We propose and analyze a nonunitary variant of the continuous time Grover search algorithm based on frequent Zeno-type measurements. We show that the algorithm scales similarly to the pure quantum version by deriving tight analytical lower bounds on its efficiency for arbitrary database sizes and measurement parameters. We also study the behavior of the algorithm subject to noise, and find that under certain oracle and operational errors our measurement-based algorithm outperforms the standard algorithm, showing robustness against these noises. Our analysis is based on deriving a non-Hermitian effective description of the algorithm, which yields a deeper insight into components responsible for the quantum and the classical operation of the protocol.

Developing schemes for efficient and broadband frequency conversion of quantum signals is an ongoing challenge in the field of modern quantum information. The coherent conversion between microwave and optical signals is an especially important milestone towards long-distance quantum communication. In this work, we propose a two-stage conversion protocol, employing a resonant interaction between magnetic and mechanical excitations as a mediator between microwave and optical photons. Based on estimates for the coupling strengths under optimized conditions for yttrium iron garnet, we predict close to unity conversion efficiency without the requirement of matching cooperativities. We predict a conversion bandwidth in the regions of largest efficiency of the order of magnitude of the coupling strengths that can be further increased at the expense of reduced conversion efficiency.

Simple and smart directional transport of impacting droplets is of great significance for future life and industry, but there are still many challenges due to complex hydrodynamics. Inspired by Setaria viridis leaves, we propose an efficient strategy to manipulate the split and transport of impacting droplets based on the simple design of liquid-repellent surfaces decorated with a ridge, and we report the large-scale, high-speed, and fast-response bidirectional transport of split droplets. Upon impacting on a wirelike ridge, the droplet splits into two parts, which have considerable horizontal transport velocity up to 34% of the initial impact velocity. The transport distance can exceed 1 order of magnitude longer than the droplet size and the response time is reduced by 50% compared to the contact time on flat surfaces. The splitting of the impacting droplet is the precondition for this bidirectional movement, and the time required for splitting strongly correlates to the horizontal transport velocity. A model is developed to accurately predict the splitting time, and a scaling law is proposed to illustrate the quantitative relationship between the horizontal transport velocity and impact parameters. These findings provide a route for using macrostructures to achieve precise droplet manipulation for diverse applications, such as anti-icing and chemical detection.

Electric fields arising from the distribution of charge in metal-halide perovskite solar cells are critical for understanding the many weird and wonderful optoelectronic properties displayed by these devices. Mobile ionic defects are thought to accumulate at interfaces to screen electric fields within the bulk of the perovskite semiconductor on application of external bias, but tools are needed to directly probe the dynamics of this process. Here, we show that electroabsorption measurements allow the electric field within the active layer to be tracked as a function of frequency or time. The magnitude of the electroabsorption signal, corresponding to the strength of the electric field in the perovskite layer, falls off for externally applied low-frequency voltages or at long times following voltage steps. Our observations are consistent with drift-diffusion simulations, impedance spectroscopy, and transient photocurrent measurements. They indicate charge redistribution on timescales ranging from 10 ms to 100 s, depending on the device interlayer material, perovskite composition, dominant charged defect, and illumination conditions. The method can be used on typical solar-cell structures and has the potential to become a routine characterization tool for optimizing hybrid perovskite devices.

We report pseudospin-dependent hybrid topological acoustic metamaterials constructed from tunable acoustic metamaterials and honeycomb-latticed sonic crystals. Using a theoretical model analogous to electrostatic interactions, we provide an efficient approach to evaluate intra- and interlattice couplings, whose competition is the major physical reason arousing the quantum spin Hall effect. The intralattice coupling is from the intrinsic design of the acoustic metamaterial, and the interlattice coupling is affected by multiple scattering among periodic scatterers. By independently manipulating the acoustic metamaterial and sonic crystal, we can successfully induce topological phase transitions at will. An alternative type of topological material is thus realized with great tunability. With identical building blocks for all hybrid topological acoustic metamaterials, a simple tuning of the corotation angle of each acoustic metamaterial can directly induce a topological phase transition, which makes the reconfiguration of the topological domains very convenient. A tunable multiport acoustic power divider is designed and demonstrated using numerical simulations and experiments. An alternative method to control the transmission rate and direction is thus reached and alternative routes for designing hybrid topological acoustic metamaterials with different functionalities and versatile applications are thus paved.

Topological crystalline insulators (TCIs) capable of supporting topological states protected by spatial symmetries have given rise to a promising platform for wave manipulation due to their robustness. Unfortunately, the methods to control the group velocity of topological states in classical wave systems are rarely discussed, which is an important issue in practical applications. In this work, we propose a method to change the frequency and propagation speed of topological edge states through on-site potential and realize a prototype of topological rainbow concentrator in a resonant acoustic system at subwavelength, which can separate different frequency components of propagating sound waves. The concepts of classical wave systems are combined with condensed matter physics, and the rigorous correspondence of TCIs and their analogs in acoustic resonant systems is demonstrated to design topological acoustic devices. Further, the implementation of controlling the group velocity of topological states precisely in a two-dimensional Su-Schrieffer-Heeger model is presented in detail, which can be extended to other TCI models and higher dimensions. We hope this work will enlarge possible applications of topological phenomena and the manufacture of acoustic devices.

We propose a free-space, inverse design of a nanostructure’s effective mode-matching fields via a backward propagation of tightly focused vector beams to the pupil plane of an aplanatic system of high numerical aperture. First, we study the nanostructure’s eigenmodes without considering any excitation fields and then extract the modal near fields in the focal plane. Each modal field is then taken as the desired focal field, the band-limited waves of which are backward propagated to the pupil plane via a reversal of the Richards-Wolf vector diffraction formula. The pupil fields can be designed to be genuinely paraxial by associating the longitudinal electric or magnetic field component with the radial one on the reference sphere. The inversely designed pupil field in turn is propagated forwardly into the focal region to generate the designed focal field, whose distribution over the nanostructure’s surface is used to evaluate the overlap between the designed focal field and the modal fields, i.e., the modal expansion coefficients. Studies for a silicon nanodisk monomer, dimer, and tetramer demonstrate the ability of our inverse approach to design the necessary tightly focused vector field that can effectively and exclusively match a certain eigenmode of interest. Compared with the forward beam-shaping method, the inverse design approach tends to yield quantitatively more precise mode-matching field profiles. This work can have a significant impact on optical applications that rely on controllable and tunable mode excitation and light scattering.

To detect a specific radio-frequency (rf) magnetic field, rf optically pumped magnetometers (OPMs) require a static magnetic field to set the Larmor frequency of the atoms equal to the frequency of interest. However, unshielded and variable magnetic field environments (e.g., an rf OPM on a moving platform) pose a problem for rf OPM operation. Here, we demonstrate the use of a natural-abundance rubidium vapor to make a comagnetometer to address this challenge. Our implementation builds upon the simultaneous application of several OPM techniques within the same vapor cell. First, we use a modified implementation of an OPM variometer based on ${}^{87}$$\mathrm{Rb}$ to detect and actively cancel unwanted external fields at frequencies $⪅60\mathrm{Hz}$ using active feedback to a set of field control coils. We exploit this stabilized field environment to implement a high-sensitivity rf magnetometer using ${}^{85}$$\mathrm{Rb}$. Using this approach, we demonstrate the ability to measure rf fields with a sensitivity of approximately $9\mathrm{fT}{\mathrm{Hz}}^{-1/2}$ inside a magnetic shield in the presence of an applied field of approximately $20\mu \mathrm{T}$ along three mutually orthogonal directions. This demonstration opens up a path toward completely unshielded operation of a high-sensitivity rf OPM.

Laser-driven ion acceleration is an attractive technique to generate compact high-energy ion sources. Currently, among various physical and technical issues to be solved, boosting the ion energy and reducing the energy spread represent the key challenges with this technique. Here we present a scheme to tackle these challenges by using a hundred-terawatt-class laser pulse irradiating a cone target. Three-dimensional particle-in-cell simulations show that a large number of electrons are dragged out of the cone walls and accelerated to hundreds of MeV by the laser fields inside the cone. When these energetic dense electron beams pass through the cone target tip into vacuum, a very high bunching acceleration field, up to tens of TV/m, quickly forms. Protons are accelerated and simultaneously bunched by this field, resulting in quasimonoenergetic proton beams with 100 MeV energy and low energy spread of about 2%. Results exploring the scaling of the proton beam energy with laser and target parameters are presented, indicating that the scheme is robust. This opens an efficient route for compact high-energy proton sources for fundamental research and biomedical applications.

Recently, higher-order topological insulators with both gapped edge states and in-gap corner states, have been simulated and observed. However, multiple higher-order extensible topological states have not yet been witnessed. Here, we fabricate two acoustic samples, each consisting of double sandwichlike heterostructures, a sonic crystal with a gapless state is inset between two sonic crystals with opposite topological phases in each heterostructure. We theoretically simulate and experimentally obtain the higher-order extensible topological states, which are induced by the Jackiw-Rebbi mechanism, and also demonstrate the robustness of the higher-order extensible topological states via experiment and numerical simulations. The distributions of the pressure fields of the higher-order extensible topological states localized within a certain range of the vertical direction, rather than at a corner, and decay exponentially in the horizontal direction. At the same time, by adjusting the number of layers of the middle sonic crystal in the double acoustic sandwichlike structures, we witness the multiple higher-order extensible topological states protected by band topology. Although the width of the middle sonic crystal is limited by the size of the sample, we provide a feasible solution for different energy harvesting, and enrich the understanding of higher-order topological states.

Spin manipulation and detection of alkali-metal and noble-gas ensembles in spin-exchange-relaxation-free (SERF) comagnetometers are widely used in fundamental physical research, and have potential for inertial navigation. The dynamic behavior of spin ensembles is a vital characteristic that determines the applicability of comagnetometers, which significantly differs from various combinations of alkali-metal and noble-gas species. We comprehensively study the critical dynamics of strongly interacting ensembles in SERF comagnetometers with different species combinations. Different from the self-compensation point, a model of strong coupling point at which the dynamics is nonlinear because two ensembles influence each other strongly is established. We verify it by comparing the transient and steady-state dynamics of K-Rb-${}^{21}\mathrm{Ne}$, K-Rb-${}^3\mathrm{He}$, and K-${}^3\mathrm{He}$ comagnetometers with various input signals. The K-Rb-${}^{21}\mathrm{Ne}$ comagnetometer has a better potential for bandwidth and sensitivity in inertial measurement. Besides, we propose a critical point where the response rate of coupling spin ensembles is optimal among all polarization, and the critical dynamics is verified experimentally to be in agreement with theoretical simulations. The damping rate and precession frequency at the critical point can be more than 5 times larger than that at typical optimal spin polarization. Enhancement of spin-ensemble coupling strength improves the response rate of SERF comagnetometers and paves the way for efficient manipulation of noble-gas atoms via alkali-metal atoms in quantum information.

Precise energy-level alignment between a metal electrode and an organic semiconductor is required to reduce contact resistance and enhance the efficiency of organic-semiconductor-based devices. Here, we introduce monolayer-thick charge-injection layers (CILs) based on aromatic carboxylic acids that can induce an energy-level shift in subsequent layers by up to 0.8 eV. Through a gradual chemical transformation of the as-deposited molecules, we achieve a highly tunable energy-level shift in the range of 0.5 eV. We reveal that the work function and energy-level positions in the CIL increase linearly with the density of induced dipoles. The energy-level position of subsequent layers follows the changes in the CIL. Our results thus connect the energy-alignment quantities, and the high tunability would allow precise tuning of the active layers deposited on the CIL, which marks a path towards efficient charge-injection layers on metal electrodes.

Recently, the applications of airborne ultrasound technology have garnered considerable attention; however, high-speed ultrasound field measurements in air have not been well researched. This study demonstrates that thermal responses to high-intensity airborne ultrasound can be used to visualize airborne ultrasound fields. Thermal images on a mesh screen enable the rapid quantitative measurement of two-dimensional ultrasound fields. Additionally, based on the temperature distribution on a surface that reflects ultrasound waves, it is possible to determine the ultrasound focus position with a resolution much finer than the wavelength. The results demonstrate that thermography observations based on ultrasound-temperature conversion, which are conventionally time-consuming or difficult to perform, can be used to visualize acoustic fields within 0.5 s. These findings will advance engineering applications that use strong airborne ultrasound, such as midair haptics and acoustic levitation, and provide scientific and technical applications for detecting surface properties and composition, including those of cells and fragile materials.

A quantum state transformation can be generally approximated by single- and two-qubit gates. This, however, does not hold with noisy intermediate-scale quantum technologies due to the errors appearing in the gate operations, where errors of two-qubit gates such as controlled-not and swap operations are dominated. In this work we present a cost efficient single-copy certification for a realization of a two-qubit gate in the presence of depolarization noise, where we aim to identify if the realization is noise free, or not. We show that entangled resources such as entangled states and a joint measurement are not necessary for the purpose, i.e., a noise-free two-qubit gate is not needed to certify an implementation of a two-qubit gate. We present a proof-of-principle demonstration with photonic qubits.

All-optical switching of the polarization of exciton polaritons is studied using a picosecond acoustic perturbation of the exciton resonance in high-$Q$ planar $\mathrm{Ga}\mathrm{As}$/$\mathrm{Al}\mathrm{As}$ microcavities. An irreversible switching of the degree of circular polarization from $22\mathrm{\%}$ up to $82\mathrm{\%}$ is realized in a microcavity pumped by a laser with a photon energy slightly exceeding the lower polariton resonance. The polarization switch is performed by a short-term, about 30-ps-long, blueshift of the exciton energy of ($\mathrm{In},\mathrm{Ga}$)$\mathrm{As}$ quantum wells in the cavity active layer by a 10-ps strain pulse generated in the $\mathrm{Ga}\mathrm{As}$ substrate by a violet femtosecond laser pulse and injected into the microcavity. The proposed all-optical control of light polarization using acoustic modulation of a polariton resonance opens the way for fast and easily tunable optical polarization switches.

Single-mode fiber lasers are capable of supporting trapped vector solitons with two similar orthogonally polarized components, due to the delicate balance between fiber birefringence and chromatic dispersion. Here, we demonstrate that heterogeneous vector pulses (HVPs) universally exist in anomalous-dispersion and near-zero-dispersion regimes, from hybrid-structure fiber lasers composed of low- and high-birefringent fibers. The vector pulses include two distinct orthogonally polarized components, one of which is a robust pulse, while the other is a gradually attenuated wavepacket composed of terahertz- (THz) repetition-rate subpulses. Simulation and analytical results fully reproduce experimental observations and demonstrate that the robust pulse couples a fraction of its energy to the orthogonally polarized component per roundtrip at the high-birefringent fiber, forming the unique HVPs. Apart from the intriguing nonlinear dynamics, the HVP can work as a flexible workhorse for various applications, ranging from optical polarization multiplexing to THz synthesis and optical precision spectroscopy.