October 2, 2026

Spiking neural networks for streaming qubit readoutTier 3

Fast and accurate qubit-state assignment is essential for feedback, calibration, and error correction in quantum processors. In superconducting platforms, frequency-multiplexed readout makes this task intrinsically multivariate as measured traces can encode crosstalk, qubit-state relaxation events, and other transient nonidealities that are not fully captured by conventional...

Loss-tolerant distributed lattice surgery using fusion networksTier 3

Networking matter-based quantum processing units (QPUs) offers a promising route to scaling fault-tolerant quantum computers. This requires distributed logical operations to be performed across photonic links, where noise is characteristically different from and stronger than in local QPUs owing to photon loss and probabilistic linear-optical operations. Measurement- and fus...

One-Shot any CodeTier 3

We first provide a simple proof showing that any single-shot code is self-correcting. We then show that any [[n,k]] CSS quantum low-density parity-check (QLDPC) code can be transformed into an [[nm,k]] CSS QLDPC code with single-shot (SS) quantum error correction and an efficient local decoder which runs in O(log m) parallel time. Below a constant threshold p_(rmRG...)

Exponential quantum advantages for decoded quantum interferometry in the streaming settingTier 3

Decoded quantum interferometry (DQI) is a polynomial-time quantum algorithm introduced by Jordan et al. (Nature 2025). For a natural optimization problem, known as optimal polynomial intersection (OPI), it achieves approximation guarantees in regimes where all known classical algorithms require exponential time. Besides time, space is another central resource: storing and ma...

Thin-capping layer epitaxial quantum dots for near-field quantum photonicsTier 3

Epitaxial quantum dots (QDs) are widely recognised as one of the best quantum light sources, given their good stability, brightness, quantum efficiency and coherence. To reach such properties, QDs are protected from potentially detrimental surface states by a relatively thick capping layer, typically exceeding 50nm. This prevents the implementation of near-field effects, lik...

Adaptivity is all you need: Optimal stabilizer learning using just single-copy measurementsTier 3

Stabilizer states are central to quantum computing, underlying quantum error correction, benchmarking, and efficient classical simulation. Yet their learnability exhibits a striking gap: an n-qubit stabilizer state can be learned from Θ(n) copies using two-copy Bell measurements, whereas non-adaptive single-copy measurements require Ω(n^2) copies. Here we show that ada...

Hardware-Efficient Ground-State Preparation using Variational Imaginary-Time Majorana EvolutionTier 3

Compact ground-state preparation circuits are essential for early fault-tolerant quantum chemistry. We introduce Variational Imaginary-time Majorana Evolution (VIME), a classical pre-training algorithm that extends operator-projected variational quantum imaginary-time evolution (OVQITE) to molecular electronic structure using a single compiled Majorana-propagation (MP) surro...

Robust exponential lower bounds for fermionic and bosonic Gaussian ranksTier 3

The power and limitations of classical simulation are central to understanding quantum computational advantages. A leading simulation paradigm is based on coherent decomposition into classically tractable free states where the decomposition rank determines the simulation complexity. Proving strong lower bounds on this number is a notoriously difficult and mathematically rich...

Learning Many-Body Hamiltonians Using a Local ProbeTier 3

Hamiltonian learning provides a systematic framework for reconstructing unknown quantum dynamics. However, existing protocols typically assume direct measurement access to the entire system. With fast single-qubit control and a connected reference backbone, we show that a single measurable qubit suffices to learn all O(N) independent parameters of a bounded-degree two-body...

From Permutation Symmetry to Communication Bounds and AdditivityTier 3

Correlations across channel uses can improve quantum communication rates, making optimization over arbitrarily large blocks a central difficulty in determining quantum capacity. We show how full permutation invariance limits this advantage for every finite-dimensional memoryless channel. The optimized coherent information per use converges to the single-use maximum and conse...

Learning SYK HamiltoniansTier 3

We study the problem of learning the dense Sachdev--Ye--Kitaev (SYK) Hamiltonian from copies of its Gibbs state. Existing algorithms for Hamiltonian learning typically rely on geometric locality or bounded interaction degree and therefore do not apply to SYK, where each quartic interaction overlaps with Θ(n^3) others. We show that this obstruction can be overcome by exploi...

Polynomial-time classical and quantum simulation of quantum impurity modelsTier 3

Quantum impurity models are paradigmatic models of interacting quantum matter, as well as key computational primitives for modern electronic-structure methods. They describe a small subsystem of interacting fermions coupled to a large, noninteracting bath. We perform a comprehensive study of the computational complexity of simulating impurity models, delineating the boundary...

D-Wave Launches Gate-Model Quantum Simulator BetaTier 2

Insider Brief PRESS RELEASE — D-Wave Quantum Inc. (NASDAQ: QBTS) (“D-Wave” or the “Company”), the only dual-platform quantum computing company providing both annealing and gate-model systems, software and services, today launched its gate-model quantum computing simulator beta program, marking an important milestone in D-Wave’s gate-model development roadmap. The beta...

Quantum Renaissance to Convene Global Quantum Leaders in Florence in April 2027Tier 2

Insider Brief PRESS RELEASE — Quantum technology leaders from research, industry, government and finance will gather at Palazzo Vecchio in Florence on April 1-2, 2027, for Quantum Renaissance, a two-day event examining the development and wider implications of quantum technology. The event is organized by Resonance and The Quantum Insider in partnership with the Comune...

The Robustness of QAC0Tier 3

In this work we study the robustness of QAC^0 with respect to error tolerance and modifications to its gate-set. First, we investigate whether the non-zero error typically allowed for QAC^0 circuits computing Boolean functions is truly necessary. We show that the error inherent in the parallel W-test of \cite{grier_morris_wu} can be eliminated entirel...

Polynomial-time additive-error estimation of output probabilities for shallow quantum circuitsTier 3

We give a deterministic classical algorithm that estimates |⟨x|U|0^n⟩|^2 to additive error ε in poly(n, 1/ε) time, where U is a constant-depth quantum circuit comprised of gates with bounded fan-in and arbitrary connectivity, and x is an arbitrary n-bit output string. This improves over prior state-of-the-art algorithms t...

A provable quantum advantage for approximate optimization via decoded quantum interferometryTier 3

Decoded quantum interferometry (DQI) is a novel paradigm for tackling approximate optimization problems on quantum computers. This framework comes with strong performance guarantees and exploits a well-established duality between optimization and coding theory. A central question, however, is whether DQI can actually provably outperform all polynomial-time classical algorith...

Random Quantum Circuits Beyond Moment MatchingTier 3

Random quantum circuits aim to efficiently reproduce the statistical properties of ideal random quantum evolution. One approach is to construct approximate unitary designs, which match the moments of Haar-random unitaries up to a prescribed order with controlled error. In this work, we establish quantitative guarantees for how accurately these designs reproduce the full dist...

Optimal transducers using symmetriesTier 3

Transducers (Belovs, Jeffery and Yolcu, 2024) are a quantum computing framework describing a quantum algorithm as a unitary converting an input state into a target state using a catalyst, an auxiliary vector that is left unchanged. They are a powerful tool in quantum algorithm design, especially in the context of quantum query complexity: feasible points of the (dual) advers...

Quantum impurity models: easy at equilibrium, universal in motionTier 3

A quantum impurity model describes a small interacting subsystem embedded into a large bath of free fermions. Here we study the computational complexity of calculating the ground energy, thermal equilibrium, and dynamical properties of these models. Our work reveals a sharp contrast: equilibrium properties can be efficiently approximated by classical means, whereas time evol...

Local random quantum circuits converge to the Porter-Thomas distribution in polynomial depthTier 3

Porter-Thomas statistics are a characteristic feature of the output distribution of random quantum states and, more broadly, chaotic quantum many-body systems. Convergence to Porter-Thomas plays a central role in random circuit sampling and experimental demonstrations of quantum advantage, where the output statistics of low-depth random quantum circuits are expected to be ap...

Quantum Advantage for Two-Party Differential PrivacyTier 3

We introduce information-theoretically private quantum protocols for two-party Hamming distance when both parties must output the same estimate. Classically, for input length n, information-theoretic protocols require Ω(√n) error under pure differential privacy and Ω(√n/log n) error under strong approximate differential privacy, whereas computational secur...

Unitary Schur Sampling of Qudits via Random SWAP Tests: Hunt for AntisymmetryTier 3

Schur sampling is a fundamental primitive for extracting permutation-invariant information from many-body quantum systems and has broad applications in quantum information science. Circuit-based implementations typically rely on coherent representation-theoretic operations such as Clebsch-Gordan transforms, generalized phase estimation, or quantum Fourier transforms over the...

On the pseudorandomness of simple quantum processesTier 3

Can simple processes appear highly complex? Gowers (Comb. Prob. Comp. '96) conjectured that repeatedly composing local random reversible operations can yield global permutations that are indistinguishable from random. In this work, we study the unitary quantum analog of this question, in an attempt to make new progress on this longstanding conjecture. Our first result shows...

An exponential separation between entanglement-assisted and unassisted one-way quantum communicationTier 3

A longstanding question in quantum communication complexity is whether some task can be accomplished with a small amount of communication in the presence of entanglement, yet require much more quantum communication in the absence of entanglement. Separations of this nature were previously known for relational problems and, in the simultaneous message passing model, for parti...

One-Way Quantum Symmetric Private Information Retrieval Protocol From A Single Database Server Using NISQ DevicesTier 3

Symmetric private information retrieval (SPIR) lets an inquirer obtain one specific bit only, without leaking any information about its index to the database owner. With a single server, this is impossible for parties with unrestricted quantum power. We show that it becomes possible, with information-theoretic security, when the server and the user hold only noisy intermedia...

Stationarity as a One-Mode Constraint on Quantum CorrelationTier 3

A stationary quantum state has one dynamical phase factor and one scalar energy even when its internal response spans a large Hilbert space. Our argument concerns not the value or observability of an absolute phase, but the one-ness of stationary time evolution. In regularized Hartree--Fock (reg-HF), the connection to the stationary mean field is established before any one-m...

Strong Simulation of 1D Quantum Circuits via Reduced Transition MatricesTier 3

Tensor networks are powerful tools for simulating quantum many-body systems, but the growth of spatial entanglement severely limits the direct evolution of pure states under chaotic unitary circuits. Here we consider a more targeted task: the approximate strong simulation of a specified output probability of a 1D chaotic brick-wall circuit at finite relative precision. Given...

Universal Bound and Phase Transition in Many-Body Fermionic Non-GaussianityTier 3

Fermionic non-Gaussianity is a resource for universal quantum computation that can be generated by interactions in quantum many-body systems. Using the magic Rényi entropy (MRE) as a measure of non-Gaussianity, we derive its universal upper bound and Haar mean, proving that typical Haar-random states attain the maximal MRE density of ln(4/3) per Majorana in the large-syst...

Sequential Capacity of Quantum Processes with Finite MemoryTier 3

How complex can the responses of a quantum device become as it runs longer with a fixed internal memory? We quantify this complexity through sequential response capacity: how many adaptive testing stages, each using a fresh run, can continue to separate possible processes by a prescribed gap in response probabilities. For fixed system and memory sizes, we establish a tight l...

Stark effect of hydrogenic ions as a test of the indefinite-metric formalism of the eight-component relativistic wave equation for spin-1/2 particlesTier 3

The eight-component relativistic wave equation for spin-1/2 particles of Robson and Staudte (FV1/2), a Feshbach--Villars linearization of the Feynman--Gell-Mann equation, reproduces the Dirac hydrogenic spectrum with a doubled solution space and an indefinite inner product. Its exact Stark shifts must equal the Dirac ones; whether its indefinite-metric pe...

Nonlocality without entanglement for multipartite quantum measurementsTier 3

We show that a pair of two-qubit product measurements can be perfectly distinguished when accessed jointly, yet cannot be perfectly distinguished when their local components are distributed between distant parties restricted to local quantum operations and classical communication (LOCC). This establishes a measurement analogue of nonlocality without entanglement that, unlike...

Sparse Hamiltonian simulation with optimal dependence on the maximum column Euclidean normTier 3

We give a quantum algorithm for simulating a d-sparse Hermitian Hamiltonian H, assuming a known upper bound Λ on its maximum column Euclidean norm ‖H‖_(1→2). For tΛ≥1/2, simulation with operator-norm error ε uses O(tΛ√d+√dlog(2/ε)) sparse-oracle queries. This removes the subpolynomial overhead in Low's algorithm [STOC 2019], re...

(A Variant of) Clifford Circuit Synthesis is NP-CompleteTier 3

Optimal circuit synthesis is the problem of finding the shortest-depth circuit representation of a given functionality with respect to a pre-specified elementary gate set. This is a central problem in both quantum and classical hardware design. While the classical version is very well understood -- both in terms of heuristics and rigorous hardness assertions -- much less is...

On the Metastability of the Mean-Field Interchange Model for Local Dimension ≥3Tier 3

Many quantum systems are believed to thermalize slowly at low temperatures due to the existence of metastable phases. However, there are cases where further cooling can restore polynomial-time thermalization: we demonstrate that the Davies dynamics of the mean-field interchange model with local dimension d≥3 and single-site generalized Pauli couplings exhibits this beh...

Fully tolerant product state testing and closest product state learningTier 3

We address the problem of testing whether an unknown n-qudit state ρ is a-close to a product state or b-far away from any product state, as measured in terms of state overlap. We provide a time-efficient algorithm to solve this problem that requires an n-independent number of copies of the unknown state. Our random coloring argument shows that for any unknown state...

Avoiding Exponentially Large Groups with Open Quantum System TechnologyTier 3

We propose a novel approach to state preparation by embracing the full power of open quantum systems. Instead of working with the whole unitary group in n qubits, we identify a small Lie group G in (n+3) qubits. The dimension of its Lie algebra is poly(n). Every state can be approximated starting from any fixed input state by repeatedly using partial trace and...

Superintegrability of a resonant ghostly tri-Hamiltonian model: polynomial first integrals and transcendental completionTier 3

We study classical and quantum superintegrability of a resonant three-dimensional Hamiltonian with indefinite kinetic energy and three Poisson descriptions of the same flow. Besides three commuting quadratic Hamiltonians, the polynomial first-integral ring contains two primitive degree-four generators, I_4^(rmo) and I_4^(rme), of odd and even momentum parity. A singl...

Symmetry considerations in chirality-induced spin selectivityTier 3

The chirality-induced spin selectivity (CISS) effect, the coupling between structural chirality and electron spin polarization, has been experimentally observed across many diverse systems. However, despite extensive theoretical effort, a unified mechanistic understanding remains elusive. In this perspective, we demonstrate how some of the basic properties of the fascinating...

Quanome CEO to Back Quantum Strategy with Up to $15 Million in Non-Dilutive Growth CapitalTier 2

Insider Brief PRESS RELEASE — Quanome Technologies, Inc. (Nasdaq: QNME) (“Quanome” or the “Company”), has entered into a revolving loan agreement with the Company’s CEO and Chairman, Yang Li, for up to $15 million in non-dilutive growth capital. The arrangement gives Quanome an additional potential source of capital as it executes its stra...

Researchers Demonstrate Building Blocks for Zinc Oxide Spin QubitsTier 2

Insider Brief PRESS RELEASE — Researchers at Tohoku University, in collaboration with the National Institute for Materials Science (NIMS) and the University of Tokyo, have taken an important step toward semiconductor quantum computing using zinc oxide (ZnO). The team successfully demonstrated charge sensing, high-frequency reflectometry, and the formation of a few-elec...

Choi Co-Leads Research on Quantum Intelligent Sensor NetworksTier 2

Insider Brief PRESS RELEASE — The National Science Foundation (NSF) has awarded a $600,000 grant to Hyeongrak “Chuck” Choi, an assistant professor in the Department of Electrical and Computer Engineering at Stony Brook University, and Bo-Han Wu, an assistant professor at the University of Hawaiʻi at Mānoa, to develop quantum intelligent sensor networks. The three-year...

Operational transformation rates of quantum statesTier 3

Typically, multiple copies of a quantum state are described by a tensor power of that state. However, from an operational point of view, an experimentalist cannot, in general, rule out imperfections at unknown positions or correlations between copies, so assuming independent and identically distributed (iid) copies is not justified a priori. In the following, we relax the ii...

A computational phase diagram for the transverse field Ising modelTier 3

We study the transverse field Ising model, defined by the Hamiltonian H =1/2Σ_(i, j∈[n]) J_(ij) Z_i Z_j +Σ_(i=1)^n h_i^z Z_i + ηΣ_i X_i where $J $ is the symmetric interaction matrix, and η is the transverse field strength. Let Δ(J)=λ_(max)(J)-λ_(min)(J) be the spectral width of J. When the inverse temperature β≥0 satisfies Δ(J)·fra...

Quantum state preparation for weighted d-DNNFTier 3

The quantum state preparation problem is to, given a description of a quantum state, efficiently generate a quantum circuit computing the state. We show that for quantum states described by weighted d-DNNF (deterministic, decomposable pseudo-Boolean circuits) a quantum circuit computing the state can be obtained in linear time up to complex arithmetic.

Optimal query complexity for fractional quantum evolutionTier 3

Given oracle access to an unknown unitary U=e^(iH) , the fractional query problem asks how many queries are required to implement a noninteger power U^t=e^(itH), $0

Previously: 2026-09-29

Time-space lower bounds for breaking quantum cryptographyTier 3

We prove near-optimal time-space lower bounds for breaking quantum cryptography in the random oracle model. Specifically, we show that a T-query adversary with S qubits of non-uniform advice can recover a random key k from the n-qubit binary phase state |ψ_k⟩∝Σ_x R(k,x) |x⟩ with probability at most O((T^2 + √ST)/N) for N=2^n...

Previously: 2026-10-01

Fermionic Gaussianity can be tested with mode-independent sample-complexityTier 3

Deciding whether an unknown quantum state either belongs to, or is far from, a given family of states is a natural question of quantum information theory. In many such cases, there is a natural 2-copy test which always accepts whenever the state indeed belongs to the target family; it is often much more difficult, however, to bound the probability of acceptance for states th...

A Generalized quantum Stein lemma on von Neumann algebrasTier 3

We prove a generalized quantum Stein lemma for i.i.d. normal states against convex, tensor-stable families on arbitrary von Neumann algebras. Assuming the existence of an alternative state with finite relative entropy from the null state, we show that, at every type-I error tolerance ε∈(0,1), the worst case type-II error exponent is achieved with the regulariz...

Pasqal Appoints Florence Lao as Chief Legal OfficerTier 2

Insider Brief PRESS RELEASE — Pasqal (NASDAQ: PSQL), a global leader in neutral-atom quantum computing, today announced the appointment of Florence Lao as Chief Legal Officer. In this role, she will serve as a strategic advisor to Pasqal’s executive leadership team and Board of Directors as the company continues to scale globally as a publicly […]

Single-Particle Spectral EstimationTier 3

We study Hamiltonian learning in a novel setting, where we are promised a physical structure that is obfuscated by a global unitary. In particular, we consider the task of learning the weights E_i of a Hamiltonian H=U^†(Σ_(i ∈I) E_i n_i + H_O)U comprised of a set of non-interacting modes I and an arbitrary ``spectator'' H_O acting on a disjoint set of m...