The Quantum Journal

arXiv:2604.25048v1 Announce Type: new Abstract: We analyze the dynamics of a quantum particle in a one-dimensional bistable potential within the framework of Bohm's quantum mechanics. We give arguments that evidence the fallacy of certain claims found in the literature dealing with the impossibilit

arXiv:2604.25058v1 Announce Type: new Abstract: The performance of the Quantum Approximate Optimization Algorithm (QAOA) on noisy intermediate-scale quantum (NISQ) devices is strongly limited by sparse qubit connectivity. When interactions required by QAOA Hamiltonians are not aligned to the hardwa

arXiv:2604.25094v1 Announce Type: new Abstract: Near-term FTQC system designs are constrained by limited error budgets and largely sequential execution of non-Clifford gates. As a result, reducing the number of the most-error prone instructions becomes critical for successful program execution. In

arXiv:2604.25137v1 Announce Type: new Abstract: We solve the time-dependent Schr\"odinger equation by learning the score function, the gradient of the log-probability density, on Bohmian trajectories. In Bohm's formulation of quantum mechanics, particles follow deterministic paths under the classic

arXiv:2604.25140v1 Announce Type: new Abstract: We propose a parallel protocol for implementing distributed nonlocal quantum gates between spatially separated stationary qubits encoded in dual-species quantum emitters (i.e., color-center and superconducting qubits). By utilizing entangled photon pa

arXiv:2604.25141v1 Announce Type: new Abstract: We present an alternative scheme to achieve nonreciprocal unconventional magnon blockade (NUMB) in a hybrid system formed by two microwave cavities and one yttrium iron garnet (YIG) sphere, where the pump and signal cavities interact nonlinearly with

arXiv:2604.25148v1 Announce Type: new Abstract: In an extension of the Unconventional Noiseless Intermediate Quantum Emulator, this work introduces a classical emulation of the quantum Harrow-Hassidim-Lloyd algorithm for sampling from the solution space of linear systems. The emulated HHL algorithm

arXiv:2604.25162v1 Announce Type: new Abstract: Demonstrating quantum advantage for combinatorial optimization requires more than standalone algorithmic results; it calls for end-to-end case studies that integrate problem modelling, quantum execution, and classical refinement into practical workflo

arXiv:2604.25170v1 Announce Type: new Abstract: Among the many solid-state emitters being explored for scalable quantum technologies, the silicon T centre is a leading candidate offering long-lived spin qubits, a telecommunications-band spin-photon interface, and integration with on-chip photonic c

arXiv:2604.25194v1 Announce Type: new Abstract: Network tomography refers to the use of inference techniques for inferring internal network states from end-to-end probes. Quantum probes, implemented by sending blocks of $n$ coherent-state pulses augmented with continuous-variable (CV) squeezing ($n

arXiv:2604.25195v1 Announce Type: new Abstract: A minimal method to fabricate Al/AlO$_x$/Al Josephson junctions (JJs) using photolithography and argon etching, before metallization and oxidation, is demonstrated. JJs with areas ranging from 1 to 6 $\mu$m$^2$ can be fabricated and, with the appropri

arXiv:2604.25225v1 Announce Type: new Abstract: Transmitter-device-dependence is a longstanding but often implicit problem in quantum key distribution (QKD), as compared to measurement-device-dependence. One-sided device-independent (1sDI) scenario relaxes the security conditions of DI framework an

arXiv:2604.25229v1 Announce Type: new Abstract: We present the first quantum-hardware implementation of a Hamiltonian simulation algorithm that produces signed vector-field solutions to the time-domain Maxwells equations using a Schrodingerisation-based approach.The electromagnetic fields are discr

arXiv:2604.25275v1 Announce Type: new Abstract: We study parameter transferability for the Quantum Approximate Optimization Algorithm (QAOA) across multiple combinatorial optimization problem classes from a parameter generation perspective. Specifically, a meta-optimizer is trained on one problem c

arXiv:2604.25286v1 Announce Type: new Abstract: Discrete time crystals are non-equilibrium phases of matter in periodically driven systems, characterized by robust subharmonic oscillations and broken discrete time-translation symmetry. Their long-lived coherent dynamics and resilience to imperfecti

arXiv:2604.25303v1 Announce Type: new Abstract: Scaling superconducting quantum processors is increasingly constrained by the wiring, heat load, and calibration overhead associated with delivering high-resolution analog signals from room temperature to qubits at millikelvin temperature. Here we dem

arXiv:2604.25311v1 Announce Type: new Abstract: We investigate the role of continuous measurement and postselection in the dynamics and entanglement of a transmon-cavity-transmon coupled system. In the dispersive regime, characterized by a large detuning between the transmons and the cavity, the tw

arXiv:2604.25333v1 Announce Type: new Abstract: We develop a systematic sign-embedding framework of operator-output quantum algorithms for matrix equations and matrix functions. Differing from the contour-integral treatment, we start with the matrix-sign embedding route: an augmented matrix $M$ who

arXiv:2604.25424v1 Announce Type: new Abstract: We formulate a bounded distance decoding strategy applicable to all stabilizer codes including both CSS and non-CSS code-families. The framework emerges out of the local Clifford equivalence between arbitrary stabilizer states and graph states. Using

arXiv:2604.25425v1 Announce Type: new Abstract: We clarified the physical mechanism of superconducting strip single photon detectors (SSPDs) with optical cavities by using transmission line and impedance models. By introducing the transmission line model, we derived the analytical formulae for the

arXiv:2604.25433v1 Announce Type: new Abstract: Minor embedding is a required compilation step for quantum annealing, mapping logical problem graphs onto sparse hardware topologies. Despite its central role in determining solution quality, no standardized benchmark exists for comparing embedding al

arXiv:2604.25480v1 Announce Type: new Abstract: Image classification is a core task of intelligent sensing, conventionally follows a sequential imaging then processing pipeline. However, redundant high-dimensional image reconstruction is inherently inefficient, especially in photon limited scenario

arXiv:2604.25494v1 Announce Type: new Abstract: We study finite-size adiabatic state preparation on Boolean hypercubes using graph-local drivers built from sector/path coordinates related to monotone Gray-code representatives. The construction is not presented as a new all-$n$ Gray-code existence t

arXiv:2604.25503v1 Announce Type: new Abstract: Bent Boolean functions extremal objects that maximally resist affine approximation are notoriously hard to construct for large numbers of variables. We propose a hybrid quantum-classical genetic algorithm (GA) that uses a \emph{quantum circuit}

arXiv:2604.25509v1 Announce Type: new Abstract: Simon's algorithm is a polynomial period-finding algorithm that has been used to exploit the algebraic structure of specific symmetric ciphers, showing that exponential speedups in their cryptanalysis are theoretically possible. While the theoretical

arXiv:2604.25524v1 Announce Type: new Abstract: Defect-adaptive surface-code methods have substantially advanced the construction of valid logical patches on imperfect hardware, but fault-tolerant computation also requires executable logical oper ations on the resulting irregular geometries. We for

arXiv:2604.25531v1 Announce Type: new Abstract: This paper studies quantum optimization baselines for the Generalized Traveling Salesman Problem (GTSP), a clustered routing problem that naturally models variant selection and sequencing problems under discrete alternatives. We propose a novel GTSP Q

arXiv:2604.25532v1 Announce Type: new Abstract: We identify a missing local-refinement stage in the cotengra tensor-network contraction pipeline and show that its impact grows monotonically with bond dimension on the \emph{connectivity graph} of Sycamore-like topologies. Appending a nearest-neighbo

arXiv:2604.25573v1 Announce Type: new Abstract: We study algorithms inspired by quantum annealing that are suited for the NISQ era. First, we analyze approximate quantum annealing (AQA), which employs a discretized annealing ansatz in which the time step and the number of layers are allowed to devi

arXiv:2604.25610v1 Announce Type: new Abstract: Artificial intelligent language-model based coding agents have significantly changed the way we interact with computers in our day-to-day, as it is common to use them to create, improve, and run programming scripts only using natural language. Agent c

arXiv:2604.25613v1 Announce Type: new Abstract: In this paper, we resolve an open question in the field of optimization algorithms for training parametrized quantum circuits: Does the popular Rotosolve algorithm converge? Until now, interpolation-based coordinate descent methods such as Rotosolve h

arXiv:2604.25615v1 Announce Type: new Abstract: Scalable optical quantum technologies require interference between large numbers of indistinguishable single-photons emitted by independent sources. Semiconductor quantum dots are known to be excellent on-demand sources of single-photons. They show re

arXiv:2604.25620v1 Announce Type: new Abstract: The security of quantum key distribution (QKD) systems relies on the physical integrity of their components. While laser-damage attacks (LDAs) using high-power continuous-wave (cw) lasers have been well studied, the threat posed by pulsed lasers at al

arXiv:2604.25631v1 Announce Type: new Abstract: A key bottleneck in quantum machine learning is the computational cost of repeated quantum circuit evaluations during the inference phase. To address this, we present a framework for constructing fast, cheap, provably accurate classical tensor-train s

arXiv:2604.25640v1 Announce Type: new Abstract: We study a random unitary quantum circuit with only reset channels, which has high feasibility for real quantum devices. In particular, we investigate the many-body statistical physics properties, "reset-induced" entanglement phase transitions compari

arXiv:2604.25644v1 Announce Type: new Abstract: Efficient quantum state preparation is a critical component in quantum algorithms that process large classical data, and it is fundamental to realizing quantum advantage in domains such as machine learning, quantum linear algebra, and quantum finance.

arXiv:2604.25660v1 Announce Type: new Abstract: To meet the growing demand for nanoscale surface analysis, nitrogen-vacancy (NV) centers offer a high-sensitivity alternative by leveraging their ability to operate in immediate proximity to the sample. In this work, we propose a quantum control proto

arXiv:2604.25663v1 Announce Type: new Abstract: Entropic uncertainty relations are universal quantifiers of fundamental uncertainties of quantum measurements and are widely discussed in the quantum metrology literature. Quantum memory is a phenomenon related to the specific type of quantum correlat

arXiv:2604.25705v1 Announce Type: new Abstract: We propose a general method to fully characterize a classical stochastic noise process causing qubit dephasing through repetitive Ramsey interferometry measurements (RIMs) on the qubit. Compared to filter-function-based spectroscopy, our method does n

arXiv:2604.25708v1 Announce Type: new Abstract: We compare four polynomial-resource measurement strategies, (I) $Z$-basis-only, (II) nearest-neighbor $ZZ$ (NN), (III) multi-basis ($Z$, $X$, $Y$), and (IV) classical shadows, for classifying three quantum circuit families: IQP, Clifford, and Clifford

arXiv:2604.25715v1 Announce Type: new Abstract: We find the ground-state energy of the Ising model using the Cascaded Variational Quantum Eigensolver (CVQE) algorithm with the Guided-Sampling Ansatz (GSA) using up to 63 qubits on a quantum computer. We study a heavy-hex lattice to match the qubit a

arXiv:2604.25747v1 Announce Type: new Abstract: We explore what the integrated use of quantum spatial distribution (QSD), or more specifically, superposition of both spin and position states of particles, and gauge symmetry (GS) within stabilizer formalism provides for quantum error correction. The

arXiv:2604.25753v1 Announce Type: new Abstract: Two-dimensional spectroscopy (2DS) is a powerful ultrafast technique for probing electronic and vibrational dynamics in complex microscopic systems. Extracting detailed information on system dynamics and system-bath interactions from 2DS experiments r

arXiv:2604.25755v1 Announce Type: new Abstract: SAR image classification naturally has to deal with huge noise and a high dynamic range particularly requiring robust classification models. Additionally, the deployment of these models on edge devices, such as drones and military aircraft, requires a

arXiv:2604.25760v1 Announce Type: new Abstract: The Quantum Approximate Optimization Algorithm (QAOA) follows a single, fixed evolution path, overlooking the potential computational advantage of coherently superposing multiple trajectories. Here we overcome this limitation with a hybrid quantum wal

arXiv:2604.25768v1 Announce Type: new Abstract: Quantum optimal control methods are widely used to design experimental control pulses such as laser amplitudes, phases, or detunings, that implement a target unitary evolution. In practice, what makes a pulse "good" depends not only on its fidelity, b

arXiv:2604.25790v1 Announce Type: new Abstract: As emerging quantum architectures evolve into heterogeneous networks combining different physical substrates, such as qubits for logic and higher-dimensional qudits for robust communication, the traditional scalar metrics of quantum error correction b

arXiv:2604.25801v1 Announce Type: new Abstract: The Nakajima-Zwanzig projected Liouvillian QLQ, the generator of the exact memory kernel in open quantum dynamics, is manifestly non-Hermitian yet has been reported to possess a purely real spectrum in the Jaynes-Cummings model -- an anomaly unexplain

arXiv:2604.25807v1 Announce Type: new Abstract: Universally robust dynamical decoupling (UR$n$) sequences were proposed to compensate pulse imperfections arising from arbitrary experimental parameters while achieving high-order error suppression with only a linear increase in the number of pulses.

arXiv:2604.25825v1 Announce Type: new Abstract: Partial differential equations (PDEs) are fundamental across numerous scientific fields. As these problems scale to high dimensions, classical numerical schemes introduce severe computational bottlenecks, known as the curse of dimensionality. Attempts

arXiv:2604.25854v1 Announce Type: new Abstract: This paper investigates the interplay between the properties of quantum states on the Hilbert space \(\ell_2(\kappa)\) and the set-theoretic nature of the cardinal $\kappa$. We focus on the existence of singular $\sigma$-additive states~ -- function

arXiv:2604.25861v1 Announce Type: new Abstract: The decomposition of complex quantum operations into experimentally feasible gate sets has been a central challenge since the early development of quantum computing. The multi-controlled Toffoli (MCT) gate is a key example, with applications across a

arXiv:2604.25863v1 Announce Type: new Abstract: Distributed Quantum Computing (DQC) and Quantum Error Correction (QEC) rely on dynamic circuits that include Mid-Circuit Measurements (MCMs) and classical feedback. These operations present a major bottleneck: MCMs suffer from high error rates that le

arXiv:2604.25864v1 Announce Type: new Abstract: There is widespread interest in many-body quantum systems that exhibit limit-cycle or time-crystalline behaviour. An ideal quantum limit cycle would be realized using fully coherent driving (to minimize noise) and also have a continuous internal symme

arXiv:2604.25884v1 Announce Type: new Abstract: Quantum computing calibration depends on interpreting experimental data, and calibration plots provide the most universal human-readable representation for this task, yet no systematic evaluation exists of how well vision-language models (VLMs) interp

arXiv:2604.25901v1 Announce Type: new Abstract: Continuous-variable quantum systems are promising candidates for quantum computing and quantum information processing. It is widely known that quadrature measurements on Gaussian continuous-variable systems can be described by a noncontextual hidden-v

arXiv:2604.25910v1 Announce Type: new Abstract: Generation of highly non-classical quantum states of light is essential for optical quantum information processing and quantum metrology. Given the lack of sufficiently strong nonlinear interactions between optical fields, the commonly employed optica

arXiv:2310.12634v1 Announce Type: cross Abstract: The KArlsruhe TRItium Neutrino experiment (KATRIN) aims to determine the effective mass of the electron antineutrino via a high-precision measurement of the tritium beta-decay spectrum in its end-point region. The target neutrino-mass sensitivity of

arXiv:2604.24773v1 Announce Type: cross Abstract: Computational molecular design requires binding arrangements that are not only energetically favorable but also chemically realizable. However, computational methods remain limited in directly recovering fragment pose pairs that can later be connect

arXiv:2604.24774v1 Announce Type: cross Abstract: We propose an orbital angular momentum (OAM) quantum holography scheme based on multi-mode Bessel-Gaussian (MBG) beams. Entangled photon pairs are generated through spontaneous parametric down-conversion (SPDC) process, and the axis prism parameters

arXiv:2604.24803v1 Announce Type: cross Abstract: In low-depth implementations of the Quantum Approximate Optimization Algorithm (QAOA), the dominant cost is often the number of objective evaluations rather than circuit depth. We introduce a graph-conditioned trust-region method for reducing this q

arXiv:2604.24829v1 Announce Type: cross Abstract: The Varenna school is a hub where generations of physicists, including numerous Nobel laureates, have shaped the field, often through collaborative exchanges across political and cultural boundaries. We examine the scientific legacy of Enrico Fermi

arXiv:2604.24847v1 Announce Type: cross Abstract: We classify mobile Pauli stabilizer codes up to gapped interfaces and coarse-graining using the framework of algebraic $\mathrm{L}$-theory. We compare this classification with that of framed TQFTs, theories that arise naturally in the continuum, hig

arXiv:2604.24871v1 Announce Type: cross Abstract: This article discusses incorrect statements appearing in textbooks on quantum field theory (QFT); some of these mistakes also appear in the research literature. The focus is not on errors made by an individual author, but on conceptual muddledness t

arXiv:2604.24889v1 Announce Type: cross Abstract: Dual-species Rydberg atom arrays extend single-species platforms by introducing competing interaction scales and enhanced quantum fluctuations, enabling phenomena beyond homogeneous settings. In this work, we study the ground-state phase diagram of

arXiv:2604.24896v1 Announce Type: cross Abstract: Quantum simulation offers a promising framework for quantum field theory calculations. Obtaining reliable results, however, requires careful characterization of systematic uncertainties. One important source is the boson truncation error, which aris

arXiv:2604.24995v1 Announce Type: cross Abstract: This paper describes the design and implementation of a two-day quantum hackathon for underrepresented high school students in Nova Scotia, Canada. The first day of the hackathon is spent introducing students to quantum computing through hands-on ac

arXiv:2604.25010v1 Announce Type: cross Abstract: Classical optical frameworks such as the discrete dipole approximation (DDA) assume that the linear spectrum of coupled quantum emitters can be computed solely from the linear susceptibilities of individual constituents. However, recent polariton st

arXiv:2604.25097v1 Announce Type: cross Abstract: Electronic band structures and the Fermi energy provide essential information for understanding the electronic properties of solids. In semiconductors, the Fermi energy level is determined by the donor and acceptor concentrations. For diamond, the r

arXiv:2604.25124v1 Announce Type: cross Abstract: To grow the quantum information science and technology workforce, opportunities for students to gain experiential learning and build a sense of belonging in the broader community are essential. The Undergraduate School on Experimental Quantum Inform

arXiv:2604.25193v1 Announce Type: cross Abstract: Inverse design has made vast physical parameter spaces a substrate for emergent behavior. In sensing, the stakes of this principle are sharpest at the analog-to-digital boundary, where any information the hardware fails to capture is information no

arXiv:2604.25248v1 Announce Type: cross Abstract: We investigate the non-equilibrium topology of a periodically driven, dissipative Su-Schrieffer-Heeger chain using the ensemble geometric phase (EGP) $\phi_{\mathrm{EGP}}$-a generalisation of the Zak phase to open quantum systems. In contrast to ear

arXiv:2604.25429v1 Announce Type: cross Abstract: Lattice Boltzmann (LB) on quantum devices must reconcile unitary gate evolution with the dissipative \emph{collision} step. In the multiple-relaxation-time (MRT) class, we work in the common setting of \emph{modewise diagonal} moment relaxation, $\d

arXiv:2604.25475v1 Announce Type: cross Abstract: A K-mirror rotates the wavefront of an incident optical field. However, the rotation always introduces polarization changes in the transmitted field. This is a serious concern for applications ranging from astronomical image derotation to orbital an

arXiv:2604.25752v1 Announce Type: cross Abstract: Nuclear magnetic resonance (NMR) spectroscopy provides unparalleled access to molecular structure and dynamics but is traditionally limited by weak signal strength, requiring large sample volumes and high magnetic fields. Here, we demonstrate nanosc

arXiv:2604.25808v1 Announce Type: cross Abstract: The theory of dynamical diffraction (DD) in perfect crystals is the backbone of high-precision neutron and X-ray diffraction experiments, enabling accurate determination of crystal structure factors and the realization of perfect crystal interferome

arXiv:2604.25883v1 Announce Type: cross Abstract: Optical resonator-enhanced nonlinear interactions are of great importance for the efficient generation of continuous-wave second harmonic generation, optical parametric oscillation, frequency mixing, and the generation of squeezed light. In order to

arXiv:2410.08937v3 Announce Type: replace Abstract: The trade-offs between error probabilities in quantum hypothesis testing are by now well-understood in the centralized setting, but much less is known for distributed settings. Here, we study a distributed binary hypothesis testing problem to infe

arXiv:2411.14434v2 Announce Type: replace Abstract: This work introduces a quantum algorithm for computing the function arcsine, with arbitrary accuracy. We leverage a technique from embedded computing and Field-Programmable Gate Arrays, called COordinate Rotation DIgital Computer (CORDIC). CORDIC

arXiv:2502.18812v4 Announce Type: replace Abstract: Quantum thermal states are known to be passive, as required by the second law of thermodynamics. This paper investigates the potential for work extraction by coupling a thermal bath to a qubit of either spin, fermionic, or topological type, which

arXiv:2505.16444v2 Announce Type: replace Abstract: Quantum Simulation-based Optimization (QuSO) is a recently proposed class of optimization problems that entails industrially relevant problems characterized by cost functions or constraints that depend on summary statistic information about the si

arXiv:2506.16949v4 Announce Type: replace Abstract: In classical physics, events follow a definite causal order: the past influences the future, but not the reverse. Quantum theory, however, permits superpositions of causal orders -- so-called indefinite causal orders -- which can provide operation

arXiv:2506.19461v4 Announce Type: replace Abstract: Quantum machine learning models that leverage quantum circuits as quantum feature maps (QFMs) are recognized for their enhanced expressive power in learning tasks. Such models have demonstrated rigorous end-to-end quantum speedups for specific fam

arXiv:2507.20101v3 Announce Type: replace Abstract: Very recently, Sharoglazova et al. performed an experiment measuring the energy-velocity relationship and Bohmian velocity in coupled waveguides. Their data show a discrepancy between the semi-classical `speed' $v=\sqrt{2|\Delta|/m}$ and Bohmian v

arXiv:2508.02788v3 Announce Type: replace Abstract: Local measurements can radically reshape patterns of many-body entanglement, especially in long-range entangled quantum-critical states. Yet, analytical results addressing the effects of measurements on many-body states remain scarce, and measurem

arXiv:2508.21288v2 Announce Type: replace Abstract: Weighted model counting (WMC) has proven effective at a range of tasks within computer science, physics, and beyond. However, existing approaches for using WMC in quantum physics only target specific problem instances, lacking a general framework

arXiv:2509.01858v4 Announce Type: replace Abstract: We propose and analyze an all-mechanical route to coherent control and quantum-state reconstruction of the fundamental flexural mode of a suspended carbon nanotube (CNT) operated in the anharmonic (Duffing/Kerr). A nearby atomic force microscope (

npj Quantum Information, Published online: 28 April 2026; doi:10.1038/s41534-026-01249-4Scaffold-assisted window junctions for superconducting qubit fabrication

npj Quantum Information, Published online: 24 April 2026; doi:10.1038/s41534-026-01242-xEfficient post-selection for general quantum LDPC Codes

npj Quantum Information, Published online: 24 April 2026; doi:10.1038/s41534-026-01243-wPlacing and routing quantum LDPC codes in multilayer superconducting hardware

npj Quantum Information, Published online: 24 April 2026; doi:10.1038/s41534-026-01248-5Near-term fermionic simulation with subspace noise tailored quantum error mitigation

npj Quantum Information, Published online: 22 April 2026; doi:10.1038/s41534-026-01241-ySurface-code hardware Hamiltonian

npj Quantum Information, Published online: 21 April 2026; doi:10.1038/s41534-026-01247-6Distributed quantum inner product estimation with structured random circuits

npj Quantum Information, Published online: 21 April 2026; doi:10.1038/s41534-026-01221-2Two-qubit gates using on-demand single-photons from ordered shape and size controlled large-volume superradiant quantum dots