In briefNonperturbative string dynamics on a superconducting quantum processor: a quantum simulation study of how electric flux strings in a 2D gauge theory evolve through charge motion, pair creation and transverse deformation.
SummaryThe paper uses 63 superconducting qubits, including 12 ancillas, to simulate a (2+1)D Z2 lattice gauge theory with dynamical matter and an explicit magnetic plaquette interaction. It covers both strongly confined and nonperturbative deconfined regimes. In the deconfined regime, charge and flux spread rapidly, matter occupation in the string interior increases near the pair-creation resonance, and spreading is suppressed at strong electric fields. Local Gauss-law constraints are used for error detection, together with ancilla checks and noise rescaling, to measure dynamics in circuits with up to 15 second-order Trotter steps.
WhyThe authors simulate nonperturbative (2+1)D Z2 string dynamics on 63 superconducting qubits, using Gauss-law constraints for error detection.
Sanziana Stelea, Anthony Gandon, Francesco Tacchino et al.
In briefKey Readiness and Authentication-Key Replenishment for Quantum-Secured UAV Edge Computing
SummaryThis paper studies the time and energy cost of obtaining fresh quantum keys from a finite-key decoy-state BB84 protocol for a UAV serving ground gateways in edge computing. It uses a count-level Monte Carlo model reproduced by a semi-analytic model to link key acceptance to protected upload, computation, and download. At 26 dB optical loss, fresh keys raise the 95th-percentile completion time of both tasks from 10.37 s to 28.65 s, and hover energy grows accordingly.
In briefCorrelation structure in the single-j nuclear model via quantum information theory
SummaryThis paper studies correlations in the mean-field ground state of the single-j model, a realistic fermionic nuclear model with abelian and non-abelian broken symmetries. The authors find that the two types of symmetry breaking affect correlations within the mean-field state very differently, which casts doubt on symmetry breaking as a mechanism for absorbing maximum correlations. They also report that symmetry restoration redistributes existing fake correlations between paired orbitals into more complex subsystems.
In briefA quantum thermal transistor based on nonlinear coupling to the environment
SummaryThis paper studies a harmonic oscillator coupled to emitter, collector, and base thermal reservoirs, showing that thermal amplification is absent when only single-quantum exchange occurs. Introducing weak nonlinearity that permits two-quantum exchange at the emitter enables amplification. The authors also propose a realization using a longitudinally coupled auxiliary two-level system with bath spectral filtering.
In briefThe energy cost of loading classical data into quantum computers
SummaryThis paper treats loading classical data into a quantum random access memory (QRAM) as a physical hardware process and quantifies the dynamic energy used by one query on a superconducting processor. It accounts for attenuation across a multi-stage refrigerator, thermal photons, and gate errors, and analyzes a linear-depth multiplexer and a bucket-brigade architecture. For a representative query with a 12-qubit address register, the authors report a fidelity of 0.969, 3.51×10⁻⁴ J of dynamic energy, and average and peak power of 4.38 W and 64.4 W. They also find that at fixed target fidelity, the operating point and attenuation profile can change average power by a factor of two or more.
Joao F. Doriguello, Alessandro Luongo, Harshit Verma
In briefMultidimensional Quantum Block Turbo Codes: extending quantum turbo decoding to multi-layer product codes
SummaryQuantum serial turbo codes and quantum block turbo codes brought iterative turbo decoding into quantum error-correcting codes. This paper presents a theory of multidimensional quantum block turbo codes, a turbo decoding method for multi-layer product codes. The authors describe the algorithm and simulate the performance of the three-dimensional case on a depolarizing channel.
Khaled Jebari, Luiz Anet Neto, Ramesh Pyndiah et al.
In briefSimulating light-matter lattice dynamics on fault-tolerant quantum computers
SummaryThis paper analyzes the logical resources needed to simulate real-time dynamics of a two-dimensional Tavis–Cummings lattice, where cavities hold several emitters coupled to photons. The authors build circuits for photon hopping and local light–matter exchange that update photon occupations in place, removing an auxiliary photon register. Across three examples, the controlled walk uses 4.75% to 8.11% fewer Toffoli gates than a two-register implementation. Closed-system evolution uses generalized quantum signal processing, while open systems use a sampled first-order dilation.
In briefOn-chip dissipation for fast superconducting qubit reset
SummaryThis paper experimentally demonstrates a scalable method for resetting superconducting transmon qubits and removing leakage, using dedicated dissipation units made of resonators coupled to on-chip resistive loads. The design provides Purcell protection while isolating the qubits from warmer external circuitry. The reported median reset time constant for the |g⟩-|e⟩ transition is about 48 ns, at an effective bath temperature of 30 mK.
In briefOperational limits of reference renewal for retained quantum-service results
SummaryThis paper applies reference renewal to re-examine retained physical quantum-service results under a prespecified protocol. Of twelve transitions, ten completed renewal and eight met the prespecified endpoint, with five succeeding using retained results alone. The authors report that incomplete references, binding failures and sequential waits reveal operational limits, and that the exact one-sided test does not establish the recovery hypothesis.
Roberto Fern\'andez-Barrios, Iker Pastor-L\'opez, Amaia Pikatza-Huerga et al.
In briefHow Invariance Helps Quantum Neural Networks Avoid Overfitting and Shortcut Learning
SummaryThis paper studies the effect of building rotation and reflection invariance (dihedral group D4) into quantum neural networks, comparing eight-qubit models with identical encoding, circuit structure and parameter counts. On four binary tasks, including MNIST and galaxy and red blood cell datasets, invariant models trained on a few tens of images generalized better than non-invariant ones. When trained with a class-dependent corner watermark, non-invariant models learned the watermark and often fell to chance level once it was moved, while invariant models were unaffected. The accuracy advantage of invariant models also persists under a realistic noise model.
Giuseppe D'Ambruoso, Giovanni Gramegna, Domenico Pomarico et al.
In briefFast control of fluxonium qubits using picosecond pulses from Josephson digital circuits
SummaryThis paper presents a method for controlling fluxonium qubits with picosecond single-flux-quantum (SFQ) pulses generated by Josephson digital circuits. Because SFQ protocols designed for transmons perform poorly on low-frequency fluxonium, the authors propose two complementary approaches: one applies high-frequency SFQ pulse packets through the flux channel, and the other combines phase-shifted flux and charge pulses to shorten gate duration. Multilevel simulations show single-qubit gate fidelities above 99.99%.
M. V. Bastrakova, D. S. Pashin, V. A. Vozhakov et al.
In briefDynamical Casimir emission from Floquet-driven Landau polaritons; gauge invariance rules out a superradiant transition
SummaryThis paper studies Landau polaritons formed by a two-dimensional electron gas in a terahertz cavity under periodic driving. The authors argue that gauge invariance forbids a superradiant phase transition even with magnetic modulation. Instead, magnetic modulation produces dynamical Casimir emission, including Faraday-driven polariton–magnetoplasmon pairs and two-color photon pairs with up to 5–10 dB of two-mode squeezing.
WhyThe authors attribute the predicted Floquet SRPT to improper averaging, give a gauge-invariance argument, and predict dynamical Casimir two-color photon pairs with up to 5–10 dB squeezing.
In briefA new computational model for spin-free sum-of-squares energy bounds of electronic Hamiltonians
SummaryThis paper reformulates the spin-free sum-of-squares (SOS) energy bound optimization for electronic Hamiltonians, which normally yields large semidefinite programs, as a convex quadratic problem over one symmetric matrix. It gives explicit maps between solutions of the two formulations and identifies the Frank–Wolfe gap with the difference between primal and dual objectives. GPU-accelerated Coulomb contractions and a cached fully corrective Frank–Wolfe method are used to solve it, with tests on 65 FCIDUMP models and hydrogen rings up to 10,000 orbitals.
In briefError Resilience and Unitary 2-Designs: a paper on how quantum information is protected from errors in encoding-error-decoding circuits, and how departures from unitary 2-design encoders affect that protection.
SummaryThis paper studies how quantum information is protected in encoding-error-decoding circuits, where recovery fidelity approaches unity below a threshold error strength. The authors show that departures from Haar second-moment statistics of the encoder can destabilize this error-protecting phase. They derive a universal inequality linking recovery fidelity to the second unitary frame potential. Matchgate circuits with tunable non-Gaussian gates and Hamiltonian encoders serve as examples, and recovery fidelity is proposed as a diagnostic of unitary 2-design behavior.
WhyThe authors derive a universal inequality linking recovery fidelity to unitary frame potential, illustrated with doped matchgate circuits and Hamiltonian encoders.
Zheng-Hang Sun, Fabian Ballar Trigueros, Xhek Turkeshi et al.
In briefElectrical Stark Tuning and In Situ Field Sensing of V2 Silicon Vacancies in a-Plane 4H-SiC Lateral pin-Diodes
SummaryThe study fabricates lateral pin-diodes on a-plane 4H-SiC wafers using a scalable CMOS process and demonstrates electrical control and optical addressing of V2 silicon vacancy color centers in their intrinsic region. The embedded centers measure local electric fields at cryogenic temperatures via the Stark effect, and the results are compared with TCAD simulations. Reverse-bias Stark tuning is also used to align the zero-phonon lines of individual emitters, which remain spectrally stable for over four hours.
Jannik H. Schwarberg (1), Fedor D. Hrunski (2), Maximilian Hollendonner (2) et al.
In briefReading long-range information from separable quantum records needs entangled measurements
SummaryThe paper studies qubit probes that record the relative orientation of neighboring Ising spins, yielding a fully separable probe record. On the square lattice, readout with separable measurements has success probability approaching 1/2 as spin separation grows, for 0<p≤1-1/√2. A joint readout of the same record keeps success probability above 1/2 by a distance-independent margin for p between 0.29181 and 1.
WhyThe authors show long-range information in a separable quantum record requires entangled measurements, with a strict overlap interval separating two readout strategies on the square lattice.
In briefEdge quantum weight of finite Chern flakes and the lower bound it imposes
SummaryThe paper studies how the edge of a finite Chern insulator flake contributes to the quantum weight that governs a circuit's zero-point energy. It shows that the dipole weight of low-frequency edge transitions is at least |C| per unit area. The measured weight depends on whether the circuit is slower or faster than the edge modes. Exact free-fermion calculations on lattice flakes support this bound and its dependence on circuit frequency.
In briefA classical post-processing method that recovers aliased energies in unitary quantum Krylov diagonalization
SummaryThis paper addresses molecular energy calculations on early fault-tolerant quantum hardware using unitary quantum Krylov subspace diagonalization (UQKSD). It notes that small time steps produce ill-conditioned overlap matrices, while larger steps improve conditioning but leave energies known only modulo 2π/τ. The authors propose CURE-QKSD, a classical post-processing method that recovers the missing multiples of 2π/τ from phase-consistency landscapes of one or two UQKSD runs, leaving the circuits unchanged. In noiseless tests on six molecules with 12 to 20 qubits, all 28 targeted energies were recovered, and under Gaussian noise, aliased time steps reached chemical accuracy with smaller Krylov bases.
Tushar Kumar Jain, Rahul Maitra, Nicholas J. Mayhall
In briefDisorder-driven logarithmic spreading and localization of quantum fluctuations
SummaryThis paper studies how quantum fluctuations beyond mean-field dynamics propagate in weakly interacting disordered bosonic systems, comparing the Bose-Hubbard model with the Gross-Pitaevskii equation. In contrast to ballistic spreading without disorder, the fluctuations spread logarithmically at intermediate times under random and quasiperiodic disorder before saturating. The spreading rate decreases algebraically with disorder strength, and this behavior persists across particle numbers and in two dimensions.
In briefTruncating low-energy spectral windows in compact U(1) lattice gauge theory
SummaryThe paper proves a non-asymptotic bound on the error from truncating electric flux in the low-energy window of the pure compact U(1) lattice Hamiltonian. The bound holds for all normalized vectors in that window on a three-dimensional periodic cubic lattice at zero theta, in the gauge-invariant zero-global-flux sector. An analytic finite-volume strong-coupling example illustrates a preserved non-vacuum band and plaquette signal. The estimate also yields precision-dependent sufficient cutoffs and local electric-square readout bounds.
In briefQuantum-assisted regret minimization for solving bounded-payoff imperfect-information games more efficiently
SummaryThis paper proposes Quantum-Assisted Counterfactual Regret Minimization, a framework for computing equilibria in bounded-payoff imperfect-information games. It uses Quantum Amplitude Estimation to reduce the computational complexity of regret updates while preserving the convergence of the classical method. The authors analyze the resulting exploitability bound and discuss NISQ-compatible amplitude-estimation variants and their resource requirements.
In briefQuantum-informed graph decomposition: shrinking graphs with QAOA to solve MaxCut more accurately
SummaryThe paper proposes Quantum Enhanced Graph Decomposition (QEGD), a heuristic that uses QAOA as a subroutine to sparsify graphs through local vertex merging. Applied to MaxCut problems solved with QAOA, it achieves higher approximation ratios than GDOA on all tested random 5-regular and 6-regular graphs. On Erdős-Rényi graphs, it reports higher average approximation ratios than QAOA² and ParaQAOA, and compared with DC-QAOA it is higher on sparse graphs and comparable on denser ones. Its average wall-clock time is between 0.4% and 5% of DC-QAOA's.
In briefQuantum-enhanced QSAR for DYRK1A: comparing two molecular representations
SummaryThe paper applies the same RBF-SVM to DYRK1A kinase compounds using either tabular molecular descriptors or a vector measured on a quantum processor. The two models propose different sets of compounds for experimental evaluation, and each includes some already-labeled actives that the other omits. The authors report these differences without claiming formal quantum advantage or explaining why the two vectors separate differently.
Alejandro Giraldo, Daniel Ruiz, Mariano Caruso et al.
In briefQuantum Advantage in Assisted Work Distillation via Complementary Correlations
SummaryThis paper links microscale work extraction in thermal operations with the characterization of nonclassical correlations in bipartite quantum systems. It treats correlations measured across mutually unbiased bases as an energy resource for local work extraction and derives work-based steering inequalities whose violations certify a one-sided device-independent thermodynamic enhancement. Under a one-sided semi-device-independent framework with restricted untrusted dimension, it introduces dynamically scaling work inequalities that witness superunsteerability in weakly correlated entangled states.
Chellasamy Jebarathinam, Debarshi Das, Ray-Kuang Lee
