In briefSecret-shared teleportation of a two-qudit gate to a later-chosen recipient
SummaryThe paper shows how the ability to apply a two-qudit entangling gate can be secret-shared among several candidate nodes in advance. A provider encrypts half of a Bell pair into one share per node, and after a later key release only the selected node can complete an exact non-local CSUM^k gate with the user's data. The authors state that any coalition smaller than the number of candidates, or the key register alone, holds no information.
In briefFastest quantum evolution under fixed-norm generators
SummaryThis paper studies quantum systems whose evolution is driven by linear generators with a fixed unitarily invariant norm. For this class, it derives a universal time-optimal generator that converts one given state into another, yielding a time-optimal non-Hermitian Hamiltonian for pure-state conversion. The general result is then used to obtain quantum speed limits for mixed-state evolutions governed by Lindbladians and non-Hermitian Hamiltonians.
WhyThe authors derive a universal time-optimal generator and quantum speed limits under fixed unitarily invariant norms, using GL(n,C) geodesic geometry for arbitrary dimension and mixed states.
In briefWeighted hypergraph quantum states as resources for quantum sensing
SummaryThis paper studies weighted hypergraph states, a family of multi-qubit quantum states, and identifies subclasses defined by their graph topology that perform better in quantum metrology. Using quantum Fisher information and a new Dicke-basis representation, the authors show these subclasses outperform separable states and standard weighted graph states over broad ranges of edge weights. Analytical formulas for any number of qubits are provided, with a detailed analysis for four qubits. The authors also find that adding higher-order hyperedges can keep a quantum advantage under higher local dephasing noise.
In briefWhich gaps survive in the unitary almost Mathieu operator, and which close
SummaryThe paper determines exactly which gap labels correspond to open spectral gaps for the unitary almost Mathieu operator at every irrational frequency and all coupling constants in (0,1]. When both couplings are below one, every permitted gap label is open, including the critical case where the couplings are equal. When at least one coupling equals one, both lifts of odd winding labels are open, while all even winding labels collapse.
WhyThe authors exactly characterize which gap labels are open for the unitary almost Mathieu operator at all irrational frequencies and couplings, including the critical case.
In briefFunctional tensor train methods for high-order Greeks and exposure tails of multi-asset structured products
SummaryThis paper proposes solving the backward pricing recursion for worst-of autocallable notes using a piecewise-polynomial functional tensor train (hp-FTT), so that one solve yields all Greeks at any spot and the potential future exposure quantile without Monte Carlo sampling noise. Comparing against strong Monte Carlo estimators on worst-of autocallables observed monthly on three to five assets, the authors find Monte Carlo cheaper for first-order Greeks at 1% accuracy, while hp-FTT is cheaper for third-order Greeks at that accuracy and for all checked Greeks at 0.1%. The results depend on derivative order, accuracy target, and number of assets.
WhyThe authors solve the backward pricing recursion with piecewise-polynomial tensor trains split at barriers, obtaining all Greeks in one solve, and report cost comparisons against Monte Carlo on three
Javier Lopez-Piqueres, Atithi Acharya, Yue Sun et al.
In briefTopologically protected edge states in a single superconducting flux qubit
SummaryThis paper shows that topological edge states can be realized in a simple superconducting circuit built from one inductively shunted flux qubit. The circuit's low-energy dynamics map analytically onto an extended Su-Schrieffer-Heeger (SSH) chain, and numerical simulations of the full circuit confirm this mapping. Near a chiral point in parameter space, the edge states are numerically found to be topologically protected against chiral-symmetry-preserving perturbations such as charge noise. The authors conclude that protection effects previously associated with multi-qubit systems can also occur in a single qubit.
In briefCharge pumping and leptogenesis analogy in a symmetric mass generation phase on a four-leg ladder
SummaryThis paper uses density-matrix renormalization group simulations on a four-leg ladder to study a chiral fermion lattice model (the 3-4-5-0 model) with six-fermion interactions at one edge. Charge pumping stays quantized across weak, intermediate, and strong coupling, though the spatial distribution of pumped charge differs between boundary phases. At intermediate coupling the edge becomes fully gapped through symmetric mass generation. The authors also draw an analogy to a topological leptogenesis scenario in the Standard Model.
In briefProof that the quartic gap between quantum and dequantized linear algebra algorithms is tight
SummaryThis paper studies quantum linear algebra algorithms that access a matrix through QRAM, and classical dequantized algorithms with sampling and query access. At fixed condition number and accuracy, quantum algorithms use Õ(ρ) queries while the best dequantized algorithms use Õ(ρ⁴), where ρ is the normalized Frobenius norm. The authors construct worst-case dense linear systems showing this quartic gap is tight up to a logarithmic factor.
WhyThe authors show the quartic gap between quantum and dequantized linear algebra algorithms is tight, via a lower bound covering many tasks.
Shouvanik Chakrabarti, Dylan Herman, Junhyung Lyle Kim et al.
In briefComparing photon sources for secure quantum key sharing without trusting detectors
SummaryThis paper compares two single-photon source types for measurement-device-independent quantum key distribution: weak coherent pulses and quantum dot sources. Using decoy-state analysis, the authors find that quantum dot implementations outperform the best-case weak coherent pulse setup across all transmission distances, even at moderate mean photon numbers. They also show that both source types are highly sensitive to imperfect photon indistinguishability, which significantly affects key rates and maximum transmission distance.
Janka Memmen, Yvonne Lasars, Tobias Heindel et al.
In briefComparing quantum and classical kernel methods for classification under controlled protocols
SummaryThis paper compares quantum kernel methods with classical kernels for classification under a protocol-controlled setup. It tunes the quantum bandwidth on the same grid budget as the classical kernel, recomputes kernels within each fold, and counts cost in hardware circuit evaluations. Across a 324-cell factorial design and four standard datasets, feature-map bandwidth tuning matters more than any quantum-classical difference. Tuned quantum kernels are statistically indistinguishable from a tuned RBF kernel on all four real datasets.
In briefLogical Bell inequalities for marginal Wigner negativity
SummaryThis paper constructs logical Bell inequalities whose violations are determined by the Wigner function of a reduced quantum state. For odd-prime qudits, each phase-space point of a nonempty proper subsystem defines an inequality that is violated when its Gross Wigner value is negative. The normalized violation gives a lower bound on the contextual fraction in the complete Weyl measurement scenario, valid for any joint state with that marginal. A family of product states that saturates this bound is also identified.
Sanchit Srivastava, Selman Ipek, Cihan Okay et al.
In briefA resource-efficient quantum method that splits molecules into fragments and runs them in parallel on virtual QPU regions
SummaryThe paper introduces FMO-QVM-HCI-HSQD, a framework that splits a large molecular problem into fragments, runs them in parallel on virtual regions of a quantum processor, and uses a half-qubit circuit to reduce circuit depth. It was tested on IBM hardware with the water trimer and the carmofur_Mpro complex using up to 52 qubits. The results show lower two-qubit depth, reduced QPU time, and access to a much smaller determinant subspace than comparison methods, while keeping energies accurate.
R. Pradeep, Anurag Chaudhary, Ashish Kumar Patra et al.
In briefSolvable coupled cluster states in infinite dimensions with prescribed momentum distributions
SummaryThe paper connects the coupled cluster wave function method with dynamical mean-field theory (DMFT). In the infinite-dimensional limit of the hypercubic lattice, static expectation values of coupled cluster states can be evaluated in exact closed form. The authors show that any momentum distribution can be realized as the exact unique ground state of an explicit parent Hamiltonian, and that these states fail in the strong-coupling regime near the Mott transition, revealing a limitation of coupled cluster doubles.
In briefNo generalised contextuality arises from the vacuum
SummaryThis paper shows that, under certain conditions, generalised contextuality in the sense introduced by Spekkens cannot be created from the vacuum of a quantum field. Initially noncontextual qudit states do not become contextual merely by interacting with a quantum field. The authors verify this in two scenarios: a perturbative approach expanding the time evolution operator in powers of the coupling constant, and the limit of zero energy gap in the spectrum of the free detector Hamiltonian.
In briefGENIE: Learned quantum circuits as embedding solvers and when they work
SummaryThe paper introduces GENIE, an impurity solver for density matrix embedding theory in which a generative transformer learns the sampling circuit, trained on the quantum-selected configuration interaction energy. On N2, hydrogen chains, water and a hydrogen ring, it compares GENIE at equal determinant budget with classical selected CI methods and with sample-based quantum diagonalization. GENIE does not beat the best classical selection, and its failures are governed by wavefunction compactness relative to the budget rather than correlation strength. A cheap coupled-cluster-based estimate of compactness works as a router that predicts when GENIE should be used.
In briefLocality, Probability and the Relevance of History: A theory paper on how quantum nonlocality relates to relativity
SummaryThe paper proposes a generalization of relativity's causal constraint to probabilistic theories: the probability of an event should be functionally determined by the probabilities of event occurrences in its immediate causal past. The author argues this differs from Bell's criterion of local causality and implies it only under an extra assumption that history is irrelevant. Consequently, Bell-inequality-violating quantum phenomena need not conflict with relativity, locality, statistical independence, or realism; they instead show that history is relevant.
In briefFrom Mixed to Pure: Understanding Quantum Phases via Canonical Purification
SummaryThis paper studies quantum phases of matter. Pure-state phases are defined through finite-depth local unitary connections, a notion recently extended to mixed states linked by locally reversible channels. The authors show that such a channel between mixed states can be lifted to a local isometry between their canonical purifications, so mixed states in the same phase have canonical purifications in the same pure-state phase. They give an explicit construction of the lifting isometry and illustrate the results with toric code under bit-flip noise and Chern insulator under fermion-number noise.
WhyThe authors show locally reversible channels lift to local isometries between canonical purifications, with explicit Petz-based construction checked on toric code and Chern insulator examples.
In briefFocusing light through two coupled multimode fibers to build compact single-atom tweezer arrays
SummaryThe paper uses a 2x1 multimode fiber fused coupler to create two independent control channels sharing one output facet. Each channel forms near-diffraction-limited optical tweezers, and a small frequency offset between the channels suppresses interference. The tweezer separation is shown to be insensitive to misalignment of the input coupling.
In briefElectron-nuclear coupling in chemical and physical processes: how it matters when Born-Oppenheimer approximations break down.
SummaryThe paper reviews the Born-Oppenheimer (BO) and Born-Oppenheimer-Huang (BOH) approaches to electron-nuclear motion, which are foundational for studying chemical and physical processes. It notes that the BO approximation often fails when excited electronic states are involved, because of coupling between states. The authors describe adiabatic potential energy surfaces and nonadiabatic coupling terms, which govern nuclear forces. Near conical intersections, these coupling terms can break molecular symmetry and qualitatively change observed behavior.
In briefControl-noise trade-offs in industrial silicon spin qubits
SummaryThis paper studies electron spin-1/2 qubits in 28Si/SiGe fabricated with Intel's 300 mm process and compares them with a reference device from RIKEN. The Intel devices reach π/2-gate fidelities at the 99.99% level and show longer idle coherence. The authors link micromagnet placement, set by the vertical stack design, to magnetic-field gradients that affect charge-noise conversion and drive efficiency, revealing a trade-off between integration layout and gate performance.
Leon C. Camenzind, Ik Kyeong Jin, Yi-Hsien Wu et al.
In briefHybrid quantum models for trade surveillance: comparing quantum and classical classifiers for detecting pump-and-dump schemes
SummaryThe paper benchmarks four quantum and hybrid classifiers against classical baselines on a synthetic pump-and-dump detection task, using a shared split of 1,000 accounts and two 20-feature representations. The best model is classical XGBoost on ANOVA features, with a suspicious-class F1 of 61.4%. The hybrid quantum neural network reaches 54.5-57.9% F1 on an ideal simulator and 55.4-59.8% on ibm_fez hardware, outperforming six of eight classical configurations. The authors observe no quantum advantage.
Bimal Mehta, Daniel musgrove, Devanshu Shekhar et al.
In briefChannel dichotomies: interconverting channels under non-signalling superchannels
SummaryThis paper studies how quantum channels can be converted into one another using non-signalling superchannels, with the asymptotic conversion rate given by the ratio of channel capacities. The main result gives the second-order expansion of the optimal target length, where the coefficient is an inverse sesquinormal distribution determined by the capacities and dispersions. The authors extend state dichotomy theory to channels and note that this characterization cannot be obtained by concatenating channel coding and simulation protocols.
In briefDesigned classification tasks on noisy quantum processors that favor quantum over classical methods
SummaryThe paper uses a projected quantum kernel on an engineered classification problem with 15, 30, and 45 qubits and reports a significant performance gap over classical methods. The results are reproduced across different quantum processors. The authors also show that error mitigation widens this gap by improving hardware performance and increasing classical difficulty, though the problem is artificial.
Esteban Payares, Nadia Milazzo, Ghada Ben Slama et al.
