The open-circuit voltage ($V_{\mathrm{oc}}$) of $\mathrm{Cd}(\mathrm{Se},\mathrm{Te})$ solar cells has stalled near 900 mV, limiting further efficiency gains despite state-of-the-art devices achieving 23.1%. As a critical step in overcoming this barrier, we report here a physics-based device model that explicitly integrates defect interactions with potential fluctuation effects to explain this long-standing limitation. By coupling first-principles defect calculations with device-level simulations, we show that voltage deficits in $\mathrm{As}$-doped $\mathrm{Cd}(\mathrm{Se},\mathrm{Te})$ are governed primarily by two mechanisms: bandgap fluctuations and electrostatic disorder induced by low dopant activation (2–4%). The combined effects of bandgap and electrostatic fluctuations contributes 90–130 mV $V_{\mathrm{oc}}$ loss for associated Urbach energy of 27–30 meV, whereas the effect of spatial variations in defect transition energies is found to be small. These results identify viable pathways for breaking the 900 mV barrier, namely enhancing dopant activation and reducing alloy disorder. More broadly, the modeling framework established here provides the transferable approach to quantitatively connect defect interactions and real-space disorder with device performance, offering guidance for other polycrystalline thin-film semiconductors with band tails.

A robust definition of quantum run time is essential for assessing the performance of quantum algorithms and claims of quantum advantage. While for most classical hardware the total run time is well approximated by computation plus a weakly varying constant, on current quantum hardware a clean experimental separation between “pure computation” and “overhead” is often not justified. Consequently, conventional quantum run-time analyses that exclude substantial system-level overheads (e.g., readout, transpilation, thermalization) can lead to biased performance assessments. In this work we introduce experimentally grounded, end-to-end definitions of quantum run-time for both digital and analog quantum computers, together with a methodology for selecting strong classical baselines for quantum-classical run-time comparisons. Within this framework, we evaluate recent claims of quantum advantage in annealing- and gate-based algorithms. We examine three representative case studies. First, we revisit quantum annealing for approximate quadratic unconstrained binary optimization problems [Phys. Rev. Lett. 134, 160601 (2025)], which employs a well-motivated time-to-epsilon metric but effectively uses annealing time as a proxy for run time. Second, we analyze a restricted implementation of Simon’s problem [Phys. Rev. X 15, 021082 (2025)], where the favorable scaling in oracle calls is undisputed; however, we show that the estimated wall-clock run time of the quantum demonstration is approximately two orders of magnitude slower than a tuned classical baseline at the tested sizes. Finally, we find that the recently reported run-time advantage of the bias-field digitized counterdiabatic quantum optimization hybrid algorithm (arXiv:2505.08663) is not observed under more comprehensive benchmarking. Therefore, on current NISQ hardware, run-time-based quantum advantage has not yet been demonstrated under experimentally grounded performance metrics, and credible claims require careful time accounting, appropriate performance measures, and properly chosen classical reference implementations, as discussed in this work.

Memory, understood as time nonlocality, is a fundamental nonequilibrium feature that can arise in physical systems, whether classical or quantum, and it has important applications in a wide variety of technologies. In the context of quantum technologies, systems with memory can be used in quantum information, communication, and sensing. Here, we demonstrate that a cavity optomechanical system driven by a pulsed laser can operate as a programmable quantum memory element. By engineering the adiabatic and nonadiabatic pulses, particularly the Gaussian and sinusoidal drives, we induce and control diverse memory phenomena such as dynamical hysteresis, quantized phononic transitions, and distinct energy-storing responses. Within a mean-field approach, we derive the analytical and numerical criteria under which the photonic and phononic observables manifest memory effects in strongly driven regimes. These memory effects are quantified through a dimensionless geometric form factor, which provides a versatile metric to characterize the memory efficiency. Our protocol is readily compatible with current optomechanical platforms, highlighting its potential for advanced memory functionalities in quantum technologies.

Scattering exceptional points (EPs) in non-Hermitian metasurfaces present significant opportunities for asymmetric wave modulation, while traditional approaches rely on the precise engineering of material losses within metasurfaces. Here, we overcome this limitation by engineering the radiation loss in a lossless optical system and introduce the concept of virtual scattering EPs, which exhibit singularity characteristics analogous to those of traditional EPs. By leveraging both broken angular symmetry of a single-layer structure and momentum compensation inherent in its bilayer configuration, we propose an all-dielectric bilayer metasurface that manifests the virtual EP. In this configuration, incident waves from one side experience perfect retroreflection, while waves from the opposite side undergo complete disappearance of reflection. Furthermore, this unique architecture supports an interlayer resonance mechanism that facilitates the transition of the reflective subsystem from a non-Hermitian to a Hermitian state, enabling a dynamic switch between angularly asymmetric and symmetric retroreflections. Our findings open different avenues for realizing scattering EPs and exploring unique non-Hermitian physics, offering exciting prospects for multifunctional and reconfigurable optical devices.

We experimentally demonstrate a differential microscopy methodology that facilitates simultaneous amplitude, phase, and differential polarization imaging. The proposed optical spatial differentiator is obtained in a remarkably simple setup by placing a glass cover slip, acting as a signum phase mask in the Fourier plane of a standard $4f$ imaging arrangement. Unlike conventional approaches, the scheme operates without polarized illumination, thereby enabling polarization to serve as an additional contrast within the framework of differential imaging, which facilitates concurrent probing of the phase and polarization gradient information throughout an object. Moreover, the proposed scheme is fully adapted to standard high-resolution microscopy and functions efficiently across a broad wavelength range. The demonstrated simple, low-cost, multifunctional optical spatial differentiator can be easily integrated with conventional bright-field microscopes. It is expected to impact the future of label-free microscopy and optical image-processing techniques, with potential applications in biomedical research, materials science, and several other disciplines.

We probe the motion of a 6-$\text{μ}\mathrm{g}$ magnetically levitated superconducting microsphere using optical interferometry at $3\mathrm{K}$, achieving a resolution of the order of $1\mathrm{nm}/\sqrt{\mathrm{Hz}}$, and use the measured signal to feedback-cool its motion. The resolution exceeds the shot-noise limit of $11\mathrm{pm}/\sqrt{\mathrm{Hz}}$ primarily due to technical noise arising from the roughness of the particle, in combination with its free rotation. These measurements demonstrate that the combination of interferometric optical readout and superconducting magnetic levitation, together with established techniques of cavity optomechanics, provides all the ingredients required for quantum physics experiments with microgram masses.

The recent proposal of altermagnetism has drawn widespread attention to antiferromagnets exhibiting spin splitting, extending beyond the realm of sign-alternating spin splitting in momentum space protected solely by rotational symmetry. Herein, we propose a shear-strain strategy that enables significant modulation of a d-wave altermagnet into a compensated nonaltermagnet. A comprehensive analysis combining the magnetic moment compensation characteristics of opposite-spin sublattices with the distribution of spin-resolved conduction channels in momentum space under the (001) crystal orientation reveals that shear strain breaks the rotational symmetry of the altermagnet. To explore the application potential of compensated nonaltermagnet, we designed ${\mathrm{Ru}\mathrm{O}}_2/{\mathrm{Ti}\mathrm{O}}_2/{\mathrm{Ru}\mathrm{O}}_2$ magnetic tunnel junctions with three crystallographic orientations [(001), (110), (100)] and investigated their transport properties under shear strain. This nonalter electronic structure not only enhances the tunneling magnetoresistance (TMR) in spin-split paths of intrinsic ${\mathrm{Ru}\mathrm{O}}_2$ (226% to 431%) but also enables substantial TMR in spin-degenerate paths (from 0% to 88%). Our work provides guidelines for alternative magnetic materials and device platforms.

Yttrium iron garnet (YIG) is known for its extremely low magnetic damping, making it a key material for magnon-based spintronic devices. Although perpendicular magnetic anisotropy (PMA) has been reported in rare-earth-substituted or $\mathrm{Bi}$-doped YIG thin films, its realization in pure YIG remains limited. In this work, we demonstrate that YIG thin films grown on the substituted gadolinium gallium garnet substrates exhibit PMA and a low damping constant. X-ray diffraction measurements revealed an in-plane tensile strain relative to bulk YIG, suggesting that the strain-induced lattice distortion plays an important role in the emergence of PMA. Spin-wave propagation with a forward-volume configuration is investigated using two separated coplanar waveguides and a network analyzer. The measured propagating spin-wave spectra show a coherent propagation over several micrometers with a group velocity of approximately 0.2 km/s. Furthermore, in a heterostructure with a heavy metal layer of Pt, current-induced spin-orbit torque successfully switches the perpendicular magnetization. These results establish sputter-deposited YIG thin films with perpendicular magnetization as a promising platform for studying low-damping spin-wave transport and current-driven magnetization dynamics.

The dc offset voltage in Hall-effect magnetic sensors is a critical factor limiting the precision of low-strength magnetic field detection, yet its behavior in graphene Hall-effect sensors (GHSs) remains underexplored beyond simplistic models such as the lumped-element Wheatstone bridge. This study presents the first comprehensive investigation of offset voltage in GHSs by incorporating physics-based analytical models into a commercial finite-element-method solver through the magnetoconductivity tensor, and the analysis is further supported by the electrical characterization of fabricated local back-gated GHS (LBG-GHS) devices. Using this framework, we perform a systematic exploration of lithographic imperfections, biasing conditions, spatial channel disorders, and structural defects affecting the offset value. A comprehensive electrical evaluation is performed on 25 LBG-GHS devices for a statistical analysis, revealing variable offset voltage patterns that show soft odd-even symmetries and comparable device resistance trends with respect to the LBG variations. Through simulation and experimental correlation, we develop a physical interpretation of this observed soft odd-even symmetry in offset voltage, attributing it to spatial variations in charge carriers. Kelvin probe force microscopy measurement on a large-area ($40\times 35\text{μ}{\mathrm{m}}^2$) LBG-GHS device is taken to map local residual carrier variations. These measured and spatially low-pass-filtered carrier profiles are incorporated into the simulations to observe the transition from soft odd to soft even symmetry in offset voltage. Our findings demonstrate that current biasing is more effective in managing offset voltage in GHSs, providing critical insights into the optimization of graphene-based magnetic sensors for high-precision applications.

Atomically thin semiconducting transition metal dichalcogenides (TMDs) offer tunable optoelectronic properties, making them prime candidates for next-generation electronic and photonic devices. A key challenge is understanding how their electronic structure evolves with thickness, a crucial step toward optimizing device performance. Here, we investigate the layer-dependent work function of $2H$-${\mathrm{Mo}\mathrm{Te}}_2$ nanoflakes using Kelvin probe force microscopy and first-principles calculations down to the monolayer limit. Contrary to earlier theoretical predictions, we experimentally observe a monotonic increase in work function, from 4.73 eV in the bulk to 4.92 eV in the monolayer. This trend correlates with the change in electronic structures below 5 nm, while, beyond this regime, dielectric screening dominates, as captured by nonlinear Thomas-Fermi theory. Our analysis identifies strong out-of-plane interlayer hopping ($t_{\perp }\simeq 0.214\mathrm{eV}$) as a key contributor to the screening behavior. These results reconcile experimental observations with theoretical models, revealing the interplay of quantum confinement and electrostatic screening. These findings provide practical guidance for tailoring band alignment and charge transport in two-dimensional (2D) TMD-based optoelectronic devices.

The negatively charged tin-vacancy center in diamond (${\mathrm{Sn}\mathrm{V}}^{-}$) is an excellent solid-state qubit with optically addressable transitions and a long electron spin-coherence time at elevated temperatures (approximately 1.7 K). However, implementing scalable quantum nodes with high-fidelity optical readout of the electron spin state requires efficient photon emission and collection from the system. In this manuscript, we report a quantum photonic interface for ${\mathrm{Sn}\mathrm{V}}^{-}$ centers based on one-dimensional photonic crystal cavities fabricated in diamond thin films. Furthermore, we provide a rigorous description of the spontaneous emission dynamics of our system, taking into account individual contributions from both the C and D transitions of the emitter. This allows for the determination of Purcell factors per transition and, by extension, the C/D branching ratio ${\mathrm{Sn}\mathrm{V}}^{-}$ zero-phonon line. We observe quality factors of up to approximately 6000 across this sample, and we measure up to a 12-fold lifetime reduction, which translates into a Purcell factor of $F_{\mathrm{C}}=26.2\pm 1.5$ for a targeted C transition. By considering the cavity-mode polarization alignment with the C- and D-transition dipole moments, we validate the C/D branching ratio to be ${\eta }_{\mathrm{BR}}=0.75\pm 0.01$, in line with previous theoretical and experimental findings.

Magnetic flux trapping is a significant hurdle limiting the reliability and scalability of superconducting electronics, yet tools for imaging flux vortices remain slow or insensitive. We present a cryogenic widefield N-V diamond magnetic microscope capable of rapid, micrometer-scale imaging of flux trapping in superconducting devices. Using this technique, we measure vortex expulsion fields in $\mathrm{Nb}$ thin films and patterned strips, revealing a crossover in expulsion behavior between 10- and 20-$\text{μ}\mathrm{m}$ strip widths. The observed scaling agrees with theoretical models and suggests the influence of film defects on vortex expulsion dynamics. This instrument enables high-throughput magnetic characterization of superconducting materials and circuits, providing new insight for flux mitigation strategies in scalable superconducting electronics.

The fluxonium qubit has emerged as a promising candidate for superconducting quantum computing due to its long coherence times and high-fidelity gates. Nonetheless, further scaling up and improving performance remain critical challenges for establishing fluxoniums as a viable alternative to transmons. A key obstacle lies in developing scalable coupling architectures. In this work, we introduce a scalable fluxonium architecture that enables decoupling of qubit states while maintaining tunable couplings between noncomputational states. Beyond the well-studied $ZZ$ crosstalk, we identify that always-on interactions involving noncomputational levels can significantly degrade the gate fidelities in large systems, thereby impeding scalability. Based on two possible physical realizations of the architecture, we demonstrate that the issue can be mitigated by implementing tunable couplings for fluxonium plasmon transitions, meanwhile enabling fast, high-fidelity gates with passive $ZZ$ suppression. This comparative analysis enables us to establish general principles for realizing the architecture while understanding and addressing implementation-specific challenges.

We develop an analytic framework to extract circuit parameters and loss tangent from superconducting transmission-line resonators terminated by reactive loads, extending analysis beyond the perturbative regime. The formulation yields closed-form relations between resonant frequency, participation ratio, and internal quality factor, removing the need for full-wave simulations. We validate the framework through circuit simulations, finite-element modeling, and experimental measurements of van der Waals parallel-plate capacitors, using it to extract the dielectric constant and loss tangent of hexagonal boron nitride. Statistical analysis across multiple reference resonators, together with multimode self-calibration, demonstrates consistent and reproducible extraction of both capacitance and loss tangent in close agreement with literature values. In addition to parameter extraction, the analytic relations provide practical design guidelines for maximizing the energy-participation ratio in the load and improving the precision of resonator-based material metrology.

This study introduces a methodology to extract multiwork function distributions directly from thermally emitted electron distribution (ThEED) data, addressing the limitations of traditional Richardson–Laue–Dushman methods for heterogeneous thermal emission cathodes. This approach involves deconvolving measured thermally emitted electron distributions with an instrument response function (derived from a homogeneous sample) and then applying a steepest-descent algorithm to determine the relative contributions of various work functions, while also considering the impact of external electrostatic fields on patch field effects. The methodology is validated using single-phase Mayenite $[{\mathrm{Ca}}_{24}{\mathrm{Al}}_{28}{\mathrm{O}}_{64}{]}^{4+}(4{\mathrm{e}}^{-})$, an electride material with spatially varying work functions, by comparing the predicted distributions with photoemission electron microscopy (PEEM) work function maps and Monte Carlo simulations. The results demonstrate excellent agreement between the predicted and measured work function distributions, highlighting the method’s accuracy in resolving surface heterogeneity. Furthermore, the technique is successfully applied to ThEED data taken at a characterized surface location, showing promise for analyzing complex emission patterns in thermal emission cathodes. This methodology eliminates the need for complementary, potentially spatially mismatched, surface characterization techniques, offering a powerful tool for understanding and designing advanced thermal emitters.

Quantum random-access memory (QRAM) is a critical primitive for quantum algorithms that require data lookup in superposition, but its lack of fault tolerance poses a major obstacle to practical deployment. Error filtration (EF) has been proposed as a hardware-efficient alternative to error correction, capable of suppressing incoherent noise without encoding overhead. However, its performance in realistic QRAM systems with moderate fidelity has remained unclear, as existing analyses rely on asymptotic approximations and numerical simulations have been limited to small sizes. We address this gap using an alternative simulator for bucket-brigade (BB) QRAM that combines sparse state encoding with a noise-aware pruning algorithm. This framework provides full quantum state access and scales efficiently, enabling us to probe EF performance in size and noise regimes far beyond previous studies. Our simulations reveal suppression anomalies at high noise levels or large address sizes, where postselection probability fundamentally constrains EF scaling. Incorporating this effect, we refine EF theory to provide conditional criteria that link the base infidelity to the achievable suppression, thereby delineating the regime in which EF yields progressive improvement. Beyond refining EF, we quantitatively characterize the runtime and memory costs of our noisy BB QRAM simulator, achieving simulations of systems with 20 layers using less than 1 GB of memory. This efficiency is what enables us to probe parameter regimes beyond previous work and to establish the simulator as a practical, “fine-print” analysis tool for assessing QRAM as a quantum resource.

The measurement-based architecture is a paradigm of quantum computing, relying on the entanglement of a cluster of qubits and the measurements of a subset of it, conditioning the state of the unmeasured output qubits. While methods to map the gate model circuits into the measurement-based are already available via intermediate steps, we introduce a paradigm for quantum compiling directly converting any quantum circuit to a class of graph states, independently from its size. This method relies on the stabilizer formalism to describe the register of the input qubits. An equivalence class between graph states able to implement the same circuit is defined, giving rise to a gauge freedom when compiling in the MBQC frame. The graph state can be rebuilt from the circuit and the input by employing a set of graphical rules. A system of equations describes the overall process. Compared with measurement calculus, the ancillary qubits are reduced by 50% on the quantum Fourier transform and 75% on the Quantum Approximate Optimization Algorithm, still preserving similar scaling laws for the number of entangling gates.

We systematically study the linewidths of multilevel exciton-polariton modes as a function of the detuning in a planar hybrid microcavity (MC) with low quality factor (Q ∼ 300) operating in the linear optical response regime. Using optical reflectivity, we observe that, counterintuitively, the linewidths of the polariton modes undergo a pronounced spectral narrowing as detuning is reduced. By benchmarking the experimental results against three commonly used constant-loss theoretical descriptions, we find that this behavior is only partially reproduced, highlighting limitations of conventional strong-coupling models when applied to nonstandard MC architectures. Our results suggest that frequency-dependent self-energy effects or correlated dissipation mechanisms, typically neglected in simplified treatments, may play an important role. These observations indicate that strong light-matter coupling with narrow polariton lines can be achieved in hybrid low-Q MCs through appropriate loss engineering, providing an alternative design pathway complementary to conventional high-Q approaches.

Gate-tunable Josephson junctions with molybdenum superconducting contacts are reported. The Josephson field-effect transistors are based on an $(\mathrm{In},\mathrm{Ga})\mathrm{As}$ quantum well heterostructure with $\mathrm{Mo}$ contacts deposited on a layer of heavily doped $(\mathrm{In},\mathrm{Ga})\mathrm{As}$ by $\mathrm{HCl}$ cleaning and sputtering. We reproduced the measured data using a quasiballistic model that captures the gate dependence of the critical current and considers contributions from both Andreev states in the discrete spectrum and leaky states in the continuous spectrum. We report the observation of multiple Andreev reflections (MARs) up to the fourth order, and the measured temperature dependence of the MAR features is consistent with a model describing an effective induced superconducting gap beneath the contacts, approximately 55% of the gap in the $\mathrm{Mo}$. The transistors are integrated into an rf-compatible geometry with ${\mathrm{Si}}_3{\mathrm{N}}_4$ spacers, enabling future implementation of highly scaled, compact, quantum-limited cryogenic amplifiers.