Entanglement enables many promising applications in quantum technology. Devising alternative generation methods and harnessing entanglement are prerequisites for practical applications. Here, we realize a distinct polarization-entangled source by simultaneously achieving type-0 and type-I backward quasiphase matching (BQPM) through spontaneous parametric down-conversion in a single bulk crystal, which is different from all previous entangled-source configurations. Pumping the crystal with a single polarized beam generates a nonmaximally polarization-entangled state, which can be further projected to a maximal Bell state with a pair of Brewster windows. Hong-Ou-Mandel interference experiments are done on polarization-degenerate photon pairs for both type-0 and type-I BQPM processes for the first time. The emitted photons in both processes have a bandwidth as narrow as 15.7 GHz. The high quality of this source is characterized by various methods. The rather simple configuration, narrow bandwidth, and high entanglement quality make the source very promising for many quantum information tasks.

The electromechanical coupling effect holds great promise in various applications, such as actuators and artificial muscles. In this study, using first-principles calculations, we demonstrate this effect in a two-dimensional (2D) buckled honeycomb configuration of lead oxide ($h\text{−}\mathrm{Pb}\mathrm{O}$). The $h\text{−}\mathrm{Pb}\mathrm{O}$ monolayer exhibits robust 2D ferroelectric polarization of about 28 pC/m along the out-of-plane direction, owing to the buckled configuration, which lifts the mirror symmetry. The direction of electric polarization can be reversed by overcoming a moderate energy barrier of about 240 meV/unit cell, and the Curie temperature is evaluated to be up to 440 K. Interestingly, the distinct hybridization of $\mathrm{O}$ and $\mathrm{Pb}$ atoms leads to self-bending of the $h\text{−}\mathrm{Pb}\mathrm{O}$ monolayer with an optimal curvature (1/R) of about 0.46 Å${}^{-1}$, exhibiting strong coupling with the electric polarization. As the direction of electric polarization is reversed, the bending of the $h\text{−}\mathrm{Pb}\mathrm{O}$ monolayer will also be reversed. With the increase of the curvature, the energy required to reverse the electric polarization direction decreases. The electrobending effect in this $h\text{−}\mathrm{Pb}\mathrm{O}$ monolayer renders a promising strategy to regulate the mechanical and electronic properties and the interplay between them and thereby concepts for nanoscale actuator devices.

This errata corrects some typographical errors and adds some relevant details that were missing in the the paper [J. Bentley, H. I Nurdin, Y. Chen, X. Li and H. Miao, “Designing optimal linear detectors—a bottom-up approach,” Phys. Rev. Applied 19, 034009 (2023)].

We developed an inductive energy participation ratio (IEPR) method and a streamlined procedure for simulating and verifying superconducting quantum chips. These advancements are increasingly vital in the context of large-scale, fault-tolerant quantum computing. Our approach efficiently extracts the key linear and nonlinear characteristic parameters, as well as the Hamiltonian of a quantum chip layout. In theory, the IEPR method provides insights into the relationship between energy distribution and representation transformation. We demonstrate its practicality by applying it to quantum chip layouts, efficiently obtaining crucial characteristic parameters in both bare and normal representations—an endeavor that challenges existing methods. Our work holds the promise of significant enhancements in simulation and verification techniques and represents a pivotal step towards quantum electronic design automation.

Super Klein tunneling is one of the intriguing phenomena found in spin-1 systems and has aroused many research interests due to its extraordinary transport properties. Compared with the traditional Klein tunneling occurring under normal incidence, super Klein tunneling releases the restriction to omnidirectional total transmission around the center of the energy or frequency barrier. Here, we observe super Klein tunneling in a heterojunction of a phononic Lieb lattice, where a single pseudospin-1 Dirac cone is located at the corner of the square Brillouin zone and consists of two linear crossed bands accompanied by an extra flat band. Airborne sound experiments evidence the near-perfect transmissions around the center of the frequency barrier for a wide range of incident angles. Our macroscopic acoustic system with a pseudospin-1 Dirac cone provides an ideal platform to explore the physics and applications related to super Klein tunneling.

Self-accelerating acoustic beams (SABs) are capable of transporting particles directionally and transmitting acoustic signals and energy along curved paths. However, the majority of prior SABs have only been able to deflect within a two-dimensional plane, with lateral acceleration impacted by the operating frequency and transverse plane size of the sound source. Here, we are committed to using designed acoustic artificial structure plates to achieve self-accelerating beams with three-dimensional (3D) helical trajectories, also known as acoustic radial self-accelerating beams. To manipulate the shape of the main lobe of a 3D self-accelerating beam, we introduce the notion of asymmetric Bessel into radial self-accelerating beams, resulting in the successful derivation of analytical expressions for acoustic radial self-accelerating asymmetric Bessel beams (RS-ABBs) propagating in free space. An artificial plate structure, engraved with Archimedean-spiral slits, is designed to produce acoustic RS-ABBs in reality. Finally, the numerical and experimental measurements of acoustic intensity field distributions for the generated acoustic RS-ABBs are demonstrated. The study outlined here can greatly benefit the development of techniques in acoustic particle manipulation, and can also offer inspiration for distance measurement, acoustic sensing, and acoustic communication.

In this paper, we discuss the possibility of achieving tunable topologically protected edge modes through the application of uniaxial prestrain in an auxetic metamaterial. The proposed structure consists of a thin slab with oriented cuts in a hexagonal lattice, where topologically protected band gaps are opened by introducing a controlled variation in selected cut lengths. Numerical simulations demonstrate the existence of topologically protected and scatter-free wave propagation in the structure at the interface between two subdomains with modified cells, in distinct frequency ranges. For the metamaterial considered in this study, this happens only in the presence of auxeticity. In addition, exploiting geometrical nonlinearity, the application of a uniaxial prestrain can be used to close the band gaps or to modify their frequency range, i.e., to weaken the localization effects or to shift the frequency at which they occur. The spatial and temporal variation of the applied strain field can thus be used for the dynamic tuning of metamaterial topological waveguiding properties, with applications in mechanical devices for logic operations and computation.

Quantum annealing is a quantum algorithm for computing solutions to combinatorial optimization problems. This study proposes a method for minor embedding optimization problems onto sparse quantum annealing hardware graphs called 4-clique network minor embedding. This method is in contrast to the standard minor embedding technique of using a path of linearly connected qubits in order to represent a logical variable state. The 4-clique minor embedding is possible on Pegasus graph connectivity, which is the native hardware graph for some of the current D-Wave quantum annealers. The Pegasus hardware graph contains many cliques of size 4, making it possible to form a graph composed entirely of paths of connected 4-cliques on which a problem can be minor-embedded. The 4-clique chains come at the cost of additional qubit usage on the hardware graph, but they allow for stronger coupling within each chain, thereby increasing chain integrity, reducing chain breaks, and allow for greater usage of the available energy scale for programming logical problem coefficients on current quantum annealers. The 4-clique minor embedding technique is compared with the standard linear path minor embedding with experiments on two D-Wave quantum annealing processors with Pegasus hardware graphs. We show proof-of-concept experiments where the 4-clique minor embeddings can use weak chain strengths while successfully carrying out the computation of minimizing random all-to-all spin glass problem instances.

High-fidelity singlet-triplet state readout is essential for large-scale quantum computing. However, the widely used threshold method of comparing a mean value with the fixed threshold will limit the judgment accuracy, especially for the relaxed triplet state, under the restriction of relaxation time and signal-to-noise ratio. Here, we achieve an enhanced latching readout based on Pauli spin blockade in a Si-MOS double quantum dot device and demonstrate an average singlet-triplet-state readout fidelity of 97.59% by the threshold method. We reveal the inherent deficiency of the threshold method for the relaxed triplet-state classification and introduce machine learning as a noise-resilient and relaxation-independent readout method to reduce the misjudgment. The readout fidelity for classifying the simulated single-shot traces can be improved to 99.67% by the machine-learning method, better than the threshold method of 97.54%, which is consistent with the experimental result. This work indicates that the machine-learning method can be a strong potential candidate for alleviating the restrictions of stably achieving high-fidelity and high-accuracy singlet-triplet-state readout in large-scale quantum computing.

Recent advances in planar optics with geometric phase superstructures have brought an alternative paradigm in the control of structured light and, in particular, have substantially enhanced the capabilities of generating and detecting orbital angular momentum (OAM) states of light and associated spatial modes. However, the structured modal interface that can reciprocally link OAM states via adiabatic control and access an associated higher-order geometric phase remains absent in planar optics. In this work, we propose and experimentally demonstrate a planar optical astigmatic retarder fabricated with a liquid-crystal (LC) geometric phase. The LC superstructure is designed based on the principle of fractional Fourier transformation and is capable of reciprocal conversion between all possible OAM states on the same modal sphere. Such a planar device paves the way towards an easily deployed modal interface of paraxial OAM states, unlocks the resource of a higher-order geometric phase, and has promising applications in high-dimensional classical and quantum information.

An intriguing property of double-zero-index metamaterials (DZIMs) is that waves propagate through them without phase variation, which has received significant attention in wave-front and dispersion engineering. Recently, Dirac-like cone dispersion has been successfully exploited to realize a DZIM that operates only at a fixed frequency, while realizing DZIMs with multiple separated Dirac-like cones remains challenging. Here, we propose the first realization of a multiplexed acoustic double-zero-index metamaterial (MADM) capable of realizing three separated Dirac-like points at the Brillouin zone center for airborne sound. The resulting device is formed by introducing a series of blind holes with different heights, which are periodically arranged on the upper and lower parts of the waveguide. The underlying mechanism is that the proposed MADM possesses three Dirac-like cones derived from an accidental degeneracy of monopolar and dipolar resonances, which can be mapped to a DZIM with zero effective compressibility and mass density. We present an experimental realization of the designed MADM with three separated Dirac-like points, and demonstrate the functionality of the resulting device by means of extraordinary wave tunneling and acoustic focusing. We anticipate that our mechanism will offer the potential for designing multiplexed acoustic double-zero-index devices and may have substantial and profound applications in a variety of fields, such as ultrasonic therapy and acoustic communication.

Solar-irradiance fluctuations possess a power-law spectrum with two different slopes in the intermediate (1/day $<f<1/$h) and high [1/h $<f<1/$(2 min)] frequency ($f$) regimes. This spectrum is a combination of a deterministic (latitude-dependent) variation of daylight duration and a stochastic component arising from various environmental attenuation factors. We propose a principled approach to decompose the solar-irradiance time series into the deterministic location-dependent clear sky and the stochastic environmental attenuation signals. Such decomposition permits one to systematically analyze the solar photovoltaic power-fluctuation spectra after accounting for the strong geographic dependence, failing which no baseline standard exists with which to compare spectra between disparate geographic locations. Our analysis for two different locations shows that the stochastic environmental factors determine the spectral power-law slope in the high-frequency range, while the deterministic clear-sky signal plays a role in the intermediate frequency range. We close by discussing its implications for solar photovoltaic power production, in particular, for the geographic smoothing of fluctuations.

Native multiqubit parity gates have various potential quantum computing applications, such as entanglement creation, logical state encoding, and parity measurement in quantum error correction. Here, using simultaneous cross-resonance drives on two control qubits with a common target, we demonstrate an efficient implementation of a three-qubit parity gate. We have developed a calibration procedure based on that for the echoed cross-resonance gate. We confirm that our use of simultaneous drives leads to higher interleaved randomized benchmarking fidelities than a naive implementation with two consecutive controlled not gates. We also demonstrate that our simultaneous parity gates can significantly improve the parity measurement error probability for the heavy-hexagon code on an IBM Quantum processor using seven superconducting qubits with all-microwave control.

We report the experimental observation of multiple standing spin modes in a three-dimensional (3D) optomagnonic nanocavity formed by a nanometer-sized iron-garnet nanocylinder. We show that launching of the standing spin modes is achieved due to a high confinement of the optically generated effective magnetic field caused by the localized optical resonance. Quantization and spin-wave mode inhomogeneity are achieved in each of the three spatial dimensions. The presented approach opens horizons for 3D optomagnonics by combining nanophotonic and magnonic functionalities within a single nanocavity.

Silica has rarely been used as a seed particle material in acoustic trapping of nanoparticles. Here we use fluorescent nanoparticles, which are frequently used as a model system, to demonstrate that throughput and nanoparticle trapping efficiency can be improved by using silica seed particles as opposed to traditionally used polystyrene seed particles. The 10 times larger dipole scattering coefficient of silica seed particles compared with polystyrene seed particles in water leads to a higher retention force against fluid flow and thus enables higher throughput. Seed particles retained at an actuation voltage of approximately 10 V p.p. can withstand flow rates up to 2100 ± 200 µl/min for silica and 200 ± 50 µl/min for polystyrene. Furthermore, silica is found to be 40%–2000% more efficient (number of trapped nanoparticles as measured by fluorescent intensity) than polystyrene seed particles in trapping 270-nm polystyrene nanoparticles from suspensions of ${10}^{10}$–${10}^{11}$ particles/ml. Moreover, after enriching nanoparticles into a silica seed particle cluster, the washing flow rate can be increased from 30 µl/min to 200 µl/min (the flow rate at which polystyrene clusters are unstable), halving the total sample processing time without losing the silica seed particle cluster or compromising the nanoparticle trapping efficiency. Thus, material properties (particularly density) of the seed particles are critical to both nanoparticle trapping efficiency and throughput.

The manipulation of the various forms of behavior of acoustic propagation holds significant importance in the realm of underwater acoustic communication and detection. Recent advancements have highlighted the efficacy of metamaterials and metasurfaces in precisely shaping acoustic wave fronts. However, unlike their counterparts in airborne environments, where air-solid boundaries are conventionally treated as rigid, underwater metastructures face challenges due to fluid-structure coupling, inevitably leading to near-field distortions. These distortions considerably impede the efficacy of manipulating acoustic wave fronts, especially at large angles. Here, we introduce an efficient underwater metasurface employing a grating structure that utilizes an overarching optimization strategy. Distinct from previous studies, this strategy comprehensively addresses both nonlocal interaction among all subunits and fluid-structure interaction. The employed methodology convincingly demonstrates the achievement of highly efficient abnormal reflections at various angles. The simulation results showcase an exceptional modulation efficiency exceeding 99% for the designed metagratings, encompassing a wide reflection-angle range of $45–85{}^{\circ }$. Additionally, experimental validation corroborates the effectiveness of these underwater metagratings. This study might present an effective technique for advancing underwater acoustic devices, offering a valuable contribution to the field.

We propose and experimentally demonstrate a general method allowing us to unravel microscopic noise events that affect a continuous quantum variable. Such unraveling is achieved by frequent measurements of a discrete variable coupled to the continuous one. The experimental realization involves photons traversing a noisy channel. There, their polarization, whose coupling to the photons’ spatial wave packet is subjected to stochastic noise, is frequently measured in the quantum Zeno regime. The measurements not only preserve the polarization state, but also enable the recording of the full noise statistics from the spatially resolved detection of the photons emerging from the channel. This method proves the possibility of employing photons as quantum noise sensors and robust carriers of information.

The generation of entangled photon pairs, which are compatible with quantum devices and standard telecommunication channels are critical for the development of long-range fiber quantum networks. Aside from wavelength, bandwidth matching, and high fidelity of produced pairs are necessary for high interfacing efficiency. High-rate, robust entanglement sources that satisfy all these conditions remain an outstanding experimental challenge. In this work, we study an entanglement source based on four-wave mixing in a diamond configuration in a warm rubidium vapor. We theoretically and experimentally investigate an alternative operating regime and demonstrate an entanglement source, which produces highly nondegenerate 795- and 1324-nm photon pairs. With this source we are able to achieve in-fiber pair-generation rates greater than ${10}^7/\mathrm{s}$, orders of magnitude higher than previously reported atomic entanglement sources. Additionally, given our source’s native compatibility with telecom infrastructure and atomic systems, it is a step towards scalable quantum networks.

Nonreciprocal superconducting devices have attracted growing interest in recent years as they potentially enable directional charge transport for applications in superconducting quantum circuits. Specifically, the superconducting diode effect has been explored in two-terminal devices that exhibit superconducting transport in one current direction while showing dissipative transport in the opposite direction. Here, we exploit multiterminal Josephson junctions (MTJJs) to engineer magnetic-field-free nonreciprocity in multiport networks. We show that when treated as a two-port electrical network, a three-terminal Josephson junction (JJ) with an asymmetric graphene region exhibits reconfigurable two-port nonreciprocity. We observe nonreciprocal (reciprocal) transport between superconducting terminals with broken (preserved) spatial mirror symmetry. We explain our observations by considering a circuit network of JJs with different critical currents.