October 1, 2026

Alice & Bob Demonstrates New Approach to Stabilizing Cat With DC Voltage BiasTier 2

Insider Brief PRESS RELEASE — Alice & Bob, a leader in fault-tolerant quantum computing, and the École Normale Supérieure de Lyon today announced a new and faster approach to stabilising cat-qubits in superconducting quantum systems enabling more compact designs that generate less heat. Cat qubits, which store information in a m...

From Random Quantum Codes to Explicit qLDPC Codes via Local PropertiesTier 3

Constructing explicit codes matching the parameters of random codes has been a central and largely elusive question in coding theory. The quantum setting is even more challenging since it is highly desirable that the quantum code be an LDPC code. Local coordinate-wise linear (LCL) [Levi, Mosheiff, and Shagrithaya, FOCS 2025] witnesses provide a unifying language for many cod...

Charles Black Leads C2QA Research on Scalable Quantum ComputingTier 2

Insider Brief PRESS RELEASE — When Charles (Chuck) Black was a doctoral student at Harvard University, he, like many other physicists, used superconducting materials as vehicles for exploring fundamental physics questions. The materials — which can conduct electricity without losing energy when cooled to very cold temperatures — had niche technology applications at the...

Classiq Introduces Fault Tolerance Engine for Quantum ApplicationsTier 2

Insider Brief PRESS RELEASE — Classiq today announced its Fault Tolerance Engine, a new product capability that translates optimized logical quantum programs into fault-tolerant execution plans, and measures from those same plans the physical resources and reliability required to run the application on a real machine. Fault-tolerant quantum computing introduces a funda...

QuantLase Tests Photonic Computing Platform on Financial Market DataTier 2

Insider Brief QuantLase Research and Development Center says it has tested an experimental light-based computing platform on seven financial market datasets, examining whether optical dynamics can process complex information that changes over time. The experiments evaluated how its Photonic Intelligence Processing Unit, or PIPU, followed observed data and generated predictio...

Gibbs Sampling in the Shattered Phase by Decoded Quantum InterferometryTier 3

We apply Decoded Quantum Interferometry (DQI) to sample from the Gibbs measures of classical Ising spin Hamiltonians. We show that this Gibbs sampling problem reduces to a quantum decoding problem, and the temperature achievable by DQI is determined by the performance of decoding algorithms. We then focus on the task of Gibbs sampling for classical Ising k-spin glasses (or...

Long-lived divergence from equilibrium of electrons, nuclear spins and lattice for a solid state ion trap at low temperatureTier 3

A fundamental problem in physics as well as engineering is equilibration. For example, the regulation of thermal and quantum fluctuations enables thermal and quantum annealing of complex systems. A key question is how different subsystems, such as electrons, nuclear spins and phonons equilibrate on their own as well as with each other. Level crossings play a special role in...

Quantum List Recovery and Decoding: Achievability and LimitationsTier 3

Quantum list recovery (QLR) and quantum list decoding (QLD) seek short lists of logically distinct Pauli corrections consistent with a syndrome and prescribed error constraints. For CSS codes, two issues arise: treating the X- and Z-sectors separately can multiply their output list sizes, while distinct classical candidates can collapse after stabilizer quotienting....

Distinguishing Coherent Crosstalk from Calibration Drift via Pauli-Transfer Signatures and Quantum Edge DetectionTier 3

Multi-tenant quantum processors expose a pulse-level attack surface in which coherent crosstalk can mimic benign calibration drift at matched average gate infidelity. We present a structural verification and detection framework based on the residual Pauli transfer matrix (PTM). We prove that products of local unital, trace-preserving channels cannot mix weight-1 and weight-2...

Bath-assisted cooling without resetsTier 3

Cooling an arbitrary mixed state to a pure ground state requires transferring its entropy to an environment. Can a single coherent bath contact accomplish this without repeated bath resets? We develop a new cooling mechanism that transfers the input information into bath degrees of freedom that subsequently decouple, while the system and the remaining bath follow a ground-st...

Quantum Enhanced Deep Reinforcement Learning for Distribution Network ReconfigurationTier 3

Modern smart grids generate increasingly rich operational data and deploy greater numbers of remotely controlled switching assets than ever before, creating new opportunities for data-driven distribution network reconfiguration (DNR). DNR optimizes grid topology to improve efficiency, reduce power losses, and maintain operational constraints, but finding optimal switch confi...

Efficient Calculation of Equilibrium Correlation FunctionsTier 3

A majority of measurable dynamic quantities of a physical system is described as an equilibrium correlation function of the form G_(AB)(t-t') =, where t' represents the impact time and t represents the response time. Conventional quantum algorithms to compute such quantities via Hamiltonian simulation such as the Hadamard test, variational method...

Fast Quantum Algorithms for Learning Linear Threshold FunctionsTier 3

Linear threshold functions are f_(w,θ)(x)=sign(⟨x,w ⟩-θ), where the weight vector w∈R^n is a unit vector, θ∈R is a threshold, and typically x∈R^n or x∈{-1,1}^n. When θ=0, the LTF is called homogeneous, and we write f_w:=f_(w,0). Such functions are among the most important objects in machine learning, sinc...

Computational Bounds for f-RoutingTier 3

The f-routing protocol is a leading candidate for quantum position verification (Kent, Munro, and Spiller, 2011), but security guarantees for explicit functions remain limited. We prove unconditional resource lower bounds for uniform attackers; our new techniques bypass communication-complexity bounds central to previous works, which are inherently at most linear in the in...

Self-testing the toric code against classical communicationTier 3

Device-independent self-testing certifies a multipartite quantum state from the correlations it produces alone, without assumptions on the inner workings of the devices. Most existing self-tests, however, break down as soon as the parties can exchange messages. We consider a relaxed setting in a quantum network, where in the honest version of the protocol, the parties never...

Quantum hypothesis testing of non-mixed-unitarity: A multifaceted hierarchy of quantum channel discriminationTier 3

Given multiple uses of an unknown quantum channel, we determine whether it is a specified non-mixed-unitary channel or belongs to the set of mixed-unitary channels. Formulating this as a composite channel hypothesis testing problem, we characterize the Stein exponents achievable by parallel strategies under progressively weaker restrictions on probe states and auxiliary memo...

All Unitaries Have Constant Depth Quantum CircuitsTier 3

It is well-known that every n-qubit unitary can be implemented by a 2^(O(n))-depth quantum circuit using single- and two-qubit gates. It has been open whether exponential depth is \emph{necessary} for general unitaries, even when allowing for unlimited number of ancilla qubits. We show, perhaps surprisingly, that all unitaries can be approximated to operator norm ε by...

On The Simplest Quantum-Secure Block CipherTier 3

Pseudorandom permutations are ubiquitous in theoretical and applied cryptography. PRPs that offer security even against adversaries making quantum queries are of increasing interest, and used in applications ranging from constructing pseudorandom unitaries to separating SZK from BQP. A successful framework for constructing classically-secure PRPs is the key-alternating Even-...

Resonances control when multiterminal Josephson currents reduce to two-terminal couplingsTier 3

Multiterminal Josephson junctions, in which one weak link couples three or more superconductors, are studied as hosts of topological Andreev bands, multi-pair supercurrents and tunable circuit elements. Their currents are modeled both as pairwise networks of two-terminal couplings and through genuinely multiterminal processes such as quartets. We ask how accurate the pairwis...

Quantum de Finetti theorems for states and channels in any distance measureTier 3

Standard finite quantum de Finetti theorems approximate the k-system marginals of permutation-invariant states of n-systems by mixtures of independent and identically distributed (iid) states, usually in trace distance. We prove both standard and Renner's exponential de Finetti theorems in the stronger form of operator inequalities, implying bounds in every Schatten norm...

The Single-Copy Quantum Bandit Is Classical: An Exact Spectral CollapseTier 3

We study multi-armed bandits whose arms supply unknown quantum states and whose mean rewards are defined by a known effect F. Each fresh copy may be measured by an arbitrary, adaptively chosen POVM. We prove an exact collapse: the measured relative entropy from an arm state to its confusing reward half-space equals the classical Burnetas-Katehakis functional of F's spect...

Local Relaxation Hierarchies for Quantum Ground State Energies: Convergence Guarantees and Message Passing AlgorithmsTier 3

Convex relaxation hierarchies provide lower bounds to the ground state energy of quantum many-body systems that can be computed in polynomial time on a classical computer, at any fixed hierarchy level. However, scaling these methods to large systems and accurate approximations remains challenging due to the computational cost of traditional solvers and the scarcity of effici...

A Noise Operator Approach to Quantum Query Complexity and Time-Space Tradeoff Lower BoundsTier 3

Time and space (memory) are two of the most important measures of cost in computation, even more so for quantum computation. In quantum computation our tools for proving unconditional tradeoffs between time and space are surprisingly limited. The first quantum time-space tradeoff lower bounds were proven for sorting by Klauck, Špalek and de Wolf. Unfortunately, their method...

Tight Universal Bounds on Quantum Data Hiding with Multipartite Werner StatesTier 3

Quantum data hiding concerns pairs of states which are highly distinguishable with global measurements, yet nearly indistinguishable when restricted to local operations and classical communication. More than two decades after Eggeling and Werner introduced a multipartite hiding scheme based on Werner states, the optimal dependence of its uniform security guarantee on the num...

Computational Work Extraction: The Complexity of CatalystsTier 3

We prove maximal separations: n-qubit systems can have Θ(n) ergotropy, while every efficient process extracts negligible work, even for Hamiltonians consisting of single-qubit terms. We establish an unconditional existential separation and give an explicit construction in the random oracle model. Assuming the existence of quantum-secure pseudorandom functions, this separ...

Exponential quantum speedup for F_3^n-Subset-Sum? Or, rigorous classical algorithms for Binary-Error LWETier 3

We study vector subset sum over F_3^n: given m random vectors from F_3^n, find a nonempty subset that sums to zero; the smaller m, the more difficult it is to find such a subset. Chen, Liu, and Zhandry (EUROCRYPT'22) introduced an efficient quantum algorithm that solves this problem when m≈n^2/2, where a naive classical algorithm would requ...

Quantum Sampling of Random Spanning Trees via Amortized Data StructuresTier 3

We present a quantum algorithm that generates a uniform superposition over the spanning trees of a graph -- also known as a q-sample -- using only a sub-linear number of queries to the graph. This goes beyond previous work that focuses on generating classical samples, including a recent quantum algorithm by Apers, Gao, Ji, and Liu [ICALP 2025]. For an n-vertex, m-edge gr...

Explicit Capacity-Achieving Quantum LDPC Codes List Decodable in Near-linear TimeTier 3

In classical coding theory, the quest for explicit codes achieving list decoding capacity has been an important driving force. While random codes are easily shown to achieve capacity, an explicit construction was only discovered decades later in the seminal work [Guruswami and Rudra, STOC 2006]. In quantum coding theory, it is highly desirable that a code family be LDPC. Whi...

More mutually unbiased basesTier 3

Mutually unbiased bases (MUBs) describe quantum measurements for which certainty in one basis gives uniform outcomes in the others. Their maximum number remains unknown in dimensions that are not powers of a prime. We introduce an ansatz that, in many dimensions, allows us to construct more MUBs than have previously been found. Each basis in the ansatz consists of a diagonal...

Planted Cliques and Quantum Symmetry-Adapted MeasurementsTier 3

The planted clique problem is a promising candidate for quantum advantage with a wide computational-statistical gap and substantial evidence for classical hardness. We study two quantum encodings of classical samples, a natural binary phase state encoding and symmetry-adapted measurements, and determine if they preserve enough information for planted-clique detection, as wel...

Decoupling of the QAOA into independent spin-boson systems and high-depth performance on pure and mixed spin glassesTier 3

The Quantum Approximate Optimization Algorithm (QAOA) is regarded as a promising candidate for near-term quantum advantage in combinatorial optimization, yet our ability to study it at scale is limited. Exact recursive formulas have been introduced for predicting QAOA performance on large spin glasses, but the computational cost of evaluating them grows exponentially with th...

A fully Gaussian quantum Stein's lemmaTier 3

A central yet mysterious problem in quantum information is the asymptotic distinguishability of quantum states under restricted measurements. Here we look at asymptotic asymmetric hypothesis testing for general multi-mode bosonic Gaussian states restricted to arbitrary collective Gaussian measurements. We establish a single-letter formula for the Stein exponent for many pair...

Solving Sparse SDPs in Sublinear Time: A Classical Algorithm Inspired by the Quantum OR LemmaTier 3

We give the first sublinear-time classical solvers for sparse semidefinite programs in the bounded-radius regime, without low-rank assumptions or Frobenius norm dependence on the constraint matrices. For constant precision and bounded primal and dual radii, prior quantum algorithms of Brandão et al. (2019) and van Apeldoorn and Gilyén (2019) achieved O(√n+...

The power of constant-depth quantum circuits of unbounded sizeTier 3

Classical circuits with unbounded fan-in can compute any Boolean function in constant depth when their size is unrestricted. We ask whether removing the restrictions on circuit size and ancillary qubits also allows quantum circuits built from arbitrary single-qubit gates and generalised Toffoli gates to implement every unitary in constant depth. We give exact constant-depth...

Quantum Fine-Grained Lower Bounds for SetDisjointness via Sub-Linear Reductions from 3SUMTier 3

In classical fine-grained complexity, the 3SUM Conjecture is used to prove a variety of conditional lower bounds on data structure and graph problems via an initial reduction to the SetDisjointness problem. However, there is an O(n)-time quantum algorithm for 3SUM and a direct application of Grover's algorithm to SetDisjointness queries beats the state-of-the-art c...

Memory dimension detection in open quantum dynamics via pseudo-controlTier 3

Characterising open quantum dynamics requires identifying the environmental degrees of freedom that shape the system's evolution. The memory dimension, defined as the size of the smallest effective memory needed to reproduce this influence, quantifies the dynamically relevant environmental resources and provides a common basis for comparing different many-body environments....

Classical simulation of coherent crosstalk in surface codesTier 3

We give a polynomial-time classical algorithm which samples from the syndrome distribution of a surface code state corrupted by coherent nearest-neighbor ZZ crosstalk. Our algorithm complements the known efficient simulation algorithms for coherent single-qubit errors in the surface code. When both single-qubit coherent noise and coherent crosstalk are present, we find a c...

Conditioning-Free Non-Uniform Quantum Fourier and Chebyshev TransformsTier 3

We present an efficient quantum algorithm for the non-uniform Chebyshev transform. It is defined as the projection of a function onto Chebyshev polynomials sampled at given nodes that are uniform in x∈[-1,1], and hence non-uniform in the angle θ=arccosx, a setting that QFT-based quantum Chebyshev transforms cannot handle. Our construction is based on an improvement o...

Refined sample complexities from the tomographic rate functionTier 3

Protocols for quantum state tomography can be characterized either by their sample complexity or by the tomographic rate function that governs the large deviation behaviour of error estimates. We establish a framework for the analysis of covariant protocols which allows us to compare these measures. First, we derive the rate functions for several protocols, including random...

Testing quantum Gaussianity with constant sample complexityTier 3

Efficiently testing whether a quantum state possesses a given structure is both a fundamental and a practical task in quantum information. Among the most important structured families are Gaussian states, which underpin quantum optics and many-body physics while defining paradigmatic regimes of efficient classical simulation. Despite the central role of Gaussian states, opti...

Two-Stage Quantum-Classical Distribution Network Reconfiguration via Cycle-Edge EncodingTier 3

Distribution network reconfiguration (DNR) is a combinatorial optimization problem that seeks a low-loss network topology subject to topological and electrical operating constraints. In this work, we propose a two-stage quantum-classical method for DNR. First, an iterative linear-ramp Quantum Alternating Operator Ansatz (LR-QAOA) searches topologically feasible subspaces con...

Superlinear Quantum Query Lower Bounds for Subgraph DetectionTier 3

Subgraph detection asks whether an n-vertex graph, accessed through queries to its adjacency matrix, contains a copy of a fixed graph H. We prove the first unconditional superlinear lower bounds on the bounded-error quantum query complexity of this problem, answering a longstanding open question. A copy of H is a certificate of constant size, so the adversary method wi...

Quantum Algorithms for Minimum Generating SetTier 3

In this paper, we present a polynomial-time quantum algorithm for computing a minimum-sized generating set of solvable black-box groups. Next, we consider the class Γ_d of black-box groups, where every non-abelian composition factor is isomorphic to a subgroup of the symmetric group S_d for a fixed d. We design polynomial-time quantum algorithms to compute the direct p...

A General Theory of Multi-Resource Theories Involving Finite-Group AsymmetryTier 3

Resource theories provide a universal framework for quantifying properties of quantum states, such as entanglement, magic, athermality, and asymmetry, as resources under various constraints encountered in quantum science. Since realistic settings typically impose several constraints at once, it is important to study multi-resource theories that combine them. Among these, com...

Quantum oblique eigenprojectionTier 3

Every square matrix decomposes its underlying Hilbert space into generalized, nonorthogonal eigensubspaces. We show that a quantum computer can perform such an oblique eigenprojection Π given block encoding access to the input matrix. Our approach has a query complexity nearly linear in the inverse gap and a normalization factor close to lVertΠrVert under a spectral-se...

An (almost) efficient classical algorithm for sampling from typical Gibbs statesTier 3

Gibbs state preparation has emerged as a potential avenue for quantum advantage in the study of physical systems. Although there is known advantage for computing local properties of worst-case Gibbs states, recent results suggest a different picture for average-case local systems: at temperatures where their Gibbs states can be efficiently prepared quantumly, quasi-polynomia...

A Quantum Algorithm for st-Transport on Flat Connection GraphsTier 3

We study a generalization of undirected st-connectivity to graphs whose edges carry quantum operations. Let G=(V,E) be an undirected graph on n vertices in which each edge {u,v} is labeled by a unitary U_(uv)∈C^(k×k), with U_(vu)=U_(uv)^†. We assume the labels form a \emph{flat} connection: the ordered product of labels along any path bet...

Perfect non-local quantum computation is impossibleTier 3

Non-local quantum computation (NLQC) asks two parties to apply a joint operation to their quantum inputs using an entangled resource state and one round of simultaneous quantum communication. NLQC has applications across quantum information, including attacks on quantum position verification, communication complexity, and quantum gravity. Every bipartite unitary has an appro...

Diraq to Establish Quantum R&D Lab in New MexicoTier 2

Insider Brief PRESS RELEASE — Diraq today announced plans to establish a new research and development laboratory in Albuquerque, New Mexico, expanding its U.S. presence as the company brings its silicon quantum computing technology toward utility scale. Diraq has signed a memorandum of understanding to establish operations at the Roadrunner Quantum Lab (RQL) powered by...

Scientists Find Structural Guide to Unusual Magnetism in Quantum MaterialsTier 2

Insider Brief Researchers in Japan have identified a structural measurement that could help scientists predict magnetic behavior in complex alloys, offering a more reliable way to search for materials with unusual quantum properties. The finding gives researchers studying quasicrystals and related materials a practical guide to selecting compounds for further investigation....

New Report Positions Florida as an Emerging Leader in Defense-Led Quantum TechnologyTier 2

Insider Brief WEST PALM BEACH, Fla. — 30th September, 2026 — The Quantum Insider today announced the release of Florida Quantum Ecosystem: A Strategic Assessment of Florida’s Quantum Technology Position and Opportunities, a comprehensive study of the state’s quantum assets, competitive position and path to leadership. The report was prepared by The Quantum Insider in […]

Quantum eMotion to Acquire Plurilock SecurityTier 2

Insider Brief PRESS RELEASE — Quantum eMotion Corp. (“QeM” or the “Company”) (NYSE American: QNC; TSXV: QNC; FSE: 34Q0), a developer of quantum-secure cybersecurity technologies, and Plurilock Security Inc. (“Plurilock”) (TSXV: PLUR) are pleased to announce that they have entered into a definitive arrangement agreement (the “Arrangement Agreement”) on September 28, 202...

Verifiable Quantum Advantage and Computation via Quantum Circuit ObfuscationTier 3

We construct protocols for classically verifiable quantum advantage and classical verification of BQP computations using \emph{quantum indistinguishability obfuscation} (qiO). Specifically, given qiO and assuming a slightly stronger version of BQP≠BPP, we construct a two-message quantum-advantage protocol that is efficiently and publicly ver...

Need for Coherent Access in Constructing Quantum CryptographyTier 3

We construct quantum oracles relative to which quantum-secure one-way functions (OWFs) exist but pseudorandom states (PRSs) with superlogarithmic output length do not. At first glance, this appears to contradict the known black-box constructions of PRS generators from quantum-secure OWFs. The distinction lies in the access model to the oracles; our oracle separation uses \em...

Compatibility of quantum instrumentsTier 3

Measurement compatibility asks whether a family of quantum measurements can be simulated by one parent measurement followed by classical post-processing. We extend this measurement compatibility to the notion of \emph{d-compatibility} for measurements, channels, and instruments whose parent passes a d-dimensional quantum system and unlimited classical information to the...

Optimal Purity Estimation with Incoherent MeasurementsTier 3

In this work, we consider the fundamental task of estimating the purity of an unknown state to within multiplicative error ε. When one can perform general collective measurements, Θ((√d)/(ε^2) + d/(ε)) copies are known to be necessary and sufficient for this problem [AISW20]. However, implementing collec...

Exponential Quantum Advantage in Numbers-on-Forehead CommunicationTier 3

We give the first exponential quantum advantage in the general interactive three-party Numbers-on-Forehead (NOF) model for a decision problem. Previous separations hold only for restricted protocols like one-way communication for a relation. We construct an explicit partial Boolean function, the Interleaved Unitary Product problem, that requires only O(log n) NOF quantum...