July 20, 2026

Fast logical operations in quantum LDPC codes using simple resource states

Quantum LPDC codes provide a substantial reduction in qubit overhead required for fault-tolerant quantum computation compared to surface code, thanks to their high encoding rate. However, operating simultaneously on multiple logical qubits encoded in the same block is more challenging and may slow down logical operations. Prior work addresses this problem by designing comple...

Radiopurity material assays and radiation exposure projections for superconducting qubit measurements at SNOLAB

Interactions of cosmic rays and other forms of ionizing radiation pose a significant challenge to the reliable operation of state-of-the-art quantum devices and error correction in quantum computing based on superconducting circuits which are typically fabricated on semiconductor substrates. Shielded by 2 km of rock overburden, the Cryogenic Underground TEst facility (CUTE)...

Quantum-classical crossover in fault-tolerant quantum dynamics simulation

While quantum computers promise to solve classically intractable problems, identifying the point at which fault-tolerant quantum computation outperforms the best classical algorithms for practical applications remains an outstanding challenge. Here we establish a concrete quantum-classical crossover for quantum many-body dynamics under realistic hardware conditions. We intro...

Combinatorial aspects of holographic quantum secret sharing

We introduce combinatorial holographic quantum secret sharing (CHQSS) for a bulk subregion in AdS_3/CFT_2 to study how logical information of the bulk subregion is encoded in the boundary and protected from erasures of boundary subregions. We introduce a distance, a reconstruction threshold, and a secret threshold to characterize CHQSS schemes. We present the phase trans...

Harnessing resonant dipolar interactions in a hybrid atom-molecule quantum system

Hybrid quantum systems offer a route to combining the complementary strengths of distinct quantum platforms while mitigating their limitations. A particularly promising architecture combines neutral atoms and polar molecules: atoms provide fast, controllable interactions through excitation to Rydberg states, while molecules possess long-lived rotational states that are attra...

Optimization of multistate STIRAP by pulse shaping

We propose a pulse-shaping method for improving population transfer in multistate stimulated Raman adiabatic passage (STIRAP) with nearest-neighbour couplings only. The method extends the quasiparallel-eigenenergy approach, previously used for two- and three-state systems, to multistate chains without introducing additional shortcut fields. The pump and Stokes fields are sha...

Reconstruction of the noise correlation spectral density from the cavity emission in a two-qubit system

A significant challenge in the field of large-scale fault-tolerant quantum computation is the influence of noise. In addition to the influence of noise on individual qubits, the smaller additional effect of noise correlations is also of high significance because correlated errors pose a challenge for quantum error correction. We describe the dynamics of two cavity-coupled qu...

Fermion parity of an Andreev molecule probed by nonlocal Josephson effect

Fermion parity is a fundamental property of superconducting many-body states. Here, we show that the global fermion parity of a delocalized superconducting state can be detected locally by exploiting the nonlocal Josephson effect. Using a carbon nanotube-based Andreev molecule formed by two coupled quantum-dot Josephson junctions, we observe a pronounced nonlocal Josephson r...

Parameterized Quantum Circuit Semantics Through Enriched Categories

It is well-known that combinatorial circuits are modeled mathematically by string diagrams in monoidal categories. Given a gate set Σ, the circuits over Σ can be thought of as string diagrams in the free monoidal category generated by Σ. In this model, circuit semantics are then given by monoidal functors out of this free category. For quantum circuits, this functor is...

Rethinking Quantum Continual Learning with Quantum Fisher Information

Quantum continual learning aims to train quantum models on sequential tasks without losing previously learned knowledge. However, variational quantum classifiers (VQCs) are prone to catastrophic forgetting under nonstationary task distributions. We propose quantum elastic weight consolidation (QEWC), a quantum Fisher information (QFI)-informed regularization method for mitig...

Parameter Estimation in a Continuously Monitored Non-Markovian Quantum System

Continuous monitoring is a powerful tool for analyzing quantum systems and is increasingly used as a non-demolition technique in quantum metrology. In this context, noisy data acquired through continuous monitoring can be used to precisely pinpoint unknown parameters of the system. However, extending the theoretical framework that connects these data to the underlying parame...

Alleviating the Sparse Matrix Scaling Bottleneck in Adaptive VQE via Greedy Operator Commutativity Partitioning and High-Order Taylor State Evolution

The Variational Quantum Eigensolver (VQE) and its adaptive variants, such as ADAPT-VQE, are central to the study of strongly correlated quantum systems. However, the classical simulation of the ansatz growth process remains constrained by the exponential scaling of operator space and the associated computational cost of unitary evolution. We introduce the Greedy Operator Com...

The Fourier Wall: Why Public Tabular Datasets Refuse Quantum Advantage, and a Certified Recipe for Where It Lives

Across public tabular benchmarks, quantum machine-learning (QML) models usually lose to carefully tuned classical baselines. We argue that this is a structural property of the datasets rather than merely a limitation of current models. Because an angle-encoded quantum neural network is a partial Fourier series, a genuine advantage can arise only when the target spectrum is s...

Growth of quartet correlations in neutron-rich Tellurium isotopes within quartet Bardeen-Cooper-Schrieffer theory

Quartet correlations in neutron-rich Te isotopes are investigated within the quartet Bardeen-Cooper-Schrieffer (BCS) framework. Taking ^(100)Sn as an inert core, we consider two valence protons and valence neutrons occupying the 2d_(5/2)⊕1g_(7/2) model space, and solve the quartet BCS variational equations with a charge-independent isovector pairing interaction....

Boundary-Phase Control of Sequentially Addressed Trapped-Ion ZZ Interactions

Motion-mediated trapped-ion gates typically apply synchronized state-dependent forces to both target ions. We consider the complementary setting in which one addressing channel alternates between the targets, so their force windows do not overlap. In a complex-amplitude near-resonant description, each window generates a displacement vector, and ordered symplectic products of...

Benchmarking Hybrid Quantum-Classical Algorithms for Power Grid Optimization Problems

Alternating Current Optimal Power Flow Unit Commitment (AC-OPF-UC) is a difficult mixed-integer nonlinear optimization problem that combines binary generator commitment decisions with nonconvex continuous AC power-flow constraints. In this work, we investigate whether hybrid quantum-classical variational algorithms can improve the solution of single-period AC-OPF-UC relative...

Grover's algorithm for image edge detection

Grover's algorithm is one of the most significant quantum algorithms, enabling the search for a marked element in an unsorted database quadratically faster than classical search algorithms. We utilize Groves's algorithm to detect the edges of a digital image faster than any classical edge detection methods. The high success probability of our method in detecting image edges,...

Enhanced Rydberg-Atom Superheterodyne Detection of Hidden-Photon Dark Matter on Chips

Although hidden-photon dark matter with masses above 10^(-4) eV is well motivated by inflationary production, it remains largely unexplored by terrestrial experiments. Through kinetic mixing, hidden photons induce a weak oscillating electric field above 10 GHz. We propose to amplify this signal using a compact high-frequency distributed cavity and det...

Who’s News: Strategic Appointments at Pasqal, PsiQuantum, and Haiqu

Pasqal has appointed Mark Armstrong as Chief Commercial Officer for Europe, the Middle East, and Africa (EMEA) and the Asia-Pacific region (APAC). Armstrong joins from Hewlett Packard Enterprise (HPE), where he served as EMEA Vice President and General Manager for High Performance Computing and AI. In his new role, he will oversee Pasqal's commercial strategy, [...] <...

Aqarios Enters Public Markets via SPAC, Becoming Germany’s First Listed Quantum Pure-Play

Munich-based quantum optimization software provider Aqarios GmbH has completed a public listing on the Düsseldorf Stock Exchange (Börse Düsseldorf) through a reverse merger transaction via a Special Purpose Acquisition Company (SPAC). Following a successful combination agreement with Fonterelli SPAC 4 AG, the newly combined capital market vehicle has been formally renamed...

Singapore’s pQCee Raises $3.9M Seed Round to Accelerate Global Crypto-Agility Deployment

Singapore-based quantum-safe cybersecurity startup pQCee has raised $3.9 million in a seed funding round. The investment reflects a significant shift as commercial and government entities transition post-quantum cryptography (PQC) out of academic theory and into practical enterprise procurement frameworks. The round was co-led by government-backed deep-tech investor SGInn...

Tennessee Launces Comprehensive K–12 Quantum Education and Career Initiative

The Chattanooga Quantum Collaborative (CQC) has launched TN QuantumWorks, one of the United States' first comprehensive K–12 quantum technology and career awareness education initiatives. Developed by workforce education innovators Dr. Dane and Sheila Boyington of Thinking Media, the curriculum will be introduced as an active pilot program within Hamilton County Schools b...

Quantinuum and Academic Partners Demonstrate First Universal Topological Gate Set via Non-Abelian Anyons

A multi-institutional collaboration including Quantinuum, the University of Chicago Pritzker School of Molecular Engineering (UChicago PME), Harvard University, and Stony Brook University has successfully demonstrated the first universal topological gate set using non-Abelian anyons. Published in Nature, the landmark experiment utilized Quantinuum’s H2 trapped-ion quantum...

Digital Catapult and NQCC Launch Third QTAP Cohort, Introducing Banking and Healthcare Streams

The UK's deep-tech innovation accelerator Digital Catapult has welcomed 11 commercial and public organizations to the third cohort of its Quantum Technology Access Programme (QTAP). Delivered in tandem with the National Quantum Computing Centre’s (NQCC) SparQ program, the initiative provides a structured incubation pathway to transition theoretical algorithms into verifia...

Reverse engineering of single-qubit quantum gates

In this work, we address the problem of designing single-qubit quantum gates by means of a linearly-polarized field. We show that any desired one-qubit gate corresponding to a special unitary matrix can be generated by a modulated sinusoidal field. The only approximation involved is the rotating-wave-approximation. The formula for the control field is obtained by inverting t...

Object-relative ultraviolet weighting of electromagnetic modes and one-loop ultraviolet finiteness in quantum electrodynamics

This work explores whether localized electromagnetic interactions can be modeled in terms of an effective object-relative ultraviolet weighting of internal modes. The proposal is motivated heuristically by two considerations: a weak-field self-backreaction estimate for sufficiently localized energy-carrying modes and a three-dimensional overlap argument for localized interac...

Operator Entanglement in Quantum Dynamics Simulations: Formalism and Analysis Tools

We review the framework of operator Hilbert space and introduce the one- and two-particle super reduced density matrices (1-SRDMs and 2-SRDMs), as well as the super mutual information (SMI). The eigenvectors of the 1-SRDMs define what we term natural single particle operator bases, and provide a way to compress vibrational and vibronic Hamiltonians with controlled error. The...

Rigorous Time-dependent Hamiltonian Learning via Continuous Weak Measurements

Characterizing the Hamiltonian that a quantum processor actually implements is central to calibrating and validating current quantum hardware. Many devices, however, operate with generators that are time dependent by design. Here we develop a rigorous and experimentally friendly protocol for learning time-dependent many-body Hamiltonians from continuous weak measurement reco...

Quantum Mechanics on Lie Groups: II. Path Integrals

We continue our study of quantum dynamics on a Lie group G, initiated in arXiv:2512.19840, by building the path integral that governs transition amplitudes in the Hilbert space L^2(G). This relies on the proper handling of both a noncommutative momentum space and the presence of compact directions in G. We show that compactness can be handled through a sum over winding...

Tunable Families of Multiqubit Elegant Joint Measurements

We give a closed-form construction of the n-qubit Elegant Joint Measurement (EJM) proposed in [PRL \textbf{136}, 190201 (2026)] and show that it is part of a tunable family of measurements with tetrahedrally arranged Bloch vectors. The construction is based on the interference pattern implied by a single phase polynomial built from the elementary symmetric functions. It re...

Hanbury-Brown Twiss effect, squeezed gravitons and the photon correlations

Unlike the gravitational waves classically generated by moving macroscopic masses, the diffuse backgrounds of gravitons originate most likely from zero-point fluctuations of the gravitational field amplified by the evolution of the space-time curvature. The resulting entangled states lead to specific second-order correlation effects that could be eventually detected. For a q...

Conditional Euclidean-Hamiltonian reductions for sign-problem toy models

Euclidean Monte Carlo methods are effective when the path-integral weight is real and nonnegative, but finite-density fermion systems often produce sign-changing or complex scalar weights after the fermionic sector is traced out. Hamiltonian formulations avoid this complex-weight sampling problem but face rapid Hilbert-space growth. This paper studies a conditional Euclidean...

Beyond the Positive Partial Transpose Squared Conjecture: The Qutrit Case

Entanglement swapping is a fundamental operation in quantum repeaters for establishing entanglement between distant parties. The positive partial transpose (PPT) squared conjecture asks whether two PPT entangled links can generate terminal entanglement through entanglement swapping, or equivalently, whether the composition of two PPT maps is always entanglement breaking. Mot...

Causality in Pure Quantum Computation with Quantum Control

Indefinite causal order is a characteristic phenomenon in quantum computation, with examples including the quantum SWITCH and the OCB process. Not all such processes are believed to be physically realizable: while some implementations of the quantum SWITCH have been proposed, the OCB process is suspected to be unrealizable. This difference in realizability is commonly attrib...

The statistical disturbance bound of quantum measurements

Quantifying the disturbance caused by a quantum measurement typically requires detailed knowledge of the underlying measurement channel. In this work, we introduce a statistical disturbance bound, which connects the statistical properties of a quantum measurement to the state disturbance induced by any compatible measurement channel. Specifically, we show that the average fi...

Programming with Quantum-Controlled Quantum Channels

In contrast to a classical bit, which can only take the value $0$ or $1$, its quantum counterpart -- a qubit -- can exist in a superposition of $0$ and $1$. This is a superposition of data values, naturally raising the question of whether one can superpose not only data but also programs. For example, a particular superposition of programs, known as the quantum SWITCH, has a...

Photoelectrical readout and Ramsey interferometry of single shallowly implanted NV centers in diamond

Photoelectrical readout of the electronic spin state of the nitrogen-vacancy (NV) center in diamond is attracting significant interest due to the numerous advantages it possesses compared with conventional fluorescence readout. The higher charge carrier rate compared to the photon rate and the integration of the detection scheme on a chip can significantly advance quantum se...

Maximal quantum leakage: operational interpretation and quantum channel analysis

Maximal quantum leakage quantifies privacy against adversaries with arbitrary intentions. In this work, we prove that computing this leakage is equivalent to minimum-error quantum state discrimination with equal priors. This establishes a computable operational interpretation, addressing the previous difficulty in computing maximal quantum leakage. We further analyze the imp...

Manipulating non-intrinsic outputs of a non-Hermitian coupled system by weak external driving

Measurement provides access to exploring and understanding nature and finds widespread applications. It is generally believed that the weak external driving used in measurement introduces negligible disturbance to the intrinsic output of the probed system. Here, we reveal that dissipation in a non-Hermitian quantum coupled system induces interference between self-excitation...

Controlling charge and spin currents through nonreciprocal dissipative processes

We investigate the generation and control of both charge and spin currents via nonreciprocal dissipative mechanisms in a two-dimensional spinful fermionic atom quantum system with broken inversion and time-reversal symmetries. Within the Gorini-Kossakowski-Sudarshan-Lindblad master equation formalism and using an approach based on the time-dependent generalized Gibbs ensembl...

Einstein crystals in Snyder and Snyder-de Sitter noncommutative backgrounds

We investigate the behavior of Einstein crystals in noncommutative backgrounds described by the Snyder and Snyder-de Sitter models. Possible novel effects, which may arise in realistic systems such as diamond crystals, are analyzed within a thermodynamical framework. We show that noncommutativity influences the key thermodynamic quantities, including internal energy and spec...

Non-Gaussianity in cat codes: global incompatibility and local geometric alignment with the magic resource

Non-Gaussianity is an essential resource for genuine quantum advantages in continuous-variable quantum systems and is regarded as a counterpart of the magic resource in discrete-variable systems. Recently, an exact correspondence between non-Gaussianity (NG) and the magic resource was identified within the Gottesman--Kitaev--Preskill (GKP) encoding framework. Whether such a...

Strong intervalley mixing between copropagating quantum Hall edge channels in a silicon MOSFET

Copropagating quantum Hall edge channels provide a promising platform for compact electron interferometry and flying quantum states. In silicon, the valley degree of freedom offers a natural alternative to spin-resolved edge channels because spin-flip scattering is strongly suppressed by the weak spin-orbit interaction. Here, we investigate interchannel transitions between c...

Spectral Attack on Continuous-Variable Quantum Key Distribution Systems

Continuous-variable quantum key distribution (CVQKD) has attracted extensive attention due to its compatibility and low costs. However, bandwidth mismatch exists to varying degrees between the transmitter and receiver. This may prevent frequency components carrying modulation information from being fully perceived by the legitimate party. In this paper, we identify a practic...

Fate of dynamical quantum phase transitions from sudden quench to slow quench limit

Previous investigations of dynamical quantum phase transition (DQPT) have predominantly focused on sudden quench protocols. In this work, we systematically explore the fate of DQPT from the sudden to the slow quench regime. We establish that DQPT remains robust under slow quenching when the protocol crosses an equilibrium quantum phase transition. Conversely, we show that ac...

Classical codes violate the conjectured square-root bound for quantum random access codes

We consider whether every quantum random access code (QRAC) with density-operator encodings and arbitrary decoding measurements obeys the conjectured bound p≤(1+√(m/n))/2, where n classical bits are encoded into m qubits and p is the worst-case success probability. We find that classical random access codes with private randomness, which form a subclass of thi...

Probing Lorentz-invariance-violation with quantum coherence of Unruh-DeWitt detector

Testing Lorentz invariance violation (LIV) is notoriously difficult, as its characteristic energy scale, M_(star), in modified dispersion relations typically lies beyond current experimental reach. To enable a low-energy probe, we investigate the quantum coherence of an inertial Unruh-DeWitt (UDW) detector interacting with a massless scalar field with a Lorentz-violating di...

Quantum states supported by matroids

In this work, we establish a structural correspondence between quantum states and matroid theory. This connection demonstrates that key properties of quantum states, including entanglement and measurement, can be characterized in purely combinatorial terms via matroids, despite the apparent conceptual distance between these two fields. Using this framework, we show that a ma...

The Complexity of Dynamical Correlators: Operator Shadows and Exponential Learning Separations

Quantum platforms can realize many-body dynamics beyond classical simulation yet complete readout remains intractable: the cost of extracting accessible information scales exponentially with system size. Classical shadows and Bell sampling offer scalable, multi-observable estimation from randomized or entanglement-assisted measurements. Here we aim to push these ideas beyond...

Efficient routing and spectrum allocation in arbitrary flex-grid entanglement networks

As practical quantum networks approach large-scale deployment, the need for efficient user-to-user frequency allocation is increasing, yet current approaches only provide partial solutions to the routing and spectrum allocation problem for an arbitrary quantum network. We address this challenge for repeater-less flex-grid quantum networks based on hyperentangled photons usin...

ESA Installs Its First On-Premises Quantum Computer to Boost Earth Observation Capabilities

The European Space Agency’s Centre for Earth Observation (ESA-ESRIN) has announced the physical installation of its first on-premises quantum computer at its data center in Frascati, Italy. Procured through a strategic hardware agreement with Irish deep-tech spinout Equal1, the Bell-1 quantum computer will be integrated directly with ESA’s existing High-Performance Comput...

DOE Advances Domestic Silicon and Germanium Isotope Supply Chains For Quantum Information Science

Guest Post: Patentability of Quantum Computing Inventions

QTREX Quantum Appoints Dr. Shlomit Chappel-Ram as Independent Director

Braided, Exotic Particles Could Build Reliable, Universal Quantum Computers

Quantum Source and Israel’s DDR&D Demonstrate Robust Single-Atom Source for Real-World Quantum Communication

Digital Catapult Welcomes New Cohort to Explore Industrial Quantum Applications