In briefSteering fidelity in noisy bosonic state preparation using risk-seeking optimization
SummaryState preparation encodes inputs into a target quantum state, which is needed to run quantum algorithms on bosonic quantum computers. Instead of optimizing only the average fidelity over the noisy ensemble, this work aims to maximize the fidelity of a subset of sampled pure states, accepting a lower overall average. Adapting objectives from risk-sensitive optimization, the authors report that risk-seeking objectives reduce the infidelities of some pure states by up to four orders of magnitude compared with standard average-fidelity optimization. They also show the trade-off between the probability of high-fidelity states and the lowest reachable infidelity can be controlled.
Riccardo Piantoni, Riccardo Pellini, Maurizio Ferrari Dacrema et al.
In briefLifting: A framework to better tell apart quantum states measured mid-circuit
SummaryThe paper presents Lifting, a framework that improves how reliably quantum computers read out mid-circuit measurements on superconducting hardware. It combines repetition encoding, neural-network decoding, and in situ calibration, using in-phase and quadrature readout signals from target and auxiliary qubits. The framework is evaluated on three IBM processors with repeated stabilizer measurement, parity-check, and teleportation workloads.
In briefExperimental C-shunt flux-qubit coupler enabling fast CZ gates between transmons
SummaryThis paper experimentally realizes a transmon-C-shunt-transmon device, in which a flux-tunable three-junction capacitively shunted flux-qubit coupler connects two transmon data qubits. At a specific bias, the residual ZZ interaction is near zero and transverse exchange is suppressed, giving a low-interaction idle region. A 45 ns nonadiabatic controlled-Z gate on this device achieves an interleaved randomized benchmarking fidelity estimate of 99.23(15)%.
In briefQuantum-controlled interferometers with equal visibility and energy but different coherent extractable work
SummaryThis paper studies a quantum battery sent through two quantum-controlled interferometers built from the same elements but in different orders. The two arrangements have identical interference visibility, stored energy, and incoherent ergotropy, yet differ in coherent ergotropy, with the difference governed by path predictability. The authors also examine decoherence and a relativistic realization, concluding that interference visibility does not fully measure coherence available as work.
Tonipe Anuradha, Andr\'e H. A. Malavazi, Borhan Ahmadi et al.
In briefOrbital angular momentum transfer and beam-quality limits in electron vortex beams made with a fork grating
SummaryThe paper studies how fork gratings create electron vortex beams when the incident beam is not ideal, including finite transverse momentum spread and an early electromagnetic phase. Using Fresnel propagation, the authors derive analytical expressions for each diffraction order and its orbital angular momentum statistics. The mean angular momentum follows a topological rule, while its variance depends on the residual transverse momentum spread. The paper also defines a transverse purity measure and notes that the ring-shaped intensity profile is governed by a separate propagation-dependent blurring effect.
In briefBeyond Gaussian Entanglement: Criteria for Polynomially Excited Quantum States
SummaryThe paper studies polynomial excitations built from creation and annihilation operators and shows they can produce and preserve entanglement between subsystems. For a class of initially separable pure states, the infinite-dimensional positivity problem is reduced to a finite-dimensional one. The authors apply the framework to quadratic excitations of a three-mode mixed Gaussian state, tracking negativity as a function of a non-locality parameter, and derive a closed expression for the covariance matrix of a general quadratic operator.
G\'abor Homa, Rich\'ard Balka, Nikolett N\'emet et al.
In briefV-type Atomic Variance Squeezing: A Study of Quantum Squeezing in a Dissipative Cavity
SummaryThis paper studies variance squeezing of a V-type atom interacting with a dissipative cavity. The squeezing alternates between the Sx and Sy components as the atomic initial state parameter changes, and environmental noise eventually makes the Sx squeezing vanish over time. Weak cavity-environment coupling and atom-cavity detuning are found to enhance the robustness of Sx squeezing, with results relevant to high-precision quantum communication.
In briefRole of dissipation dilution in achieving high mechanical quality factors in van der Waals resonators
SummaryThe study reports monolayer MoS2 drums reaching quality factors up to 372,000 at 4 K, nearly ten times the previous best for van der Waals materials at that temperature. The authors develop a dissipation-dilution model for circular drums and analyze intrinsic and extrinsic loss mechanisms. They conclude that dissipation dilution governs high-Q mechanical van der Waals resonators.
WhyApplies dissipation dilution to van der Waals resonators, reaching Q near 372,000 in monolayer MoS2, roughly tenfold above prior best, with a supporting model.
Lukas Schleicher, Leonard Geilen, Alexander Musta et al.
In briefA complete quantum model of realistic photodetection across photon-number and spectral degrees of freedom
SummaryThis paper presents a complete quantum process model describing how real photodetectors respond, accounting for both photon-number effects and frequency-dependent detector response. The model is expressed through explicitly derived Kraus operators in the operator-sum representation, accommodating realistic inefficiencies and detection within finite spectral windows. It can directly replace idealized detector models in quantum optical analyses and helps identify how a detector's window should match the incident photons' spectral distribution to maximize the observability of quantum effects.
In briefZeus-256: a room-temperature NV-diamond quantum processor with a protein-based quantum bus
SummaryThe paper reports Zeus-256, a room-temperature nitrogen-vacancy diamond processor with 256 simultaneously active logical qubits in a 16 x 16 array, linked by an optically programmable protein-chromophore quantum bus. It benchmarks circuits including QFT, GHZ, Grover search and Shor-family factoring, reporting factor recovery for 8-84 bit integers and Bell-CHSH and GHZ fidelity measurements. The authors state timing metrics are partial and do not establish quantum advantage, and that scaling to 9,984 logical qubits is an engineering target.
In briefAutonomous optomechanical Maxwell demon engine: a quantum heat engine where a mechanical oscillator acts as the demon
SummaryThis paper presents a fully autonomous model of a mechanical Maxwell demon engine that converts heat absorbed by a qubit into population inversion in a quantum battery. A damped mechanical oscillator serves as a pointer, using a Holstein-type Hamiltonian so its equilibrium position depends on the qubit state, producing a state-dependent resonance shift. The authors derive local and global Lindblad master equations and measure performance by the battery's steady-state ergotropy.
Sander Stammbach, Giulio Gasbarri, Stefan Nimmrichter
In briefReliability of quantum-coherent devices measured by remaining task resource
SummaryThe paper proposes a resource-based reliability framework for quantum devices that can lose the resource needed for a task without entering a fixed failure subspace. It quantifies the remaining task-relevant resource relative to an ideal capacity. The approach is developed for a trusted quantum random-number generator and a calibrated two-port interferometer, and illustrated with an exactly solvable multi-spin spin-boson model.
In briefPPVM: A Simulation Framework for Digital Twins of Quantum Processors
SummaryThis paper presents PPVM, an open-source framework for building digital twins of quantum processors. It unifies Pauli propagation and generalized tableau simulation in one virtual machine, with bytecode supporting arbitrary classical control flow. The authors derive atom-loss channels for neutral-atom hardware and demonstrate loss-aware magic state distillation on over a thousand physical qubits, integrated with classical decoding via Bloqade QEC Studio.
Xiu-Zhe Luo, David Plankensteiner, Kai-Hsin Wu et al.
In briefAutomated Methods for Checking Whether Quantum Error-Correction Codes Are Equivalent
SummaryThis paper studies how to automatically decide whether two descriptions of quantum error-correction codes are equivalent under specified transformations. The authors formalize permutation equivalence for stabilizer and CSS codes and local-Clifford equivalence for stabilizer codes, and develop three decision strategies with invariants for preprocessing. Their evaluation finds that no single approach performs best across all cases, so they combine the methods into a staged hybrid checker and report its runtimes.
In briefAmplifying spatiotemporal optical vortices with parametric gain
SummarySpatiotemporal optical vortices are structured light with a phase singularity in space and time. This work presents the first theoretical analysis and experimental demonstration of optical parametric amplification of these vortices. The signal pulse energy increases about 60-fold while its spatiotemporal structure is preserved. The generated idler carries the phase-conjugated vortex with opposite topological charge, and the approach enables wavelength tuning from visible to near-infrared.
In briefTrotter Error with Changing Weights: A method that varies the coefficients step by step in quantum simulation to cancel approximation error at the endpoint.
SummaryThe paper introduces scheduled trotterization, in which the coefficients of a local linear decomposition change from step to step. Using Lie group geometry and the Baker-Campbell-Hausdorff formula, the global error is split into internal and external accumulation parts. For exact infinitesimal synthesis, the authors prove the error improves from fixed-weight O(N^{-1}) to O(N^{-2}), and numerical tests on random SU(2) targets support this.
In briefSpectrally enhanced gravitational redshift signals in photonic interferometers
SummaryThis paper proposes boosting the gravitational redshift effect in photonic interferometers by coupling the two arms to optical scatterers based on ultranarrow atomic transitions, which act as local spectral references. Redshift shifts each photon's detuning from these resonances, producing large reflection amplitude differences and so noticeable visibility loss and phase shift even for centimetre-scale height differences. The authors also assess the feasibility of implementation with current or near-term technology.
Jerzy Paczos, Piotr T. Grochowski, Natalia Bruno et al.
In briefPredicting Quantum Code Distance with a Neural Network for Bivariate Bicycle Codes
SummaryThe distance of a quantum code determines its error-correction capability, but computing it is computationally expensive for exact solvers and heuristic searches. The authors build a dataset of Bivariate Bicycle codes with distance upper bounds from high-budget heuristic searches and train BB-Net, an attention-based neural network, to predict distances. BB-Net reaches 96.39% accuracy on test references, versus 94.86% for state-of-the-art heuristics using up to 10^4 times more runtime, and 98.94% on a subset with certified exact distances.
In briefLocal error correction extends the lifetime of a time-crystal memory
SummaryThis paper studies a discrete time crystal in a driven, spatially disordered two-dimensional Ising model on a superconducting quantum processor. The authors apply stochastic local bit-flip error correction with repetition codes of distance three and five on a honeycomb lattice of up to 68 physical qubits. The stochastic drive increases the memory decay time by up to a factor of two. Syndrome measurements without correction shorten the memory, showing that conditional correction is essential.
In briefLong-distance quantum fan-out gates with fewer resources
SummaryThis paper proposes a scheme for implementing an n-qubit fan-out gate (a controlled-NOT generalized to many targets) across spatially separated parties. It needs only a pre-shared n-qubit GHZ state, n local CNOT gates, and feed-forward operations, reducing CNOT and Hadamard gate counts by (n-2) compared with the standard decomposition approach. The authors also present two optical architectures for heralded and post-selected n-photon fan-out gates, which use fewer single photons and achieve higher success probabilities.
In briefA tight lower bound on how many copies are needed for coherent classical shadows of mixed quantum states.
SummaryThe paper studies coherent classical shadow protocols for an unknown d-dimensional quantum state of rank at most r, allowing arbitrary joint measurements on all copies. It proves a lower bound on the minimum number of copies T needed to succeed with probability 1-δ, depending on δ and the number M of post-measurement observables. The bound nearly matches the known upper bound and the conjectured strengthening of it.
WhyProves a near-optimal sample complexity lower bound for coherent classical shadows of mixed states, nearly matching known upper bounds via Grassmannian hypercontractivity arguments.
In briefLossless graph reductions and hybrid sampling for maximum compatibility phylogeny
SummaryThis paper addresses the bottleneck of enumerating optimal solutions in maximum compatibility phylogenetic reconstruction by casting it as maximum weight independent set enumeration on the complement graph. Sampled bit strings are mapped to maximal feasible solutions through deterministic postprocessing, and the authors build correction-in-the-loop QAOA instances for noisy quantum devices. They also introduce lossless graph reductions that preserve all optimal solutions, and demonstrate the methods on graphs built from SARS-CoV-2 sequences.
In briefExtractable work (ergotropy) of multipartite entangled states near a black hole
SummaryThis paper studies how the extractable work, or ergotropy, of tripartite GHZ and W states is redistributed in the quantum atmosphere of a Schwarzschild black hole under Hawking-induced thermalization. GHZ states yield two degenerate ergotropy families separated by an energy gap independent of radial position, while W states follow a linear averaging relation. The Hartle-Hawking constant and normalized radial distance play competing roles in how extractable work evolves.
In briefNoise characterisation methods tested on a superconducting quantum processor
SummaryThis paper develops and experimentally implements noise characterisation methods on a superconducting quantum processor with a square-lattice layout. The authors revise the cycle-benchmarking protocol using a regularised cost function and extend a tensor-network tomography method to match the device layout. They use these methods to map noise structure, track drift, and check the learnt noise models against benchmark physics and chemistry circuits.
Nelson M. M. Fern\'andez, Francesco Grieco, Hetta Vappula et al.
In briefWannierSTM: A fast method for simulating superconducting STM spectroscopy using localized Wannier functions
SummaryThis paper presents a Python program that combines maximally localized Wannier functions from first-principles calculations with nonequilibrium Green's function methods to simulate scanning tunneling microscopy (STM). Superconductivity is included through an effective pairing potential in the Nambu-spinor formalism, and the tip and substrate are modeled in the wide-band limit. The authors show that current-voltage and differential conductance can be computed in closed analytical form, and they demonstrate the method on spin chains, two-dimensional magnets, and molecular magnets on a superconductor.
Oscar Moreno Segura, Dorye L. Esteras, Andrei Shumilin et al.
In briefDynamical BEC formation and entropy vanishing for trapped bosons coupled to radiation
SummaryThis paper studies trapped bosons coupled to a quantized radiation field and tracks their macroscopic one-particle density matrix through a nonlinear resonance cascade. It proves that radiative relaxation depletes excited trap modes even when the initial state is mixed, leading to strong trace-norm convergence to a pure condensate. The von Neumann entropy also vanishes asymptotically. The proof derives the Hartree hierarchy from the finite-N BBGKY hierarchy in the mean-field limit.
In briefLow-energy wave packet dynamics in the one-dimensional quantum Heisenberg ferromagnet
SummarySpin wave theory is central to analyzing low-energy properties of the quantum ferromagnetic Heisenberg model. This paper takes a first step toward rigorously justifying this approximation for quantum dynamics in one dimension. The main result proves that, for a class of spin wave packets, the evolution is well approximated by the free evolution of magnons, the free quasiparticles. The work focuses on spin-1/2 systems with two-magnon wave packets and argues the result is optimal with respect to timescales.
Mateusz Kwa\'snicki, Marcin Napi\'orkowski, S\"oren Petrat et al.
In briefNon-biorthogonal Born rule emerging at dynamical quantum phase transitions
SummaryThe paper starts from a globally Hermitian system obeying the standard Born rule and extends dynamical quantum phase transitions from a reference state to a physical subspace. When left and right states are each normalized to themselves, their mutual overlap gives a directly accessible dynamical transition rate, offering a probabilistic reading of non-Hermitian eigenstates. The authors also identify exceptional-point DQPTs, which occur where eigenstates of the critical propagator coalesce.
Wei-Wei Yang, Henning Schomerus, Jiangping Hu et al.
In briefTutorial on Quantum Amplitude Embedding with Data Re-Uploading
SummaryThis tutorial explains how re-uploading input data into an amplitude-embedded variational quantum model increases its expressive power. It presents sequential and parallel re-uploading in one notation and shows each upload raises the reachable polynomial order by two. Simulations show gains on fourth- and sixth-order targets, while one upload remains best for a quadratic target and handwritten digits.
In briefEngineering emitter-waveguide coupling to widen the reflection band of atomic mirrors
SummaryThis paper theoretically studies single-photon coherent transport through finite waveguide QED arrays whose emitter-waveguide couplings vary in space. Using exact scattering calculations, spectral factorization and a semiclassical WKB analysis, the authors show how the coupling profile sets the reflection bandwidth and its dependence on array size. A Gaussian transverse displacement broadens the high-reflectivity window and suppresses boundary-induced Fabry-Perot oscillations relative to a uniform array. The authors also derive a 1/N scaling law for the bandwidth's approach to its bulk value and note that an optimal profile width exists.
In briefHow many switches two Hamiltonians need for universal control
SummaryThe paper studies how many times one must alternate between two generic Hamiltonians to synthesize any unitary on C^d. It shows that the minimal switching number scales linearly in d in expectation, and gives constructive upper bounds depending on the change-of-basis matrix between the two eigenbases. If that matrix has a column with equal-modulus entries, such as a complex Hadamard matrix, 9d switches suffice to reach every unitary.
WhyGives an exact decomposition of any unitary into alternating diagonal unitaries in two bases, with linear switching bounds; a substantive theoretical advance mainly affecting quantum control theory.
In briefNoise cost of local reservoirs in broadband quantum amplifier chains
SummaryThe paper studies how finite-band noise suppression in directional quantum amplifiers must balance frequency-dependent responses against fixed local couplings and finite rates. It compares fixed reservoirs on uniform and dimerized chains under matched conditions against an unrestricted single-frequency noise benchmark. Boundary-response bounds identify the rates and range-two targets needed, and the results are intended to guide reservoir design and noise calibration for a proposed cryogenic microwave array.
In briefMulti-parameter estimation boosted by level crossings and Bayesian feedback
SummaryThis paper links level crossings, where two quantum energy levels intersect, to the precision limits of quantum metrology. The authors analyze a Hamiltonian with such level crossings and identify conditions for estimating several parameters simultaneously with high sensitivity near the crossing point. They propose a resource-efficient protocol based on unitary quench dynamics and Bayesian estimation, whose precision saturates the Holevo Cramér-Rao bound. The method is illustrated with a two-level model and a two-spin Ising model.
In briefBoson sampling with on-demand single-photon arrays: quantum complexity and dephasing effects
SummaryThis paper studies boson sampling using arrays of on-demand single photons (Fock states) as resource states, which offers complexity-scaling advantages over continuous-variable states from nonlinear photonics. The authors present a framework linking the physical sources of decoherence to multiphoton correlation measurement outcomes. They estimate the probability of generating a 4-photon NOON state from an optical circuit fed by four identical single-photon wave packets. The results show that these probabilities depend on two-photon interference visibility, which is set by the pure dephasing time relative to the radiative decay time.
In briefPADO-Pauli: A GPU-accelerated engine for Pauli propagation
SummaryThis paper presents PADO-Pauli, a GPU engine that approximates expectation values of variational quantum circuits by Pauli propagation. It precompiles circuits into sparse matrices and supports batched parameter and data evaluation, with gradients integrated into PyTorch autodiff. The authors report up to 10 times faster evaluation than cuPauliProp on an NVIDIA A100 for 4 to 12 qubits, and check accuracy against exact statevector simulation up to 28 qubits.
In briefGeometry of Representations in Quantum Classifiers on Classical Image Benchmarks
SummaryThis paper examines whether quantum classifiers offer practical benefits on realistic classical data such as natural images. The authors use strong classical feature extractors to compare classifiers fairly, while controlling data scale and supervision strength. They find that quantum classifier effectiveness depends strongly on the geometry of the input representations, favoring classical features aligned with quantum feature spaces. Kernel alignment is used to identify such compatible representations.
SummaryThis paper presents QEDIA, a framework for verifying quantum programs with classical variables in Lean 4. Its core is an open library that formalizes the quantum Hoare logic QHL+ and proves it sound for partial and total correctness. The library and program proofs were built under human supervision using an LLM-based prover agent. The framework is illustrated with verified examples including the quantum Fourier transform, phase estimation, repeat-until-success circuits, and Hamiltonian simulation.
Yuanjie (Collin) Ren, Zhicheng Zhang, Junyi Liu et al.
In briefGWPTools: An Extensible Wolfram Language Framework for Time-Dependent Gaussian Wave Packets
SummaryThis paper presents GWPTools, a Wolfram Language framework for computing exact time-dependent Gaussian wave packet dynamics using a unified symbolic-numeric design. It serves both as an interactive teaching tool for quantum theory and as an exact algebraic engine for benchmarking numerical methods. Version 1.0.0 focuses on exact time evolution in driven one-dimensional quadratic potentials, with extensions planned for quantum hydrodynamics and phase space representations.
Jeremy B. Maddox, Ismail Giliani, Carter M. Heck et al.
SummaryThis paper proposes a protocol for weak-signal sensing in a trapped-ion spin-oscillator system that combines detuned motional squeezing with spin-oscillator entanglement. The combination accelerates phase accumulation, which the authors report gives an exponential sensitivity gain over unsqueezed cases. The sensitivity is said to remain below the standard quantum limit in noisy environments, with a clear advantage for short interrogation times.
In briefNear-optimal quantum sample complexity for learning sparse Boolean functions
SummaryThis paper studies how many uniform quantum examples are needed to exactly learn a Boolean function with at most k nonzero Fourier coefficients. It gives a learner with near-optimal Õ(k) sample complexity, independent of input length n, that uses only separate measurements of individual examples. This improves the previous O(k^{3/2} log^2 k) upper bound. For comparison, the authors derive the tight classical bound Θ(nk) from known results.
WhyImproves quantum sample complexity for learning k-sparse Fourier Boolean functions to near-optimal Õ(k), a notable theoretical advance with rigorous proofs.
In briefFrom Syndromes to Computation: A General Framework for Logical Operations in Quantum Error-Correcting Codes
SummaryThis paper presents a general framework that uses stabilizer syndromes of commuting Pauli rotations to guide the design of logical gates in quantum error-correcting codes. It derives an exact codespace-preservation condition for arbitrary rotation angles and a generator weight bound for equal-syndrome cases. The framework is applied to bivariate-bicycle and non-CSS Mirror codes, producing explicit low-weight Clifford and controlled-phase gates.
WhyGives a general syndrome-based framework with an exact codespace-preservation condition, and constructs new low-weight logical gates on several code families.
Hunter Nelson, Arshag Danageozian, ChunJun Cao et al.
In briefFaster quantum battery charging using nonlinear charger-battery coupling
SummaryThis paper theoretically shows that nonlinear interactions between a charger and a quantum battery can substantially speed up charging. In the weak-driving regime, sufficiently strong nonlinear coupling outweighs dephasing and shortens charging time. In strong and optimal driving regimes, it creates a new charging-time optimum with nearly critically damped dynamics. Even without external driving, nonlinear coupling alone can significantly reduce charging time.
In briefA general method for detecting quantum entanglement using geometrically optimal witnesses
SummaryThis paper introduces a unified framework for constructing geometrically optimal entanglement witnesses, using the geometry of a target quantum state relative to a given entanglement structure in Hilbert-Schmidt space. Among all nontrivial witnesses, these provide maximal distinguishability between the target state and states lacking that structure. The approach is claimed to detect bipartite, multipartite, and high-dimensional entanglement. The authors demonstrate experimental feasibility on a four-qubit nuclear spin system and report improved noise robustness and construction efficiency over existing methods.
In briefCoherent optical control of over a thousand qubits in a three-dimensional trapped-ion crystal
SummaryResearchers cooled about 3,600 vibrational modes of a crystal of over 1,200 trapped ions to below single-phonon occupation, so the crystal can serve as a register of optical qubits. They demonstrated ensemble optical coherence of 21.6 milliseconds. They reduced the optical-transition frequency uncertainty from 389 Hz for one ion to 12 Hz for over a thousand ions, approaching projection-noise scaling.
WhyFirst coherent optical control of over a thousand ions in a 3D crystal, cooling about 3,600 modes and reaching 21.6 ms ensemble coherence.
In briefParallel Stochastic Decoding of Quantum LDPC Codes Using p-Bits
SummaryThis paper presents a parallel decoder for quantum LDPC codes built on probabilistic bits (p-bits). Error configurations are updated stochastically using local Gibbs conditionals, while a progressively stronger parity penalty steers the search toward syndrome-consistent solutions. Graph coloring enables parallel block updates. Under the stated update budgets, its logical error rates are comparable to leading decoders, suggesting a competitive stochastic alternative.
In briefA 3/8 upper bound on the stabilizer-rank exponent of face-center magic states
SummaryThe paper gives an explicit construction showing that the exact stabilizer rank of m copies of the qubit face-center magic state is O(2^{3m/8}). Two symmetry-related fifteen-term identities combine into a twenty-four-term decomposition at twelve copies, which yields a substitution adding eight copies at a cost of eight terms per existing term. The resulting bound γ_T ≤ 3/8 improves the previously published exponent log₂(3)/4.
In briefAn Aubry-André localized optical lattice clock: using a two-color lattice to suppress atomic tunneling for better space clock coherence
SummaryOptical lattice clocks in space could aid satellite navigation and fundamental physics tests, but in microgravity atoms tunnel between lattice sites, broadening the clock transition. The authors create a bichromatic optical lattice from two magic-wavelength lasers to achieve Aubry-André localization, suppressing tunneling in a horizontal lattice clock that emulates free fall. They recover a Fourier-limited Rabi spectrum and measure Ramsey coherence times up to 2 s in shallow lattices, up to 100-fold better than the delocalized regime.
WhyApplies Aubry-André localization to suppress tunneling in optical lattice clocks, achieving Fourier-limited spectra and up to 100-fold coherence gains.
Shuo Ma, Anke St\"oltzel, Bennett Christensen et al.
In briefA mathematical framework for simulating non-perturbative cavity optomechanics with plate-like dielectrics, where a thin dielectric slab inside an optical cavity affects the light field and the mechanics together.
SummaryThe paper develops a framework for modeling a finite-thickness planar dielectric that intercepts the whole optical mode in a cavity. It solves for the cavity field, optical force, mechanical equilibrium and back-action self-consistently by extending a vacuum two-photon formalism. The authors derive carrier and sideband transfer functions covering optomechanical cooling and response to external perturbations.
In briefTime-domain measurements for resonant scattering in quantum simulations of lattice gauge theory
SummaryThis paper studies glueball scattering on a line of plaquettes in pure SU(3) lattice gauge theory, a benchmark for quantum simulation. It characterizes low-energy glueball scattering with classical exact diagonalization and identifies the continuum resonance structure using real-time simulations and approximate analytic methods. The authors propose time-domain observables for extracting resonance properties from quantum simulations and demonstrate them on a toy model simulated on Quantinuum H2-2 hardware using 28 qubits.
Praveen Balaji, Patrick Draper, and Enrico Rinaldi
In briefMapping the sign of a Dirac mass in magnetic topological surfaces with spin-polarized tunneling
SummaryThe paper notes that local spectroscopy of magnetic topological surfaces has only measured the gap size |M|, not the sign of the Dirac mass M. The authors propose using an axial tip on a C3 axis, where a fully spin-polarized state's tunneling asymmetry reveals the sign of the occupied-band Berry curvature. They also state that the zeroth Landau level gives an independent mass-sign measurement with an unpolarized tip, and that opposite domains and their chiral domain-wall modes serve as self-consistency checks.
Payman Kazemikhah, Ruolun Zhang, Byunghoon Kim et al.
In briefNorm properties of quantum uniformity measures
SummaryThis paper gives a complete classification of the norm properties of quantum uniformity measures, which Bu, Gu, and Jaffe introduced to characterize the Clifford hierarchy analytically. These measures define norms exactly for k=2, 3, and 4, with the triangle inequality holding for k=4 but failing in some dimension for every k≥5. The authors also derive explicit bounds on the modulus of convexity where norms are defined, and show that matrix-valued Gowers uniformity functionals define a norm only for k=2.
WhyGives a complete classification of norm properties of quantum uniformity measures, resolving an open question with rigorous proofs for k=4 and k≥5.
In briefDistributed quantum phase sensing with SU(1,1) Perelomov coherent states in interferometer networks
SummaryThis paper theoretically studies a reconfigurable network of N Mach-Zehnder interferometers that simultaneously estimates weighted linear combinations of relative phase shifts. The scheme injects a Perelomov coherent state from the SU(1,1) group into one port of a passive circuit, with other modes in vacuum, creating quantum correlations among sensors. The analysis shows this entangled strategy beats the shot-noise limit and asymptotically reaches the Heisenberg limit.
Seloua Boulifa, Abdallah Slaoui, Hanane EL Hadfi et al.
In briefA controlled null result for Riemannian optimization in VQE gate training
SummaryThe paper tests whether optimizing single-qubit gates directly on U(2) with Riemannian methods beats Adam on Euler-angle coordinates in a variational quantum eigensolver. On a hydrogen-chain benchmark, it finds no measurable practical advantage for the Riemannian approach. It also identifies four failure modes that can produce a misleading positive result. The main output is this null result and a validation checklist for VQE optimizer comparisons.
In briefUsing periodic pulses to control light emission and photon statistics from two coupled quantum emitters
SummaryThis paper studies two identical, dipole-dipole coupled quantum emitters driven either continuously or by periodic pulses, examining their collective emission spectra and photon correlations. A periodic train of instantaneous π_x pulses produces spectra whose main features resemble those under continuous-wave excitation. Finite-duration pulses with high Rabi frequencies closely reproduce the ideal instantaneous-pulse results.
Kavalambramalil George Paulson, Fu Li, and Hanna Terletska
In briefQGrAT: A quantum transformer for classifying particle jets using spacetime symmetry
SummaryThe paper introduces QGrAT, a quantum transformer that builds Lorentz-symmetry and three-prong top-decay structure into interactions between qubits. Its attention couplings come from grade-specific inner products of spacetime Clifford algebra features, and an auxiliary qubit adds explicit three-particle interactions. In state-vector simulations on Top Tagging benchmarks, a twelve-qubit, 144-parameter configuration reaches AUC 0.944, competitive with the L-GATr-Slim baseline. The three-particle ancilla gave the main gain in background rejection among the variants tested.
In briefGenerating Superpositions of Transverse Ising Ground States via Quantum Interaction
SummaryThis paper studies how to prepare superpositions of quantum Ising ground states by making the nearest-neighbor coupling an operator acting on a central auxiliary spin. The states are obtained by adiabatic evolution of the joint system, followed by measuring the central spin and post-selecting an outcome. The authors show superpositions spanning the paramagnetic, ferromagnetic, and antiferromagnetic phases, and derive analytic expressions for magnetization, spin correlations, and entanglement. The quantum Fisher information, relevant to estimating the Ising coupling, shows multiple peaks near critical points and a maximum exhibiting Heisenberg scaling for the parameters and system sizes examined.
In briefKrylov Complexity and Quantum Many-Body Scars in Non-Hermitian Constrained Models
SummaryThis paper studies non-Hermitian versions of the PXP and PPXPP kinetically constrained quantum models, examining their Krylov complexity, eigenstate structure, and dynamics. Using the Arnoldi algorithm, the authors find that as non-Hermiticity increases, Krylov complexity behaves differently in the left and right eigenstate ensembles: it oscillates persistently in the right ensemble and gradually saturates in the left. In the non-Hermitian PXP model, the right ensemble keeps its scar structure while the left develops additional non-scar eigenstates.
Arkaprava Sil, Rudraksh Kaushik, Souvik Kundu et al.
In briefOptical interferometry tools for detecting memory effects in quantum systems
SummaryThis paper proposes using interferometric methods, namely phase shift and visibility, to probe environmental effects and detect non-Markovian dynamics. Suitably constructed witness operators allow non-Markovianity to be detected through measurable phase shifts in the interference pattern. The authors prove that interferometric visibility is monotonically non-increasing under incoherent CP-divisible (Markovian) dynamics, so any revival of optimized visibility signals information backflow. The effectiveness of both approaches is illustrated with representative examples of non-Markovian dynamics.
Saheli Mukherjee, Bivas Mallick, Samyadeb Bhattacharya et al.
In briefGhost-unitary method for loss-resilient photonic resource-state generation
SummaryThis paper studies how to generate entangled few-photon resource states, such as Bell and GHZ states, from biphoton sources and linear-optical interferometers. The authors use the transpose identity of multi-mode squeezed vacuum states to propose "ghost-unitary" implementations, which apply the interferometer to heralding modes instead of output modes. When interferometric loss dominates, this approach suppresses false-positive heralding events at low squeezing, yielding higher-fidelity conditional states. The authors identify parameter regimes where this method outperforms direct implementation across several examples, and prove that direct n-GHZ outputs are identically damped.
Kevin J. Randles, Manuel H. Mu\~noz-Arias, Kevin Thompson
In briefFormally verifying quantum key distribution security in Lean using LLM-based autoformalization
SummaryThe paper formalizes an end-to-end security theorem for the entanglement-based BB84 quantum key distribution protocol in the Lean proof assistant. It proves composable security against coherent attacks using postselection, accounting for finite block size, and relies only on Lean's standard axioms. The proof was produced with LLM-based autoformalization, and the same pipeline was then used to reduce the finite-size penalty on the key rate.
WhyFormalizes an end-to-end BB84 QKD security proof in Lean via LLM autoformalization, then uses it to reduce finite-size penalties.
Maor Ben Shahar, Jonathan Morag, Dirk Englund et al.
In briefUsing a superconducting diode as a Feynman ratchet to build a nanoscale heat engine
SummaryThe paper proposes a physical realization of Feynman's ratchet using Josephson junctions that show the superconducting diode effect. The device acts as a heat engine that produces work only from thermal fluctuations driven by a temperature difference. The authors analyze its output power and efficiency and use the Seebeck coefficient to identify when the device runs in reverse as a Peltier cooler.
Konstantinos Kontogeorgiou, \.Inan\c{c} Adagideli, G\'eraldine Haack et al.
In briefClassical lower bounds for Max-Cut on large-girth 3-regular graphs, challenging quantum advantage
SummaryThe paper studies how large a cut can be guaranteed in 3-regular graphs whose shortest cycle is at least g. The authors apply VIRAL, a classical local algorithm, to the depth-p tree and obtain lower bounds exceeding those previously obtained with QAOA for every p of at least 4. The range of girths covered extends from 36 to 66. At girth 66 they report a bound of 0.9127, raising the asymptotic lower bound from 0.912 to 0.9127.
In briefObserving photon bunching in broadband thermal light using temporal imaging
SummaryThe paper proposes and demonstrates pre-detection temporal magnification of an optical field before measuring its intensity autocorrelation in a conventional HBT setup. Using an electro-optic time lens with a temporal magnification of 660, the authors resolve the autocorrelation of 250 GHz bandwidth thermal light generated by non-degenerate spontaneous parametric down-conversion. This directly observes thermal photon bunching on sub-3.5 picosecond timescales without narrow spectral filtering.
WhyProposes pre-detection temporal magnification to observe broadband thermal photon bunching, demonstrated experimentally with a 660x electro-optic time lens.
Filip So\'snicki, Micha{\l} Miko{\l}ajczyk, Sanjay Kapoor et al.
In briefQuantum reference frames modeled as tetrads
SummaryThis paper adapts the relativity-theory notion of a reference frame as a tetrad, a set of four orthonormal vectors at a spacetime point, to quantum theory. It proposes that the state of a quantum reference frame is an assignment of complex amplitudes to a set of tetrads. The paper serves as a conceptual companion to two other papers and explains the contrast between them: one treats a single fixed spacetime geometry, while the other does not assume a geometry a priori.
In briefMeasuring how far interacting fermion states depart from Gaussian states
SummaryThe paper defines a geometric measure of fermionic non-Gaussianity, the fidelity distance from a target state to the manifold of fermionic Gaussian states. It introduces an iterative numerical method for computing this distance that also works at strong coupling. The authors prove a sharpened operator Jensen inequality and use it to derive a witness requiring only two- and four-point correlators. Numerical tests on the one-dimensional Fermi-Hubbard model show the witness improves with system size and is tighter than antiflatness at strong coupling.
Leela Ganesh Chandra Lakkaraju, Naga Dileep Varikuti, Philipp Hauke
In briefTesting topological protection in a Majorana parity qubit via unprotected operations
SummaryA recent experiment demonstrated a Majorana parity qubit by observing coherent parity oscillations between minimal Kitaev chains. This paper develops an analytical theory of quasistatic dephasing for two coupled N-site Kitaev chains at the sweet spot. It shows that Rabi and Ramsey experiments can reveal the protection as chain length grows, and identifies how residual noise limits the chain-length range where this scaling is observable.
Sebastian Miles, Juan Daniel Torres Luna, Francesco Zatelli et al.
In briefPrinciples and techniques for AI agents doing experimental physics research
SummaryThe paper outlines ten requirements for collaborative AI agents in experimental physics, treating them as tools that amplify a human researcher's expertise. It presents a framework that adds custom scaffolding to large language models and uses closed-loop campaigns in which agents iterate toward a defined goal. Six case studies covering device design, hardware control, neural network optimization, physical model identification, and data analysis are used to demonstrate the approach.
Niko R. Reed, Declan M. Daly, Andrew J. Beling et al.
In briefError-corrected quantum RAM queries using a one-fault-tolerant controlled-SWAP gate
SummaryThis paper studies protecting quantum random-access memory (QRAM) queries from noise. It proposes a one-fault-tolerant repeat-until-success logical controlled-SWAP gate built on the [[4,2,2]] code that corrects single erasure errors. It also defines local parity checks on bucket-brigade router states, using routing validity constraints rather than extra data qubits, with minimum-weight perfect matching for bit-flip correction. Monte Carlo simulations show quadratic suppression of errors for the protected controlled-SWAP and improved depth scaling for decoded router-state snapshots.
In briefMoving quantum sensors: using spatial coherence and entanglement to speed up field detection
SummaryThis paper studies whether controlled motion of a quantum sensor gives a metrological advantage when detecting a localized field of known strength in an unknown region. It compares classical motion along a fixed trajectory with quantum motion, where the sensor can be in a coherent superposition of locations. For one sensor, coherent motion reduces the required interrogation time from Θ(N/B) to Θ(√N/B). With multiple sensors, entanglement can further improve the time scaling, and matching lower bounds show these scalings are optimal.
Evan Zhang, Erfan Abbasgholinejad, Yu-Xin Wang et al.
In briefFractional and quantum Latin squares: a real solution to the quantum 36 officers problem
SummaryThis paper studies extending Latin squares by replacing symbols with probabilities or quantum states. It constructs a real absolutely maximally entangled state of four six-level systems, giving a real solution to Euler's quantum 36 officers problem. The authors also derive fractional Latin squares and compare local-unitary classes that differ in sign.
WhyGives a real AME-state solution to Euler's quantum 36 officers problem, separates local-unitary classes, and extends the probability representation to seven- and nine-party states.
In briefBosonic unstructured search: quantum speedup without entanglement
SummaryThis paper studies unstructured search over N possible modes using multimode bosonic quantum systems under a mean boson-number energy budget. It gives algorithms for continuous-time and discrete phase-shift oracles and proves matching query lower bounds showing they are asymptotically optimal. The authors find that non-Gaussianity, but not entanglement, is needed for optimal scaling without loss.
WhyProves matching query lower bounds for bosonic unstructured search, showing non-Gaussianity rather than entanglement is key; a strong theoretical contribution.
Yu-Xin Wang, Erfan Abbasgholinejad, Supratik Sarkar et al.
In briefProgrammable Floquet responses for quantum sensing: a new way to encode signals in relaxation dynamics
SummaryThis paper proposes a quantum sensing approach using programmable Floquet locking in periodically driven two-level systems, rather than relying on phase accumulation. Information is encoded in the population relaxation dynamics, with response characteristics set by the driving sequence. The authors numerically demonstrate the method for DC and frequency-selective AC sensing. They report that temporal encoding can improve precision in the presence of slow instrumental fluctuations.
Dionisio Cendoya, Kang Xu, Lisandro Buljubasich et al.
In briefComputational complexity of blind quantum machine learning, with a circuit-to-brickwork transpiler
SummaryThe paper introduces MasonQ, a transpiler that converts arbitrary quantum circuits into brickwork graph states for universal blind quantum computation (UBQC). The authors give new upper bounds on brickwork graph depth and derive depth bounds for several blind quantum machine learning algorithms, including HHL and quantum transformers. They also propose a minimal implementation requiring only a 12-qubit quantum server.
In briefExact periodic recurrence in periodically driven quantum many-body systems, studied via cyclotomic number theory
SummaryThis paper studies periodically driven quantum many-body systems (Floquet systems) that exactly return to their initial dynamics at special parameter values. The authors derive a necessary and sufficient arithmetic condition for exact recurrence and determine the minimal recurrence period when one exists, requiring only the number field tied to the Hamiltonian parameters. Using the kicked Ising chain, they show exact recurrences in both Clifford and non-Clifford regimes. In the non-Clifford recurrent regime, magic, a resource for quantum computation, is generated at intermediate times and undergoes exact periodic revivals.
In briefDesigning Instruction Execution Architecture for Scalable Fault-Tolerant Quantum Computers
SummaryThis paper examines where the boundary between classical control and quantum hardware, the Quantum Instruction Set Architecture (QISA), should sit for fault-tolerant quantum computing. The authors propose the ARIES instruction set hierarchy, which groups QISAs into abstraction levels, and build a cycle-accurate simulation toolflow. Using eight quantum applications on superconducting and topological qubit platforms, they measure instruction bandwidth, transceiver power, and measurement overheads. They report that physical-level abstractions exceed dilution refrigerator thermal limits, while canonical-level abstractions underestimate routing congestion and runtimes, and they identify Level 4 (local logical operations) as an optimal balance.
Dmitry Filippov, Justin Hogaboam, Mathias Soeken et al.
In briefOptically detected coherent nuclear spin control in a molecule at room temperature
SummaryThis paper reports the first optical detection of nuclear magnetic resonance and coherent nuclear spin control in a molecular system at room temperature. The authors observe optically detected Rabi oscillations of 14N nuclear spins in the photoexcited triplet state of the organic chromophore 6,13-diazapentacene. Strong hyperfine coupling between the electron spin and the 14N nucleus increases the nuclear Rabi frequency, allowing fast coherent nuclear-spin rotations. The work aims to lay the groundwork for using nuclear spins as memories in molecular quantum sensing.
In briefQuantum metrology boosted by saddle-point scrambling in phase space
SummaryThis paper proposes a quantum metrology scheme that uses nonlinear dynamical trajectories and their geometry in phase space to choose initial states and encode parameters. Using a two-mode Bose-Einstein condensate as an example, uncorrelated spin coherent states placed at saddle points and separatrices can reach Heisenberg scaling within a certain parameter range. An analytical expression for the quantum Fisher information under long-time evolution is given, and the enhancement is attributed to the sensitivity of the energy spectrum to parameter changes.
In briefEntanglement Sudden Death in Gapped Ground States
SummaryThis paper studies how quantum entanglement between two subsystems disappears beyond a certain distance, called the entanglement length. The authors show that for gapped ground states in any dimension, this length is finite on finite subsystems. In one dimension, they prove that normal matrix product states have a finite entanglement length independent of the subsystems, which distinguishes them from other pure states.
WhyProves finite entanglement length for gapped ground states in any dimension and characterizes matrix product states in one dimension via uniform entanglement length.
Robert Ferydouni, Thomas Jackson, Samuel O. Scalet
In briefPhoton-stimulated decay of ancilla qubits causes unflagged bit flips in bosonic codes
SummaryBosonic codes often read out syndromes with a transmon ancilla whose levels are matched so that the f→e decay is flagged. This paper shows that the code's photons open a f→g Raman decay path at first order in the ancilla decay rate, causing bit flips that are not flagged. In a microscopic model of the Ocelot repetition cat code, the bit-flip floor grows linearly with cat size, by about 1.2 to 1.7 times from four to ten photons. This could limit noise bias to roughly 10^3, while published gate data only reach four photons and do not yet test this growth.
WhyIdentifies a new unheralded bit-flip channel from photon-stimulated ancilla decay; supported by analytic derivation and a microscopic model, lacking experimental tests.
In briefVortex patterns in momentum distributions of multi-pair particle production
SummaryThis paper studies vortex structures in the momentum distributions of multiple particle-antiparticle pairs created from the vacuum by a uniform, time-varying electric field of arbitrary polarization, using the Bogoliubov transformation. For linear polarization, nodal lines split into vortex-antivortex pairs, while circular polarization produces a central vortex. Elliptical polarization with suitable ellipticity shows discrete vortices coexisting with a central vortex. The results provide a theoretical basis for understanding vortex topology in multi-pair production in strong-field QED.
In briefFoundations for a Lens of Quantum Governance: a framework for how quantum technologies may affect authority, accountability, and legitimacy
SummaryThis paper proposes a quantum governance lens linking governance scholarship with quantum information science, focusing on how technical design, institutional arrangements, and infrastructural dependencies interact. It applies the lens to five areas: quantum computation, quantum key distribution, Quantum Byzantine Agreement, blind quantum computation, and dual-use quantum sensing. The authors argue that technical guarantees cannot by themselves resolve institutional questions. They conclude that quantum technologies do not necessarily require entirely new governance frameworks, but call for reconsidering established questions of legitimacy, accountability, and equity.
