September 17, 2026

Entanglement swapping across a five-node relay in a multiplexed quantum-classical networkTier 3

Quantum networks are resources for scaling quantum computers and distributed sensing technologies while offering post-quantum security benefits. Teleporting non-classical resources like entanglement, via so called entanglement swapping, is essential for networks in particular overcoming rate-loss limits via quantum repeaters. Deploying these systems on real infrastructure wi...

Gold’s Quantum MomentTier 2

How two research teams and a London based quantum hardware company are betting nanoscale gold can crack the stability-scalability problem that has stalled every other qubit platform. Insider Brief Quantum computing’s race for a stable, scalable qubit has never lacked contenders. Trapped ions, superconducting circuits, photonic systems, neutral atoms, silicon spin — eac...

Continuous variable distributed quantum sensing in integrated photonicsTier 3

Distributed quantum sensing is an emerging application of quantum networking, where entangled probe states are employed to sense combinations of delocalized parameters with enhanced precision relative to using separable states. Squeezed states of light are a prime resource for experimental demonstrations of entanglement-enhanced sensing, because they can be generated and ent...

Securing quantum error correction against misleading advice from AI agentsTier 3

Can an attacker turn influence over an artificial intelligence (AI) adviser into a harmful quantum error-correction update? We identify an ambiguity in passive syndrome records that obstructs recovery selection, then show how additional calibration measurements support certified recovery updates under uncertainty and drift. In an odd-distance square toric code with error-fre...

Better Together: IBM Researchers Cut Sampling Demands 63-Fold by Combining Quantum Error Detection And MitigationTier 2

Insider Brief Quantum error correction may not simply replace error mitigation as quantum computers improve. In fact, the two methods could instead work together to make reliable computations possible with fewer resources, according to an IBM study. IBM researchers combined an error-detection protocol with a statistical error-mitigation technique and tested the approach on a...

Previously: 2026-09-15, 2026-09-15, 2026-09-15

Comparing magic state cultivation methods using matrix product statesTier 3

Magic state cultivation prepares high-fidelity magic states at low expected space-time costs; however, the exact performance of some schemes is unsettled due to the difficulty in simulating non-Clifford circuits. Here, we use matrix-product states (MPS) based methods to compute the exact performance of two types of fold-transversal cultivation schemes: (i) the Sahay et al me...

Theory-agnostic nonclassicality certification in an integrated photonic circuitTier 3

Certifying nonclassicality without assuming any particular underlying physical theory constitutes both a foundational challenge and a requirement for device-independent protocols. Realizing such theory-independent certification in scalable architectures is essential for connecting fundamental tests with emerging quantum technologies. Integrated photonic circuits are a leadin...

Impact of a CSS quantum error correction code in underwater quantum key distributionTier 3

Quantum key distribution (QKD) enables secure underwater communications essential for maritime infrastructure. Underwater optical channels introduce substantial photon loss (erasures) and ambient noise that degrade QKD performance. This paper investigates whether two four-qubit Calderbank-Shor-Steane (CSS) quantum error correction codes (QECC) mitigate these impairments in v...

Fast Evaluation of the Sixth-Order Time-Convolutionless Master-Equation Generator and BeyondTier 3

Direct quadrature of the Hadamard-reduced sixth-order time-convolutionless (TCL6) generator at all N_t sampled times requires O(N_t^3) operations at fixed system dimension. We derive an exact reduction for a finite-dimensional system coupled through one Hermitian operator to a stationary centered Gaussian bath. By separating fixed operator coefficients from scalar bath k...

Learning to Program Adaptive Non-Local Observables for Machine LearningTier 3

Quantum neural networks (QNNs) are typically built from variational quantum circuits (VQCs), which are limited by local measurements. Adaptive non-local observables (ANO) address this by jointly optimizing circuit parameters and multi-qubit measurements. However, existing ANO-based VQCs learn only a single static observable that remains invariant across all inputs. We propos...

Bath dimension and initial entropy for closed repeated use of a quantum channelTier 3

We characterize the bath resources needed to supply repeated uses of a fixed finite-dimensional quantum channel in a closed device. For each horizon T, one bath, one initial state and one repeated unitary are fixed before the user. Each output is returned before the next input arrives; no reset, discard, fresh ancilla or uncounted controller is available. Approximation err...

New directions in dynamical expectation estimationTier 3

Computing dynamical expectation values typically relies on approximations optimized for the state or observable separately, without accounting for how their errors combine in the final expression.This work explores an alternative approach in which each approximation is guided by both the state and the observable, accounting for how they jointly determine the target expectati...

The Expressive Power of Constrained QAOA: What You Might Have MISsedTier 3

Feasibility-preserving mixer Hamiltonians offer an attractive alternative to penalty encodings for constrained quantum optimization, yet how enforcing constraints alters the state space reachable by the Quantum Approximate Optimization Algorithm (QAOA) remains largely unexplored. We address this question within the context of the Maximum Independent Set (MIS) problem. Alongs...

Optical Quantum ComputingTier 3

Under the label of optical quantum computing, there are a variety of protocols and experiments that use the quantum properties of light to achieve a computational advantage over classical computing machines. In this review, we describe some of the main implementations, which differ in the type of encoding and in how the computation is performed, whether using gates or cluste...

A Programmable Rydberg Quantum Bus for Nonlocal ConnectivityTier 3

Scalable quantum networks require processing nodes with flexible internal connectivity, yet neutral-atom architectures remain constrained by the strong spatial dependence of native Rydberg interactions. Here we show that a Rydberg atom chain can act as a coherent quantum bus, converting a locally connected one-dimensional architecture into an effectively nonlocal interaction...

Exact and fast series expansions for quantum models with long-range interactionsTier 3

Over the past decade, high-order series expansions based on linked-cluster methods have become an important tool for studying low-energy properties of gapped quantum systems with long-range interactions. We introduce a deterministic framework that removes a central computational bottleneck of this method. Our graph zeta method replaces the costly and statistically noisy Mont...

IonQ and ORNL Demonstrate Generative AI for Quantum OptimizationTier 2

Insider Brief PRESS RELEASE — IonQ (NYSE: IONQ), the world’s leading full-stack quantum platform and foundry, today detailed joint research with Oak Ridge National Laboratory (ORNL), NVIDIA, and the University of Tennessee, Knoxville (UT) showing that a trained generative model can write quantum optimization circuits directly, eliminating the trial-and-error para...

Previously: 2026-09-15

Quobly Demonstrates Key Quantum Operations on 300 mm Silicon ChipTier 2

Insider Brief PRESS RELEASE — Quobly, a French quantum computing company developing industrially scalable quantum computers based on silicon spin qubits, today announces new results showing qubit readout, single-qubit gates and two-qubit gates on a single quantum chip fabricated on its proprietary QSOI® technology. The results were obtained on QSOI® devices fabri...

Anderon Finalizes $1 Billion CHIPS Award for Quantum Wafer ManufacturingTier 2

Insider Brief PRESS RELEASE — Today, Anderon LLC (“Anderon”), an IBM (NYSE: IBM) company, announced the finalization of a $1 billion award under the CHIPS and Science Act with the U.S. Department of Commerce (the “Department”). The award will accelerate Anderon’s R&D efforts to advance the nation’s quantum wafer manufacturing cap...

Filter-Free Indistinguishable Photon Generation from Continuous-Wave-Driven Integrated MicroresonatorsTier 3

Quantum networks require scalable photon sources combining narrow linewidth, high efficiency, and high indistinguishability. Microresonator photon-pair sources are promising candidates, yet a source-only description based on the joint spectral amplitude (JSA) predicts near-zero Hong-Ou-Mandel (HOM) interference visibility between photons generated by independent, CW-driven m...

Quantum Probability Current Guided Reduction of Coupling Control Degrees of Freedom for Excitation TransportTier 3

Time-dependent coherent control can enhance excitation transport in open quantum networks, but independently controlling every inter-site coupling creates a control space of high dimension and leads to difficult optimization problems. We introduce an edge-ranking strategy based on the control-induced change in the gradient component of the time-integrated quantum probability...

Graph lattice sums and graph zeta functions for long-range interacting quantum lattice modelsTier 3

Taming the exponential increase of the Hilbert space dimension with system size in the simulation of gapped quantum lattice models is of the highest relevance for understanding and designing exotic quantum materials, where nonlocal interactions are of particular interest. High-order linked-cluster expansions provide access the solution of the eigenvalue problem for the infin...

Hamiltonian engineering via pulses: beyond group averagingTier 3

We develop a geometric framework for Hamiltonian engineering in finite-dimensional quantum systems using ideal control pulses. Starting from a bilinear Schrödinger equation with unbounded control amplitudes, we construct the closed pulse group and use extensions of control systems and Filippov's relaxation theorem to obtain a family of effective Hamiltonians given by the con...

Logarithmic-depth quantum simulation of boson samplingTier 3

We show that boson sampling with an arbitrary m-mode interferometer and n≤m single-photon inputs can be simulated to inverse-polynomial total-variation error by a logarithmic-depth qubit circuit with polynomially many qubits. The circuit uses Clifford+T gates, arbitrary qubit connectivity, and a single final measurement, and its family is logspace uniform. The key i...

Liouvillian exceptional points in the emergence of quantum synchronizationTier 3

The coupling between self-sustained oscillators, such as lasers or polariton condensates, leads to different steady-states in different regimes. Weak coupling allows the oscillators to behave independently, with different frequencies and uncorrelated phases, while stronger coupling can produce synchronization. In classical or semiclassical theories transitions between these...

Quantum Behaviors Are Not SemialgebraicTier 3

The conditional probabilities achievable by local measurements on a shared quantum state in a Bell scenario form the set of quantum behaviors, whose structure was studied by Tsirelson. In 1993, Tsirelson asked whether this set is semialgebraic, that is, describable by finite Boolean combinations of polynomial equations and inequalities. This question has remained open. We an...

Feasibility Ordering of Entanglement-Source Placement for Qubit ChannelsTier 3

This work studies the placement of an entanglement source along a communication line formed by two noisy qubit channels. Recent work argued, on analytical and numerical grounds, that midpoint placement should be at least as favorable as endpoint placement. Here it is shown that, for arbitrary qubit channels, if a sequential composition can preserve entanglement, then the cor...

Cavity-induced intertwining of density and pairing order in a degenerate Fermi gasTier 3

Recent quantum gas cavity-QED experiments demonstrated simultaneous coupling of photons to single atom transitions as well as correlated pairs of ultracold fermions trapped inside optical cavities. This enables simultaneous control over density ordering and pairing. Using extensive numerical simulations, we show that in a transversely driven, two-component degenerate Fermi g...

Query-Optimal and Gate-Efficient Lindbladian SimulationTier 3

We give a quantum algorithm for Lindbladian simulation given a block encoding of the Hamiltonian H and a projected unitary encoding of the stacked jump operator B=Σ_(k=1)^m lvertk⟩⊗L_k, with normalization factors α_H and α_B, respectively. For evolution time t, set τ=(α_H+α_B^2)t. The algorithm approximates the evolution channel to diamond-norm...

Almost One Bit Violation of Minimum-Output Rényi Entropy Additivity Simultaneously at All OrdersTier 3

We prove that minimum-output Rényi-entropy additivity can fail by almost one bit simultaneously at every nonnegative order. For every ε∈(0,log 2), there exists a finite-dimensional quantum channel with a real Stinespring isometry such that the same maximally entangled input witnesses a tensor-square entropy gap of at least log 2-ε for all p∈[0,i...

All coherent measurements provide observational ergotropic advantageTier 3

The use of quantum resources in the work extraction from a quantum system is an emerging research topic. Recently, [arXiv:2602.22893] established the necessity of measurement coherence for obtaining advantage in work extraction from an unknown isolated quantum system. However, a quantitative relation between the magnitude of this advantage and established measures of measure...

Resonance-Protected Pointer States: Stationary-Phase Analysis of Entanglement in an Environment-Coupled Two-Spin SystemTier 3

In this manuscript, we analyze the dynamics of a model in which two spin-1/2 systems are each coupled noncommutingly to a static environmental field and to a self-Hamiltonian, while also being mutually coupled through a σ_y^((1))σ_y^((2)) interaction. By constructing an exact solution that exploits parity symmetry, and by applying the stationary-phase approximation (the sa...

From Reversible Quantum Dynamics to Statistical Probability: A dynamical solution to the origin of probability and Hilbert's sixth problemTier 3

Hilbert's sixth problem placed probability and mechanics at the center of the axiomatization of physics. It asks how irreversible statistical probability and thermodynamics can produce from the reversible, deterministic dynamics of a system. Building on an exact open quantum system theory developed in the past two decades, we construct a dynamical route from the reversible q...

Spectral Optimization for Absolutely PPT States: Purity, Entropy, and Volume DecayTier 3

We study maximum purity and minimum von Neumann entropy of absolutely positive partial transpose (APPT) states, together with the relative volume of their spectral sets. A consequence of Hildebrand's criterion gives an explicit outer spectral polytope, whose vertices we classify. Optimizing purity over this polytope, together with the Song--Chen result for the 2⊗3 sy...

Extensibly Causally Separable Processes Admit Realizations as Quantum Circuits with Classical Control of Causal OrderTier 3

Indefinite causal order extends the conventional circuit paradigm by allowing local quantum operations to be connected without a predetermined global order. Within the process-matrix framework, it is characterized by causal nonseparability, whereas extensible causal separability (ECS) requires that, under arbitrary input-ancilla extensions, a process admit a recursive decomp...

Information Geometry of Four-Parameter Single-Qutrit States: From Quantum to Semiclassical Geometric TensorsTier 3

The gap between the classical and quantum Fisher information matrices (CFIM and QFIM) separates what is operationally accessible through measurements from what is intrinsic to a quantum state. In the multiparameter setting, this quantum obstruction is generically not saturable. Motivated by the recently introduced semiclassical geometric tensor (SCGT), we perform an explicit...

Giant-atom-mediated photon blockadeTier 3

Photon blockade is a phenomenon where the presence of system nonlinearity causes the output to consist of single photons, which has been extensively studied in point atom systems, but it is barely explored in giant atom ones. In this paper, we propose giant atom-mediated photon blockade scheme based on two cavities and three cavities systems with driving field applied to the...

Programmable Hong--Ou--Mandel interference in a giant-atom beam splitterTier 3

The Hong--Ou--Mandel (HOM) effect is a hallmark of two-photon quantum interference, in which two indistinguishable photons impinging on a balanced beam splitter bunch into the same output port. Here, we show that a giant atom (GA), coupled to two waveguides through two coupling points each, can function as a programmable HOM interferometer, enabling continuous control over s...

Lindbladian quantum chaos beyond classical strange attractorsTier 3

We investigate the connection between classical and quantum chaos in a dissipative system of two coupled collective spins. Although the classical dynamics possesses a stable fixed-point attractor, we find pronounced signatures of chaos in the transient dynamics preceding relaxation. In the quantum model, such transient chaos is accompanied by a transition to random-matrix st...

Simplification Rules for Continuous-Time Quantum Walks on Dynamic GraphsTier 3

Continuous-time quantum walks (CTQWs) on dynamic graphs realize quantum gates as sequences of time-evolving graph Hamiltonians, but naive constructions produce long sequences with redundancy. Simplification rules, which are graph rewrite rules that shorten a dynamic graph sequence while preserving the unitary it implements, are the CTQW analogue of circuit identities in the...

Measuring correlations in quantum and statistical systemsTier 3

The survey discusses the problem of measuring correlations in composite quantum and statistical systems. After briefly recalling the standard methods of describing correlations, the emphasis is on the method of correlation indices. The latter method for quantifying the strength of correlations in composite physical systems is sufficiently general allowing for measuring in a...

Benchmarking indirect quantum control schemes via higher-order quantum operationsTier 3

Indirect quantum control aims to manipulate a target system through interventions on an auxiliary controller with which it interacts. We formulate finite-step indirect-control protocols using the language of higher-order quantum operations, representing admissible controller manipulations as deterministic superinstruments. This representation separates the uncontrolled but f...

Signatures of Chaos in a Quasiperiodically Driven Quantum Impact OscillatorTier 3

We demonstrate the emergence of quantum-chaotic dynamics in a quasiperiodically driven impact oscillator near the grazing condition. While previous studies of the quantum impact oscillator under periodic driving reported strange nonchaotic dynamics, we show that quasiperiodic driving produces robust signatures of chaos. The corresponding classical system undergoes a sharp gr...

Quantum electrodynamics of equilibrium systems: A rigorous Maxwell-regularized functional-theoretic formulationTier 3

A framework for quantum electrodynamics of equilibrium systems is proposed that takes the Maxwell equations as foundational and links them to the structure of density-functional theory for the quantum system. By switching from purely internal observables like the one-particle density to combined internal and external quantities, the external sources and their energy are take...

Spectral-Gap Bounds and Timescales for Purity Loss in Hamiltonian--Pointer InteractionsTier 3

We investigate the purity dynamics of a quantum system coupled to a continuous-variable pointer through a von Neumann-type interaction Hamiltonian of the form H_(int)=g H⊗p. For an initially Gaussian pointer state, the interaction generates energy-dependent conditional translations whose mutual overlaps are determined explicitly by the popula...

Growing Einstein-Rosen Bridge with Multi-partite EntanglementTier 3

Can quantum entanglement continue to grow even after the entanglement entropies of subsystems have saturated? We address this question using genuine multi-entropy, which probes multi-partite entanglement structure beyond bipartite entanglement. In a two-sided BTZ black hole, this quantity grows linearly with time after every subsystem entropy of a fixed tripartition has satu...

Unbounded Holevo additivity gaps in finite dimensionsTier 3

We establish unbounded two-use Holevo additivity gaps in finite dimensions. For each sufficiently large fixed integer K and all sufficiently large n, we construct channels T_n with output dimension K^n, input dimension exp(Θ_K(n^2)), and χ(T_n^(⊗2))-2χ(T_n) ≥n[log_2K/K-2log_2(1+9/K)]-O(1/n). The gap is linear in output qubits, w...

Proof of Heisenberg's Error-Disturbance Relation for Individual MeasurementsTier 3

Heisenberg originally envisioned the error-disturbance relation under the premise that the state after measurement must remain consistent with the Kennard-Robertson uncertainty relation. This implies that the measurement error must be formulated via a posterior observable x_t, rather than a prior observable x_0, because the posterior measurement error determi...

Matter Venture Partners Closes $450 Million Fund IITier 2

Insider Brief PRESS RELEASE — Matter Venture Partners today announced the close of its second fund at $450 million. The fund will go towards backing early-stage HardTech startups across semiconductors, robotics and Physical AI, AI infrastructure, quantum computing, advanced manufacturing, energy building blocks, and AI for the advancement of science. HardTech has attra...

Planckian Selected for Phase 1 of EuroHPC Quantum Grand ChallengeTier 2

Insider Brief PRESS RELEASE — Planckian today announced that it has been selected for Phase 1 of the EuroHPC Quantum Grand Challenge, the European Union programme backing the quantum computing platforms with the most credible path to industrial-scale systems. Thirteen companies were selected from 27 eligible proposals across Europe. Planckian is the only Italian compan...

CSIC Opens Quantum Nanofabrication Facility in BarcelonaTier 2

Insider Brief PRESS RELEASE — The Spanish National Research Council (CSIC), an organization under the Ministry of Science, Innovation, and Universities (MICIU), has inaugurated the Quantum Nanofabrication Area of the Micro and Nanofabrication Clean Room at the Institute of Microelectronics of Barcelona (IMB-CNM), the largest research facility of its kind in Spain. CSIC...

Casper College Receives $444,059 NSF Grant for Quantum EducationTier 2

Insider Brief PRESS RELEASE — An NSF Grant awarded to Casper College is bringing quantum physics into hands-on reality for students across the state. Thanks to a recently awarded $444,059 grant from the National Science Foundation, Casper College is leading a statewide initiative to prepare students from Wyoming and around the country for the next […]

Exact logical error rates for magic state cultivationTier 3

We compute exactly the acceptance and logical error rates for the distance d=3 and d=5 magic state cultivation circuits from Clifft [arXiv:2604.27058] and SOFT [arXiv:2512.23037] using Pauli propagation and binary tensor contraction. Actual T gates are studied, not the S-gate proxy used for sampling. The calculation includes every fault order at several circuit-level...

Catalytic Activation of Genuine Multipartite Entanglement and NonlocalityTier 3

We demonstrate the possibility to activate genuine multipartite entanglement (GME), the strongest form of entanglement for multipartite states, within the framework of quantum catalysis. Specifically, we show that any biseparable state (i.e. not GME) that is not partition separable can be deterministically transformed into a GME state via the help of a catalyst and local ope...