Controlling the transport and nature of quantum excitations in low-dimensional systems is a key requirement for scalable quantum devices, including communication networks and quantum simulators. We propose a one-dimensional hybrid quantum lattice model, in which each lattice unit integrates a single-mode resonator that interacts with a two-level system, featuring direct coupling between adjacent two-level systems. This configuration enables the coherent propagation of excitations with tunable atomic, photonic, or polaritonic character. Beyond conventional single excitation transport, we demonstrate that appropriate impedance-matching and resonance conditions allow for the controlled swapping of excitation type as the excitation propagates along the lattice. We analyze the resulting dynamics using local observables and pairwise concurrence to track both transport and quantum correlations. Our results establish a minimal platform for controlled single excitation conversion, with direct relevance to hybrid quantum networks, on-chip quantum interconnects, and engineered quantum simulators.

In this work, we introduce a comprehensive statistical framework for assessing single-qubit quantum teleportation performance beyond the conventional average-fidelity benchmark. First, we derive a closed-form expression for the full probability density function of actual teleportation fidelities and apply it to both classical “measurement-and-prepare” schemes and standard quantum teleportation, considering two relevant noise models: Bell-diagonal resource states and local amplitude-damping channels. The results reveal that protocols with identical average fidelities can exhibit markedly different statistical behaviors, and that relying solely on average fidelity can mask inherent asymmetries introduced by local noise, potentially leading to spurious conclusions about symmetry. Second, we introduce a certification method based on prior importance functions (e.g., beta distributions), which unifies moment-based criteria and threshold-based success probabilities into a single figure of merit. Applying this framework, we see that certifying high-fidelity teleportation requires increasingly stronger entanglement or nonlocality, and we show that the “fighting noise with noise” effect is a feature specific to the first statistical moment (average fidelity), which masks the asymmetric degradation of local marginals, and vanishes for higher-order criteria. Our approach thus provides versatile tools for tailored, application-specific teleportation benchmarks.

Time-bin entanglement is a commonly used form of entanglement for quantum communication protocols over fiber networks, due to the natural resilience of this encoding scheme to thermal phase fluctuations and to birefringence in optical fibers. Projective measurements on some bases in the time-bin encoding need, however, postselection in the time domain of the measured events, introducing a loophole in Bell tests and requiring high temporal resolution. In this work, we demonstrate chip-integrated receivers for time-bin entanglement certification, including a high-speed optical switch to remove the temporal postselection loophole. The receivers are realized using thin-film lithium niobate and operate at a switching frequency of 5 GHz. We demonstrate a Bell inequality violation by more than 24 standard deviations without the need for time resolution at the time-bin separation level.

This article presents the experimental validation of an energy harvesting approach based on stationary solitons in nonlinear metastructures. Building on the theoretical framework introduced in Part I, this work is an experimental investigation of a reduced-order model governed by the disordered damped nonlinear Schrödinger equation (DDNLS). The experimental setup consists of a multiphysics lattice composed of clamped-clamped beams, coupled through magnetic interactions and equipped with piezoelectric transducers, replicating the assumptions underlying the derivation of the DDNLS. The experimental results demonstrate that the DDNLS accurately captures the steady-state space-frequency energy distribution, thereby validating its use as a predictive and design-oriented tool. To further assess the model’s robustness, the influence of disorder and the number of oscillators on soliton stability is investigated, revealing consistent qualitative agreement with theoretical predictions. To the best of the authors’ knowledge, this work constitutes the first experimental investigation of frequency-domain soliton-based energy harvesting in mechanical lattices, establishing a robust and scalable framework for the design of smart metastructures aimed at applications involving vibratory phenomena.

We experimentally realize an angular filter using a microwave network of coaxial cables, guided by the theoretical framework of quantum graphs with beyond-nearest-neighbor coupling. Our setup implements a resonant metamaterial interface that selectively transmits waves only at discrete output directions. The experimental results confirm the presence of angular filtering predicted in quantum graph models. A signal introduced at one side of a finite square lattice network is transmitted through the filter only along certain directional components at specific frequencies. The effect is caused by a resonance-induced switching of boundary conditions at the filter interface. Our findings validate theoretical predictions and demonstrate the practical applicability of graph-based metamaterial concepts in real-world wave systems.

This study introduces a framework for vibrational energy harvesting using stationary solitons as a design guide for nonlinear vibrating metastructures. While previous research primarily focused on propagating solitary waves, the present work investigates localized oscillations enabled by standing solitons, serving as a strategy for vibrational energy management. A mathematical model is developed that is based on the disordered damped nonlinear Schrödinger equation, derived from a multiphysical nonlinear lattice equipped with piezoelectric transducers. The proposed model elucidates the influence of physical parameters on soliton nucleation, providing practical tools for metastructure engineering beyond purely mathematical analyses. Numerical simulations demonstrate that localized vibrational energy can be efficiently harvested by tuning system parameters, including electrical load, coupling stiffness, nonlinearity, and chain stiffness. This work offers a scalable design approach for soliton-based metastructures, paving the way not only for nonlinear energy harvesting but also for sensing technologies. It establishes the theoretical foundations that are experimentally validated elsewhere. The preliminary numerical results demonstrate the predictive capability of the developed models, enabling the application of heuristic optimization strategies in the design of multiphysical nonlinear arrays.

We introduce a protocol that modifies dynamical decoupling (DD) sequences to be robust to static $ZZ$ crosstalk when implemented with bounded control on 2-colorable qubit topologies. The protocol, which relies on modifications of the pulse timing, can be applied to any sequence with equidistant $\pi$ pulses. We motivate the method using suppression conditions identified through time-dependent perturbation theory. Theoretical findings are supported by demonstrations of widely studied sequences on several superconducting qubit devices offered by the IBM Quantum Platform. Using up to 20 qubits on fixed-coupler devices, we observe an at least 3 times improvement in the fidelity decay rate via our approach when compared with nonrobust DD variants. In addition, we leverage our approach to assess the impact of $ZZ$ errors on tunable-coupler devices. We find that $ZZ$-robust sequences perform nearly equivalently to nonrobust DD, affirming the reduced impact of such errors in a tunable-coupler architecture. Nevertheless, our demonstrations indicate that fixed-coupler devices, when subject to DD protection, can outperform tunable-coupler devices. Our method broadens the scope of practical DD protocols: with modest overhead and a reasonable constraint on the qubit topology, the method attains significant performance improvements on modern quantum computing devices.

Layered oxides are regarded as highly promising cathode candidates for sodium-ion batteries (SIBs) due to their high-energy density. However, interlayer migration of dopant ions during the charge-discharge cycle process is widely considered detrimental to phase stability and electrochemical activity. Moreover, the origin of this migration and its link to phase transitions and anionic redox reaction (ARR) activity remain unclear due to the insufficient insight into the underlying thermodynamics and dynamics, thereby restricting further application. Herein, the classic ${\mathrm{Na}}_x{\mathrm{Mn}\mathrm{O}}_2$ cathode is taken as an example. From the perspective of lattice dynamics, we demonstrate that it is the soft vibration mode along the out-of-plane direction that triggers the interlayer migration of substituent $\mathrm{Na}$ from the transition metal (TM) layer to the alkali metal (AM) layer, with a low barrier of 0.11 eV/atom. Furthermore, the resulting stable pinning of substituent $\mathrm{Na}$ within the AM layer would act as a “pillar” to stabilize the P2-type layered structure and then effectively mitigate the P-to-O phase transition caused by interlayer sliding during charging-discharging. Moreover, the ARR activity can be effectively enhanced by elevating the $\mathrm{O}$-2p band centers and adjusting the orbital distribution, which is attributed to the formation of $\mathrm{Mn}$ vacancies following interlayer migration. Finally, it is further confirmed via experimental evaluation that the proposed strategy can greatly improve the electrochemical performance of P2-${\mathrm{Na}}_x{\mathrm{Mn}\mathrm{O}}_2$ due to the enhanced ARR activity and minimized structure changes. This study offers pivotal insights into the underlying physical mechanisms that govern ion interlayer migration and its correlation with ARR activity, thereby facilitating the fundamental design of advanced layered oxide cathode materials for SIBs.

Achieving dynamic control of elastic waves in plate structures is critical for advanced sensing and actuation but typically requires complex external active systems. To overcome this limitation, we propose a passive, dual-focus hybrid metamaterial lens with a continuous-zoom feature. By integrating locally resonant units with aluminum diffraction grating superstrates, the design exploits the differential dispersion sensitivities of these two mechanisms to modulate focal positions via excitation frequency alone. Numerical simulations and experimental validations demonstrate three distinct wavefield states: separating, overlapping, and merging foci. This approach provides a robust solution for adaptive wavefield manipulation in nondestructive evaluation and energy harvesting, eliminating the need for real-time mechanical or electrical reconfiguration.

The development of fault-tolerant quantum computers (FTQCs) is receiving increasing attention within the quantum computing community. Like conventional digital computers, FTQCs, which utilize error correction and millions of physical qubits, have the potential to address some of humanity’s grand challenges. However, accurate estimates of the tangible scale of future FTQCs, based on transparent assumptions, are uncommon. How many physical qubits are necessary to solve a practical problem intractable for classical hardware? What costs arise from distributing quantum computation across multiple machines? This paper presents an architectural model of a potential FTQC based on superconducting qubits, divided into discrete modules and interconnected via coherent links. We employ a resource-estimation framework and software tool to assess the physical resources required to execute specific quantum algorithms compiled into their graph-state form and arranged onto a modular superconducting hardware architecture. Our tool can predict the size, power consumption, and execution time of these algorithms based on explicit assumptions about the physical layout, thermal load, and modular connectivity of the system. We assess the resources needed for quantum computation examples that serve as building blocks of proposed applications, quantifying the architectural bottlenecks and trade-offs that remain to be addressed to deliver utility.

Ferrimagnets, composed of antiferromagnetically coupled magnetic sublattices whose net magnetization can be tuned by temperature, offer a unique platform for probing the symmetry of the spin currents they generate and for identifying the sublattice contributions to these currents. Here, we investigate the spin-current symmetries produced by a $\mathrm{Gd}\mathrm{Fe}\mathrm{Co}$ ferrimagnet at a fixed concentration and across a broad temperature range, including the magnetization-compensation point. Using complementary techniques based on spin-torque ferromagnetic resonance spectroscopy, we separate the contributions of the spin Hall effect (SHE) and the spin anomalous Hall effect (SAHE). We show that the torques arising from both mechanisms retain their sign across the magnetization-compensation temperature, and that the SAHE-driven damping-like torque has the opposite sign to the SHE-driven term. We suggest that both effects originate from distinct electronic subsystems: the SHE emerging from $\mathrm{Gd}$ $5d$ electrons, and the SAHE from $\mathrm{Fe}\mathrm{Co}$ $3d$ electrons. Consequently, the SHE sign remains insensitive to the magnetization state, whereas the SAHE sign does not invert at compensation, reproducing our observations. Together, these insights clarify the interplay between sublattices in ferrimagnetic spin transport and highlight the potential of ferrimagnetic spin currents to generate spin torques in adjacent layers or within the ferrimagnet itself.

Heterodyne interferometry for precision science often comes with an optical phase modulation, for example, for intersatellite clock noise transfer for gravitational-wave (GW) detectors in space, exemplified by the Laser Interferometer Space Antenna (LISA). The phase modulation potentially causes various noise couplings to the final phase extraction of heterodyne beatnotes by a phasemeter. In this paper, in the format of space-based GW detectors, we establish an analytical framework to systematically search for the coupling of various noises from the heterodyne and modulation frequency bands, which are relatively unexplored so far. In addition to the noise caused by the phase modulation, the high-frequency laser phase noise is also discussed in the same framework. The analytical result is also compared with a numerical experiment to confirm that our framework successfully captures the major noise couplings. We also demonstrate a use case of this study by taking the LISA-like parameters as an example, which enables us to derive requirements on the level of the laser and phase-modulation noises in the high-frequency regimes.

Piezoelectric phononic integrated circuits (PnICs), chip-scale platforms in which GHz frequency acoustic fields are routed in µm-scale waveguide geometries, have steadily advanced in performance and complexity, providing new degrees of freedom for manipulating microwave signals. Here, we consider the use of PnICs for implementing on-chip microwave interferometers ($f=3.4\mathrm{GHz}$) using a gallium nitride ($\mathrm{Ga}\mathrm{N}$) on silicon carbide ($\mathrm{Si}\mathrm{C}$) PnIC platform. We demonstrate controlled mode amplitude splitting, differential control (local phase shift), and mode recombination in an unbalanced ($\mathrm{\Delta }L=1.6\mathrm{mm}$) phononic Mach-Zehnder interferometer (MZI), achieving a maximum fringe visibility $>0.985$. The high visibility does not imply high sensitivity due to the presence of parasitic acoustic modes in the MZI. We quantify the effect of these parasitic guided modes in the interferometer, and discuss potential design improvements for achieving quasi-single-mode operation in PnICs, with a view toward enabling applications in microwave and acoustic signal processing and sensing.

We have designed, fabricated, and characterized microwave resonators made of granular-aluminum thin films with different oxygen content. The kinetic inductance fraction of these disordered superconductors was determined by electromagnetic finite-element simulations, conformal mapping techniques, and the frequency shift of the resonators with temperature. We compare these methods to assess model-dependent variations and to highlight their main limitations. This analysis aims to guide the community in choosing the most suitable method for designing kinetic inductance detectors, high -mpedance resonators, and superinductors. Additionally, we measured the internal quality factor as a function of microwave power at low temperature to characterize losses, which we identify as arising from two-level systems.

We theoretically propose a symmetric encryption scheme based on restricted Boltzmann machines that functions as a probabilistic Enigma device, encoding information in the marginal distributions of visible states while using bias permutations as cryptographic keys. Theoretical analysis demonstrates proven resistance against differential attacks through distribution-based encoding and computational complexity rooted in #P-hard partition function evaluation. Compatible with probabilistic computing hardware, the scheme establishes a physical-computational asymmetry where legitimate users can efficiently, the ciphertext, while adversaries face exponential-time complexity. Unlike conventional symmetric ciphers on digital computers that collapse immediately upon key exposure, this asymmetry preserves time-limited security even with fully exposed keys. This framework unlocks the potential of probabilistic computers for cryptographic systems, offering an emerging encryption paradigm between classical and quantum regimes for postquantum security.

We propose a neural-network-based model capable of learning the broad landscape of working regimes in quantum dot simulators and using this knowledge to autotune these devices—based on transport measurements—toward obtaining Majorana modes in the structure. The model is trained in an unsupervised manner on synthetic data in the form of conductance maps, using a physics-informed loss that incorporates key properties of Majorana zero modes. We show that, with appropriate training, a deep vision-transformer network can efficiently memorize the relations between Hamiltonian parameters and structures on conductance maps and use them to propose parameter updates for a quantum dot chain that drives the system toward a topological phase. Starting from a broad range of initial detunings in parameter space, a single update step is sufficient to generate nontrivial zero modes. Moreover, by enabling an iterative tuning procedure—where the system acquires updated conductance maps at each step—we demonstrate that the method can address a much larger region of the parameter space.

Transmission peak degeneracies (TPDs) have emerged as a promising alternative to exceptional points (EPs) for non-Hermitian sensing, providing square-root frequency splitting without the eigenbasis collapse and associated noise amplification that limit EP sensors. However, existing treatments of TPDs remain fragmented, lacking a unified theoretical framework, systematic figures of merit, or design principles for practical implementation. Here, we develop a comprehensive theory of two-dimensional TPDs that clarifies their relationship to EPs, maps their locations in parameter space, and provides analytic figures of merit for sensor design. We validate our theory using a tunable cavity-magnonics platform with in situ control of mode frequency, dissipation, and complex coupling via an effective synthetic gauge field. Our platform enables systematic exploration of six representative EP-TPD configurations spanning $\mathcal{P}\mathcal{T}$-symmetric, anti-$\mathcal{P}\mathcal{T}$-symmetric and anyonic-$\mathcal{P}\mathcal{T}$-symmetric regimes. Crucially, we show that TPDs, unlike EPs, can retain square-root splitting even under nuisance parameter drift through generalized transmission extrema degeneracies (TEDs). We further identify specific robust TPD configurations that minimize the impact of nuisance drift. These findings establish a unified theoretical and experimental framework for TPD-based non-Hermitian sensing.

Space-borne gravitational-wave detectors suppress overwhelming laser phase noise by recombining time-delayed heterodyne beatnote phases via time-delay interferometry (TDI). Simultaneously, TDI reshapes secondary noises in the phase, quantified through frequency-domain transfer functions. The dynamic orbits of the detectors modulate secondary noise by affecting arm-length variations, which couples into these transfer functions. We propose using a Fourier series to parameterize arm lengths. This yields an analytical method for calculating noise-transfer functions applicable to dynamic configurations for arbitrary TDI combinations. Using this method, we analyze three kinds of TDI combinations. For some TDI combinations, the secondary noise-transfer functions remain identical under both static equal-arm and dynamic triangular configuration assumptions. However, for zero-response combinations, the static equal-arm configuration assumption renders their secondary noise-transfer functions to zero. Thus, the transfer functions must be defined under dynamic triangular configuration conditions. For the $T[X,Y,Z]$ channel, the secondary noise-transfer function under the static equal-arm triangular configuration assumption is about 2 orders of magnitude lower than under dynamic triangular configuration assumptions. The proposed calculation method, being better aligned with realistic detector constellations, enables precise analytical expressions of secondary noise-transfer functions to be delivered for space-borne gravitational-wave detection data processing.