July 30, 2026

Fault-Tolerant Logical Operations and Efficient State Preparation in Modular Quantum Architectures with Noisy Interfaces

Modular quantum computing is a leading paradigm for scaling quantum computation beyond the resource limitations of monolithic devices. In this architecture, multiple quantum processing units (QPUs), employing identical or distinct qubit modalities, are interconnected via shared entanglement. Here, we investigate how errors at module interfaces and within individual QPUs affe...

Reconfigurable Optical Platform for One-way Quantum Communication Complexity

Demonstrating a practical quantum advantage remains a central goal in quantum information science. While quantum computational supremacy is still technologically demanding, communication complexity offers a promising route to showcase quantum advantage with current photonic platforms. Here we introduce a reconfigurable optical platform for one-way quantum communication compl...

Improved Methods for Determining Quantum Error Correcting Code Performance and Fault Tolerance

One of the central challenges in quantum error correction is determining the performance of a code in the low-error regimes needed to implement utility-scale computations. While performance at these error rates is not amenable to direct Monte Carlo simulation, it can be extrapolated from simulations at higher logical error rates, assuming the logical error rate scales predic...

Parity-Based Time-Bin Encoding Enabling SWAP Between Polarization and Time-Bin Qubits

Multi-degree-of-freedom photonic quantum processing requires routing between degree-of-freedom (DOF) qubit encodings on a single photon. A SWAP between polarization and time-bin qubits is Multi-degree-of-freedom photonic quantum processing requires routing between degree-of-freedom (DOF) qubit encodings on a single photon. A SWAP between polarization and time-bin qubits is a...

Hardware-efficient erasure-error detection with an integer fluxonium

Erasure-error detection can improve the efficiency of quantum error correction by revealing the times and locations of their error events. In this work, we demonstrate erasure conversions and mid-circuit erasure detections in a single integer fluxonium, in which the states |g⟩, |f⟩ encode the logical states and |e⟩ encodes the erasure...

Effective Hamiltonians for Predictive Quantum Control

High-fidelity quantum control relies on accurate models of driven dynamics. We examine this re- quirement for single-qubit gates in superconducting transmons by comparing control pulses derived from the standard Duffing approximation and from a Hamiltonian constructed by diagonalizing the transmon eigenbasis. Using the same correction-pulse construction for both models, we s...

Native CCZ Gate with Fluxonium Qubits and a Microwave-Driven Coupler

Native multi-qubit gates could reduce the overhead associated with decompositions into single- and two-qubit operations, but whether they can simultaneously provide high fidelity, simple control and robustness against parasitic interactions in scalable architectures remains unclear. Here we experimentally realize a 65-ns native controlled-controlled-phase operation, locally...

Adaptive Multi-Backend Simulation of Near-Clifford Quantum Circuits via Spatial Stabilizer-Frame Partitioning

We present an exact amplitude simulator for Clifford+T quantum circuits that combines a Feynman path sum across a balanced qubit bipartition with stabilizer-frame simulation on each half. The construction extends prior stabilizer-based Schrödinger-Feynman methods in three directions: recursive multilevel bipartition into a binary tree, automatic fallback to dense state-vecto...

Training Quantum Dragons

The Non-Equilibrium Green's Function (NEGF) is the standard formalism for nano-scale electron transport. By recasting the NEGF scattering problem as a linear system of equations whose solution encodes the transmission and reflection amplitudes, we present the first quantum computerized implementation of NEGF. We apply both the Harrow--Hassidim--Lloyd and Variational Quantum...

Quasi-polar Decomposition of Quantum Neural Networks via Adaptive Non-local Observables

We use Diagonal Adaptive Non-local Observables (DANO) as a canonical decomposition for studying Variational Quantum Circuit model evolution. Separating each learned observable into a diagonal spectrum and a unitary basis gives a quasi-polar description: the spectral weights are viewed as radial coordinates, while the unitary circuit serves as angular coordinates through Lie...

Calibrated Pressure-Observable Born and Hessian Actions for Quantum-Assisted Waveform Inversion

We construct a pressure-consistent operator-and-readout interface for Born, adjoint, and Gauss--Newton actions in constant-density acoustic full-waveform inversion (FWI) using Schrödingerised propagation. The energy variables π=c^(-1)∂_t u and q=∇u yield an auxiliary-space Hamiltonian, while physical pressure p=cπ depends explicitly on wavespeed. Its deriv...

Relational Quantum Causal Processes: Exact Models, Continuum Limits, and the Boundary of Emergent Gravity

Relational quantum causal processes formulate finite operational contexts as normal positive functionals on local completely positive maps. Response differences generate an influence algebra, and its central projections define jointly readable Boolean events. We develop this starting point through a sequence of exact and controlled models. Fresh-environment unitary collision...

Quantum random number generation using spatial quantum noise of light

Generating high-speed, verifiable random numbers is a fundamental requirement for cryptography, large-scale stochastic simulations, and secure quantum communication. Here, we present a robust quantum random number generator that utilizes the spatial distribution of quantum fluctuations captured by an electron-multiplying charge-coupled device operated in high-speed kinetic m...

Horizon Quantum Partners With Quantum Machines to Improve Quantum Computer Operations

Practical Quantum Topological Data Analysis with Applications to High-Dimensional Feature Extraction and Time Series Analysis

Topological data analysis (TDA) provides a powerful framework for extracting information about the shape of complex, unstructured data, but the classical cost of computing high dimensional topological features limits its application. Quantum algorithms for TDA offer a route around this bottleneck, yet existing approaches typically focus on exact or high precision Betti numbe...

Sparse Quantum Voxel Encoding for Readout-Efficient Molecular Geometry Reconstruction on NISQ Devices

We propose a sparse computational-basis encoding of voxelized molecular geometries that converts molecular reconstruction from full-state tomography into support recovery by computational-basis sampling. To realize the encoding scheme, the molecular space is discretized into a 3D grid, and each atom's position and chemical species is mapped to a single computational basis st...

Optimization of C-band quantum traffic coexisting with O-band classical traffic: preliminary results

The coexistence of quantum and classical signals in the same optical fiber is a critical challenge for the deployment of quantum networks. Indeed, selecting an optimal channel for quantum signal transmission is crucial to minimize noise arising from co-propagating classical signals. This work experimentally investigates spontaneous Raman scattering (SpRS), a major source of...

Enhancing the security of coherent one-way quantum key distribution using CHSH correlations

The coherent one-way (COW) protocol is a quantum key distribution scheme that has attracted significant attention, leading to the development and commercialization of practical implementations. Despite this progress, the security of the COW protocol has remained a fundamental challenge since its introduction. Numerous studies have investigated its security, and several secur...

Label and Recover Coherent Errors: Randomized Compiling Does Not Destroy Coherent-Error Information

Randomized compiling (RC) is the standard technique for converting coherent (systematic) gate errors into stochastic noise. The prevailing view is that the twirl destroys coherent-error information. An exact Fisher-information conservation law shows the opposite: the coherent-error information RC removes from the averaged output is preserved in full in the twirl labels -- th...

QED-C Roadmap Outlines Technology Requirements for Future Quantum Networks

Very Strong Irreversibility of Quantum Entanglement

The manipulation of quantum entanglement is fundamentally irreversible: some mixed entangled states require pure entanglement for their preparation, although no pure entanglement can be recovered from them by local operations and classical communication. This irreversibility is known to persist even under the maximal class of operations that do not generate entanglement, rev...

Sharp Bounds on Ground State Energy of the SYK Model

We study the Sachdev-Ye-Kitaev (SYK) Hamiltonian H_(SYK) on n Majorana modes with k-body interactions, and prove that E‖H_(SYK)‖_(op) = (1 - o(1))·√2n/k for super-constant k≤o(√n), where the expectation is over the disorder variables in the Hamiltonian. This confirms the predictions due to...

Robust quantum state certification and uncertainty principles for total influence

We show that nonadaptive single-qubit Pauli measurements suffice to test whether an unknown n-qubit state ρ is ε-close to or O(ε)-far from an ideal target state |ψ⟩, for all but a 2^(-Ω(n)) fraction of target states. The test uses O(ε^(-2)log(1/δ)) copies of ρ to achieve confidence 1-δ, which is information-theoretically...

Classical and Quantum MacWilliams Transforms as Spin Kinematics

Spin is the hidden engine behind the zoo of MacWilliams transforms in weight enumerator theories - not only for qubits and qudits, but even for classical codes. From nothing more than a split into trivial and nontrivial errors, we kinematically derive the MacWilliams transform as a Wigner-D rotation between two canonical bases. Within each classical and quantum theory, cha...

OQRAM: Oblivious Quantum Random Access Memory for Securing Delegated Quantum Queries

Quantum query is a basic subroutine in many quantum algorithms, and Quantum Random Access Memory (QRAM) provides a natural way to realize such coherent query access. In delegated settings, however, a standard QRAM query interface can expose sensitive information to the server. This paper introduces oblivious QRAM, a cryptographic abstraction for privacy-preserving delegated...

The Keyl-Werner algorithm is not optimal for spectrum estimation

We give an algorithm which, given n = O(d^2 ·(loglog(d)/log(d))^2) copies of ρ, estimates the eigenvalues of ρ to constant error in total variation distance. Thus, we can learn the eigenvalues of a quantum state with fewer copies than the Θ(d^2) needed to run full state tomography. This is the first improvement to spectrum estimation over the influential Keyl...

Ky Fan majorization for binary tensor products

We provide a short proof of a Ky Fan-type majorization relation for the singular values of a sum of binary tensor products of matrices. This generalizes Alhejji's result (arXiv:2410.18254) from two summands to arbitrary sums and from positive matrices to arbitrary matrices. As an application, we show a majorization relation between the singular values of a completely positiv...

A Degenerate Singlet-Triplet Qubit with All-Electrical Orthogonal Control

Singlet-triplet qubits offer an attractive encoding for semiconductor quantum computing, combining ancilla-free readout, reduced sensitivity to common-mode noise, and baseband voltage control. However, the Zeeman energy difference ΔE_Z is typically fixed by local magnetic field gradients or g-factor inhomogeneities, leaving the exchange interaction J as the on...

Optimising Trotter-Suzuki Simulations of Markovian Open Quantum Systems via Classical Search

Simulating an open quantum system on a digital quantum computer often involves the use of Trotter-Suzuki (TS) Product Formulas (PF) to approximate the system's time evolution. Precise estimates for the required number of Trotter steps (and hence the overall gate count) can be crucial for minimising the computational cost of these methods. Building on established theoretical...

Temporal Interference from Topological Transitions in Monitored Quantum Dynamics

Temporal interference patterns can be detected with stroboscopic monitoring that treats the back action of measurements and the unitary dynamics. Previous work established that the mean detected recurrence time is integer-quantized and given by a topological invariant, a winding number w. When measurement periods are at resonance with the system's timescales, the winding n...

Quantum random-number generator with non-demolition measurements: semi-device-independent implementation

We propose and analyze a novel quantum random-number generator based on a tripartite quantum system in which two subsystems act as detectors. Within a quantum non-demolition measurement scheme, one detector is used to certify the presence of genuine quantum effects in the system's evolution, while the second generates random numbers from a distribution that can be optimized...

Reliability Functions of Quantum Soft Covering and Privacy Amplification via a Mixed-Order Rényi Divergence

In this paper, we introduce a novel mixed-order Rényi divergence and investigate its fundamental properties. Using this divergence, we define a family of mixed-order order-two Rényi mutual information and Rényi conditional entropy. We derive exact reliability functions of quantum soft covering and privacy amplification under the sandwiched Rényi divergence with order α∈[2...

Finite size scaling of bitstring probability distributions for Rydberg arrays

We calculate the probabilities p_({n}) of the measured bitstrings {n} for the vacuum of Rydberg ladders with N_q atoms. As N_q increases, the p_({n}) decrease but become more dense in the low p region raising the possibility that their smallness could be compensated by their large number. The importance of the low probability states can be estimated from th...

Two-state generator extraction: property currents and a two-layer arrow of time in pre- and post-selected quantum dynamics

Conditioning on both past and future assigns intermediate-time properties a causal observer does not; these time-symmetric assignments obey exact symmetry theorems and are measurable from trajectories. We use two-state generator extended dynamic mode decomposition (gEDMD): because weak values obey dA_w/dt=i⟨[H,A]⟩_w exactly, generator extraction, with an exact-...

Mean-field Pulse Adaptation for the Circulatization of Interacting Rydberg Atoms

Arrays of circular Rydberg atoms provide a promising platform for quantum simulation and computation; however, their preparation in the presence of interatomic interactions remains a major challenge. While optimal control methods have enabled the design of fast and accurate radio-frequency pulses for the circularization of a single atom and of an atom pair, the extension to...

Two-photon interference from as-grown InAsP/InP quantum dots under detuned excitation

In this study, we investigate as-grown InAsP/InP quantum dots emitting in the third telecommunication window under detuned quasi-resonant excitation. A large excitation-emission detuning of 32 meV enables efficient suppression of scattered laser light while retaining several advantages of near-resonant excitation. The single-photon nature of the emission is confirmed by a Ha...

Quantum Fisher information of the Klein--Gordon, φ^4, and Dirac vacua

The quantum Fisher information (QFI) of the vacuum of three quantum field theories is evaluated with respect to the mass parameter of each theory. All field theories are considered on a (d+1)-dimensional Euclidean spacetime. We consider the Klein-Gordon field, a quartic interaction (φ^4) field theory, and the free Dirac field. In the case of the quartic interaction theor...

Revival of transport reciprocity via quantum interference in asymmetric nonlinear devices

Structural asymmetry combined with optical nonlinearity often leads to nonreciprocal light transport. We explore the mechanism by which 1-photon interference effects can revive reciprocity in such nonlinear models. To this end, we study correlated 2-photon scattering where an artificial atom is asymmetrically (a) side-coupled to an infinite waveguide at two spatially separat...

Analytical Series Expansion for Efficient Gradient Evaluation in Multi-Qubit Optimal Control

The open-loop optimization of quantum dynamics using gradient-based quantum optimal control methods involves calculating the time-ordered propagator and its gradient. In this Letter, we present a unifying framework for gradient-based quantum optimal control with respect to any general pulse parameterization by deriving the formal solution from first principles. For the case...

Enforcing IID structure on time-bin encoded QKD protocols via coarse-graining

Many security proofs for quantum key distribution (QKD) require Bob's measurement to have a tensor-product structure across protocol rounds, with some techniques requiring the stronger independent-and-identically-distributed (IID) condition. Time-bin encoded protocols often rely on interferometers whose detector outcomes depend on the interference between optical modes from...

High-fidelity multiqubit gates with Rydberg atoms via level-crossing-free Rapid adiabatic passage

We propose a rapid adiabatic passage (RAP) scheme based on level-crossing-free pulses for deterministic generation of multiqubit entangled states in Rydberg atom systems. Unlike conventional RAP protocols that rely on level crossings, our approach uses an antisymmetric Rabi frequency and an even-symmetric detuning, enabling robust population transfer without passing through...

Coherent electric field manipulation of nuclear spin qudit

Spins in condensed matter, especially well-isolated nuclear spins, offer attractive quantum degrees of freedom for computing, sensing, and networking because of their long coherence times. The possibility of electric-field control is an important feature for practical scalable quantum technologies, but, typically, nuclear spins couple only weakly to electric fields in conven...

Quantum model reduction based on Oja's flow

We propose a novel approach to numerically derive approximate reduced dynamical models for Markovian quantum open systems without perturbative iterations, projecting the evolution to the subspace associated to their slowest degrees of freedom. The two algorithms we develop are based on Oja's continuous-time principal component flow: the first returns the optimal reduction to...

Critical non-thermal fixed point and the dynamical condensation phase transition

Using a non-perturbative quantum kinetic framework, we develop a unified description of the far-from-equilibrium dynamics of three-dimensional Bose gases following cooling quenches across the Bose-Einstein condensation transition. By tracking the spatio-temporal evolution of the momentum distribution, we show that the equilibrium condensation threshold simultaneously acts as...

QKD-Integrated Quantum Noise Stream Cipher: An Overview

Quantum Noise Stream Cipher (QNSC) has emerged as a physical-layer encryption technique that exploits quantum noise and non-orthogonal coherent-state modulation to secure optical communication. However, the security of QNSC relies exceedingly on the secrecy and freshness of its seed key. Quantum Key Distribution (QKD), on the other hand, provides information-theoretically se...

The Growing Quantum Security Challenge Facing Bitcoin and Digital Assets

EY Announces On-Site Quantum Computing

IQM Quantum Computers Registers 183,619 New Shares Following ESOP 1 Subscriptions

Scientists Say New Chip Architecture Could Tackle a Barrier to Scaling Quantum Computers Towards 1 Million Qubits

Israel Pushes For National Quantum R&D Center to Unite Industry

AI Finds New Weaknesses in Cryptographic Algorithms, Anthropic Says