In briefTeaching quantum mechanics in high school: a qubit-first route to Bell's inequalities
SummaryThe paper presents a secondary-school curriculum that introduces quantum mechanics through two-level systems realized with light polarization, progressing from superposition and entanglement to experimental tests of Bell's inequalities. In a newly equipped quantum optics lab at an Italian high school, students carried out a Bell test with polarization-entangled photons, reported as a first in Italy. The authors report preliminary mixed-methods results showing gains in conceptual understanding and confidence with mathematical formalism.
Alberto Carlini, Andrea Lanza, Dalida Monti et al.
In briefDoes conservation hold for every individual quantum measurement outcome?
SummaryThe paper examines conservation laws in quantum mechanics, which are usually understood only statistically and only under unitary evolution, while individual measurement outcomes break even that weak form. A recent proposal claims a stronger, non-statistical conservation at the level of single outcomes by including the preparing apparatus as a correlated reference frame. The authors analyze this proposal and argue that its mechanism is not adequately justified and does not establish conservation for individual outcomes.
In briefQuantum charge as a particle/antiparticle label via the Weyl-Heisenberg group
SummaryThis paper argues that particles and antiparticles are linked to the Weyl-Heisenberg group, using a central element that defines quantum charges of +1/ħ and −1/ħ for their wave functions. The authors treat these charges as intrinsic properties of the wave functions, similar to spin and electric charge. They attribute negative probabilities and energies, and the Klein paradox in Klein-Gordon and Dirac theories, to a violation of U(1)_v invariance. Restoring this invariance is said to eliminate these paradoxes at the first-quantized relativistic level.
In briefMamba Quantum Eigensolver (MQE): A selective state space model for ground-state chemistry simulation
SummaryThis paper proposes the Mamba Quantum Eigensolver (Mamba-QE), which replaces the Transformer in the Generative Quantum Eigensolver with a Selective State Space Model to process operator sequences with linear complexity. It also adds a distance-conditioned mechanism to predict complete potential energy surfaces directly. On the H2 molecule, the authors report energy errors below 3×10⁻⁶ Ha across 16 geometries, within chemical accuracy of Full Configuration Interaction references, and no variational violations.
G. X. A. Petronilo, M. R. Ara\'ujo, Erico S. Teixeira et al.
In briefEncoding bosonic modes into qubits to simulate boson-matter interactions
SummaryThe paper compares three ways of encoding a bosonic mode into qubits: unary Fock state encoding, a novel Dicke encoding, and binary quadrature encoding. Using classical simulations of displacement operations and a Dicke model, the authors assess accuracy and space-time costs in qubits, circuit depth, and CNOT count. Binary quadrature encoding is found to be overall most favorable, while Dicke encoding yields shallow circuits but requires many more qubits. Small-scale tests on a Quantinuum trapped-ion device show noise causing visible deviations from ideal dynamics.
Maarten Stroeks, Jelena Mackeprang, Yaroslav Herasymenko et al.
In briefSimulating laser cooling of 2D and 3D trapped-ion crystals in a Penning trap
SummaryThis paper implements a semiclassical model of electromagnetically induced transparency (EIT) cooling in a new molecular dynamics code that evolves both ions' internal quantum states and classical motion. The code is validated by comparing single-ion cooling rates with fully quantum simulations. The authors then study cooling of drumhead modes in planar ion crystals and of axial modes in 3D ellipsoidal crystals containing up to 500 ions.
John Zaris, Wes Johnson, Krishna Balaji Sogathur et al.
In briefQuantum f-divergences via a unified classical variational principle based on retrodictive tests
SummaryThe paper addresses how one classical f-divergence can be extended to quantum states in inequivalent ways, and seeks a common variational principle for these extensions. It introduces retrodictive tests relative to a reference state, linking forward and reverse processes through Petz transposition. For faithful states in finite dimension, the authors show one spectral implementation simultaneously attains the minimum classical f-divergence for every operator-convex f. Different reference choices recover standard and maximal quantum f-divergences, including the passage from Umegaki to Belavkin-Staszewski relative entropy.
WhyGeneralizes Matsumoto's reverse tests via retrodictive tests, unifying several quantum f-divergences with a rigorous proof; impact is largely confined to quantum information theory.
In briefWhether five four-party orthogonal product states can be told apart using local operations and classical communication
SummaryThis paper studies whether five quadripartite orthogonal product states (OPSs) can be distinguished using only local operations and classical communication (LOCC). The authors classify sets of five such states into nine categories based on the numbers of pairwise orthogonality relations, corresponding to 371 orthogonality graphs. They show that 355 of these cases can be perfectly distinguished by LOCC, while the remaining 16 cannot be exactly distinguished.
In briefPrecise Wichmann-Kroll vacuum polarization calculations using Gaussian basis sets
SummaryThis paper uses Gaussian basis sets up to size N=500 to compute the all-order Wichmann-Kroll vacuum polarization correction in highly charged ions. For hydrogen-like systems, the method yields corrections with precision comparable to traditional approaches. The authors show that effects computed as differences of two quantities, such as the nuclear model correction, converge faster than the absolute correction, and they discuss basis extrapolation for estimating incomplete-convergence errors. The method is also applied to the vacuum polarization screening correction in lithium-like ions.
In briefQuantum-enhanced matter-wave interferometer in a ring waveguide
SummaryThis paper proposes a matter-wave interferometry protocol using fractional-revival dynamics of a Bose-Einstein condensate in a ring, combined with a controlled interaction quench. Using the Truncated Wigner Approximation, it shows that applying the quench after the initial quarter-revival beam splitter from a non-interacting condensate yields -14.57±0.27 dB spin squeezing, much stronger than the -2.03±0.28 dB from nonlinear evolution alone. Phase control and further quarter-revival evolution then convert the squeezed state into a number-squeezed state suitable for population-difference readout.
In briefSplitting Probability in Monitored Quantum Dynamics: how likely a quantum walker is to be detected first at each of two monitored targets.
SummaryThis paper studies a continuous-time quantum walk subjected to stroboscopic projective measurements on two targets with sampling period τ. The authors build a renewal framework for first-detection amplitudes and derive exact splitting probabilities, using reflection symmetry in the Hamiltonian. In a one-dimensional tight-binding chain, the splitting probabilities approach 1/2 for τ below a critical value τc and oscillate with initial position above it.
Prashant Singh, Sabine Tornow, David A Kessler et al.
In briefA compact ultracold strontium experiment setup
SummaryThis paper describes a small, simplified apparatus for producing ultracold strontium atoms. Its low-power oven and coil-free Zeeman slower keep the whole vacuum system only 40 cm long. The oven draws 14 W at 460°C and produces a collimated flux of 3×10^10 atoms/(s·cm²). The laser system uses a master-slave architecture without second-harmonic generation or tapered amplifiers, reducing cost and complexity. The system has been in continuous use for over a year.
Mathieu Bertrand, Torben P\"opplau, Lucas B\'eguin et al.
In briefShorter qudit triorthogonal codes built by doubling
SummaryThe paper generalizes doubling to qudits of odd prime dimension to build shorter triorthogonal codes with distance raised by up to two. It gives new parameters such as [[28,1,4]]_3 and [[20,1,4]]_7, and finds by exhaustive search the shortest distance-three codes for p=5 and p=7. The authors report that these codes can reduce qutrit magic state distillation cost by up to an order of magnitude at high input noise.
In briefQuantum belief characterization: a multi-shot equivalence
SummaryThis paper studies quantum belief over multiple update rounds, where each extended posterior serves as the prior for the next update. The authors define n-shot equivalence and, using the quantum de Finetti representation, restrict one-copy belief to candidate-state ensemble belief. Within that class, two beliefs are n-shot equivalent if and only if their (n+1)-th moments are equal.
In briefHow photon correlations shape quantum Fisher information in coherent multidimensional spectroscopy
SummaryThis paper examines how correlations in excitation light affect how precisely molecular parameters can be estimated from the emitted signal in coherent multidimensional spectroscopy. Under weak-emission and single Schmidt pair approximations, the authors derive a normally ordered information law and compare two-mode squeezed vacuum with coherent excitation. They find that different sources weight amplitude and phase sensitivity differently, and give a leading-order bound on the enhancement of total quantum Fisher information.
In briefLimits on how much a quantum transition rate can be tuned
SummaryThe paper addresses controlling transition rates of weakly coupled processes, writing Fermi's golden-rule rates as quadratic forms of the interaction. It derives rigorous bounds on how much the rate can be modulated over a specified interaction space. Applied to energy transfer from a donor to a molecular vibration coupled to an optical cavity, enhancement and suppression are shown to depend jointly on the interaction and cavity detuning, with the rate response continuously reversible for a fixed interaction.
Kaisei Ohata, Jun-Yu Dong, Yasutaka Kitahama et al.
In briefLévy wave packets and fractional uncertainty relations
SummaryThis paper revisits a debate about fractional uncertainty relations that arose about a decade ago and aims to settle it. The authors study the position-momentum uncertainty product of the Lévy wave packet in detail. They propose a new lower bound for uncertainty relations in fractional quantum mechanics, which is nearly linear in the Lévy index and is satisfied by exact, calculable solutions found in the literature.
In briefConvergence rate of a quantum algorithm and contraction coefficients for qubit amplitude-damping channels
SummaryThis paper studies how fast the quantum Blahut-Arimoto algorithm, used to compute coherent information of less noisy quantum channels, converges. For injective degradable channels whose degrading channel has a relative-entropy contraction coefficient below one, the authors show exponential convergence after enough iterations, and verify this condition for qubit amplitude-damping channels in a relevant parameter regime. Using the Bogoliubov-Kubo-Mori metric on the Bloch ball, they explicitly characterize the relative-entropy contraction coefficient of qubit amplitude-damping channels. The approach is also extended to compute relative contraction and expansion coefficients for two such channels.
In briefQuantum simulation of non-Markovian open systems using low-rank kernel compression and coupling dilution
SummaryThis paper presents an error-controlled framework for simulating non-Markovian open-system dynamics in Gaussian environments on quantum computers. It replaces the microscopic environment with an equivalent bosonic bath that has the same correlation kernel, compressed to a finite number of modes via a low-rank approximation. Coupling dilution is introduced to handle large occupations while preserving the kernel, and the authors derive reduced-state error bounds. Under stated spectral-decay and coupling-regularity assumptions, circuit width and depth scale polynomially with simulation time and inverse accuracy.
In briefA Modified Fröhlich-Pizzo Model for Horizon-Induced Decoherence
SummaryThe Fröhlich-Pizzo (FP) model is a quantum model originally built to describe an atom interacting with the electromagnetic field in the nonrelativistic limit. This paper adapts the FP model using local algebras of a U(1) chiral current to capture key features of the horizon-induced decoherence mechanism identified by Danielson, Satishchandran, and Wald (DSW) for long holding times. The authors suggest the effective dynamics of the system decohering in the DSW setting retains non-Markovian features.
In briefSpin-resolved momentum distributions and vortex evolution in multiphoton pair production
SummaryThis paper studies how electron-positron pairs produced by multiphoton processes are distributed in momentum and spin, using a modified two-level model. The model keeps diagonal spinor inner-product terms that the adiabatic approximation neglects, which creates spin-resolved transverse asymmetries. For circularly polarized pulses, handedness sets the winding direction of quantized vortices, while linearly polarized pulses produce nodal lines instead. For two time-delayed circularly polarized pulses, the delay sets a relative phase that controls interference and vortex evolution.
In briefBoundary exceptional-point-driven chiral switching of topological edge states
SummaryThis paper studies a finite Su-Schrieffer-Heeger chain with non-Hermitian gain and loss potentials at its two ends. Using the finite-size hybridization of two mid-gap edge states, the authors derive exact boundary exceptional point coordinates, Γ_EP = ±i v^N/w^(N-1). Dynamically encircling these points transfers an edge state chirally, either fully to the opposite end or back to its start via double switching. Because the non-Hermiticity is confined to the boundaries, the bulk band spectrum is unaffected.
In briefDephasing time of optically polarized NV⁻ spin baths at low field, beyond the P1 limit
SummaryDense NV⁻ centres in nitrogen-rich diamond dephase on substitutional nitrogen (P1) electron spins. This study converts nitrogen to NV⁻ so the initialization laser polarizes the bath into the m_s=0 state, and compares dephasing with a P1 bath of equal density using cluster-correlation-expansion calculations and an exact solver. At 25 G the polarized bath dephases more slowly than P1, but the advantage shrinks at 300 G and reverses at 800 G. For the Hahn echo the gain is limited to about 1.2 times the P1 value at 25 G.
In briefGeometry-controlled zeros in resonant Kelvin-wave conversion in four dimensions
SummaryThe paper studies Kelvin waves on a vortex surface in four spatial dimensions, where geometry can suppress wave conversion even under exact momentum and frequency resonance. Perpendicular incidence removes the local four-wave coupling, revealing a nonlocal interaction from the surrounding fluid. Gross-Pitaevskii calculations show the coupling changes sign, with the zero ratio approaching about 1.469 at long wavelengths.
In briefAligning stored-state amplitudes for associative memory via quantum annealing
SummaryThe paper studies how quantum annealing can solve the associative memory problem by aligning the amplitudes of states stored in memory. It uses an auxiliary Hamiltonian that is switched off at the end of evolution, with results obtained through numerical modeling and perturbation theory. Examples include systems of two and three qutrits represented by spin-1. Because the Hamiltonian is written through projectors onto stored states, it can be applied to other quantum platforms.
In briefReadout-dependent parameter identifiability in quantum kernels
SummaryThe paper studies when a quantum circuit parameter can change measured features yet leave the projected Gaussian kernel unchanged. An exact four-qubit family shows that diagonal metrics reach rank two, dense metrics at most rank three, and fixed affine expansions cannot exceed that ceiling. Adding one nonlinear scalar coordinate, or using a pairwise product, achieves rank four.
Hyong Keun Park, Jahoon Jeong, Joonkyo Shim et al.
In briefA top-down paradigm for choosing quantum compiler settings
SummaryThe paper proposes a top-down approach that jointly chooses hardware and compiler settings, instead of picking a device first and tuning compiler options afterward. The authors build QuOPTBench, an exhaustively searched benchmark of oracle configurations for 268 quantum circuits, and use an LLM to extract transferable selection rules. They also present QuTOP, a rule-guided machine learning framework that selects configurations without iterative online search.
In briefEvaluating quantum Fisher information in large systems using an ancilla
SummaryQuantum Fisher information is a fundamental quantity in quantum information and mechanics, but evaluating it in large systems remains difficult. The paper proposes an ancilla-based protocol for this task and establishes conditions under which it can theoretically evaluate the quantum Fisher information perfectly. As a demonstration, the protocol is applied to quantum circuits to evaluate the Fisher information of the Greenberger-Horne-Zeilinger state.
In briefFaster quantum circuit simplification by template matching on hypergraphs
SummaryThis paper proposes a hypergraph representation (HG) for template matching in quantum circuit optimization. It merges commuting gates into a single super-node while keeping local connectivity, so matches can be extended by updating only nearby parts of the circuit. Experiments report 11 to 606 times speed-up over the DAG-based implementation in Qiskit on random and arithmetic benchmarks, with the same optimization quality.
In briefAlgebraic conditions for complete relaxation in open quantum systems, autonomous and periodically driven
SummaryThe paper derives sufficient conditions under which open quantum systems described by GKSL master equations on finite-dimensional spaces converge to a unique long-time state regardless of the initial state, a behavior called complete relaxation. For autonomous systems, the criteria are algebraic conditions on the Lindblad operators and Hamiltonian, recovering three previously known criteria. For periodically driven systems, a new criterion adds a local continuity requirement on the time-dependent generator and implies an earlier result.
In briefQUBO-based conformer selection using quantum-classical hybrid optimization for modeling ligands with multiple conformations
SummaryThe paper reformulates ligand conformer selection as a QUBO problem with finite penalties and discrete occupancies, solved with a quantum-classical hybrid solver. It compares this against the MIQP-based qFit-ligand workflow on 83 paired X-ray ligand entries. The QUBO approach gave higher ligand-region RSCC in 62 entries and lower occupancy-weighted torsional strain in 66 entries. However, the atom-level EDIAm score decreased in most entries.
In briefBuffer-qubit circuit allocation to defend quantum clouds against crosstalk attacks
SummaryThis paper addresses crosstalk attacks in quantum multi-programming, where a malicious user on a shared chip can disrupt other users' circuits. The authors extend OQTOPUS, open-source software already used in production, with a buffer-qubit-based circuit allocation method that keeps idle qubits between circuits. Experiments on a real device show observable degradation in dephasing characteristics of qubits adjacent to the attacker circuit. The method has been released as part of OQTOPUS, and the buffer qubits were confirmed to be reserved correctly around allocated circuits.
Haruki Nakayama, Satoyuki Tsukano, Satoshi Kono et al.
In briefOptimization vs. Fair Sampling in Quantum Annealing: An Exact Frustrated Ising Benchmark
SummaryThe paper builds an Ising ring with extra couplings between far-apart sites as a benchmark, exactly deriving ground-state energy, degeneracy, and defect structure to separate ground-state hit probability from conditional sampling bias. Instances with up to 162 logical spins are embedded on a D-Wave Advantage processor using length-two chains and compared with simulated annealing. The results show that optimization success and sampling quality need not improve together: the processor has a higher ground-state hit probability but also a larger total-variation distance from uniformity.
In briefQuantum computer simulations of how strongly interacting particles evolve over time, plus a method to shorten the quantum circuits.
SummaryThis dissertation studies real-time dynamics of strongly interacting quantum systems, such as those in quantum chromodynamics, which are difficult for classical computers to simulate. The authors simulate energy loss and hadronization in 1+1-dimensional SU(2) lattice gauge theory on IBM's quantum processor ibm_pittsburgh, and develop a quantum simulation of the fully gauge-fixed Hamiltonian. To address hardware limits, they introduce Sequency Hierarchy Truncation (SeqHT), which reduces circuit depth by about 30% in adiabatic preparation of the λφ⁴ ground state on ibm_sherbrooke. All simulations are validated against classical benchmarks.
In briefCan quantum layers improve vision-language models’ performance and security?
SummaryThis study inserts or substitutes classically simulated quantum layers into the LLaVA-OneVision vision-language model and compares accuracy, trainable parameters and computational cost with classical models. On the Visual Spatial Reasoning dataset, a quantum layer after the visual projector reaches 80.7% development accuracy, 2.28 points above classical full fine-tuning. Replacing the final decoder feed-forward sublayer keeps 79.22% accuracy with 13.07 million fewer trainable parameters. The authors also test robustness under six attack settings, and find that benefits depend strongly on placement and whether the gains generalize remains open.
In briefVerified compiler for fault-tolerant quantum circuits using Pauli-product measurements
SummaryThis paper introduces QPPM, a language for programs built from Pauli-product measurements and classical feedback, with its results mechanized in Lean. The authors verify lowering of Clifford+T circuits into QPPM and an optimizer that removes measurements, fuses and reorders rotations, and schedules logical rounds while preserving outcomes that later code reads. On QASMBench, verified fusion and scheduling reduce logical measurement depth by a median, and complete resource allowances are certified for all 35 valid small-suite inputs.
In briefProving Lieb-Robinson bounds with the Combes-Thomas estimate
SummaryThis paper studies quantum spin systems, networks of spins coupled by local interactions. The Lieb-Robinson bound says information propagates at an essentially finite speed in these systems. The authors give a new proof that relies on the Combes-Thomas estimate, a spectral bound on resolvent entries of band matrices, instead of the standard path-counting argument.
In briefTransferring qubit inequalities to Gaussian optimizers for bosonic systems
SummaryThe paper develops a method that derives Gaussian optimality results for bosonic quantum systems from inequalities for qubit systems. It lifts bosonic Weyl operators to pseudo-Weyl operators on large qubit systems and proves two transfer theorems that convert tensorized qubit inequalities into inequalities for bosonic Gaussian channels. Applications include showing that the sharp 2-logarithmic Sobolev inequality for the bosonic Ornstein–Uhlenbeck semigroup tensorizes without loss in the constant, and a sharp output entropy inequality for tensor powers of certain qubit channels.
WhyTransfers qubit tensorization inequalities to bosonic Gaussian optimality, proving a sharp 2-log-Sobolev tensorization with rigorous theorems.
In briefLow-latency, high-throughput quantum error decoders on NVIDIA GPUs
SummaryThis paper presents a quantum error correction decoder for NVIDIA GPUs that combines Relay belief propagation with order-zero ordered statistics post-processing. The authors use CUDA Graphs, memory access optimizations, mixed FP16-FP32 arithmetic, and INT8 quantization to improve speed. On the bivariate bicycle code at error probability 0.003, INT8 roughly halves amortized decoding time on the RTX 5080, which reaches 91% of GH200's peak throughput with an 8.9x shorter median latency.
In briefFinding many “straight-shot” paths in quantum control space for optimal performance
SummaryThis paper studies straight shots, control paths along which a quantum objective rises monotonically all the way to its optimal value, which is less demanding than ordinary steepest-ascent methods. The authors introduce a non-stochastic search algorithm, STSA, and generate over 10,000 distinct straight-shot paths. They analyze these paths for three objectives: state-to-state transitions, general observables, and unitary transformation generation. Results show nearest-neighbor distances among straight shots decrease as sample size grows, suggesting they are prevalent in control space.
In briefTunable flat bands generated from a parent chiral Hamiltonian
SummaryThe paper proposes a method for constructing flat-band systems by projecting a parent bipartite system onto its Hilbert space. The approach requires little fine-tuning and identifies conditions under which a Hamiltonian has flat bands at desired energies with a chosen degree of degeneracy. The authors also show how the touching points between the flat band and dispersive bands can be placed at any chosen point in the Brillouin zone, and which perturbations preserve or controllably split the flat bands.
In briefMethods for deriving nonlinear kinetic equations from quantum system dynamics
SummaryThis paper outlines key issues in deriving kinetic equations from the evolution equations of quantum many-particle systems. It examines the mathematical origin of quantum kinetic equations, new methods for obtaining them from hierarchies of evolution equations, with a focus on kinetics within the evolution of observables, and a generalization of the quantum kinetic equation to non-separable initial states.
In briefOvercoming Memory Limits in Pauli Propagation Using Randomization
SummaryThis paper presents a randomized method that combines a resampling schedule, merging of terms, and a small controlled bias to keep the propagated Pauli sum within a fixed memory budget. Spare computing resources can be used for parallel repetitions that systematically improve accuracy. Using the open-source PauliPropagation.jl library, the authors report that the framework reproduces deterministic results while needing several orders of magnitude less memory.
Manuel S. Rudolph, Ricard Puig, Slimane Thabet et al.
In briefGravitational Lamb shift of rotor energy levels in quantum gravity
SummaryThis paper studies the coupling between quantized metric perturbations and an anisotropic quantum rigid rotor. The authors argue that a heavy rotor, made of many constituents, may amplify otherwise negligible quantum gravity effects. They derive the gravitational Lamb shift of the rotor's energy eigenstates, which are dressed by a cloud of virtual gravitons. The authors suggest this shift could serve as a concrete test of whether gravity is truly quantum.
In briefBias-preserving entangling gates for Kerr-cat qubits using an ATS coupler
SummaryThis paper proposes an asymmetrically threaded SQUID (ATS) parametric coupler to create bias-preserving entangling gates between Kerr-cat qubits. By engineering photon-number asymmetry between control and target modes, the gates operate quickly without complex pulse shaping. Simulations report a 99.69% fidelity CX gate with a 50 ns duration without photon loss, and a noise bias of 9922 under a 100 kHz single-photon loss rate.
Kerem Yurtseven, Shantanu R. Jha, Apoorva Limaye et al.
In briefCoDecoder: Faster and More Accurate Quantum Error Decoding
SummaryThis paper presents CoDecoder, a small neural network frontend that works with an existing quantum error decoder. It predicts each shot's logical outcome, keeps confident predictions, and sends the remaining shots to the original fallback decoder. In tests under circuit-level noise, the combined approach reduces failures compared with correlated matching on surface codes and Relay-BP on two bivariate-bicycle codes, with 2.3 to 124 times speed-ups.
WhyProposes a neural frontend composable with existing decoders plus a joint logical-operator head, with multi-code experiments showing lower failure rates and speedups.
In briefConverting stabilizer codes to CSS form via local Clifford equivalence
SummaryThe paper presents a deterministic polynomial-time algorithm that decides whether an arbitrary stabilizer code is locally Clifford-equivalent to a CSS code and constructs the transformation and CSS checks when it is. The problem is reduced to affine linear systems by characterizing local projectors that preserve the span of binary stabilizer labels. For graph states, a necessary-and-sufficient adjacency-matrix criterion is derived, and a bipartite graph is constructed whenever one exists.
WhyGives a polynomial-time test for local Clifford equivalence to CSS codes and an adjacency-matrix criterion for graph states, resolving open classification questions.
In briefInteracting quantum reference frames: a framework for quantum reference frames that interact with the systems they describe, keeping frame changes unitary.
SummaryThe paper formulates quantum reference frames within Dirac quantization of gauge theories, defining them as coherent-state systems tied to a group of frame orientations, with physical states obtained by group averaging. It shows the physical inner product can be written using a chosen frame orientation and an operator measure, while the physical Hilbert space is independent of that choice, generalizing the Page-Wootters reduction map. The main result is that the map implementing a change of frame is unitary even when the gauge group does not act as a tensor product. Applied to temporal frames, this yields a unitary Schrödinger equation for an interacting clock and system.
In briefContinuity of supersolid phase transitions in trapped dipolar gases at finite temperature
SummaryThis paper theoretically studies phase transitions in a trapped dipolar quantum gas as contact interaction strength and dipole orientation are tuned, motivated by a recent experiment. Using extended Gross-Pitaevskii simulations with thermal and quantum effects, it maps a phase diagram with unmodulated superfluids, triangular droplet arrays and stripe states. Imaginary-time hysteresis analysis characterizes whether each transition is discontinuous or continuous, with the unmodulated-to-modulated transition changing with dipole tilt.
In briefCumulative locality governs collective quantum charging: a theoretical paper on conditions for collective quantum battery charging advantage.
SummaryThe paper examines when quantum batteries can outperform classical ones through collective quantum effects, using a generic class of free-fermionic chargers. It proves that global operators alone are insufficient for scalable superextensive charging, and that a cumulative hierarchy of many-body operators is required, with battery structure determining the degree of advantage. The authors also propose an effective definition of participation number linked to the scaling of charging power.
In briefComplete modified log-Sobolev inequality for 1D quantum spin chains
SummaryThe paper proves a complete modified logarithmic Sobolev inequality, with a constant independent of system size, for Chen-Kastoryano-Gilyén Gibbs samplers on one-dimensional spin chains at every fixed positive temperature. It applies to bounded finite-range Hamiltonians, including noncommuting and spatially nonuniform interactions. This gives trace and diamond mixing times of order O(log N + log(1/ε)).
WhyProves a system-size-independent complete modified log-Sobolev inequality for 1D spin chains at all positive temperatures, including noncommuting interactions.
In briefQuantum switch networks: how much memory is needed to share entanglement
SummaryThis paper studies the minimum persistent memory a central quantum switch needs to distribute a graph state to multiple remote users. Each user shares a probabilistically generated Bell pair with the switch, so qubits may have to wait in memory until other links succeed. The authors characterize the minimum persistent memory required after any subset of links is generated and processed, and present an online stabilizer-transition protocol that achieves this limit in polynomial time. For path graphs, the proposed protocol needs only one persistent switch qubit under the order (1,2,…,n), while the Piecemaker protocol needs at least ⌊n/2⌋ qubits for every generation order.
WhyCharacterizes minimal persistent memory bound and gives polynomial-time optimal protocol, substantially beating Piecemaker on path graphs; influential for quantum network subfield.
In briefNeST: High-rate quantum error-correcting codes on silicon spin qubits with fast stabiliser cycles
SummaryThis paper proposes NeST, a co-designed hardware and code architecture for silicon spin qubits that uses electron shuttling on a square lattice of tracks to implement high-rate quantum LDPC codes. The authors report circuit-level simulations with thresholds above 10^-3 and stabiliser cycles under 50 microseconds, which they state is two to three orders of magnitude faster than neutral-atom implementations. They also present a code-surgery logic gadget for a [[150,30,10]] code using only rigid belt motions.
WhyProposes a spin-shuttling architecture matching non-abelian group geometry with high-rate codes and logic gadgets; evidence rests mainly on circuit simulations and extrapolation rather than hardware d
In briefClassical post-processing that expands quantum-generated solutions for Rydberg atom arrays
SummaryThis paper proposes a hybrid method in which quantum hardware supplies initial solutions and a classical Houdayer cluster update algorithm expands them to explore ground-state manifolds of maximum independent set problems. Tested on 43 instances from QuEra's Aquila device, it raised solution diversity by up to 11923x, with a median of 24.3x. Post-processing recovered a median of 21% of the ground-state manifold, and all of it for six instances, and in some cases found larger independent sets than the hardware alone.
Andrew J. Ochoa, Martin J. A. Schuetz, Helmut G. Katzgraber
In briefSwitching a spin model between collective dynamics and fast scrambling by changing its initial state
SummaryThis paper studies a deterministic, translation-invariant XY spin model with long-range couplings, where both collective dynamics and fast scrambling of quantum information can arise. By applying local perturbations to a fully symmetric initial state, the authors show the dynamics shifts from collective to scrambling, as indicated by bipartite and multipartite entanglement measures. The crossover is characterized using Lyapunov exponents, and spectral properties of the coupling graph's adjacency matrix are shown to predict the onset of fast scrambling.
Sridevi Kuriyattil, Johannes Kombe, Andrew J. Daley et al.
In briefSimulating the static Yukawa model on a trapped-ion quantum computer using effective particles
SummaryThis paper studies the static Yukawa model, a simple coupled fermion-boson system, on Sandia's QSCOUT trapped-ion platform. The authors use similarity renormalization to describe the same physics with effective particles labeled by different parameter values, mapping data from accessible boson occupancies to higher occupancies. They demonstrate the time evolution of the static Yukawa model on a qubit-boson device.
Qingfeng Wang, Christopher G. Yale, Edward C. Tortorici et al.
In briefChaos and scrambling in anisotropic Dicke and Rabi models
SummaryThis paper compares two limits of the same model to see how classical chaos and quantum scrambling correspond across regimes. In the thermodynamic limit, the anisotropic Dicke model shows chaos closely matching scrambling, but in the large-frequency-ratio limit of the anisotropic Rabi model (ARM) this correspondence breaks down. The authors attribute the different chaotic behavior to differing numbers of classical degrees of freedom, and the similar scrambling to eigenstate delocalization. They conclude that eigenstate delocalization alone does not qualify the ARM as classically chaotic.
In briefScrambling Separates Superradiance from Quantum Chaos
SummaryThe paper reconciles conflicting findings on the Dicke and Rabi models, which link superradiance to quantum chaos. It separates global chaos from local instability and uses a fidelity out-of-time-order correlator (FOTOC) to probe the local stability of stationary points. The authors find superradiance is neither necessary nor sufficient for global chaos, and that FOTOC dynamics can reconstruct the absolute amplitudes of spectral singularities.
In briefControlling localized Floquet states and photocurrents in Weyl semimetals with light's orbital angular momentum
SummaryThis paper studies a Weyl semimetal driven by a vortex light beam carrying orbital angular momentum. The authors show that this light generates highly localized Floquet vortex states with circulating photocurrents. Both a continuum theory and a Wilson-lattice calculation identify these vortex states around the beam axis. The lattice results indicate that the localized states carry much stronger circulating current densities than more extended surface states.
Kyle S. Netherwood, Juan I. Aranzadi, Nils Jacobsen et al.
In briefStable charged energy and phase transitions in an anisotropic Dicke quantum battery with Kerr nonlinearity
SummaryThis paper studies an anisotropic Dicke quantum battery with Kerr nonlinearity, examining how phase transitions affect its charging process. The authors find that multiple near-degeneracies appear at certain nonlinearity strengths, with the stable stored energy governed by an ergodic-nonergodic transition away from that region and by first- and second-order dissipative phase transitions within it. The work also uses Liouvillian spectral theory, Wigner functions, and reinforcement learning to analyze and optimize charging.
In briefA quantum polynomial-time algorithm for hidden parabolic subgroups of GL_n over finite chain rings
SummaryThe paper presents a bounded-error quantum polynomial-time algorithm for finding hidden parabolic subgroups of GL_n(R) over any effectively presented finite chain ring R. It uses auxiliary group elements or subgroups, called probes, to extract information via oracle queries. Depending on whether the residue field size q is at least 3 or equals 2, the algorithm reconstructs the complete flag or lifts a conjugate parabolic subgroup. It outputs generators with probability at least 1−ε in time poly(n, log|R|, log(1/ε)), with consequences for GL_n(Z/NZ) and GL_n(O_K/NO_K) for number fields K.
WhyGives a general quantum algorithm for hidden parabolic subgroups over finite chain rings, handling q≥3 and q=2 separately, extending to Z/NZ and number-field residue rings.
In briefCompact dressed Hamiltonians for simulating open quantum system dynamics
SummaryThis paper extends the compact dressed Hamiltonian (CDH) framework to simulate open quantum systems strongly coupled to structured bosonic environments. The method combines reaction-coordinate mapping with a polaron transformation and truncates the collective bosonic mode after incorporating strong coupling, requiring far fewer states. Benchmarks against hierarchical equations of motion and converged reaction-coordinate calculations show accurate reproduction of oscillation frequencies, relaxation, and long-time populations across a broad parameter range. The framework also captures cooperative effects and gives direct access to the Liouvillian spectrum and eigenmodes.
In briefCO$\Phi$: Compiling photonic programs into digital quantum circuits
SummaryThis paper proposes a method for mapping quantum-optical systems onto qubit-based quantum circuits, using a truncated Fock-space encoding of single-mode optical states. It gives circuit representations for phase rotation, displacement, squeezing, and beam splitter operations, with explicit constructions for truncation dimensions N=2 and N=4. The authors benchmark the operations and discuss applicability and limitations, and release the Python compiler CO$\Phi$ that converts Blackbird programs into OpenQASM circuits.
Grzegorz Czelusta, Marcin Markiewicz, Jakub Mielczarek et al.
In briefQuantum Broker: a QoS-aware framework for distributing quantum computations across multiple quantum processors
SummaryThis paper presents the Quantum Broker, an open-source, provider-agnostic framework that manages quantum circuit execution according to Quality-of-Service requirements. It splits a circuit's measurement shots across several heterogeneous quantum processors based on user-defined constraints, using a declarative language called QQSpec and two solvers, a MILP solver and a nonlinear dual-annealing solver. Experiments on benchmark circuits and noisy simulators show feasible dispatch plans and better QoS satisfaction than single-backend and naive multi-backend baselines. The nonlinear solver yields better allocations but requires more planning time.
Giuseppe Bisicchia, Alessandro Bocci, Jose Garcia-Alonso et al.
In briefFloquet ground states show stable quantum order under periodic driving
SummaryThis paper studies periodically driven interacting quantum systems, arguing that their ground states can host stable order rather than thermalizing. The authors decompose time evolution into geometric and average-energy parts and use Geometric Floquet theory to identify the Floquet ground state. Numerical matrix product state simulations of driven chains with over 100 spins show a gapped, area-law entangled ground state.
WhyIntroduces a geometric Floquet framework and variational principle for stable driven quantum order, validated by MPS simulations on over 100 spins.
In briefBasis-free coherence of quantum ensembles for communication
SummaryThis paper studies coherence for ensembles of quantum states, the objects used in quantum communication. The authors show that in every finite dimension, a continuous ensemble of pure states drawn from the normalized Haar measure attains the tight upper bound on basis-free relative entropy ensemble coherence. They also prove that ensemble coherence bounds the effective informational advantage of postselective measurements over the Holevo quantity for two equiprobable pure states. For the qubit B92 QKD protocol, they show that the coherence of Alice's ensemble upper-bounds the secret key rate asymptotically.
