter coupling
SummaryThis paper studies how quantum precision depends on the gauge choice in ultrastrongly coupled light-matter systems. The transformation between gauges involves the coupling strength g, so each truncation gives a different family of results. The quantum Fisher information follows an exact parabola across gauges, and for harmonic matter it is minimized at a universal value set by the matter and cavity frequencies. Only the minimal-coupling bound can be reached, and the gauges differ by a factor of 9.6 with opposite trends.
In briefDiscrete time crystals kept stable by limiting measurement noise
SummaryThis paper asks whether continuous weak measurement on a periodically driven, long-range interacting spin chain can sustain discrete time-crystalline period doubling. Typical quantum trajectories reach a state without subharmonic response, while the most-probable trajectory, with measurement fluctuations suppressed, shows robust period doubling. The authors introduce a bounded-noise protocol restricting measurement fluctuations to a finite window, finding that narrow windows preserve the order, intermediate windows give coexisting ordered and disordered trajectories, and wide windows destroy it.
In briefCalibration-free temperature sensing using strain-swept two-level defects in quantum devices
SummaryThis paper examines whether intrinsic two-level defects in Josephson-junction barriers can serve as local thermometers by using the shape of their population response, without calibrating readout offset or contrast. It shows that for narrow sweeps the usable information scales with the fourth power of the sweep width. The approach is illustrated with a strain-swept defect in a Josephson junction.
Asghar ullah, \"Ozg\"ur E. M\"ustecapl{\i}o\u{g}lu, Mehmet Cengiz Onba\c{s}l\i
In briefDeploying quantum key distribution on Sweden's national fiber network
SummaryThis paper describes the deployment of quantum key distribution (QKD) on fiber links of Sweden's National Quantum Communication Infrastructure. The authors present procedures for characterizing fiber links and assessing their suitability for QKD. They relate measurable link properties to the factors that affect the secret key rate using a simplified model. They also report a successful one-month test on one of the links, confirming that QKD is feasible there.
Giulio Foletto, Mira Abu Yahia, Shreya Gouravaram Navalur et al.
In briefCommuting-check gauging for fault-tolerant logical measurements: adding completion qubits so local checks commute, enabling fault-tolerant logical measurement
SummaryThe paper introduces completion qubits that make local checks commute for Clifford Z2 symmetries of qubit stabilizer codes, adding one per noncommuting pair while preserving the gauged code space, its distance, and the Clifford property of the checks. It extends the approach to qudits and shows that gauging and ungauging a distance-d code implements a logical measurement with circuit fault distance Ω(d) in O(d) rounds. The construction is demonstrated by gauging two toric codes into the D(D4) quantum double and back.
WhyThe authors introduce completion qubits that make gauging checks commute, preserving distance and Clifford structure, with circuit fault distance Omega(d) for logical measurement.
In briefTesting whether gravity's phase dynamics are quantum under strong noise
SummaryThe paper asks whether gravity must be quantum by examining its phase dynamics rather than entanglement, which noise often destroys. Within a dephased Bose–Marletto–Vedral setup, the authors prove an exact finite-time difference between gravitational conditional-phase evolution and any passive stochastic local-phase model driven by a classical mediator. The distinction persists, with modified sensitivity, when population-preserving classical measurement and feedback are included.
WhyThe authors report an exact finite-time criterion separating gravitational conditional-phase dynamics from passive stochastic local-phase models under strong dephasing, extended to classical measureme
SummaryThis paper studies new high-rate quantum block turbo codes. Quantum block turbo codes are an iterative decoding technique for concatenated quantum error-correcting codes in product form. The authors use different constituent codes and examine how changing code parameters and the order of constituent codes affects turbo decoding performance.
Khaled Jebari, Luiz Anet Neto, Ramesh Pyndiah et al.
In briefA modular, loop-based photonic processor design for universal quantum computing.
SummaryThis paper proposes an architecture for a universal photonic quantum computer that is modular and built around a loop-based structure, which reduces the number of physical components needed. The authors show that the architecture is universal, deterministic, compatible with the quantum circuit model, reprogrammable, and capable of adaptive measurements. They demonstrate its operation through numerical simulations on specific examples, using machine learning to obtain some of its building blocks.
In briefA universal fault-tolerant quantum computing architecture using globally driven atom arrays
SummaryThis paper proposes a universal fault-tolerant quantum computing architecture based on globally driven dual-species atom arrays. Qubits are selected through interspecies Rydberg interactions in a hybrid neutral-atom system, avoiding locally addressed quantum gates. The authors define a native instruction set, GRAIL, into which surface-code error correction and magic state cultivation are compiled, and report an error-correction threshold of 1.43% for the resulting quantum memory.
WhyThe authors propose a globally driven dual-species atom architecture with a native instruction set, reporting a 1.43% threshold under a hardware-inferred noise model.
In briefChecking quantum circuit generators for equivalence across all parameters
SummaryThis paper presents a method to check whether a quantum circuit generator matches a reference for all parameter values, under six equivalence relations. The generator builds circuits from a qubit count and a bit string. For ladder programs, the authors prove that above a computable threshold the circuit matrices form a uniform matrix product operator, a weighted automaton whose dimension does not depend on qubit count. Equivalence reduces to a zeroness check on a difference automaton, performed modulo primes. Experiments show the method finds errors missed by fixed-size checks and gave no incorrect verdicts.
In briefFast, high-purity loading of barium ions using step-by-step isotope selection from natural sources
SummaryThis study presents a rapid method for selectively loading isotopes 137Ba+ or 135Ba+, which are promising ion qubits, from naturally abundant material. It uses a three-step, ultraviolet-free photoionization scheme: atoms are first selected on a narrow 791 nm transition, then resonantly excited at 554 nm, and finally ionized with an existing 532 nm Raman beam. No contaminant ions were detected during the experiment, and the resonant second step gave a high loading rate for the target ions.
In briefSemiclassical asymptotics of entanglement in torus-link quantum states
SummaryThis paper studies the entanglement entropy of topological quantum states built from T_{d,dn} torus links in SU(2) Chern-Simons theory at level k. In the semiclassical limit k→∞, the authors derive the asymptotic behavior of moments of the reduced density matrix, finding that the limiting entropy is governed by the two edge regions while the bulk contribution is suppressed. The result is expressed using Hurwitz zeta functions and depends on k modulo n. For large d, the entropy reduces to a binary entropy set by left and right edge weights, and the two limits k→∞ and d→∞ are shown to commute.
In briefAI-discovered entanglement witnesses for spin Hamiltonians
SummaryThis paper introduces EntNet, an AI framework that finds compact combinations of low-order spin correlators to tell entangled many-body states apart from separable ones. It targets one-dimensional spin-1/2 chains and uses a Transformer with rotary positional embeddings to learn spatial structure. The method reports over 98% recall on certified entangled states with near-zero false positives on separable states, and it transfers across system sizes and Hamiltonian families.
In briefProof of the QNEC without extra assumptions, using a weight
SummaryThe paper completes a proof of the quantum null energy condition (QNEC) within the half-sided translations and modular inclusions framework, removing an assumption required by earlier proofs. It establishes that the relative entropy between the state of fields outside a stationary black hole and a Hartle-Hawking state is always a convex function of the horizon cut. The authors also present a generalization of the QNEC in which the Hartle-Hawking Hilbert space is replaced by one built on a weight.
WhyThe authors remove an assumption from prior QNEC proofs and generalize the result to a weight-based Hilbert space.
In briefEncoding Optimization Objectives as Quantum Rotations
SummaryThis paper introduces the Angular Rotational Counter (ARC), which encodes objective functions written as weighted sums of Boolean functions by accumulating quantum rotations on a single-qubit register. The authors apply this to build a quantum oracle for the state assignment problem of finite automata using a weighted Hamming distance cost. Across 26 benchmarks, compared with Boolean-based oracles, it reduces qubit count by a mean of 20.8%, gate count by 89.3%, circuit depth by 92.4%, and quantum cost by 90.6%.
In briefLong-distance secure direct communication using GKP qubits
SummaryThis paper proposes a quantum secure direct communication protocol that uses Gottesman-Kitaev-Preskill encoding to transmit secret messages directly. It uses third-generation quantum repeaters to overcome the exponential photon loss. Numerical simulations indicate secure transmission beyond 1000 km at a 23 dB squeezing level. The authors also present a cost-based optimization framework balancing secure distance, secrecy capacity, and repeater resources.
In briefSuper-resolution imaging via multiphoton correlation of thermal light
SummaryThis paper shows that classical thermal light can overcome the diffraction limit by correlating multiphoton subsystems detected in a Hanbury Brown-Twiss interferometer. The correlation function shows a narrowed peak or dip whose width can be tuned by the average photon number. Experiments achieved temporal and spatial super-resolution enhancements of up to 11.8-fold and 5.1-fold, respectively.
SummaryThis paper proves the Rényi version of the quantum null energy condition (QNEC). The proof uses Araki-Masuda weighted L_p norms for all p > 2 and generalizes the algebraic proof for p=2. The authors also examine properties of the corresponding weighted conditional entropy. The p=2 limit corresponds to a conditional dynamical entropy originally defined in black hole dynamics.
WhyThe authors extend the algebraic QNEC proof to Rényi versions for all p>2 using weighted conditional Lp norms.
In briefAn optimal quantum strategy for the 2-hat game
SummaryThis paper studies the two-player hat game as a non-local game with two inputs and three outputs. The authors compute its quantum commuting value and show it equals the quantum value, which is (15+√33)/36, approximately 0.576238. The optimal quantum advantage is achieved using a shared non-maximally entangled qutrit state. The authors also determine the no-signalling value to be 2/3.
In briefChoosing model families and designing recovery gates in generator-based noise tomography
SummaryThe paper treats selecting a noise model family in generator-based noise tomography as a hypothesis test whose minimum shot count has a closed form. It compares two platforms and sixty-four gate placements, finding that the required shots vary greatly with design and that placement mainly affects conditioning. The authors conclude that controlling systematic bias matters more than the raw shot count.
In briefInteger electron-count cuts for real-space pair-density representability: a convergent set of rigorous relaxations
SummaryThis paper extends Part I by placing integer electron-count conditions in a convergent hierarchy of rigorous relaxations, defined by finite occupation linear programs on spatial partitions, for real-space pair densities at fixed one-particle density. Every level contains all representable pair densities and tightens under nested refinement, and their intersection characterizes pair densities admitting a symmetric N-particle probability-measure extension. In a fixed orbital basis, the levels give monotonically increasing lower bounds to the full configuration-interaction energy, which need not be reached.
In briefLieb-Robinson bound for one-dimensional continuum fermions
SummaryThis paper proves a Lieb-Robinson bound (LRB), which describes an approximate causal structure in quantum many-body dynamics, for a standard system of one-dimensional continuum fermions. Previously such bounds were established only for quantum spin systems and certain lattice boson systems. The result applies to initial states with controlled local particle number and energy moments, and is therefore thermodynamically stable.
WhyThe authors report the first Lieb-Robinson bound for one-dimensional continuum fermions, for initial states with controlled local particle number and energy moments.
In briefPauli propagation in adaptive local frames: a method to cut simulation costs by choosing better local bases.
SummaryThis paper studies how the cost of Pauli propagation depends on the local basis used to expand an evolving operator. It introduces frame-adaptive Pauli propagation (FAPP), which rotates each qubit's basis gate by gate to the principal axes of the operator's local polarisation. On Ising chains and infinite two-dimensional lattices, FAPP reduces truncation error and the number of strings needed at a given accuracy.
In briefProof of the Aaronson-Ambainis Conjecture: An Exposition
SummaryThis paper explains a recent proof of the Aaronson-Ambainis conjecture. The conjecture states that every degree-d polynomial mapping bits to [0,1] has a variable with influence at least poly(Var(p)/d). The authors organize the proof into four main steps and relate each to the analysis of boolean functions and probabilistic combinatorics. The exposition does not optimize parameters, so its exponents are weaker than the original.
WhyThe paper expounds a recent proof of the Aaronson-Ambainis conjecture, giving a polynomial influence lower bound and linking it to BPP versus BQP.
In briefA geometric method for exact analytical solutions of a scalar field in a one-dimensional moving cavity
SummaryThis paper studies the dynamical Casimir effect, in which a scalar field inside a one-dimensional cavity changes as a mirror moves. The authors show that the Cole-Schieve geometrical approach, long used only numerically, can yield exact analytical solutions to the Moore equation. They obtain solutions for an expanding cavity, a contracting cavity, and a resonant mirror motion. The method is extended to generate an infinite set of solvable laws of motion.
Maxwell F. de Ara\'{u}jo, Odemar Juli\~{a}o do N. Neto, Stanley S. Coelho et al.
In briefComments on a paper about optimizing thermal control in a dual-wavelength resonant nonlinear cavity
SummaryThis is a comment on a 2026 Applied Optics paper claiming to optimize a patented thermal management scheme for a dual-wavelength-resonant nonlinear cavity. The author argues the proposed variant reduces the maximum achievable temperature differential, which is a regression rather than an optimization. The comment states that maximizing this differential is needed to compensate phase differences in short crystals.
In briefSpin entanglement in proton-proton and proton-nucleus collisions: high-energy TMD effects and fragmentation probes
SummaryThis paper studies spin correlations between a quark and antiquark produced in proton-proton or proton-nucleus collisions, using k_T-factorization within the shockwave formalism. The authors construct full spin-density matrices for inclusive and diffractive channels and find a cos(2φ) modulation linked to linearly polarized small-x gluon TMDs. They also propose accessing these spin correlations in unpolarized hadron collisions via Collins and dihadron fragmentation functions.
In briefA microscopic model basis for macroscopic quantum electrodynamics in active media
SummaryThis paper builds a microscopic foundation for macroscopic quantum electrodynamics in active media. Starting from a driven three-level system, it derives an effective two-level description with nonequilibrium stationary populations and uses a quantum central limit approach to obtain collective Langevin dynamics. The same microscopic stationary state yields both the electromagnetic susceptibility and the quantum noise-current correlations. At optical transparency, the susceptibility's imaginary part vanishes while quantum fluctuations remain finite.
In briefWriting Quantum Circuit Angles Directly with LLMs, Without an Optimizer
SummaryThis paper asks whether a large language model can write the rotation angles of variational quantum circuits directly, without repeated quantum-device evaluations or gradient-based optimization. It tests the approach on 139 requests covering handwritten-digit classification, VQE ground-state estimation for spin chains and H2, and MaxCut QAOA, comparing against random weights, classical optimization, and optimization warm-started from LLM weights. When parameters have interpretable structure, the LLM matches or approaches the optimizer, but accuracy falls to chance in opaque weight spaces and results are sensitive to gate conventions.
In briefReconstructing Quantum States from Sklar-Type Relational Data
SummaryThe paper applies Sklar's theorem from classical probability to the context-dependent probability tables produced by the Born rule for a quantum state. For each table, it discards the marginal statistics of individual subsystems and keeps only the relational data among them. The authors prove that collecting these relational data over all contexts, together with quantum compatibility constraints, suffices to reconstruct any irreducible multiqubit quantum state.
In briefOne Bit, Many Records: Copying Information in Quantum Many-Body Dynamics
SummaryThis paper studies how a single locally encoded classical bit can become readable in many disjoint regions of a quantum many-body system at once. It proposes dynamical selection, in which an unperturbed nonthermal reference stays locally recognizable while a locally perturbed version spreads and relaxes under the same Hamiltonian. The authors give an entropy-capacity criterion and illustrate it with an embedded-dimer chain and stabilized PXP dynamics.
In briefTransferable circuit parameters for variational quantum eigensolvers, found without retraining
SummaryThis paper proposes predicting variational quantum eigensolver circuit parameters directly with machine learning, replacing the slow classical optimization loop. A geometric projection places surrogate hydrogen atoms along the target molecule's bond directions, so existing hydrogenic solvers can be reused. Only one projection radius per bond type is fitted, on a small reference molecule. The approach is demonstrated on separable-pair circuit designs and extended to multi-circuit methods spanning effective bases for quantum subspaces.
