October 6, 2026

Germany Advances Key Consortia in €640 Million ($717.2 Million USD) Fault-Tolerant Quantum Computing CompetitionTier 2

Germany's Federal Ministry of Research, Technology and Space (BMFTR) is investing €640 million in a quantum computing competition to develop fault-tolerant quantum processing units by 2030. Six consortia, two each in neutral atoms, trapped ions, and superconducting circuits, have been selected. Notable projects include LOGIQC, led by planqc, focusing on neutral ytterbium...

Rewire and reset are all you need: Minimal resources for manipulating non-AbelionsTier 3

Braiding and fusing anyons are fundamental to topological quantum computation, yet existing circuit protocols often employ ancillas and measurements. We determine the minimal circuit resources for performing such anyon operations in quantum double models of generic finite groups. Our approach braids anyons through a sequential unitary circuit without ancillas. Intuitively, t...

Designing Group-Valued Codes with Full Regular Low-Weight BasesTier 3

Efficient fault-tolerant quantum computing architectures benefit from low-weight logical operators. However, reported canonical bases for high-rate, high-distance codes can be several times heavier than the code distance, and fundamental obstructions can prevent minimum-weight logical operators from forming a complete canonical basis. To address this issue, we develop design...

Protecting Quantum Computers against Untrusted UsersTier 3

Publicly accessible fault-tolerant quantum computers must preserve scientific utility while limiting cryptanalytic power. We propose the restricted model of computation, 1/2BQP_1: a quantum server provides random computational-basis inputs, revealed only after execution, and one designated output bit. This interface permits arbitrary circuits and system sizes. We conjecture...

Polynomial-time simulation of non-Clifford quantum error correctionTier 3

We show that every intermediate state of a broad class of non-Clifford quantum error-correction circuits is a third-order phase-polynomial state, even under stochastic Pauli noise. The class includes magic state distillation and cultivation, code switching and gauge fixing, transversal non-Clifford gates with syndrome extraction, and injection of diagonal magic states. Third...

Engineering logical gates with irrep surface codesTier 3

Fault-tolerant quantum computation typically relies on a fixed set of logical primitives, while realizing other desired operations can require substantial resources. We introduce irrep surface codes (ISCs), two-dimensional topological quantum error-correcting codes engineered to transversally implement a prescribed set of logical gates. The engineered gates only need to sati...

Nonadditivity in fermionic quantum Shannon theoryTier 3

We study collective state preparation and channel encoding in fermionic systems under parity superselection and composition governed by the canonical anticommutation relations. For a two-mode Gaussian state τ, we obtain the exact entanglement of formation, E_F^(phys)(τ^(⊗m))=lceilm/2rceillog 2 for every m≥1. Two copies have the same form...

Characterizing Photonic Partial Distinguishability Through Gram Matrix TomographyTier 3

Partial distinguishability affects multiphoton interference, which is central to large-scale photonic experiments such as Boson Sampling and to applications of multiphoton states across quantum technologies. Characterizing the internal degrees of freedom responsible for this behavior is challenging: in many scenarios they cannot be accessed directly and even their dimension...

CV-QAOA: Efficient Low-Depth Quantum Optimization of Continuous VariablesTier 3

We study a Continuous-Variable Quantum Approximate Optimization Algorithm (CV-QAOA) for high-dimensional continuous optimization. Our formulation extends an earlier CV-QAOA proposal with a variationally optimized initial state and recovers the convergence guarantees of Quantum Hamiltonian Descent (QHD) in the high-depth limit. We prove rigorous performance guarantees of CV-Q...

The Grothendieck Game and Self-Testing Continuous GroupsTier 3

Self-testing certifies quantum states and measurements from observed correlations alone, without requiring a description of the devices that produce them. In this work we establish, to the best of our knowledge, the first robust self-test of the full continuous family of measurements generated by Majorana operators. We achieve this by showing that the Grothendieck game, a tw...

PQShield Appoints New Commercial and Sovereign Security LeadersTier 2

Insider Brief PRESS RELEASE — PQShield, a global leader in post-quantum cryptography (PQC), is strengthening its leadership team with two major hires, as demand for quantum-safe security accelerates across governments, critical infrastructure and major technology providers. Hal Conklin, joins as Chief Commercial Officer bringing more than 30 years of experience turning...

Polynomial-time classical algorithms for mean-field models up to the glass transitionTier 3

The Sachdev-Ye-Kitaev model is a strongly interacting fermionic system that has been well-studied in condensed matter and high energy physics. It is highly quantum: Gaussian states are far from the thermal state (Hastings and O'Donnell, STOC'22) and representing the thermal state requires large polynomial-size quantum circuits (Anschuetz et al., QIP'25). Very recently, it wa...

Informed Trading model with quantum walksTier 3

The seminal Kyle model offers a framework to understand the price impact of an informed trader in a market model for a single asset. We study variants in which the asset's future value is modeled by a classical random walk and by a continuous-time quantum walk, respectively. With these assumptions, we analytically approximate and numerically identify the market equilibrium b...

Quantinuum and The University of Western Australia Partner to Advance Australia’s Hybrid Quantum-AI-HPC EcosystemTier 2

Quantinuum and The University of Western Australia (UWA) have partnered to advance Australia's quantum-AI-HPC ecosystem. This collaboration grants UWA access to Quantinuum's 98-qubit Helios trapped-ion system and focuses on co-designing hybrid workflows for critical Australian sectors like minerals, energy, agriculture, and healthcare. The agreement also includes plans fo...

D-Wave Partners with University of Arkansas to Establish Quantum Supply Chain InitiativeTier 2

D-Wave Quantum Inc. has partnered with the University of Arkansas's Supply Chain Management Research Center to create the Quantum Supply Chain Initiative Support Fund. This collaboration aims to advance quantum optimization tools for global supply chains, focusing on complex logistics and operations challenges. The initiative will leverage quantum annealing and hybrid qua...

VTT Appoints Jani Kivioja to Lead Quantum Technologies ResearchTier 2

Insider Brief PRESS RELEASE — “Finland already has strong scientific expertise in quantum technologies. What is still needed is determined R&D, piloting and innovation to accelerate commercialisation,” says Jani Kivioja, who has been appointed Vice President of VTT’s Quantum Technologies research area from 1 November 2026. Kivioja brings experience in both quantum...

Netherlands’s Quantum Strategy Sets 2035 Goals, Links Industry Growth to CybersecurityTier 2

Insider Brief The Netherlands plans to turn its quantum research strengths into commercial products while preparing government systems for computers that could defeat widely used encryption. A new governmentwide quantum strategy sets a 2035 goal for technological leadership, greater independence from suppliers outside the European Union and resilience against quantum-related...

The AI Lab Launches Post-Quantum TIP Protocol for Content VerificationTier 2

Insider Brief PRESS RELEASE — Journalists, authors, filmmakers, and other creators can now prove that their work is theirs, and that it has not been changed, with a tag built for the post-quantum era and recorded on an immutable, decentralized distributed ledger. The AI Lab (theailab.org) today made the Trust Identity Protocol (TIP) available to […]

D-Wave and University of Arkansas Launch Quantum Supply Chain InitiativeTier 2

Insider Brief PRESS RELEASE — D-Wave Quantum Inc. (NASDAQ: QBTS) (“D-Wave”), the only dual-platform quantum computing company providing annealing and gate-model systems, software and services, and the Supply Chain Management Research Center in the Sam M. Walton College of Business at the University of Arkansas (SCMRC) today announced a collaboration to explore quantum...

Boundary-accessible work in a collision-charged topological quantum batteryTier 3

Quantum batteries store energy in nonequilibrium quantum states. The ergotropy sets the work extractable by an arbitrary global unitary, but a device usually exchanges energy through a single local port. It remains unclear how much stored work such a port can deliver, and whether topological edge modes help. We study a dimerized spin chain of Su-Schrieffer-Heeger (SSH) type....

Quantum information processing under maximal distance measuresTier 3

The measures of distance frequently used in quantum information, such as trace distance or fidelity-based purified distance, are the smallest extensions of the corresponding distance measures in classical information theory. However, this way of extending classical distances is not unique, and a whole spectrum of other extensions can be defined. Here we study the question of...

A Spectrum-Based Converse for Quantum State Discrimination and Its Applications to Classical-Quantum Channel CodingTier 3

We investigate converse bounds on the average decoding error probability in finite-blocklength classical-quantum channel coding. We first present a lower bound for multiple quantum hypothesis testing in terms of pairwise trace distances and derive a corresponding fidelity bound. We then obtain a spectrum-based converse that depends only on the a priori probabilities and spec...

Semi-Cliffordness of the Clifford hierarchy for a single qudit in composite dimensionsTier 3

An important question in quantum information theory asks whether every gate in the Clifford hierarchy is semi-Clifford or not, as such gates admit resource-efficient implementations via gate teleportation. Extending recent results for prime dimensions~\cite{silva_clifford_2025}, we prove that every hierarchy gate on a single qudit of dimension d is semi-Clifford, if and...

Distributional Quantum Query ComplexityTier 3

Quantum query complexity enjoys a variety of pleasing joint computation properties: for example, a composition theorem asserting Q(f∘g)=Θ(Q(f)Q(g)) for all Boolean functions f and g; a direct sum theorem asserting that computing k copies of a function (or search problem) costs Ω(k) times as much as the cost of computing one copy; and a direct product theorem a...

Energy-constrained two-way capacities of the pure-loss bosonic channelTier 3

We determine the two-way quantum, entanglement-distribution, private, and secret-key capacities of the pure-loss bosonic channel under an unconditional mean transmitted-photon-number constraint. For transmissivity η and mean photon number N, all four capacities coincide and are given by g(N)-g((1-η)N), where g is the entropy of a thermal mode. This resolves the longs...

The complete phase diagram of detailed-balanced Gibbs samplers for the mean-field Heisenberg modelTier 3

We study the spectral gap of recently discovered families of KMS-detailed-balanced Gibbs-sampler Lindbladians for the mean-field Heisenberg model on n spins. We show that the spectral gaps of these natural families of Lindbladians admit the same phase diagram: the gap is constant above the critical temperature (i.e., in the disordered phase), scales as 1/√n at the...

Finding Gaussian Structure in Bosonic StatesTier 3

We study agnostic tomography of pure bosonic Gaussian states: given copies of an arbitrary n-mode bosonic state ρ, the goal is to output a pure Gaussian state whose infidelity with ρ is at most opt + ε, where opt is the minimum infidelity achievable by any pure Gaussian state. We give efficient protocols achieving this in both the high and low fid...

Quantum 1-PCA with Pauli Measurements in Nearly Linear TimeTier 3

We consider the problem of quantum 1-PCA: given copies of an unknown n-qubit mixed state, recover a classical description of its leading eigenvector. Our goal is to do so using non-adaptive and single-qubit measurements. For an n-qubit state with top eigenvalue λ and spectral gap at least Δ> 0, we give an algorithm that recovers the leading eigenvector to fidelity at...

Tight bounds for hybrid quantum-classical query algorithmsTier 3

We study hybrid quantum-classical algorithms in the query model. The computation consists of quantum subroutines that make at most q oracle queries; between subroutines, all qubits are measured and discarded. We prove matching upper and lower bounds for several problems in this model: (i) (Unbiased) Phase estimation up to a precision ε requires Θ(1/(q ε^2)) queri...

Bell nonlocality does not imply violation of nonlocal gamesTier 3

Nonlocal games offer a conceptually clear way to reason about Bell nonlocality. However, we show that as originally defined, and most commonly used, i.e. with a deterministic predicate, they cannot be complete witnesses of nonlocality. Concretely, we prove the existence of nonlocal behaviours which do not violate any such nonlocal game. Furthermore, we also show that quantum...

Imaginary magnetic fields for ultracold atomsTier 3

We propose a four-level scheme for generating a uniform imaginary magnetic field for ultracold atoms using Raman coupling and state-dependent particle losses. Eliminating two lossy auxiliary states and subsequently projecting onto one of the two remaining Raman dressed atomic states, the atomic motion is affected by an imaginary vector potential with a constant curl correspo...

Local universality of non-local quantum resources in rotationally invariant scatteringTier 3

Elastic scattering can generate entanglement and non-local magic between the spins of the two outgoing particles. The amount of entanglement and magic produced is encoded in the S-matrix; a unitary quantum gate that acts on the joint Hilbert space of the two spin-J particles. Previous work derived the entanglement power in terms of the scattering phase shifts for rotationall...

Characterizing Quantum Advantage for Generalizations of the Boolean Hidden Matching ProblemTier 3

We study the one-way communication complexity of the f-Boolean Hidden Partition problem. Here, Alice is given an n-bit string and Bob is given Ω(n) disjoint blocks of its indices together with a string of labels. Under the promise that the evaluations of f on these blocks either agree with all of the labels or disagree with all of them, Bob must determine which is th...

Computational entanglement distillation beyond pure states: efficient protocols and fundamental limitationsTier 3

The information-theoretic approach to entanglement typically relies on arbitrarily many input copies and unboundedly complex operations; however, the available resources are constrained in reality. This motivates the study of entanglement theory with limited resources. One of its central questions is which quantities characterize entanglement manipulations, and so far, only...

Quantum-optimized phase closure for robust interferometric imagingTier 3

Closure phase enables imaging with ground-based interferometric arrays by canceling telescope-dependent phase errors due to atmospheric fluctuations. It can be obtained by measuring fringe phases on individual baselines forming a triangle and summing them. We show that closure phases can be measured more accurately with fewer photons by performing joint measurements on multi...

Pretty good shadow tomographyTier 3

We give a shadow tomography algorithm that uses O(log(m) log(m/δ) / ε^2) copies of the input state. Specifically, given a quantum state ρ and observables O_1,…,O_m, the algorithm outputs estimates of tr(O_iρ) for all i∈[m] that are all accurate to within ±ε, except with probability at most δ. The key idea is to work in th...

Fast convergence of propagation algorithms for open quantum systemsTier 3

We establish general conditions for the rapid convergence of propagation algorithms for computing expectation values of local observables in quantum many-body systems, covering both spin and fermionic systems. Our results apply to evolutions that are sufficiently contractive, providing a general mechanism by which contractivity controls the growth generated by local interact...

Complexity separations for optimal matchgate-Clifford synthesisTier 3

Clifford and matchgate circuits are canonical families of classically simulable quantum circuits. Their intersection, the matchgate-Clifford group, plays an important role in randomized fermionic protocols and in matchgate synthesis. Its adjoint action is isomorphic to the group of unit-determinant signed permutations of 2n Majorana modes, and we study optimal exact synthe...

Hypercontractivity and entropy decay for infinite-dimensional quantum Gibbs samplersTier 3

We derive rates of exponential relative-entropy decay for a broad class of infinite-dimensional quantum Gibbs samplers. A key technical ingredient is a perturbative stability theory for hypercontractive estimates and logarithmic Sobolev inequalities. For suitably chosen dissipative couplings, we obtain exponential entropy decay for full multimode Bose-Hubbard samplers with a...

A classical oracle separation between QMA and QMA(2)Tier 3

We exhibit a classical oracle relative to which QMA \neq QMA(2). The separation is based on a separable Hamiltonian problem defined by signed edge constraints on a graph. The YES instances have zero-energy product states, while the NO instances, constructed using the antisymmetric subspace, have entangled zero-energy states but no low-energy product states. For the QMA lower...

Previously: 2026-09-03, 2026-08-13

Finite-bath projected ensembles in dual-unitary circuitsTier 3

We study the emergent randomness in projected ensembles generated by dual-unitary circuits. Specifically, we consider evolution by solvable dual-unitary brickwork circuits followed by measurements on part of the system, which induce an ensemble of states on the unmeasured subsystem. Previous work has established that this projected ensemble of states forms a quantum state de...

Quantum minimum description of density matricesTier 3

We study a variant of Schumacher compression. The task asks for the minimal memory cost for compressing many copies of a density matrix with known spectrum and unknown eigenbasis, without preserving its purification. For fixed dimension and distinct positive eigenvalues, we obtain the cost through its additive constant. Achievability uses a generalization of Werner's cloning...

Free entropy and quantum minimum description lengthTier 3

In free probability, Voiculescu's free entropy counts matrix microstates that approximate an operator. It is a non-commutative analog of the Shannon entropy, distinct from any quantum entropy of a density operator, but it has had no physical meaning in quantum theory. We define a finite-dimensional physical free entropy at finite resolution and show that it directly characte...

Separating ClonableQMA and QCMA Relative to a Classical OracleTier 3

Since the introduction of the complexity class QMA as a quantum-verifier analogue of NP (Kitaev, 1997), many have wondered whether quantum proofs are necessary or classical proofs suffice - that is, whether QMA = QCMA or QCMA != QMA (Aharonov and Naveh, 2002; Aaronson and Kuperberg, CCC '07). This longstanding question was recently answered by works of Bostanci, Haferkamp, N...

Anti-symmetrization is cheap and usefulTier 3

We consider the computational task of anti-symmetrization of an unknown mixed quantum state: Given iid copies of a rank-r qudit state ρ=Σ_(i=1)^r λ_i |φ_i⟩⟨φ_i|, prepare a copy of the state proportional to Π_(anti)^r (|φ_1⟩⊗…⊗|φ_r⟩), with Π_(anti)^r the anti-symmetric subspace pr...

Streaming Regev's Quantum Factoring AlgorithmTier 3

A major practical obstacle to Regev's factoring algorithm is its large space usage. In particular, the algorithm was believed to be incompatible with "qubit recycling," which streams the control qubits in phase estimation rather than storing them all simultaneously. We show how to fix this streaming problem. We build on the construction of Ragavan and Vaikuntanathan, which u...

Random Order in Quantum Streaming: Replenishment and Robust Lower BoundsTier 3

How can random order change the role of quantum memory in streaming? Later classical input can restore the usefulness of a quantum state consumed by earlier queries. We call this replenishment. We construct an artificial problem based on Hidden Matching, with repeated coordinate data and online matching requests. It admits a one-pass quantum algorithm using polylogarithmic s...

Certifying Measurement Incompatibility under Bounded Classical CommunicationTier 3

Measurement incompatibility enables quantum advantages in communication and state discrimination. It is also necessary for Bell nonlocality, which is used in device-independent protocols for quantum key distribution and private randomness generation. Classical communication can influence the receiver's outcome and must therefore be accounted for when certifying measurement i...

Midwest Quantum Collaboratory Expands to Eight Universities with Addition of UIC, Northwestern, and Regional PartnersTier 2

The Midwest Quantum Collaboratory (MQC) has expanded to include UIC, Northwestern, Indiana University, Washington University in St. Louis, and The Ohio State University, bringing its total to eight universities focused on quantum research and development.

University of Illinois Researchers Store Quantum Information on a Chip for Over a MicrosecondTier 2

Insider Brief PRESS RELEASE — For highly fragile quantum information systems, the ability to store quantum information is vital — but also challenging. Quantum information is transported in particles of light called photons, which often must be temporarily paused (or “stored”) while other, slower quantum operations catch up. This storage must be performed on microchips...

Quantum Systems Never Quite Forget Where They Came FromTier 2

Insider Brief PRESS RELEASE — Even the most chaotic quantum systems keep a permanent mark of their own past – a “quantum birthmark” – that never fades. Researchers from Tampere University, Harvard University, and TU Dresden discovered the feature in their recent study. Their findings shed new light on the elusive relationship between classical and […]

planqc and LOGIQC Selected for Germany’s Quantum Computing CompetitionTier 2

Insider Brief PRESS RELEASE — planqc and the LOGIQC consortium have been selected as one of six consortia to compete in Germany’s Quantum Computing Competition (QCC). The QCC is a major initiative of the Federal Ministry of Research, Technology and Space (BMFTR) to advance error-corrected quantum computing in Germany. With up to €640 million in […]

AIDAQ 2026: AI is Now a staple of The Quantum storyTier 2

The Quantum Insider joined more than 2,500 participants in Berlin for Bitkom’s AI, Data & Quantum Summit, where AI kept turning up inside quantum. Berlin became the meeting point for Europe’s AI and quantum communities on 22 and 23 September, when Bitkom’s AI, Data & Quantum Summit (AIDAQ) returned to the bcc Berlin Congress Center. […]

From Quantum Tunneling to Classical Optimization through InstantonsTier 3

We use an instanton-based analysis to show that Path Integral Stochastic Gradient Descent (PISGD), a classical optimization algorithm instantiated from path integral Monte Carlo (PIMC), can inherit the quantum tunneling mechanism. Quantum tunneling is the phenomenon in which a quantum particle passes through a potential barrier that a classical trajectory cannot cross in the...

Fermions and the Tsirelson Problem in Real Quantum TheoryTier 3

In a previous work, we showed that real quantum theory (RQT) cannot be experimentally distinguished from ordinary quantum theory (QT). In this paper, we investigate whether this indistinguishability survives two natural extensions of the setting: allowing separated measurements to be represented by commuting rather than tensor-product observables, and imposing superselection...

Natural proofs for quantum state preparation lower boundsTier 3

We identify a barrier that helps explain why proving stronger quantum state-preparation lower bounds has been so difficult. In particular, we establish a quantum analogue of the Razborov-Rudich natural proofs barrier for state-preparation lower bounds. We call a property of quantum states \emph{natural} if it holds for a sufficiently large fraction of Haar-random states and...

Testing bosonic and fermionic Gaussian states with a constant number of copiesTier 3

Bosonic and fermionic Gaussian quantum states are families of quantum states that play a central role in quantum physics and quantum information processing. We study the problem of testing whether a given state is either Gaussian, or has bounded overlap with any Gaussian state. Previous analyses of this testing problem led to tests that require a number of copies of the stat...

QNu Labs, BISAG-N, and IIT Gandhinagar Demonstrate India’s First 5.56 km Free-Space QKD LinkTier 2

QNu Labs, BISAG-N, and IIT Gandhinagar successfully conducted India's first 5.56 km free-space Quantum Key Distribution (QKD) link. This trial, utilizing QNu Labs' PAT optical system, achieved a secure key rate of 230–260 bps and integrated with BISAG-N's Vedic Kavach platform for enhanced security. This breakthrough establishes a baseline for future multi-node optical me...