In briefSeparability criteria and lower bounds of entanglement via realignment
SummaryThis paper builds a family of enhanced separability criteria for bipartite and multipartite quantum systems, using realignment of density matrices and vectorization of reduced density matrices. The criteria include earlier realignment-based criteria as special cases and detect more entanglement. The authors also derive tighter lower bounds for concurrence and convex-roof extended negativity, and criteria for detecting genuine tripartite entanglement.
In briefNon-stationary quantum systems linked to one-dimensional stationary scattering
SummaryThis paper shows that stationary scattering in one dimension can be reformulated as the evolution of an effective non-stationary, non-unitary two-level quantum system, from which reflection and transmission amplitudes are extracted. The system's states map to points on a Bloch sphere, and quantum measurements can yield information about the reflection amplitudes. Reflectionless configurations correspond to cyclic evolution of one or both poles, while spectral singularities and coherent perfect absorption correspond to dynamical spin flips between the poles.
In briefProposal for a Multi-Ion Optical Clock Using Hundreds of Trapped Ions
SummaryThe paper proposes a circular surface-trap design for an optical clock using hundreds of trapped ions, addressing frequency inhomogeneity in large ion crystals. Using a ring crystal of 400 40Ca+ ions as a case study, the authors report that the circular geometry suppresses quadrupole shift by about two orders of magnitude compared with a linear trap. Combined with stray-field compensation and dynamical decoupling, they state the architecture could reach fractional frequency uncertainty at the 10^-18 level.
Pavel Kamenskikh, Vasiliy Smirnov, Ilya Gerasin et al.
In briefQuantum Covering Lemma: Limits of Exact Anonymous Network Counting
SummaryThe paper asks whether quantum communication can determine the size of an anonymous network when no size bound is known. Quantum interference breaks the classical covering-lemma argument, yet the authors show exact counting remains impossible. They prove a quantum covering lemma preserving local possible outcomes across cyclic covering families. For uniform synchronous protocols, this rules out zero-error counting, guaranteed finite size bounds, and probability-one terminating exact leader election on anonymous rings and similar families.
WhyProposes a quantum covering lemma preserving local outcomes, with proofs ruling out exact counting on anonymous rings; strong theory, no experiments.
In briefQuantum Krylov sampling solver for elliptic problems with energy-norm error guarantees
SummaryThis paper studies a sample-based quantum linear solver that measures quantum Krylov states and reconstructs the solution of positive-definite systems from elliptic PDEs using a Galerkin solve on the sampled set. It derives energy-norm error bounds, a sample complexity result, and a computable residual certificate. The method is applied to pulsatile flow in elliptic, lens-shaped, and curved ducts, with simulations of up to 12 qubits and measurements on a six-qubit trapped-ion processor. A classical residual-greedy selection is reported to outperform quantum sampling in all cases studied.
Doyeol "David" Ahn (1, 2), Byeongyong Park (1) ((1) Center for Quantum Information Processing et al.
In briefErgodicity-breaking transition in qudit models beyond qubits
SummaryThis paper studies how the local Hilbert space dimension affects the ergodicity-breaking transition in quantum many-body systems. The authors introduce zero-dimensional toy models of qudits and use the hybridization condition to analytically derive how the critical interaction strength depends on local dimension. Numerical spectral correlation measures agree with the predictions, and a higher-spin variant shows the same critical behavior.
In briefThermalization breakdown in quantum spin systems with long-range interactions
SummaryThis paper studies quantum spin systems with long-range ferromagnetic coupling in one spin component and a field coupling in another, finding that they generally fail to thermalize to a paramagnetic state at finite, negative energy per spin. The effect is not tied to integrability and arises from anomalous thermodynamics in the paramagnetic phase, breaking eigenstate typicality and the eigenstate thermalization hypothesis. The non-thermal states reached at long times show long-range multipartite entanglement.
In briefQuantum circuit model of Compton scattering and incomplete Bell measurements
SummaryThe paper treats massless tree-level Compton scattering as an effective two-qubit operation on electron and photon helicities. In the Bell basis the scattering map splits into two parity sectors and can be represented by a simple quantum circuit containing one nonunitary filter. After Kraus normalization, this filter acts as an unsharp incomplete Bell measurement that distinguishes the two parity sectors but not the relative Bell label within each. The authors show the incomplete measurement alone does not exceed the classical teleportation threshold, while a subsequent complete Bell-basis readout yields unit conditional teleportation fidelity.
In briefShows genuine information backflow requires noncommuting initial system states
SummaryThis paper studies when a revival of information in an open quantum system certifies backflow from a non-Markovian environment. Such revivals can instead be extrinsic, arising from noise correlations carried by inert degrees of freedom unconnected to the system. The authors extend the existing framework to restricted families of initial states. They show genuine backflow is possible only if the available family contains noncommuting states.
WhyExtends the backflow framework to restricted state families and proves genuine backflow requires noncommuting states, a novel rigorous theoretical result.
In briefCriticality concentrates large-scale sensing information into a single local readout
SummaryThis paper studies sensing information in an all-to-all dissipative feedback network near criticality. The authors show that a single local binary trajectory has a Fisher-information rate that grows linearly with N, like the full record, and that it keeps more than half the full information across the whole channel-parameter range. A sparse-readout theorem states that only Θ(ε⁻¹) trajectories are needed to retain a fraction 1−ε of the full information rate.
In briefWhere to Place Recovery in Qutrit Teleportation Under Monitored Decay
SummaryThe paper studies where to apply recovery operations in teleportation of encoded qutrits subject to monitored decay. It compares the success advantage of reversing a no-jump map only on the encoded support under two receiver capabilities. For a specific model it derives timing results and identifies regimes where intermediate sender reversal helps and where omitting it is optimal.
In briefOptical realization of a cavity field with uniformly moving mirrors
SummaryThis paper mathematically studies the effective Hamiltonian of a non-stationary electromagnetic cavity field with uniform linear mirror motion, introduced by C. K. Law. The authors reinterpret bosonic coupling terms as generators of the symplectic algebra Sp(4,R), which can be implemented with linear optical elements, allowing strong effective interactions. They derive analytical expressions for the average photon number in each mode and show generation of two-mode squeezed states. Statistical properties such as intermode correlations, the Mandel parameter, and linear entropy are analyzed, and the Wigner function visualizes the system's behavior in phase space.
A.R. Urz\'ua, I. Ramos-Prieto, R. Rom\'an-Ancheyta et al.
In briefAtomic-comb Rydberg quantum receiver design for OFDM wireless signals
SummaryThis paper proposes a Rydberg atomic quantum receiver with an atomic-comb response, built on six-wave mixing transduction and driven by a multi-tone local oscillator. By tuning the amplitude and phase of each tone, the receiver preserves desired response components while attenuating harmful frequency offsets. The design is further optimized to suppress inter-carrier and inter-symbol interference jointly, reducing cyclic prefix overhead. Simulations are reported to validate the approach.
In briefEntanglement of primordial gravitons during quasicrystalline inflation
SummaryThis paper studies how gravitons become entangled during quasicrystalline inflation. Both parity-even and parity-odd interactions produce graviton pairs with nonzero total momentum, though the parity-odd contribution vanishes for opposite-helicity pairs with identical momenta. The transition to radiation domination adds conventional two-mode squeezing. The authors show that homogeneous, helicity-preserving evolution is unitary within each helicity sector, preserving entanglement between the full right- and left-helicity sectors, but it can remove entanglement from the reduced state of a co-propagating pair.
In briefMonogamy of quantum steering in an exciton-cavity optomechanical system
SummaryThis paper studies how quantum steering is shared among exciton, photon, and mechanical modes in a hybrid exciton-cavity optomechanical system. Using the Gaussian-state formalism, the authors verify CKW-type monogamy inequalities for Gaussian steering and show that the bipartite steering distribution can be tuned by system parameters. They also find that higher temperature generally weakens Gaussian steering, while in the dynamical regime steerability can increase with evolution time over suitable windows.
Hamza Harraf, Mohamed Amazioug, Rachid Ahl Laamara
In briefWhy quantum computing still needs variance reduction, not just sign-problem avoidance
SummaryThis paper argues that quantum computers avoid the sign problem of classical Monte Carlo, but quantum measurements are inherently random. Estimating observables can still require sample numbers that grow exponentially with system size, time separation, or inverse temperature. The authors analyze the signal-to-noise problem in quantum computation by drawing parallels with classical methods. They propose a quantum generalization of Stein control variates and validate its variance reduction on exactly solvable numerical examples.
In briefDisproves the Rényi area law conjecture below α=1 in high dimensions
SummaryThis paper studies whether entanglement in gapped quantum ground states scales with a boundary or a volume. The authors construct finite-range Hamiltonians in two or more dimensions whose ground states show volume-law Rényi entanglement while still obeying a von Neumann area law. This disproves the Rényi area-law conjecture for 0<α<1 and identifies α=1 as the sharp threshold within this class.
WhyConstructs high-dimensional finite-range Hamiltonians disproving the Rényi area-law conjecture, with a tight rank-error trade-off; novel, well-supported, and highly consequential.
In briefQuantum AI method that creates synthetic breast ultrasound images to help detect cancer
SummaryThis paper proposes a generative quantum machine learning method that creates synthetic images from the compressed breast ultrasound dataset (BUSI) to augment training data. A convolutional neural network was trained on real, synthetic, and combined real and synthetic images, then tested on real images. The classifier trained only on synthetic images reached an AUC-ROC of 0.802, compared with 0.760 for the real-data baseline.
Sophia Knutson, Nandika Goyal, Gennaro De Luca et al.
In briefQuantum circuit method for generating time series with fixed qubits
SummaryThis paper introduces holographic quantum circuit sampling (HQCS), which uses mid-circuit measurements, qubit reuse, and independently parameterized temporal blocks to generate time-series trajectories with a fixed number of qubits. The authors prove inverse-polynomial bounds on loss variance for Haar-random HQCS under a normalized exponential kernel, contrasting with exponential concentration in global Haar-random generators. Simulations on Gaussian autoregressive processes and historical VIX trajectories show that the VIX results achieve over tenfold lower maximum mean discrepancy than the tested classical benchmarks.
In briefDetecting entanglement in dynamical quantum systems using evolving stabilizers
SummaryThis paper addresses entanglement detection in large quantum systems whose Hamiltonians lack symmetries, making many-body dynamics hard to track. The authors follow the evolution of generalized stabilizers of the state and use them to build linear entanglement witnesses. Numerical experiments on Heisenberg-type Hamiltonians with up to twelve qubits show that the number of measurement settings stays modest as system size grows, and detection remains effective over longer evolution times than naive approaches.
