In briefA new butterfly in the meadow: lattice graphs in a magnetic field with circulant coupling
SummaryThe paper studies the spectrum of a quantum square lattice graph placed in a uniform magnetic field with rational flux per plaquette. It considers all nontrivial cases of circulant, scale-invariant vertex coupling, focusing on those that break time-reversal invariance. Apart from two cases with partially decoupled edges, the remaining twelve fall into two spectral classes, and the second class shows a previously unknown butterfly pattern.
In briefDispersion forces between two objects of any shape
SummaryThis paper uses the vacuum tensor Green's functions of electrodynamics to derive Lippmann-Schwinger-type equations for electromagnetic field correlations. These correlations are inserted into the Maxwell stress tensor and the Lorentz force formula to compute Casimir dispersion forces between two arbitrarily shaped bodies. The analysis excites the bodies using electric and magnetic dipoles.
In briefHidden Coherence and Controlled Quasihole Motion in a Superconducting Quantum Processor
SummaryThis paper prepares a three-electron, nu=1/3 Laughlin state on a superconducting quantum processor using seven qubits and reconstructs its many-body density matrix. Using Read's composite-boson construction, it reveals vortex-dressed coherence that persists over a larger separation range than electron coherence, and shows this depends on off-diagonal many-body coherence. The authors also prepare a quasihole with one added flux, characterize its fractional charge response, and extract an effective geometric-phase signature from the reconstructed dominant-eigenstate trajectory.
In briefFrom Machine-Discovered Graphs to Analytic NOON State Families
SummaryThis paper studies how graphs discovered by machines can generate NOON states after heralding and output-number selection. It derives analytic weight conditions for any photon number N and gives quantum experiment designs using a Hong-Ou-Mandel interferometer and an exact Gaussian implementation via Takagi decomposition. The authors report that pure, zero-displacement Gaussian schemes need at least N-2 herald photons, a bound both constructions reach.
Ozra Mahmoudi, Fatemeh Ahmadi, and Rahman Nouroozi
In briefDemonstration of a partial-knowledge quantum key distribution protocol
SummaryThe paper presents Bridge[d,q], a new quantum key distribution protocol that generalizes SARG04 to d dimensions and q bases. Alice and Bob each learn only partial information about the other's raw key, yet this is enough to distill a definite mutual encryption key. The authors experimentally demonstrate the Bridge[2,3] protocol, switching three unbiased polarization bases with a single Pockels cell.
In briefA Grover-amplified oracle for maximum clique and minimum hitting set, with hypergraph dualization via quantum phase estimation
SummaryThe paper introduces a Graph Encoding Operator that, applied to the complement of a graph, yields an oracle for the maximum clique problem usable with Grover amplification. A Hypergraph Encoding Operator plays the analogous role for the minimum hitting set problem, and its measurement approximates the number of hitting sets, addressing dualization of positive Boolean functions. The authors give full constructions, correctness proofs, complexity analysis, and a quantum simulator implementation. They claim both operators need only O(N) qubits in the number of vertices N.
Francisco Pi\~nero, Fernando L.\Pelayo, Hernan I. de la Cruz et al.
In briefQuantum circuits cannot exactly simulate the quantum switch
SummaryThe quantum switch is a higher-order operation that combines input quantum channels in an indefinite causal order. The paper proves that no quantum circuit with classically controlled causal order can exactly and deterministically simulate it for arbitrary input channels using any finite number of calls. The result already holds for qubit channels and extends to the complete r-switch, which controls all permutations of r input channels.
WhyThe authors prove quantum circuits with classically controlled causal order cannot exactly and deterministically simulate the quantum switch, extending to the complete r-switch.
In briefDeterministic pure-state method for thermal quantum states via Markov-shielded typicality
SummaryThe paper introduces a deterministic variational framework for constructing a Markov-Shielded Typical (MST) state, a pure-state representative of thermal equilibrium whose local reduced density matrices closely approximate those of the Gibbs state. The method reformulates free-energy minimization by replacing the nonlocal von Neumann entropy with a local, computationally tractable Markov entropy. The authors establish rigorous upper and lower bounds showing the MST free energy lies very close to the thermal free energy.
In briefInitialization masks overcome decoding obstructions in compressed QAOA
SummaryThis paper studies how converting a variational quantum state into a classical assignment by decoding noncommuting observables creates structural limits in compressed quantum optimization. The authors construct a family of connected cubic graphs showing that, under a fixed Pauli encoding and deterministic sign decoder, all-plus QAOA circuits have cut at most 2r at any depth. Selecting a suitable initialization mask yields a linear depth-one advantage and higher mean approximation ratios on random MaxCut instances. The authors distinguish decoded expressivity from optimized energy and empirical performance and state that the results do not establish a quantum computational advantage.
In briefConserved quantities for the deformed W-algebra W_{q,t}(D_l)
SummaryThe paper studies the deformed W-algebra W_{q,t}(D_l) of type D_l and constructs an infinite family of commuting local integrals of motion, viewed as a two-parameter deformation of the classical KdV hierarchy Hamiltonians. Using four free field representations of the quantum toroidal algebra U_q(D_l^), one for each end node of the affine Dynkin diagram, it defines corresponding non-local integrals of motion. Both families act on a common Fock space of l+1 free fields, and the authors give a direct computational proof that they mutually commute.
In briefA compact quantum attention module for static sign language recognition, tested against matched classical baselines
SummaryThe paper proposes QCA-DenseNet, which uses an eight-qubit variational circuit as a channel-attention gate on DenseNet121 features for static American Sign Language recognition. The quantum gate has 17,464 parameters, 7.51 times fewer than a squeeze-and-excitation block. Tested by holding out one of five signers at a time, it reaches 94.50% mean accuracy, slightly above SE at 93.72%. Parameter-matched classical and no-attention models perform about the same, and the differences are not significant, so the authors report a much smaller attention gate without a quantum advantage.
In briefBeyond the Mean Gap: Retention in Transferred-Angle QAOA on a Superconducting Chip
SummaryThis paper runs depth-2 QAOA circuits with transferred angles on the IBM Heron processor ibm_marrakesh, solving binary subproblems from an alternating-direction decomposition. The authors show that comparing only mean cost between device and simulation can miss what matters for optimization. At 12 qubits, circuits kept far less of their probability of the optimum than of their mean-gap improvement. The authors argue that validations should report retention of the optimum and of near-optimal sets.
In briefQAOA inside ADMM: subproblem wins don't carry over to decomposition at equal budgets
SummaryThe paper benchmarks QAOA as the binary subproblem solver in a two-block ADMM for mixed-binary problems against classical solvers under matched budgets. Scored on its final readout, QAOA loses to random search at 12 and 16 binary variables, but wins when credited with its best sample. In a noiseless 12-qubit simulation, depth-2 QAOA finds exact optima of planted-family subproblems more often than the strongest local heuristics, yet no family gave it a better ADMM outcome than the best classical solver and penalty.
In briefDelta-corrected shot allocation to escape plateaus in variational quantum eigensolvers
SummaryThis paper addresses the heavy measurement cost of the variational quantum eigensolver (VQE) by proposing delta-corrected shot reduction (DCSR), a shot allocation strategy. Using the multivariate delta method, the authors derive higher-order bias correction terms for the empirical reduction factor to reduce finite-sample instability. The authors report that DCSR converges faster than standard VPSR across diverse noise and resource regimes while matching or lowering cumulative measurement costs.
Jamie Evander Ghozaly, Pekik Nurwantoro, Gagus Ketut Sunnardianto et al.
In briefQuantized pumping in a driven SSH chain that mirrors 2D Haldane topology
SummaryThis paper studies topological pumping in a one-dimensional extended Su-Schrieffer-Heeger (SSH) chain with tunable next-nearest-neighbor hoppings. A Bloch-space graphical method is used to design pumping schemes, with the Chern number of the synthetic band set by the closed loop traced by the Bloch vector. The authors demonstrate quantized pumping for a filled band and for a bosonic wave packet under Bloch oscillations. They also show that the Haldane model maps onto this driven chain, so a two-dimensional Chern number can be read from a one-dimensional pumping protocol.
In briefEstimating Linear-Optical Amplitudes with Entangled Inputs
SummaryThe paper studies how to estimate output amplitudes of a linear-optical interferometer when the input photons are entangled. The authors give an unbiased estimator whose mean-square error falls as 1/N with the number of draws, regardless of the interferometer, output pattern, or entanglement. It applies to inputs that are matrix-product states of bounded bond dimension, such as light from sequential quantum emitters. The guarantees are additive, and the method also estimates traced-memory probabilities, overlaps and marginals.
WhyThe authors extend unbiased amplitude estimation to entangled matrix-product-state inputs, giving an interferometer-independent mean-square error bound and polynomial cost for sequential quantum-emitt
In briefTrace adds one quantifier: exact complexity of perfect play in nonlocal games
SummaryThe paper asks whether players of a finite nonlocal game can win with certainty, meaning a perfect strategy exists. It proves that for normal spatial strategies this existence question is Σ⁰₂-complete, so it stays undecidable even with a halting-problem oracle, which is harder than the finite-dimensional and commuting-operator models. The authors also show that requiring finite trace adds one existential number quantifier, and several related results are included, with key parts formally verified in Lean.
WhyThe authors show perfect spatial strategy existence in nonlocal games is Σ^0_2-complete, a tight classification with trace costing one existential quantifier, and report Lean formal verification.
In briefForecasting unstructured PDEs on superconducting quantum processors
SummaryThe paper implements a quantum reservoir network (QRN) on IBM superconducting hardware using up to 52 qubits to forecast high-dimensional unstructured partial differential equations. The method is gradient-free and uses partial measure-and-reset so circuit runtime can reach about 24 times the qubit coherence time. On a 2D cylinder flow and a Gray-Scott reaction-diffusion problem, adding QRN features to an autoencoder linear prediction pipeline reduced prediction error by 21% to 43%, and closed-loop autoregressive forecasting was demonstrated.
WhyThe authors apply a gradient-free quantum reservoir network to unstructured PDE forecasting on 52-qubit hardware, reporting 21%-43% error reduction over an autoencoder baseline.
Erik Connerty, Jonathan Eastridge, Taylor Patti et al.
In briefAn adaptive protocol for estimating Rényi entropy
SummaryThe second-order Rényi entropy is a key measure for characterizing the entanglement structure of states prepared in quantum many-body experiments. The paper proposes an adaptive protocol that starts from a small initial set of measurements and uses a gradient-based method to iteratively optimize the ratio of random local unitary settings to projective measurements per setting. On synthetic data for several prototypical states, the method converges to ratios comparable to those found by brute-force grid search, and it requires slower growth of the measurement budget than fixed-ratio protocols to reach a given accuracy.
In briefLimits on light intensity for phase-only holographic optical tweezer arrays
SummaryThis paper studies how efficiently a phase-only hologram can distribute light across an array of optical tweezer traps. The authors derive upper bounds on the minimum intensity at each trapping site, accounting for illumination, target geometry, and diffraction from spatial light modulator pixels. Numerical experiments show that optimized holograms come close to these limits, suggesting that choices of illumination and trap geometry matter more for power efficiency than further phase optimization.
In briefDynamically tunable light-matter coupling using protected superconducting oscillators
SummaryThis thesis addresses how flux tuning of superconducting microwave cavities degrades their photon lifetimes. It explores hardware solutions, including remote off-plane flux sources and on-chip lines with multiple filtering stages. These raise photon lifetimes to several hundred microseconds and allow real-time control of detuning and coupling strength in the Rabi model.
In briefPractical Ellipse Fitting Methods for Atom Interferometry Data
SummaryThis paper addresses extracting the differential phase shift between two noisy atom interferometers, a task handled by ellipse fitting. It compares statistical, algebraic, geometric and Bayesian ellipse fitting methods in terms of parameters and performance relevant to atom interferometry. The authors describe a novel "reciprocal" geometric method and note that each approach has trade-offs depending on the use case. Supplemental basic Python and Matlab code is provided for each method.
In briefRegev's reduction reaches the reconstruction threshold for spin-glass sampling
SummaryThe paper applies Regev's quantum Fourier transform reduction to sampling from Gibbs distributions of classical spin glass Hamiltonians, equivalent to cost functions for a D-regular max-k-LINSAT optimization problem. It decodes the resulting problem with Belief Propagation with Quantum Messages (BPQM). The authors prove that the minimum temperature reachable by Regev+BPQM equals the reconstruction threshold temperature for noisy channels on tree networks. Large numerical experiments across hundreds of problem parameters agree closely with the predicted dynamical glass transition.
WhyThe authors prove Regev+BPQM reaches the reconstruction threshold temperature, linking quantum decoding duality to conjectured limits of classical local sampling.
In briefExperimental visual quantum state discrimination: AI-optimized quantum measurement extracts more information per photon
SummaryThe paper proposes a trainable quantum measurement for vision tasks under photon-limited and noisy conditions, consisting of a diffractive optical neural network followed by a detector array. It is trained to maximize the rate at which discrimination error decays as photons accumulate. The measurement achieves exponentially lower error than direct imaging and a network optimized for single-photon discrimination, and the advantage is validated in noiseless and electron-multiplying CCD photon-counting experiments.
WhyThe authors train a diffractive optical network with a quantum objective, reporting exponentially lower error than imaging and validation in an EMCCD photon-counting experiment.
In briefA coherent electrometer built from a hybridised double quantum dot and resonator, for fast, low-power charge readout.
SummaryThe paper presents a charge detector based on coherent interaction between a microwave resonator and a double quantum dot, rather than the conventional conductance or reactance shift method. The device resolves two charge states with an SNR of 11.7 in 16 microseconds, using a readout signal power two orders of magnitude lower than previously needed for this speed. Its low dissipation makes sample heating negligible.
Samuel Andersson, Pierre Glidic, Andrea Cicovic et al.
In briefCan One Hear the Size of a Clock? (a counting bound for random-jump systems)
SummaryThe paper adapts Weyl's law, which counts vibration modes fitting in a cavity, to systems that jump randomly between states. For a system with d states and a frequency-to-decay-rate ratio Q, it shows that fewer than 2(d-1)/(πQ) oscillations can exceed ratio Q. Nested cycles approach this bound, and measured oscillations indicate how large a hidden system must be.
In briefSymplectic Reck: learning Gaussian quantum operations directly on hardware
SummaryThis paper proposes a physical learning method and circuit architecture for continuous-variable quantum photonic systems, where a programmable circuit is trained in situ to invert an unknown lossless Gaussian quantum operation. The authors prove that any symplectic matrix decomposes into a triangular array of two-mode symplectic gates followed by single-mode gates, and introduce the symplectic Reck mesh that physically realizes this factorization. They define a local condition number that quantifies the squeezing needed per nulling step and its sensitivity to measurement error. Numerical experiments show training with finite measurements and robustness to systematic gate-calibration errors.
In briefConvex-design method for optimal quantum sensors that classify phases
SummaryThis paper studies quantum sensors that directly classify a binary phase, skipping an intermediate parameter estimate. For a fixed number of queries, the authors express classification error as a linear function of the sensor response, which they restrict to a bounded trigonometric polynomial, yielding a semidefinite program that gives the globally Bayes-optimal response. Fejér–Riesz factorization and GQSP synthesis then produce a physically realizable control sequence. Numerical tests report better accuracy and more reliable optimization than training control angles directly.
Amirhossein Taherpour, Alireza Sadeghi, Georgios B. Giannakis
In briefEntanglement percolation boosted by a power-of-choice protocol
SummaryQuantum communication networks need maximally entangled states, but imperfect entanglement generation leaves distributed states only partially entangled. The paper introduces a power-of-choice (PoC) protocol that reverses the selection criteria of the Achlioptas process from classical explosive percolation. The PoC protocol brings forward the entanglement percolation transition, reducing the entanglement resources needed for quantum communication. Unlike explosive percolation, it can be implemented using only local information without appreciable loss of performance.
In briefBaby universes form when observers are hidden from the boundary
SummaryThis paper studies two double-scaled Sachdev-Ye-Kitaev models coupled by a four-parameter interaction, with a heavy particle representing an observer. When the particle is present, the wormhole connecting the two systems can only grow. Rare products of Hamiltonian strings cancel the particle's string, producing a closed baby universe that carries the observer, while the emptied wormhole recovers discrete states of finite length. This is described as a first-order transition in which Krylov complexity drops, allowing the emergence of the baby universe to be detected from the boundary.
In briefA master equation for quantum systems driven by correlated classical noise
SummaryThe paper presents a modular framework for deriving time-local quantum master equations for driven systems affected by temporally correlated classical noise. It combines the Donsker-Furutsu-Novikov relation with the Magnus expansion to derive the Novikov-Magnus master equation for zero-mean Gaussian noise through fourth order in the noise strength. For a driven qubit under Ornstein-Uhlenbeck and band-limited 1/f noise, the second- and fourth-order maps remain CPTP in the perturbative regime and accurately reproduce stochastic simulations.
Nada Khogeer, Jerison Parra, Caroline Desgranges et al.
In briefHow moving multi-spin qubits between locations affects their decoherence and leakage
SummaryThis paper analyzes how logical qubits encoded in multiple spins lose fidelity and leak while being shuttled, under spatio-temporally correlated 1/f noise, for two-, three-, and four-spin encodings. It finds that parallel shuttling protects best over short distances, while sequential shuttling performs better for long-range transport, with exact boundaries depending on device parameters. The authors give explicit expressions for fidelity and leakage that can be predicted from a few independently measured pairwise dephasing factors.
Yu-Ning Zhang, Aleksandr S. Mokeev, Maximilian Rimbach-Russ et al.
In briefA Quantum Mechanical Description of Active Matter: a framework treating self-propelled microscopic systems with quantum-style equations
SummaryThe paper treats energy expenditure rate and momentum generation rate as the fundamental quantities driving swimming active matter, and builds corresponding Lagrangian and Hamiltonian formulations. Analysing periodic motion in Fourier space, it introduces a complex field describing the probability distribution of a single unit and the population density of non-interacting particles. The authors report a Dirac-like equation with minimal coupling and a Schrödinger-like equation, and formalize two-way coupling between swimmers and fluid via a multipole expansion of the active force.
In briefRaman-coupled lattice model of 1D anyons with unbounded statistics
SummaryThis paper proposes loading a Raman-coupled Bose gas into a one-dimensional optical lattice to realize a lattice anyon model called the Raman anyon-Hubbard model. For a small statistical phase it reduces to the anyon-Hubbard model, while beyond that limit it defines a distinct lattice anyon model. Numerical results show features of 1D anyons, including density-dependent asymmetry of the ground-state momentum distribution, interaction-induced asymmetric transport, and chiral bound states.
Josep Cabedo, Claudio Iacovelli, Leticia Tarruell et al.
In briefControlling quantum relaxation of hydrogen molecules in crystals by classical effects
SummaryThis paper studies hydrogen molecules trapped in crystalline CO2 and N2O at 10 K. Infrared spectroscopy measures how their ortho and para nuclear-spin states convert into each other. Increasing hydrogen concentration suppresses this conversion nearly tenfold, and fully at 20% loading. Simulations attribute this to changes in available phonon modes and strain-driven clustering of hydrogen molecules.
In briefGibbs-type entropy for general Wigner distributions
SummaryThis paper proposes a non-equilibrium Gibbs-type entropy for general quantum systems that can be computed from Wigner functions, covering both Gaussian and non-Gaussian states. Using large deviation theory, it builds a positive-definite entropy based on uncertainty about the underlying state after repeated measurements of cumulants, applicable out of equilibrium. The authors also derive relative, conditional, and mutual entropy and Rényi entropy, and compare results with Wehrl entropy for the 1D harmonic oscillator.
Gabriel Rabelo-Soares, Yevgeniy Kovchegov, Giorgio Torrieri
In briefDeterministic quantum search for NP problems via verifier-based oracles
SummaryThis paper proposes a general method for constructing quantum oracles for NP problems from their classical verifier functions, and uses it in a deterministic quantum search framework that identifies satisfying assignments. The framework keeps the quadratic query speedup of quantum search over classical exhaustive search. The authors show the oracle's gate count is polynomial in the binary encoding length of the verifier and that the total qubit requirement is polynomial. Circuit-level simulations on multiple N-SAT instances confirm deterministic identification of satisfying assignments.
Soumyajyoti Chatterjee, Harishankar Mishra, Asvija Balasubramanyam et al.
In briefAI-driven discovery of formally verified quantum programs
SummaryThe paper builds a quantum program library in the Lean theorem prover, where Gemini 4 agents synthesize new programs against formal specifications and verify their correctness and cost. Agent teams share results through wikis and organized discussions. Reported gains over prior baselines include up to 2.55x for parallel search, 290x for quantum arithmetic, and 11x, 8x and 2.5x for fusion, photochemistry and drug-metabolism simulations.
WhyThe authors report AI agents discovering and formally verifying quantum programs in Lean, with large gains on arithmetic and simulation tasks.
Sergey Shirobokov, Ben Jaderberg, Katerina Hristova et al.
In briefArrival-time problem in quantum information: observing a Zeno crossover in monitored distributions
SummaryThis paper studies when quantum particles arrive at a detector in periodically monitored spin chains and quantum circuits. It identifies a quantum Zeno regime and a low-monitoring regime, separated by an optimal monitoring period set by the single-particle bandwidth. The authors measured arrival-time distributions on superconducting quantum hardware in one- and two-dimensional circuits, finding close agreement with quantum-trajectory theory.
WhyThe authors study arrival times in periodically monitored spin chains, report Zeno and low-monitoring regimes, and measure distributions on superconducting hardware matching quantum-trajectory theory.
Yousef Mafi, K. G. S. H. Gunawardana, Kim P\"oyh\"onen et al.
In briefBeyond the n/2 Threshold: Quantum Query Complexity of Hamming Weight and Symmetric Functions
SummaryThis paper studies how many quantum queries are needed to compute n-bit Boolean functions. The known van Dam algorithm computes any n-bit Boolean function with bounded error using n/2+O(√n) quantum queries. The authors construct an explicit family of symmetric Boolean functions that require n/2+Ω(n^{1/3}) quantum queries at a fixed positive constant error. They also give an algorithm that recovers the exact Hamming weight with bounded error using n/2+O(n^{1/3}) quantum queries, which computes all symmetric Boolean functions within the same bound.
WhyThe authors give an n/2+Ω(n^{1/3}) query lower bound for symmetric Boolean functions and a matching n/2+O(n^{1/3}) algorithm for Hamming weight recovery.
In briefDifferentiable digital twins for tuning and testing neutral-atom and ion quantum computers
SummaryThis paper presents a software toolset that models atomic quantum systems with high precision and simulates qubit gate dynamics. It combines quantum optimal control and benchmarking with automatic differentiation for efficient gradient-based optimization. Case studies on neutral atoms and trapped ions show improved quantum gate fidelities and insights for experiments.
Marco Rossignolo, Lorena C. Bianchet, Anurag Saha Roy et al.
In briefProof of the Aaronson-Ambainis conjecture on influential variables in low-degree polynomials
SummaryThis paper proves the Aaronson-Ambainis conjecture, which states that bounded low-degree polynomials on the discrete cube have an influential variable. The authors show that any function of degree at most d with values in [-1,1] has a variable of influence at least c·Var(f)^{5/2}/d^6 for an absolute constant c. The result implies that superpolynomial quantum speedups in the query model require structure, such as a promise on the inputs.
WhyThe authors prove the Aaronson-Ambainis conjecture, giving a polynomial lower bound on influence for low-degree bounded functions and implying quantum query speedups need structure.
In briefScalable encoding of large data into quantum states using fewer gates
SummaryThis paper presents deterministic, scalable methods for amplitude-encoding data into quantum states with low two-qubit gate costs and adjustable trade-offs between circuit depth and fidelity. The methods need no amplitude amplification or mid-circuit measurement and can use tensor networks to handle data too large for classical memory. Compared with the default Qiskit state-preparation method, the authors report circuit-depth reductions of up to orders of magnitude at equivalent state fidelity, and good fidelity on IQM hardware with square-lattice connectivity.
Vittorio Pagni, Peter K. Schuhmacher, Michael Felderer et al.
In briefA universal photonic converter that reshapes single-photon time waveforms for heterogeneous quantum networks
SummaryThe paper proposes a synthetic temporal-mode converter (STC) built from programmable couplers and optical delays. It reshapes known single-photon temporal waveforms through interference between time bins and concentrates amplitudes into a single common bin mode. Simulations show mode overlaps above 99.9% for exponential and Gaussian inputs.
In briefVerifying Entanglement of Annihilation Photons Using Compton Scattering
SummaryPolarization entanglement in annihilation photons is hard to verify experimentally because polarizers do not work at high energies, so Compton polarimetry is needed. The authors reformulate Compton scattering as a continuous-outcome quantum instrument that predicts scattering angles and post-scattering polarization states. They derive experimentally accessible lower bounds on Bell state fidelities for arbitrary two-photon polarization states, extractable from coarse-grained coincidence measurements. The method needs no knowledge of detector efficiencies or source activity, offering a feasible route to certify entanglement in para-positronium decay with current technology.
In briefControlling frequency-bin photon-pair correlations using programmable optical frequency combs
SummaryThis paper demonstrates model-free control of a cascaded photon-pair source driven by a programmable optical frequency comb, using measured joint spectral intensity as feedback. A blockwise simultaneous perturbation stochastic approximation controller optimizes up to 22 parameters and converges to diverse target patterns on 3×3, 4×4, and 5×5 frequency-bin grids. The optimized distributions reach Pearson correlations of 0.66 to 0.98. Because joint spectral intensity contains no phase information, the results control measured frequency-bin populations and correlations rather than fully reconstructing the two-photon state.
Usman Khan, Daniel Lopez, Venkat Aneesh Padmasola et al.
In briefAdaptive quantum search when the number of solutions is unknown, minimizing queries to the first solution
SummaryThis paper studies quantum search when the number of solutions is unknown, a problem for Grover's algorithm. The authors compare three methods (BBHT, Fixed-Point search, and Density Estimation) and tune them to minimize the expected number of queries needed to find the first solution under two initialization-cost conventions. They also propose a hybrid quantum-classical framework combining hill-climbing-assisted Grover Adaptive Search with Wang-Landau density estimation. In ideal simulations, it achieves 18.8%-63.4% lower mean accumulated query costs than the tested randomized and fixed-point baselines.
In briefNeutron spin-to-orbital angular momentum conversion in the weak interaction
SummaryThis paper studies a tiny parity-violating rotation of neutron spin caused by the weak interaction between neutrons and nuclei as neutrons pass through matter. For slow neutrons in 139La, near a p-wave resonance at 0.7 eV, the rotation can reach about 2.2e-3 rad/cm. The authors show that total angular momentum is conserved because the spin rotation generates neutron orbital angular momentum, and they experimentally demonstrate that a neutron initially in a longitudinal spin-orbit state shows no change in total angular momentum.
Niels Geerits, Stephan Sponar, Hartmut Lemmel et al.
In briefLocal Correlations Set the Dephasing Threshold of Z₂ Topology
SummaryThis paper studies whether band topology survives dephasing, using the Kane-Mele Z₂ topological insulator as a test case. The authors construct an auxiliary single-particle Hamiltonian that reproduces the same correlations, and locate the topological-to-trivial transition at its gap closing, which is tied to the purity gap. In the nontrivial region this auxiliary Hamiltonian shows quantized two-terminal conductance, but this does not establish the physical conductance under dephasing.
Rishith Reddy V, Ashutosh Dubey, Partha Sarathi et al.
In briefA software suite for integrating HPC and quantum computing workflows.
SummaryThe paper addresses modelling the integration of conventional high-performance computing and quantum computing. It introduces QASC, a compiler for OpenQASM 3.0 files that produces executables simulating quantum programs with the QuEST simulator. It also presents QACC-perf, a tool estimating the cost of integrating quantum computing into classical HPC workflows and quantum circuit execution time. The tools are demonstrated on multiscale quantum chemistry workflows within the ChemShell environment.
Mateusz Meller, Joseph C. R. Thacker, Thomas W. Keal et al.
In briefA phase-balanced differential Rydberg-atom receiver for detecting weak GNSS signals
SummaryThis paper proposes a phase-balanced differential Rydberg atomic quantum receiver (DRAQR) for recovering weak signals. It uses local-oscillator phase control to strengthen differential signal responses and a shared squeezed-reservoir model to correlate quantum projection noise and photon shot noise. An analytical model including multiple noise sources and inter-cell correlations gives the SNR gain, minimum detectable power under outage constraints, and bit-error rate for square M-QAM.
In briefSlices for normal forms in quantum information and a Riccati-type equation: a paper on quantum state normal forms and a matrix ODE
SummaryIt is known that the normal space to an orbit of a compact group's linear action meets every orbit. The authors show this result yields known normal forms for quantum states. They also compute a gradient flow converging to this normal form and find it is a Riccati-type matrix-valued ODE.
In briefEfficient one-shot simulation of network instruments and multi-party purity distillation
SummaryThis paper studies instrument compression problems in several network configurations from an information-theoretic standpoint. The goal is to simulate specific quantum-classical correlations among distributed parties, some holding parts of a quantum state and others holding classical registers, using minimal communication. The authors present a unified protocol framework based on likelihood instruments that yields new inner bounds in one-shot and asymptotic settings. They also address multi-party purity distillation, in which three parties distill pure states through local operations and limited communication.
In briefError-free quantum state subset discrimination and key sifting with unit success probability
SummaryThe paper proposes a method for error-free discrimination between subsets of quantum states with significantly higher success probability, which can reach one even for non-orthogonal and linearly dependent input states. The authors apply this method to quantum cryptography, describing an alternative basis reconciliation procedure. They state that it may achieve unit sifting probability even with many bases and non-orthogonal states within each basis.
In briefModular Hamiltonian and Typicality of Degenerate States
SummaryThe paper revisits eigenstate typicality for free fermions, where a single typical excited eigenstate yields a Gaussian reduced density matrix for small subsystems with a modular Hamiltonian proportional to the free-fermion Hamiltonian, giving the Fermi-Dirac distribution. It considers superpositions of degenerate eigenstates and shows that, in a 1-d free fermion lattice, the corresponding modular Hamiltonian is interacting, so the reduced density matrix is non-Gaussian and single-particle distributions deviate from Fermi-Dirac. These effects are linked to a violation of Wick's theorem. The authors develop perturbation theory for weak mixtures of degenerate states and compute the modular Hamiltonian numerically.
SummaryThis paper studies whether environmental magic, a non-stabilizer resource, can let two quantum channels that each have zero quantum capacity transmit quantum information jointly. The authors demonstrate this superactivation in a family of discrete quantum convolution channels with fixed Clifford interactions. They construct a mixed magic environment whose channel has positive private capacity but zero quantum capacity, and bound the activated capacity by the modified relative entropy of magic of the main environment.
In briefScanning probe control and dispersive readout of suspended carbon nanotube resonators
SummaryThis paper presents a theoretical framework for controlling and reading out a suspended carbon nanotube driven by an atomic force microscope tip and capacitively coupled to a Cooper-pair box. It derives the linear and nonlinear Duffing response of the nanotube and examines how force gradients, tip-position fluctuations, and voltage noise affect stability, dephasing, and heating. The authors quantize the oscillator, derive its Kerr anharmonicity, and derive the nanotube-box interaction and its dispersive limit, showing how phonon number and parity can be mapped onto the box via Ramsey interferometry and detected by quantum-capacitance readout.
In briefBQP-complete susceptibility measurable at ballistic times in local quantum dynamics
SummaryThe paper constructs time-independent dynamics with bounded nearest-neighbor interactions, in which a fixed single-site detector responds to a remote bond phase after a time proportional to their separation. The susceptibility has a positive lower bound independent of distance. With product-state preparations, estimating it to constant additive accuracy is complete for bounded-error quantum polynomial time (BQP), with a decision gap independent of distance.
