October 12, 2026

Correlation-Based Measurement of Entanglement in Rank-2 Mixed StatesTier 3

We study correlation-based entanglement evaluation in rank-2 mixed states of two- and multi-qubit systems. The relevant two-dimensional subspace is treated as a logical qubit embedded in the physical Hilbert space, and factorizable realizations of its logical Pauli operators are classified. For two qubits, this yields nontrivial canonical encodings related by local Clifford...

Previously: 2026-10-11, 2026-09-17, 2026-09-15

Graphene double quantum dot as a solid-state two-level system in the THz rangeTier 3

Matter-based two-level quantum systems are fundamental building blocks of quantum technologies, underpinning applications in quantum computing, simulation, communication, and sensing. Today, most of these two-level quantum systems, including Rydberg atoms, trapped ions, superconducting circuits, molecules, and quantum dots, involve transition frequencies in microwave or opti...

GPU-Based Parallel BP Decoding for Quantum LDPC MemoryTier 3

Quantum low-density parity-check (qLDPC) decoding requires reliable corrections and low latency over long syndrome histories. We extend BP-SF, an oscillation-guided belief-propagation (BP) decoder with independent syndrome-flip trials, by introducing windowed and streaming operations. Our CUDA implementation combines disordered-memory retries, sliding windows, correlation-aw...

Enhanced analogue quantum computation with a logically-encoded XX gadgetTier 3

The introduction of two-body XX interactions has been shown to improve the performance of quantum annealing in solving certain combinatorial optimisation problems and would enable the simulation of a broader class of many-body Hamiltonians. Due to experimental constraints, such interactions are typically not natively available on analogue quantum devices. To overcome this li...

A Hardware-Native Trapped-Ion Hybrid Qudit-Oscillator Instruction SetTier 3

Scaling trapped-ion processors by adding ions remains challenging. A complementary route exploits the multilevel internal structure of each ion to increase the computational Hilbert space per ion. We introduce a hardware-native hybrid qudit-oscillator instruction set for a general d-level internal register coupled to bosonic modes and prove that three of its native operation...

Modelling Josephson Junctions with Boundary Conditions: Towards High-Fidelity Models for Superconducting QubitsTier 3

Josephson junctions are the central nonlinear element of superconducting qubits, yet their standard description is reached through a chain of approximations. We propose a purely quantum-mechanical model of the junction, formulated directly in Hilbert space: a charged particle moves on a one-dimensional loop, and the junction is a point at which the wave function obeys self-a...

Decoder- and Noise-Aware Optimization Framework for Clifford-Deformed Quantum Error-Correcting CodesTier 3

Practical fault-tolerant quantum computing requires qubit-efficient quantum error correction (QEC). Clifford deformations (CDs) modify the stabilizers of a QEC code to lower its logical error rate at no additional resource cost. However, the number of possible CDs grows exponentially with the number of qubits, making exhaustive search infeasible beyond small codes. In this w...

An Annealing-based Quantum Neural Network with Discrete Wavelet Transforms for Enhanced Air Pollution NowcastingTier 3

Air pollution poses a significant threat to public health, exacerbated by the rapid industrialization and urbanization of modern society. While traditional deep learning offers predictive capabilities, recent advancements in quantum machine learning (QML) present a compelling alternative. Here, we introduce a scalable hybrid framework that integrates variational quantum circ...

Diversity-Aware Ensemble of Quantum-Classical Models via Combinatorial FusionTier 3

Variational quantum circuits (VQCs) are highly sensitive to circuit architecture, yet most quantum machine learning pipelines select a single best design and discard the remaining candidates. This paper addresses whether the structural diversity across quantum circuit search spaces can be used to produce stronger predictions through model fusion. We apply Combinatorial Fusio...

Dynamical Lie Algebras for Fixed-Gate Quantum AnsätzeTier 3

Parameterized Quantum Circuits have emerged as a central framework for variational quantum algorithms in the NISQ regime, with major applications in quantum simulation, combinatorial optimization, and, more recently, quantum machine learning (QML). By developing a new approach for computing dynamical Lie algebras associated with quantum circuits combining parametrized gates...

Percolation of Data Constraints and Reorganization of Boolean Function States in Parity LearningTier 3

We study how a neural network reorganizes its learned function as training proceeds and as previously unseen parity data accumulate. The trained model is itself a Boolean function on binary strings of finite length. We then evaluate it on all data, inside and outside the training set, and read off its complete sign table. Its ±1 entries are the amplitudes of a normalized...

Verifiable Sampling for Delegated Generative Quantum Machine LearningTier 3

Generative machine learning has shown remarkable results across a wide range of interdisciplinary tasks, motivating significant efforts toward Quantum Generative Models as a path to beyond-classical performance, given their capability of generating classically intractable distributions. However, comparatively little attention has been paid to securely delegating such computa...

Error Mitigation by Zero-Noise Extrapolation (ZNE) in Indirect-Control SystemTier 3

The indirect-control paradigm offers a scalable approach to quantum computation by restricting external operations to a small subset of qubits, whereas the entire system evolves under its intrinsic many-body Hamiltonian. This framework reduces hardware complexity and limits the noise introduced through control channels. Recently, Anan et al. proposed an implementation of the...

QTN-RQNN: Quantum Tensor Network-Based Recurrent Quantum Neural NetworkTier 3

Resource constraints and imperfect quantum operations remain major challenges for quantum machine learning (QML) on noisy intermediate-scale quantum (NISQ) devices, particularly for fault-diagnosis tasks involving imbalanced and heterogeneous data. This work proposes QTN-RQNN, a Quantum Tensor Network-Based Recurrent Quantum Neural Network that integrates tensor-network-insp...

An entangling Hubbard quasiparticle collider on a digital quantum processorTier 3

Scattering of quasiparticles provides direct access to the interactions that govern strongly correlated systems. In this work, we realize the quasiparticle scattering experiment of the Fermi-Hubbard model on a digital quantum processor by colliding a doublon and a holon in the half-filled chain of 21 sites encoded on 42 qubits of the ibm_boston processor. For the first time,...

Quantum Meet Quantum: Hybrid Quantum Computer Lets Scientists Peak in on Foundational Quantum EffectTier 2

Insider Brief PRESS RELEASE — Physicists in the Department of Physics, University of Oxford, have used a hybrid quantum computer, formed by qubits and quantum oscillators, to observe the Aharonov-Bohm effect in a quantum simulation. The effect is a quantum phenomenon in which a particle can acquire a measurable phase by travelling around a magnetic […]

A Warped Born Rule Turns an Observer into a Maxwell's DemonTier 3

Quantum mechanics seems to be an incredibly delicate theory. Slight alterations to nearly any part of its structure can lead to huge qualitative differences and wildly unphysical predictions. Here, we explore the many-body consequences of replacing the Born rule p(m)∝‖P_m|ψ⟩|^2 by a warped rule p_b(m)∝‖P_m|ψ⟩‖^(2b). Specifically, in systems wit...

A scalable sample-based quantum diagonalization solver for general Pauli-sum HamiltoniansTier 3

A scalable ground-state solver to be used in sample-based quantum diagonalization (SQD) is presented. The solver is built on JAX API, and is intended to be run on GPU platforms and possibly many-GPU high-performance computing facilities. It is capable of subspace diagonalization in up to 2^(30)-dimensional subspace, with possible upgrades to enable even larger-scale operat...

Quantum Query Complexity of Maximum Degree and its GeneralizationsTier 3

We study the quantum query complexity of several basic graph problems. 1) We prove a tight Θ(n^(3/2)) bound for finding a maximum-out-degree vertex in an n-vertex tournament, resolving a conjecture of Mande, Paraashar, and Saurabh [FSTTCS'23]. 2) Using the same proof idea, we give a direct proof that finding a maximum-degree vertex in an n-vertex undirected graph requi...

Maximally antiflat fixed-particle-number fermionic statesTier 3

Fermionic Gaussian states are completely characterized by their two-point correlations, making the covariance matrix a natural reference for quantifying non-Gaussian structure. Motivated by fermionic antiflatness, we study its extremal form for pure number-conserving states and ask which states can be maximally antiflat and how they can be constructed. We show that, at fixed...

Bicycle Race: small two-block codes on the Pareto frontierTier 3

Two-block group-algebra codes are among the simplest quantum LDPC codes, and many of them are translation invariant on a twisted torus, which suits neutral-atom arrays and other platforms with movable qubits. We ask how far they go at small sizes when searched systematically across all groups. To tackle this question, we use a series of algebraic constraints and screens to d...

No advantage from classical assistance for energy-constrained bosonic dephasing channelsTier 3

We prove that four capacities of single-mode bosonic dephasing channels coincide under an average photon-number constraint: the unassisted quantum capacity, the unassisted private capacity, the two-way classically assisted quantum capacity, and the two-way public-classically assisted private capacity. The assistance may be interactive: the parties can exchange classical mess...

QTestBench: A Test Framework for Evaluating LLM-Generated Quantum CodeTier 3

Large language models (LLMs) have shown strong results in classical code generation and are increasingly used to write the unit tests that safeguard that code. Whether they can do the same for quantum software is less clear, because quantum programs are probabilistic, depend on numerical tolerances, and are judged by domain-specific checkers, so a well-formed test can still...

Replica Transition at Measurement-Altered Ising CriticalityTier 3

Performing measurements on gapless quantum ground states can give rise to new universal phenomena, whose origins remain poorly understood even for the paradigmatic Ising critical point. Replica methods offer a natural framework to study such post-measurement ensembles, with the replica limit Q→1 describing physical Born-averaged observables. Here we show that, for the m...

Locality-Preparation Time Tradeoffs in Dissipative Quantum SystemsTier 3

Dissipative state preparation engineers quantum many-body states as steady states of an open-system dynamics. The spatial range of the required dissipation sets both the feasibility of analog implementations and the connectivity and control complexity of digital ones. Yet how this locality quantitatively constrains preparation times remains largely unknown. Here, we establis...

Judd-Ofelt analysis and coherent spectroscopy of europium-based molecular complexes for quantum information applicationsTier 3

Rare-earth-ion based molecular crystals are emerging as a promising platform for quantum information applications, combining long optical coherence times with the chemical tunability of coordination chemistry. Here we present a comprehensive optical characterisation of twelve Eu^(3+)-based molecular complexes, with a focus on the coherent ^5D_0 longrightarrow...

Finite-Size Limits of Adaptive Pauli PredictionTier 3

Can quantum data reliably answer questions chosen from earlier results? We prove that M adaptive Pauli predictions on n qubits require Ω(√(min{n,M})) copies at fixed accuracy. Published upper bounds make this tight for M≤n. Thus n adaptive predictions cost Θ(√n) copies, whereas a fixed list costs only O(log n). The lower bound uses diagonal stat...

Operational signatures of exceptional quantum channelsTier 3

Exceptional points (EPs) are usually introduced as defective degeneracies of non-Hermitian Hamiltonians and, in fully open quantum dynamics, of Liouvillian generators. Here we formulate an operational theory of exceptional points that does not invoke a Hamiltonian or a master equation. The primitive dynamical object is a completely positive trace-preserving (CPTP) quantum ch...

Encoding Matters: A Qubit-Efficient Reformulation for Quantum Resilient RoutingTier 3

Qubits are powerful computational resources because each additional qubit doubles the size of the accessible state space. This expressive power comes at a cost: adding qubits also increases circuit size, constraint overhead, and exposure to hardware noise. These limitations are especially critical for near-term quantum computers, making the number of qubits required to formu...

Genuine multipartite nonlocality detection in graph statesTier 3

Experimental detection of multipartite Bell nonlocality faces many challenges. The increase in the size of the system demands a higher fidelity of state preparation, a higher detection efficiency, and a larger number of correlators that need to be estimated. These issues are even more pronounced if one wishes to detect a more restrictive variant of Bell nonlocality called ge...

Entanglement Catalysis Beyond the Asymptotic RateTier 3

Quantum entanglement is a fundamental resource in quantum information science, commonly consumed to perform tasks like quantum teleportation and quantum key distribution. Entanglement concentration converts partially entangled pure states into nearly perfect Bell pairs. While its efficiency is well understood in the asymptotic limit, practical protocols must operate with fin...

Holographic Krylov complexity in confining backgrounds: particle, string, and framesTier 3

We investigate holographic Krylov complexity in bottom-up holographic QCD models describing the confined phase, using the recently proposed correspondence between the growth rate of Krylov complexity and the proper radial momentum of probes, such as particles and strings, falling in the bulk spacetime. As representative confining backgrounds, we consider two horizonless geom...

Construction of isoscattering non-isospectral quantum graphs using the concept of a germ graphTier 3

The recently developed concept of germ graphs (P. Kurasov {\it et al.}, Phys. Rev. Research {\bf 7}, L022071 (2025)) is employed to construct families of isocattering, non-isospectral graphs that exhibit dissipation. More specifically, a new pair of isoscattering non-isospectral graphs is constructed by connecting the existing isoscattering non-isospectral graphs, so called...

Finite Quantum Engineering ThermodynamicsTier 3

A useful thermodynamic model predicts what a device will do without tracking its full microscopic state. For a finite quantum working medium, the difficult question is which quantities should actually be measured. We develop a task-based method that keeps exact energy accounting separate from calibrated macroscopic prediction. Operator geometry identifies what a measured rec...

Harmonic analysis and circuit approximation of Sobolev functions on quantum input spacesTier 3

We derive approximation rates for Sobolev functions defined on the complex unit sphere and complex projective space, representing quantum states, and on the special and projective unitary groups, representing quantum unitary operations. By using harmonic analysis on compact groups and compact homogeneous spaces, we characterize the corresponding Peter--Weyl decompositions an...

Quantum extreme learning for forecasting experimental chaotic electronic circuitsTier 3

Quantum reservoir computing and its special case, quantum extreme learning, are powerful tools for predicting classical discrete time-series with quantum devices. Forecasting continuous signals, however, requires careful discretization as oversampling artificially boosts short-term accuracy but fails over realistic intervals, while undersampling captures too few features and...

Wideband microwave resonator for NV center vector magnetometryTier 3

The nitrogen-vacancy (NV) color center in diamond has found applications in magnetometry across various geometrical scales. In particular, vector magnetometry using hand-held devices with low power consumption is of interest for mobile and geological applications. However, such a device requires efficient driving of the four different orientations of the NV center, thus plac...

System-Design Optimization of a Single-Transmitter, Single-Fiber QKD-based ITS Communication LinkTier 3

Deploying QKD-based secure communication at scale requires reducing duplicated optical hardware while preserving the rate of protected user data. Earlier studies established the physical feasibility of carrying CV-QKD and classical signals over shared infrastructure, motivating a quantitative comparison between optical hardware savings and the OTP-encrypted rate. We perform...

Second quantization and compactness of induced Gaussian quantum Markov semigroupsTier 3

We characterize compactness of the Hilbert-Schmidt semigroups induced by finite-mode Gaussian quantum Markov semigroups with a faithful normal invariant state. A unitary second-quantization representation for every $ s $-embedding shows that compactness at one positive time, compact resolvent, drift stability, and uniqueness of the normal invariant state are equivalent. Thes...

A General Method for Extending Isoscattering Non-Isospectral Quantum GraphsTier 3

The present paper sets out a general method for extending the isoscattering, non-isospectral quantum graphs. The methodology is illustrated by considering two graphs, denoted by Γ_1 and Γ_2, which have the same total metric length but different topologies. It is demonstrated that, despite the fact that their scattering matrices are identical, their eigenvalues, denoted b...

Circuit Design Problems in Binary Polynomial Quantum OptimizationTier 3

Solving combinatorial optimization problems on near-term quantum computers mainly relies on their quadratic unconstrained binary formulation. Lately, binary polynomial formulations start to take the center stage, having a better scaling with respect to the number of used qubits. However, while quadratic forms are straightforward to implement on quantum circuits, polynomial f...

Zak Phase Quantization without Global Symmetry through Destructive InterferenceTier 3

The Zak phase provides a fundamental geometric characterization of one-dimensional band structures and, when quantized by symmetry, serves as a bulk indicator of polarization and boundary phenomena. Conventionally, its exact quantization is tied to a global symmetry of the Bloch Hamiltonian, such as inversion or reflection symmetry. Here, we demonstrate a distinct mechanism...

Theory of exciton-exciton interactions in crystalline systemsTier 3

Excitons are bound electron-hole pairs in semiconductors whose interactions influence optical properties and determine their collective behavior and emergent correlated phases. Despite the theoretical and experimental significance of these phenomena, a microscopic theory of exciton-exciton interactions that takes into account the full composite nature of these quasiparticles...

Block encoding of semiseparable matrices via their generatorsTier 3

We present an explicit quantum circuit that constructs a block encoding of a generator-representable semiseparable (one-pair) matrix directly from its two generators. For an N×N semiseparable matrix with N=2^n, the circuit uses 2n+2 ancilla qubits and has O(rmpolylog N) depth, and it realizes a (2√N, 2n+2, 2 √2 ε)-block encoding...

Real Fiducial Vectors Only Exist in Dimensions d≡3 pmod4Tier 3

We investigate restrictions on the dimensions and coordinate fields of real Weyl-Heisenberg fiducial vectors. Our main result is that such vectors can exist only in dimensions d≡3pmod4. This result is motivated by evidence showing that real Weyl-Heisenberg fiducial vectors can exist only in dimensions d = 4m^2 + 3, m ∈Z_(≥0). We further restrict...

Continuous-wave AC magnetometry up to hundreds of megahertz using nitrogen-vacancy centers under a strong transverse magnetic fieldTier 3

Nitrogen-vacancy (NV) centers in diamond are promising quantum sensors for AC magnetic fields. However, conventional dynamical-decoupling-based magnetometry becomes technically demanding at high frequencies because of the requirement for increasingly short and high-power microwave pulses. This paper describes an AC magnetometry technique based on continuous-wave optically de...

Pulsed control of an entanglement-breaking index: thermal valleys, a certified valve, and its open-close asymmetryTier 3

The entanglement-breaking index of a channel is the number of self-compositions after which all entanglement with a reference system is destroyed. In a thermal qubit collision loop whose round is affine in the bath polarisation p, some circuits have thermal valleys: on an interior window of p the index falls below its infinite-temperature value. Rounds at different p compose...

Temporal-Access Resource Theory for Continuous Process TensorsTier 3

The uncontrolled endpoint channel can conceal how well a quantum process can protect a logical task under time-resolved control. We formulate a fixed-task resource theory of continuous process tensors with physical access interfaces, entrance-erasing free objects, and budgeted free conversions. Complete-record total-variation error measures performance; the calibrated capabi...

A robust digital receiver architecture for continuous-variable quantum key distributionTier 3

Continuous-variable quantum key distribution utilizes advanced digital signal processing techniques to mitigate channel impairments, driving the progress of high-performance quantum secure communications. Specifically, digital heterodyne receivers are commonly implemented using down-conversion algorithms to detect both components simultaneously where the signal is modulated...

Evolution and breakdown of chiral anomaly in Weyl semiconductor telluriumTier 3

Chiral anomaly in topological materials manifests as negative longitudinal magnetoresistance, yet the tunability and evolution of this effect remain elusive. Here we show that doped tellurium serves as a versatile platform to realize a giant negative longitudinal magnetoresistance that is highly tunable via the Fermi level and magnetic field. By moving the Fermi level toward...

All-optical deconvolution via quantum cross-correlation spectroscopy with bright twin beamsTier 3

The resolution of spectroscopic measurements is fundamentally limited by the convolution between a system's intrinsic response and the instrument response function, creating an ill-posed inverse problem. While entangled photons can theoretically bypass these limits, low photon flux has hindered their experimental realization. Here, we propose quantum cross-correlation spectr...