Exactly Identifying Quantum Correlations in the Simplest Bell Setup
WhyGives a computable necessary-and-sufficient criterion for the quantum boundary, proving each quantum-advantage Bell functional has a unique quantum maximizer, resolving a long-open problem.
Meter-scale quantum links connecting two large quantum processors
WhyDemonstrates four high-fidelity meter-scale couplers between two 120-qubit processors, with distant CZ gates and entanglement; strong novelty and experimental evidence for modular quantum computing.
Testing whether a quantum state-over-time lies in its cone is NP-hard
WhyEmbeds the separable cone as an exposed face, proving NP-hardness of membership for the cone of states over time with rigorous reductions and a semidefinite-representability limit.
A sharp gradient-corrected Lieb–Thirring inequality in one dimension and its use in density functional theory
WhyProves a sharp one-dimensional gradient-corrected Lieb-Thirring inequality with characterized optimizers and explicit error bounds for TFW approximation, a novel and rigorous theoretical advance.
Stripes versus superconductivity in the hole-doped Hubbard model
WhyNeural tensor and backflow simulations on lattices up to 1024 sites reveal near-degenerate stripe and superconducting states, challenging the single-order narrative for the Hubbard model.
Proof of a strengthened quantum Hamming bound by Yu, Lai, and Oh
WhyProves a conjecture of Yu, Lai, and Oh, extending their interpolating quantum Hamming bounds to impure, nonadditive codes and general local dimensions.
Measurement incompatibility and noiseless quantum codes: a theory paper on whether quantum channels can preserve measurement incompatibility
WhyConstructs a rank-one MIC and proves equivalence with noiseless codes, resolving a conjecture with thorough proofs; impact mainly within quantum information theory.
A control-line multiplexing method for scaling up quantum computers
WhyProposes all-microwave frequency-multiplexed gate control filling the two-qubit gap, with a 1:4 demonstration of parallel CZ and XY gates, though scale is modest.
Limits on how efficiently magic states can be distilled, a key cost in quantum computing
WhyProves any stabilizer distillation protocol cannot beat one code projection, and exhaustive searches establish nine-input optimality for quadratic T distillation and eight for CCZ, a strong result.
Stars are a rough AI assessment based on the title and abstract: each paper is scored for novelty, strength of evidence and breadth of impact, then mapped to 1–5 stars (about 2% get five stars and 10% get four). The site only marks four- and five-star papers as Notable, with a one-line reason; no mark does not mean a paper is weak. The full text is not read, so treat the stars as a reading aid, not a verdict on quality. "Code" means the abstract states that code, data or tools are released.
In briefExact analytical solution for collectively pumped superradiance in Dicke states
SummaryThis paper studies a group of N two-level emitters that decay collectively and are pumped collectively, staying within the symmetric Dicke states. The authors sum up the infinitely many quantum trajectories created by competing pumping and decay to obtain an exact finite continued fraction for the Dicke-state populations. They also give perturbative transient solutions for strong and weak pumping, along with relaxation eigenvalues and emission observables for balanced pumping and decay.
Avishi Poddar, Nico Ba{\ss}ler, Julian Lyne et al.
In briefOptimal quantum discrimination at Liouvillian exceptional points
SummaryThis paper examines whether exceptional points (EPs) in non-Hermitian systems help detect weak perturbations. In finite-dimensional Lindblad systems with a unique stationary state and nonzero relaxation gap, the authors show EPs give no fundamental advantage in how observation time scales with perturbation strength. However, by selecting perturbations that boost the quantum Fisher information rate, EPs can reach a set detection accuracy faster than a non-EP reference with the same decay rate. An optomechanical model illustrates detecting a weak force at an EP in less time.
In briefRepulsive Landau Interactions Between Fermi Polarons at Strong Coupling
SummaryThis paper studies mediated interactions between quasiparticles emerging from a Fermi sea, known as Fermi polarons, using zero-temperature quantum Monte Carlo methods. The main result is that the Landau interaction between polarons stays repulsive across all coupling strengths on the polaronic branch in the strongly interacting regime. The authors also compute the real-space interaction between static impurities, which shows RKKY-like behavior at weak coupling and matches the nonperturbative Born-Oppenheimer result at strong coupling.
Renato Pessoa, S. A. Vitiello, Luis A. Pe\~na Ardila
In briefDynamical quantum simulations used as testbeds for quantum information
SummaryThis paper shows that dynamical quantum simulations built to compute response functions prepare many-body states that carry information beyond their original observable. Using local-pulse protocols for Green functions in finite XX and XXX spin chains as a case study, the authors encode a classical bit via opposite source rotations and track how this record spreads across local subsystems and how readily different measurements access it. They find that fermionic covariance reconstructs the signed response in the XX chain, while simple spin measurements recover more local information in the XXX chain. The analysis is extended to Bell state recovery, quantum communication rates, and bipartite and multipartite entanglement.
Su Yeon Chang, Hailey S. Murray, Brian Barch et al.
In briefMeet-in-the-Middle Compilation of the [CNOT] Class with Fibonacci Anyons
SummaryThis paper studies how to compile two-qubit gates for Fibonacci anyons, where errors arise from leakage out of the computational subspace into a fifth fusion state. The authors build a GPU pipeline that searches braid group subsets for low-leakage representatives of the [CNOT] class, narrowing the search space to reach braid length L=72. They prove that leakage lies in Z[φ], that nonzero leakage has an exponential lower bound in braid length, and derive limit distribution laws.
In briefRecovering classical gauge geometry from quantum master constraints
SummaryThe paper asks how the degenerate directions of classical first-class constraints can be recovered when quantum theory is taken as fundamental and the constraints are imposed through a single positive master operator. For a nonnegative master function whose zero set is a Morse–Bott critical manifold, the image of the linearized Hamiltonian vector field is shown to be the symplectic orthogonal of the zero set, with coisotropy equivalent to the linearization having square zero. Three realizations are discussed, including the spectral bottom for quadratic masters and results for the non-Abelian SL(2,R) model.
In briefAdaptive Information Mining: Reaching the Quantum Limit of Super-Resolution Imaging
SummaryThis paper presents Adaptive Information Mining (AIM), a framework that achieves super-resolution by refining measurements of incoming photons in sequence. A reconfigurable imaging system reshapes its measurement responses to maximize Fisher information. When imaging point sources, the authors report estimation errors 2 to 5 times closer to the fundamental quantum limit than traditional direct imaging.
Seungman Choi, Peter Menart, Andrew Schramka et al.
In briefPaper on homodyne-based tracking and parameter estimation for quantum systems in squeezed thermal baths.
SummaryThe paper derives an alternative stochastic master equation for quantum systems continuously measured by homodyne detection in a squeezed-thermal environment. This form identifies two collapse operators for monitored and unmonitored channels and expresses state evolution through Kraus-like operators, aiding numerical methods and Cramér-Rao bound evaluation. For qubit frequency estimation, the authors compute the Fisher information of continuous homodyne monitoring and find that its steady-state rate still scales exponentially with squeezing at nonzero temperature.
Eoin O'Connor, Francesco Albarelli, Marco G. Genoni
In briefMeasurement incompatibility and noiseless quantum codes: a theory paper on whether quantum channels can preserve measurement incompatibility
SummaryThe paper studies when a quantum channel universally preserves the incompatibility of measurements. The authors construct a rank-one minimal informationally complete measurement and prove that such preservation holds if and only if the input space contains a noiseless code subspace of full output dimension. They also give an explicit construction of exact encodings and connect the results to quantum steering and quantum error correction.
WhyConstructs a rank-one MIC and proves equivalence with noiseless codes, resolving a conjecture with thorough proofs; impact mainly within quantum information theory.
In briefSecurity analysis of an Ekert-type QKD protocol under cloning attacks
SummaryThis paper analyzes the security of an Ekert-type bipartite key distribution protocol when an untrusted observer performs cloning attacks. An eavesdropper intercepts qubits sent over a public channel and applies an asymmetric, phase-variant cloner to one or both of them. The authors partially characterize two-qubit states and use the Devetak-Winter framework to compute key rates, identifying states from which a secret key can still be distilled under such attacks.
In briefQuantum key distribution secured by a bound on information leakage
SummaryThis paper examines whether, in prepare-and-measure quantum key distribution, a single bound on information leakage from the sender's source can replace a detailed model of the source. The authors show that this bound, quantified by the probability of guessing the input from everything the source emits, suffices to prove security against collective attacks, with no assumptions on the form, dimension, energy or purity of the emitted states. They note that the standard B92 and BB84 protocols cannot certify a key under this assumption, whereas closely related protocols can reach one secret bit per round in the ideal limit. For noisy implementations, key rates are computed with semidefinite programming relaxations, and the best protocols tolerate visibilities down to 0.84, corresponding to an 8% quantum bit error rate, versus the 11% threshold of device-dependent BB84.
WhyProves security from a single leakage bound without device modeling, reaching near-ideal key rates; validation rests mainly on theory and SDP computations.
Abhishek Mishra, Michele Masini, Maria Balanz\'o-Juand\'o et al.
In briefExperimental evidence that quantum Brownian motion drives electron decoherence in metals
SummaryThis paper reports experiments showing that quantum Brownian motion plays a key role in the decoherence of electron motion. The authors observe clear signatures of electron-metal decoherence for the first time and show it can be continuously tuned. Agreement between experiment and theory is quantitative, which the authors say paves the way for testing the Caldeira-Leggett dissipation theory with free electrons.
Wayne Cheng-Wei Huang, Zilin Chen, Herman Batelaan
In briefField-deployed entanglement-based BBM92 quantum key distribution using quantum-dot photons converted to telecom wavelengths
SummaryThis paper uses a quantum dot to generate polarization-entangled photon pairs at a 1 GHz excitation rate, then converts them to telecom wavelengths while preserving entanglement. The researchers ran BBM92 quantum key distribution over a 1.59 km field-deployed fibre link at the University of Stuttgart's Vaihingen campus. Over 19 hours of stable operation they achieved a secure key rate of 206 Hz and a total secure key length of 14.2 Mbit, which was used to encrypt and decrypt a colour image.
Michal Vyvlecka, Raphael Joos, Benjamin Breiholz et al.
In briefHTM: A Hybrid Model Combining Classical and Quantum Computing
SummaryThis paper addresses the lack of a unified hybrid model for collaborative classical and quantum computation. It proposes HTM, a hybrid classical-quantum computation model built on unified state sets and transition function representations. The model clarifies hybrid control logic, implements a control-sharing mechanism, and introduces a complexity calculation method based on entanglement and superposition to support task partitioning and resource scheduling.
In briefQuantum circuits for elastic wave equations using Schrödingerisation
SummaryThis paper builds explicit quantum circuits for the velocity-stress form of elastic wave equations in homogeneous media, using Schrödingerisation. The equations are rewritten in symmetric matrix form, with Fourier spectral discretization for periodic problems and staggered-grid finite differences for physical boundaries. The authors analyze splitting errors and CNOT-gate counts for higher-order Trotter-Suzuki formulas and compare with classical partitioned splitting, finding a polynomial improvement in spatial-resolution dependence. Noiseless circuit simulations illustrate the constructions and quantify errors against exact and classical reference solutions.
In briefQNETSIM: A Simulator for Designing Satellite and Hybrid Quantum Networks with Memory
SummaryThe paper introduces QNETSIM, a modular discrete-event simulator for designing and evaluating satellite and hybrid space-ground quantum networks. It combines orbital geometry, free-space optical and fiber channels, quantum memories, entanglement generation, and Bell-state measurements in one event-driven framework. The simulator models optical loss, atmospheric turbulence, detector imperfections, finite memory capacity, and storage decoherence. It links these components to entanglement fidelity, throughput, latency, availability, and memory utilization.
In briefThreshold conditions for boson and fermion three-body bound states on a square lattice
SummaryThe paper compares two three-particle models on a square lattice at zero total quasimomentum: three identical bosons with attractive contact interactions, and two fermions plus one distinguishable particle with attractive interspecies contact. It uses the Birman–Schwinger principle with symmetry reduction and strong-coupling asymptotics to separate shared methods from model-specific spectral results. For bosons, exactly two bound states lie below threshold at large coupling, the second being a true eigenvalue 0.03542 below threshold. For fermions, the critical mass ratio is π/(π−2), about 2.75194, above which a doubly degenerate level appears at strong coupling.
In briefMatrix samplers and quantum-proof extractors: equivalence and near-optimal constructions
SummaryThe paper establishes an equivalence between matrix samplers and quantum-proof randomness extractors, extending Zuckerman's classical sampler-extractor correspondence. Using this equivalence, the authors construct explicit strong matrix samplers with optimal randomness overhead and near-optimal sample complexity. They also obtain strong quantum-proof extractors with improved seed and output lengths.
WhyEstablishes equivalence between matrix samplers and quantum-proof extractors, improving sample complexity and seed length over prior matrix samplers.
In briefQuantum generative model that trains only a linear output layer, not the circuit
SummaryThe paper proposes a quantum generative method that encodes a random latent vector into a quantum state, applies a fixed unitary and measures, training only a linear output layer so the circuit itself is never trained. Using Pauli propagation, the authors show that Clifford circuits do not create new functions, while Haar-random brickwork circuits have features whose variation with the latent variable decreases with depth. Across one- and two-dimensional distributions, entangling reservoirs do not systematically improve the generator, and a reservoir with no gates performs competitively.
In briefTime needed to confirm weak-force entanglement between levitated particles
SummaryThis paper studies how to certify motional entanglement generated by weak forces between levitated nanoparticles using finite, noisy measurement records. The authors derive a lower bound on the number of measurements needed to certify Gaussian entanglement and translate it into certification time. They compare release-recapture and continuous monitoring protocols, finding that release-recapture enables certification at interaction strengths several orders of magnitude weaker.
Yao-Tong Chen, Salambo Dago, Oriol Romero-Isart et al.
In briefQuantum Fisher information deficit as a geometric sign of strong-to-weak symmetry breaking
SummaryThe paper studies strong-to-weak spontaneous symmetry breaking (SW-SSB), a phase of open quantum systems that conventional charged two-point correlators cannot detect. For strongly Z2-symmetric states with local charged involutions, the authors show that SW-SSB appears as a persistent gap between the quantum Fisher information and its maximum under symmetry-neutral pair rotations. This deficit is shown to be equivalent to fidelity and Rényi-1 correlator diagnostics of asymptotic long-range order, and a lower bound is derived for symmetry-projected Gibbs states.
In briefExact decoherence of a detector in bounded vacuum geometries
SummaryThis paper studies how a two-level detector coupled to a vacuum scalar field loses coherence over time in three settings: free space, a single perfectly reflecting boundary, and a cavity between two parallel reflecting boundaries. The authors derive an exact decoherence function for the detector. Coherence decays monotonically in free space, partially persists with one boundary, and oscillates with a larger surviving fraction inside the cavity. The results suggest that boundary conditions can be used to engineer quantum coherence.
In briefMaking the TEMPO network independent of system size
SummaryThe TEMPO method simulates non-Markovian open quantum system dynamics by contracting a two-dimensional tensor network. The paper shows that, within the usual second-order time-step error, all internal bond dimensions can be reduced to (2m+1)(m+1), where m is the number of independent coupling channels. This dimension does not depend on the number of distinct eigenvalues of the coupling operators. System size enters only through the final boundary layer, making large systems accessible to TEMPO.
In briefQuantum entanglement in momentum space after Kaluza-Klein reduction
SummaryThis paper studies how a four-dimensional observer's reduced state, obtained by tracing out massive Kaluza-Klein modes of a five-dimensional scalar with cubic or quartic self-interaction, is entangled in momentum space. At leading order in the coupling, it computes the mutual information between low-energy zero modes and a single Kaluza-Klein level, finding a tail that falls as one over the level mass in the cubic theory. The authors conclude that the local four-dimensional effective theory describes low-energy observables but not the state of the reduced system.
In briefQuantum evolution kernel for embedding attributed graphs on neutral-atom computers
SummaryThis paper proposes a way to embed node-attributed graphs on neutral-atom quantum computers and applies it to digit recognition. It extends PASQAL's quantum evolution kernel with a node-level encoding based on three-level quantum states, and uses the resulting correlation-based information for classification. The quantum process is simulated with the Pulser library, which limits dataset size. On digit recognition, the method using the Wasserstein distance achieves higher mean accuracy than commonly used Jensen-Shannon distance-based methods.
Manuel Padovani, Alessandra Di Pierro, Claudia Daffara
In briefCircuit-aware mutation testing for quantum programs: exact visibility and execution planning
SummaryThis paper proposes a circuit-aware framework for mutation testing of quantum programs, distinguishing whether surviving mutants leave behavior unchanged, are hidden by input or measurement choices, or lack sufficient statistical evidence. It targets ideal, noiseless programs with mutations that replace one gate or subcircuit, combining mathematical checks with statistical estimates. For supported cases, it gives conditions under which a test cannot reveal a mutation and exact effect formulas, along with a decision procedure, guarantees, and a small-circuit reference implementation.
In briefQuantum and Classical Memory Needed to Store and Retrieve Quantum Measurements
SummaryThis paper studies how much persistent quantum and classical memory is needed to store and retrieve quantum measurements exactly and with heralding. Assuming only black-box access to the measurement channel, the authors compress a port-based program into an outcome-type record and a quantum register whose total dimension grows polynomially with the number of queries. For n-outcome POVMs on C^d with d ≥ 2, they prove lower bounds Q+C ≥ log₂n and 2Q+C ≥ log₂((n−1)d²+1) on the qubits Q and bits C of any retrieval program.
Filip Turobo\'s, Ludmi{\l}a Marcinkowska, Zbigniew Pucha{\l}a
In briefFrom QCCD trapped-ion hardware to quantum compilers: architectures and compilation methods
SummaryThis paper examines shuttling-based trapped-ion quantum computers (QCCD) and their compilers, abstracting QCCD architectures and native operations so that computer scientists can address compilation problems without deep knowledge of the platform's physics. The design space is organized into a few architectural archetypes, and compilation methods are applied to one- and two-dimensional QCCD architectures. Routing overhead is found to scale roughly cubically with qubit number in one dimension and roughly quadratically in two dimensions. The authors also compare physical and logical levels when a quantum error-correction layer is added, and conclude that hardware-software co-design is required.
Ludwig Schmid, Jurek Eisinger, Daniel Schoenberger et al.
In briefCorrelation-sensitive magic-state distillation from spin-squeezed neutral atoms
SummaryThe paper shows that correlations between blocks can reverse magic-state distillation gain even when each input exceeds the independent-state threshold. Using the five-to-one Bravyi-Kitaev protocol, it expresses the output through measurable target-axis moments and gives a direct sign test for gain. It links this mechanism to neutral-atom resource preparation via finite-range Ising dynamics.
In briefEntanglement between a qubit and its environment during pure dephasing when the qubit starts mixed
SummaryThe paper studies entanglement between a qubit and its environment under interactions that cause pure dephasing, allowing the qubit's initial state to be mixed. The authors find that separability criteria valid for pure initial states reduce to entanglement witnesses in this setting. Using a spin qubit coupled to a sparse spin environment as an example, they illustrate the evolution of entanglement and note that witnesses are numerically more practical for large environments.
Ma{\l}gorzata Strza{\l}ka, Nico Peters, Laura Ares et al.
In briefOpen effective field theories: a framework for noisy, dissipative environments in gravity and cosmology
SummaryThese are lecture notes on Open Effective Field Theories, based on lectures given at the La Ricotta Summer School "The Disordered Universe 2025". The text notes that traditional effective field theories were developed for particle physics with clean, isolated initial states, while realistic environments are often noisy and dissipative. It presents an approach that models the gravitational sector as evolving in the presence of an unobservable medium, and uses the Schwinger-Keldysh formalism to show how unknown environments appear as dissipation and noise in observational probes.
Alessandro Fumagalli, Francesco Paronetto, Leonardo Stanzani et al.
In briefA unified six-step protocol for arbitrary Z rotations on a class of bosonic cQED qubits
SummaryThis paper examines a class of bosonic Fock-based qubits in circuit QED and shows that different ways of implementing arbitrary Z rotations on them share a common structure. The authors formulate this structure as a six-step protocol that gives a unified procedure for arbitrary Z rotations across this qubit class. Whether the protocol applies depends on a specific condition on the encoding, which serves as a criterion for identifying which bosonic Fock-based cQED qubits admit this common implementation.
In briefStoring and extracting energy in V-type quantum batteries via dark states
SummaryThis paper studies a quantum battery made of V-type qutrits coupled to a lossy cavity. A finite splitting pulse converts cavity-bright excitations into atomic dark states, which keep their stored energy even after degeneracy is restored. The authors also bound the passive energy in the symmetric atomic subspace and compare coherent and Fock initial states for finite-time ergotropy and extractable work.
In briefLifting Quasi-Cyclic Additive Codes to Certified Quantum Codes
SummaryThis paper studies additive codes over F4 that correspond to binary quantum stabilizer codes, focusing on 1-generator (1,2)-quasi-cyclic additive codes. It gives an ancestor-lifting theorem for composite lengths, dimension laws, and a palindromic criterion for symplectic self-orthogonality. Exact quantum distances are determined through information-set decoding screening, Brouwer–Zimmermann computation, and independent witness verification. The authors certify a set of record-breaking binary quantum codes and report further propagated entries and upper bounds.
In briefQuantum state preparation for complex amplitudes
SummaryThis paper presents a procedure that prepares a quantum amplitude approximating z/α for a complex number z=x+iy, starting from registers holding its real and imaginary parts, with α a normalization constant. It computes the magnitude and argument with the CORDIC algorithm, encodes the magnitude into an amplitude, and applies phase gates for the argument. The method uses O(n²) T gates and O(n) extra qubits. Compared with encoding real and imaginary parts separately and combining them via LCU, it can allow a smaller normalization and reduce amplitude-amplification costs.
In briefDiagnostic-dependent lasting Mpemba effect in a parametrically driven oscillator
SummaryThis paper studies relaxation of two Gaussian states in a detuned degenerate parametric amplifier below threshold. The trace distance shows a lasting Mpemba reversal, while relative entropy eventually restores the initial order and Hilbert-Schmidt distance alternates indefinitely. The three diagnostics agree on the initial order but can disagree because a real mode and a complex pair share the leading decay rate.
In briefKinetic Slush in Dissipative Rydberg Arrays: a nonequilibrium soft-matter state in driven atom arrays
SummaryThe paper studies a kinetic slush state in a two-dimensional dissipative Rydberg atom array, where excitations are facilitated by neighboring atoms. Using kinetic Monte Carlo simulations in the strong dephasing regime, the authors show that detuning compensates nearest-neighbor interactions, while residual next-nearest-neighbor interactions create kinetic frustration. The competition yields a slush phase with liquid- and solid-like configurations and strong dynamical heterogeneity.
In briefNoise thresholds for reliable quantum approximate optimisation under noise
SummaryThis paper studies how much noise the quantum approximate optimisation algorithm (QAOA) can tolerate at each circuit depth. The authors run GPU-accelerated noisy simulations on MaxCut for three graph families and fit approximation ratios with a generalised logistic surface. They define an effective noise threshold, which generally decreases as depth increases, and use it to separate reliable from unreliable noise regimes.
Yozef Tjandra, Hendrik Santoso Sugiarto, Celine Vania Setiadi et al.
In briefMeasurement-induced entanglement phases in hyperbolic gauge-Higgs models
SummaryThis paper studies entanglement phases of gauge-Higgs models on hyperbolic lattices, described by measurement-only dynamics. The authors map two-dimensional phase diagrams using topological entanglement entropy and a generalized measurement-induced entanglement suited to hyperbolic Higgs phases. They identify an "archipelago" phase absent in Euclidean space, where separated clusters of symmetry-protected topological order exist, and its transitions have mean-field critical exponents.
Cole Kelson-Packer, Hiroki Sukeno, and Akimasa Miyake
In briefFewest Measurement Settings for Estimating Several Quantum Observables
SummaryThis paper studies the minimum number of orthogonal projective measurement settings needed to estimate several observables without bias for any input state. The authors derive structural lower bounds beyond dimension counting and give explicit constructions that certify minimum setting counts for chosen target spaces. A classical variational algorithm searches for shared measurement bases and optimizes readout coefficients and sample allocation. For the collective first and second moments of two qubits, four projective settings are shown to be both necessary and sufficient.
In briefUnusual shapes of Fisher zero lines in biorthogonal dynamical quantum phase transitions
SummaryThis paper studies how Fisher zero lines of the Loschmidt amplitude in non-Hermitian quenches can form unusual patterns in the complex time plane, such as divergence, separation, or branches lying on the real or imaginary axis. It uses a biorthogonal framework to explain these patterns and sets critical momentum conditions based on the dot product of normalized prequench and postquench complex Bloch vectors. The results are verified in a generalized non-Hermitian SSH model, and Jordan form is used to analyze dynamics at postquench exceptional points.
In briefDynamical behaviour of the mass tensor in the lattice
SummaryThis paper studies, with a semiclassical model, how a particle hopping through an orthorhombic lattice moves under a static Coulomb field and a rapidly oscillating homogeneous field. Applying the oscillating field reparameterizes the effective masses so they become equal in both directions, turning a chaotic trajectory into an elliptic one in the continuum limit, as confirmed by Lyapunov exponents. The authors also show that an external magnetic field along the Z direction can control chaos, and extend the scheme to three-dimensional trajectories.
In briefCoherent optical control of a single donor electron spin
SummaryThis paper demonstrates optical initialization, coherent control, and readout of a single donor-bound electron spin in ZnSe. Using spin-selective donor-bound exciton transitions and off-resonant picosecond pulses, the authors observe spin Rabi oscillations, Ramsey interference, and high-contrast coherent population trapping. At higher driving strengths, multiple dark resonances reveal the hyperfine interaction with the I = 3/2 Cl nucleus, and the authors identify isolated optical donors as a promising platform for solid-state optically active qubits.
WhyFirst coherent optical control of a single donor electron spin in a II-VI semiconductor, with coherent population trapping and hyperfine resolution.
Yuxi Jiang, Amirehsan Alizadehherfati, Christine Falter et al.
In briefAnalytic energy formulas for radial power-like potentials via new Bohr-Sommerfeld quantization conditions
SummaryThe paper proposes two new Bohr-Sommerfeld type quantization conditions for d-dimensional radial singular and non-singular potentials. It studies power-like potentials and the logarithmic potential across many radial quantum numbers and angular momenta in dimensions two and three. For large radial quantum numbers the approximate energies approach the exact ones, and a dimensionless WKB correction reproduces exact energies within the cases examined.
In briefSideways position shift of a spinning particle's wave packet under Lorentz boosts
SummaryThis paper studies how spin-orbit coupling makes the average position of a spinning particle shift unusually under a Lorentz boost, an effect called a side jump. The authors develop a trace method that yields an exact, compact transformation kernel for the probability center of a general three-dimensional Dirac wave packet under any finite boost, without a semiclassical expansion. They find that side jumps depend on the wave packet's internal structure and that, for Gaussian packets, they show a non-monotonic dependence on mass.
In briefConsensus and information spreading in quantum networks: how nodes learn global quantum information from local measurements
SummaryThis paper studies decentralized quantum consensus in qudit networks evolving under discrete random unitary dynamics. The authors analyze asymptotic behavior, identify global information preserved by the evolution, and give conditions under which different forms of quantum consensus arise. They present a general theorem for extracting globally encoded information from local measurements, examine CNOT networks, and identify two-qubit interactions that asymptotically reach consensus on average excitation number.
In briefFinite-temperature quantum theory of lossy magnon-cavity resonators
SummaryThis paper develops a finite-temperature quantum quasinormal mode (QNM) theory for cavity magnonic systems containing non-reciprocal magnetic media, material dissipation, open-cavity radiation losses and thermal fluctuations. It uses macroscopic quantum electrodynamics and complex coordinate transformations to quantize the QNMs. The authors apply the theory to hybrid dielectric-magnonic resonators coupled to spin and superconducting qubits, showing modal interference, a transition from coherent to dissipative coupling, and magnon-mediated qubit synchronization.
In briefSuppressing microwave crosstalk in superconducting quantum processors by designing parasitic capacitances
SummaryThis paper studies how unwanted microwave drive crosstalk between qubits in a superconducting quantum processor can be reduced. The authors build a detailed circuit model of a processor with two fixed-frequency transmon qubits and a tunable coupler, and experimentally show that crosstalk can be suppressed. They find the suppression comes not only from cancelling the effective qubit-qubit coupling but also from interference among other coupling paths. The authors conclude that choosing suitable parasitic capacitances can suppress crosstalk, suggesting that parasitic coupling paths should be engineered rather than simply minimized.
Anuj Aggarwal, Jorge Fern\'andez-Pend\'as, Simon Pettersson Fors et al.
In briefMulti-day magnetic imaging of single living cancer cells using a quantum sensor
SummaryThis paper presents Quantum Cell Monitoring (QCM), a widefield nitrogen-vacancy magnetometry platform that records single-cell information from stray magnetic fields instead of emitted photons, at subcellular resolution. Combined with a live-cell incubator, it tracks magnetically labeled living cancer cells for up to 72 hours. The authors report observing mitosis, morphological changes, and cluster formation, splitting, and migration.
Andre Pointner, Sarah Belasi, Regine Schneider-Stock et al.
In briefUpper bounds on how often feedback-controlled quantum trajectories exceed quantum speed limits
SummaryThis paper studies the probability that a single conditioned quantum trajectory, under continuous measurement feedback, exceeds a quantum speed limit (QSL) velocity derived from an ensemble. Using the finite-time average fidelity velocity, the authors bound this exceedance probability in terms of its mean and variance, and obtain state-independent bounds, including an exponential concentration bound. For a feedback-controlled qubit they give explicit model-specific bounds that are nontrivial at short times. They also identify a finite-time regime where the exceedance probability is exactly zero because the conditioned dynamics have restricted support. Monte Carlo simulations confirm the analytical bounds and show their tightness.
