In briefStructural limits of QAOA mixer design: transport and causal reach
SummaryThe paper examines mixer design in the Quantum Approximate Optimization Algorithm (QAOA), identifying two structural bottlenecks for shallow circuits: probability transport across configuration space and finite-depth causal reach. It derives mixer-dependent first-order objective bounds and a non-perturbative spreading condition. For MaxCut, it adds problem-graph-aligned two-local interactions to the transverse-field mixer, and reports that X+XX and X+YY improve approximation ratios over the standard X mixer at equal depth.
In briefElectric field control of spin transport anisotropy in a layered antiferromagnet
SummaryThis paper studies a dual-gate field-effect transistor built on CrSBr, a layered A-type antiferromagnetic semiconductor. The measurements show that the displacement field, rather than carrier doping, mainly determines the sign and magnitude of the magnetoresistance ratio. The authors explain the effect using ab initio calculations and an effective spin-circuit model. They conclude that the displacement field is an efficient electrical knob for controlling spin transport in CrSBr.
Mohamed Soliman, Jaime Garrido Aldea, Davy Borowski et al.
In briefMicromagnetic Lagrangian and Hamiltonian formulation of magnon-photon coupling in cavities
SummaryThis paper studies how magnons and photons interact inside a resonant microwave cavity, starting from linearized Maxwell and Landau-Lifshitz equations. The authors introduce an electric vector potential and an interaction Lagrangian, expand fields in normal modes, and derive a Hamiltonian using the Faddeev-Jackiw approach. A generalized Bogoliubov transformation then diagonalizes the coupled system into polariton variables. As an example, a perpendicularly magnetized YIG disk in a rectangular cavity shows hybridization of the cavity mode with several magnetostatic modes and frequency shifts near conducting walls.
In briefFault-tolerant Heisenberg-limited quantum sensing using bosonic probes
SummaryThis paper proposes a fault-tolerant protocol that uses bosonic probes to estimate displacements in the presence of dephasing noise. The authors construct an optimal error-correcting code under a mean photon-number constraint, with a repetition-encoded qubit register and repeated boson-parity measurements. Under circuit-level bit-flip noise, a distance-d code suppresses logical failures to order p^((d+1)/2). The Fisher information scales as NT² over interrogation times of order γ_A^(-(d+1)/2), compared with γ_A^(-1) for the non-fault-tolerant approach.
Daniel G. Li, Lorc\'an O Conlon, Yu-Xin Wang et al.
In briefClassifying cavity-modified reaction types via linear free-energy relationships
SummaryThis paper extends nonempirical linear free-energy relationships to reactions inside optical cavities and finds that they fall into four reaction types set by simple response-crossing rules. Reactions may follow conventional Bell-Evans-Polanyi (BEP) or counterintuitive Opposite-BEP behavior, or switch between them as cavity frequency changes. The framework is demonstrated in the Shin-Metiu model and four molecular reactions, and the complexity is reduced to competition between permanent-dipole and polarizability responses.
Jillian G. Hoffstadt, Davis M. Welakuh, Norah M. Hoffmann
In briefQuantum computing via computational imaging: representation, measurement, and inference
SummaryThis paper, aimed at computational-imaging and engineering readers, examines how the representation, measurement, and decoding of a quantum state determine what information can be returned. It distinguishes amplitude encodings of input values from encodings of complete candidate labelings, and studies unknown-phase inference under complex-field interference. It links singular-value decomposition of reshaped joint amplitudes to pure-state entanglement. In a four-pixel segmentation example, one QAOA layer lowers mean energy relative to uniform sampling yet makes a nonoptimal labeling more probable than the optimum.
George Kourousias, Sergio Carrato, Roberto Pugliese et al.
In briefFast mixing of Gibbs samplers for quantum spin systems with all-to-all coupling
SummaryThis paper studies how quickly Gibbs states of two-local quantum Hamiltonians on arbitrary interaction graphs, including fully connected systems, can be prepared using Lindblad dynamics satisfying KMS detailed balance. The authors adapt the classical Dobrushin condition to the quantum setting and use the order-1 quantum Wasserstein distance to measure how local perturbations spread. In a high-temperature regime set by the maximum total interaction strength per site, they derive contraction estimates that yield mixing times logarithmic in system size and inverse error tolerance.
In briefQuantum communication via a state discrimination method
SummaryThis paper proposes a state discrimination approach to unassisted quantum communication over a noisy quantum channel. Building on the operational duality between entanglement recovery and state discrimination, the authors construct entanglement-generation codes with explicit decoders based on Petz recovery maps. The error bounds hold for any number of channel uses and are expressed in terms of Petz-Rényi coherent information. For product sources, the error decays exponentially at rates below the coherent information.
In briefSubsystem Spacetime Code: A Quantum Error-Correction Framework for Measuring Clifford Circuit Fault Distance
SummaryThe paper constructs a subsystem spacetime code and uses it to characterize the distances of Clifford circuits. Its gauge group can be explicitly constructed and classified using masking properties of instantaneous stabilizer groups, and consists of faults that are harmless to the circuit. The framework is also used to identify where a dynamical code loses distance and to analyze how fault distance changes when circuits are composed from smaller components.
Esther Xiaozhen Fu, Aranya Chakraborty, Daniel Gottesman
In briefMultidimensional Revival Dynamics in a Bosonic Many-Body System: A study of how localized quantum states collapse and revive in a two-site Bose-Hubbard model
SummaryThis paper studies quantum interference in a symmetric two-site Bose-Hubbard model. Starting from a coherent state prepared on one site in the strongly self-trapping regime, the authors derive revival behaviors in expectation values, coherences, and the autocorrelation function, and illustrate the entanglement behavior. They identify several new features and show that a comprehensive semiclassical theory explains them, with excellent agreement to quantitative comparisons.
In briefLocal determination of low-energy states in weakly interacting gapped fermion systems
SummaryThis paper studies gapped fermion systems obtained by adding sufficiently weak even many-body interactions to a free Hamiltonian with a spectral gap. It proves that if another interaction matches the bulk interaction inside a region U, its low-energy states in the range [0, 3g/4] have local expectations close to the bulk ground state deep inside U, with errors decaying with distance from the complement of U. The results imply, among other things, that the bulk interaction has a unique algebraic ground state.
WhyThe authors prove quantitative local determination of low-energy states in gapped fermion systems with weak long-range interactions, yielding uniqueness of the algebraic ground state and localization
In briefHigh-fidelity universal quantum gates in a cryogenic atom array
SummaryThis paper demonstrates a universal quantum gate set in a cryogenic cesium-133 atom array. Single-qubit gates reach 99.970(2)% fidelity and raw two-qubit entangling gates reach 99.76(8)%, within the range of leading room-temperature implementations. The entangling gate uses direct single-photon coupling to a Rydberg P state, avoiding the scattering and light shifts of two-photon coupling.
WhyThe authors demonstrate a universal gate set in a cryogenic cesium atom array, using direct single-photon Rydberg coupling for entangling gates, and report single-qubit fidelity of 99.970(2)% and raw
In briefQDMin: Quantum Search for Energy Minima in Nuclear Shape Landscapes
SummaryThis paper presents QDMin, a method for locating the minimum of a nuclear collective energy landscape. It searches a parameterized Hamiltonian family using a coherent collective-coordinate register and an on-demand ground-energy threshold oracle, avoiding point-by-point construction of the landscape. The method is implemented for a schematic pairing-plus-multipole model, with calculations at four points and on a 4×4 quadrupole–octupole grid.
In briefTransport in spinful non-Hermitian gauge lattices: spin-dependent skin effects and transmission in one-dimensional lattices with gauge fields
SummaryThis paper extends a generalized transfer-matrix method to one-dimensional non-Hermitian tight-binding lattices with spin and matrix-valued Abelian and non-Abelian gauge couplings. In the Abelian case the spin sectors separate, giving exact spectra and closed transport expressions with spin-dependent skin localization. In the non-Abelian case noncommuting couplings mix the spin sectors, producing spin-hybridized lasing, coherent perfect absorption, and direction-dependent reflectionless transport with spin conversion.
In briefStability of the bulk gap and spectral flow for fermions with weak long-range interactions
SummaryThe paper proves that weak long-range many-body interactions preserve the bulk gap of a free fermion system. It constructs a quasi-local spectral flow that maps the free ground state to ground states of the interacting system. The results hold under polynomial decay conditions on the coefficients and interactions.
WhyThe authors prove bulk gap stability and construct a quasi-local spectral flow under weak long-range interactions, with polynomial decay conditions.
In briefUpper bounds on general (r,δ) quantum locally recoverable codes
SummaryThis paper studies general (r,δ) quantum locally recoverable codes without assuming purity or stabilizer structure, allowing recovery blocks to overlap arbitrarily. It establishes a Singleton-like upper bound for general quantum subspaces and tightens it with an explicit remainder correction. The authors also extend a known pure-code parameter bound to arbitrary pure quantum subspaces and analyze three code families that attain these bounds.
In briefThree-dimensional quantum cellular automata that cannot be stabilized into circuits
SummaryThe paper proves that for every odd prime p, the three-dimensional chiral Z_p Clifford quantum cellular automata of Haah and of Sun, Yang, Wang, Tantivasadakarn and Chen are not finite-depth quantum circuits, even after tensoring with arbitrary ancillary degrees of freedom and composing with translations. Previously such results were known only within the Clifford category. As a consequence, the group of three-dimensional QCA modulo stabilized circuits and translations is not finitely generated.
WhyThe authors introduce a new invariant for invertible subalgebras, proving 3D QCA are not finite-depth circuits beyond the Clifford setting; one key claim remains conjectural.
In briefStabilizing fluctuating Cooper pairs using a terahertz resonator
SummaryThis paper develops an equilibrium theory of a mesoscopic, disordered two-dimensional superconductor coupled to a subwavelength terahertz resonator, focusing on how superconducting phase fluctuations interact with the resonator's electromagnetic fluctuations. Modeling the resonator as a lumped-element circuit, the authors find that coupling raises the superconducting transition temperature Tc rather than suppressing it. For a 1 µm × 1 µm, 8 nm-thick disordered film, they estimate a relative Tc enhancement of about 1%, roughly ten times the 0.1% obtained when phase fluctuations are neglected.
Frieder Lindel, Jonathan B. Curtis, J\'er\^ome Faist et al.
