We investigate numerical and experimental nonadiabatic relocation of a topological interface. We construct a reconfigurable electroacoustic Su-Schreiffer-Heeger lattice using negative-capacitance (NC) shunted piezoelectric patches attached to a host beam. Tuning the NC circuits allows us to create a topological-interface state by varying the effective elastic modulus along the beam. We then use a microcontroller to switch relays placed in the NC shunt circuits to move the interface by one unit cell. We present the results for continuous and pulse inputs and show the shift of energy localization in the experiment. Further, to distinguish topological protection, we simulate the nonadiabatic shifting of a trivial defect in a discrete lattice. Numerical simulations indicate higher mean energy at the interface after shifting a topological state as compared to a defect state. Topological interfaces as shown in our experiment may have interesting applications in acoustic communication, such as source switching and signal encoding.

Antireflection coatings with a broad relative bandwidth (RBW) and reduced electrical length are desirable for a variety of applications in the microwave frequencies. Here, we propose the design principle of bilayer metasurfaces with 100% RBW and subwavelength thickness based on the traditional Chebyshev transformer, with excellent agreement with our experimental validation for both transverse electric and magnetic polarizations. We utilize the multiple-beam interference theory to reveal the underlying mechanism of the preferred choices for nonresonant or weakly resonant metasurface unit cells. Being able to manipulate the transmissions and reflections within the bilayer structure, we further demonstrate the universality and sensitivity of the designs capable of providing near-unity microwave transmission from air into the full range of natural media, with prescribed RBW and reduced electrical length.

Prior work showed the efficacy of pausing midanneal: such a pause improved the probability of success by orders of magnitude in a class of native problem instances and improved the time to solution in a class of embedded problem instances. A physics-based picture provides qualitative suggestions for where pausing midanneal is effective, for the interplay between annealing schedule parameters and other annealing properties and parameters such as embedding size and strength of the ferromagnetic coupling $|J_F|$, and for the conditions under which pausing can improve the time to solution. Here, through demonstrations on an updated annealing architecture that has higher connectivity than previous annealers, and on multiple embedded problem classes, we are able to confirm various aspects of this picture. We demonstrate the robustness of the optimal pause parameters across platforms and problem classes, explore how to set $|J_F|$ to optimize performance in different scenarios, and provide empirical evidence that short pauses trump longer overall annealing times in time to solution. We also identify the number of different coefficients in a problem as a predictor of problem hardness, and explore its interplay with the optimal $|J_F|$ and embedding size. Based on these results we are able to present qualitative guidelines for parameter setting in quantum annealers.

With the advent of quantum technologies, control issues are becoming increasingly important. In this paper, we address control in phase space under a global constraint provided by a minimal energylike cost function and a local (in Fourier space) constraint resulting from a robustness criterion. The inverse-engineering Lagrangian formalism developed here generalizes the formalism commonly used to describe the superoscillation phenomenon. It is applied to both nondissipative and dissipative quantum mechanics, and extended to stochastic thermodynamics. Interestingly, our approach also allows one to improve sensing capabilities by appropriate control of the system.

The best performance from compact, portable, and repeatably manufactured electromagnetic (EM) oscillators has for decades been built upon crystalline quartz resonators operating at radio frequencies. Such a source of frequency-stable EM waves has enabled a wide range of applications of significant technical and societal benefit, such as navigation and communication systems, distributed sensing, geodesy, and fundamental physics. However, meeting demands for increased measurement sensitivity requires pushing beyond a fractional frequency stability of ${10}^{-13}$, typical of the best ovenized quartz. To date, such performance has been available in the microwave domain only with the use of complex cryogenic systems, or in the optical domain at the expense of larger volume and weight. In either case, the size, weight, and power of state-of-the-art EM oscillators has relegated their use to laboratory experiments. Here we demonstrate the validity of a manufacturable, compact Fabry-Perot reference that improves upon all other centimeter-scale oscillators by more than a factor of 10, including those based on solid-state optical resonators as well as quartz. In a specific implementation, we show an 8 ml bonded assembly containing three vacuum-gap Fabry-Perot optical cavities with mirrors lithographically fabricated on a single substrate, each with quality factor exceeding 10 billion. A laser stabilized to one of the cavities exhibits thermal-noise-limited phase noise for offset frequencies ranging from 1 Hz to nearly 1 kHz, and fractional frequency stability of $7\times {10}^{-15}$ at 1 s. Our advance with lithographically defined and microfabricated mirrors is validated by rigorous models, which highlight a path to oscillators with size comparable to ovenized quartz, but with significantly improved performance. For example, we predict sub-${10}^{-14}$ performance is readily attainable with a Fabry-Perot cavity volume less than 2 ml.

Bell states are the most fundamental resource in realizing quantum information tasks and have a very unique position in quantum mechanics. Utilizing orbital angular momentum (OAM) to encode single-photon Bell states enables the realization of high-dimensional Hilbert space, which is crucial for the field of quantum information. In this paper, we design a single-photon OAM Bell-state evolution device based on the Sagnac interferometer, which can make one-to-one correspondence between the input Bell states and the output states. Moreover, we also develop a single-photon single-pixel imaging (SPI) technique, which improves spatial resolution and decreases acquisition time in the meantime, to capture interference images of output states. The results show that single-photon OAM Bell states can be fully recognized by comparing the differences of interference images. We innovatively utilize the SPI technique for single-photon OAM Bell-state recognition. This indicates that the SPI technique effectively promotes the study of quantum information based on OAM, while the quantum information based on OAM provides a clear application scenario for the SPI technique.

Materials with a negative and tunable Poisson ratio have great potential applications in fracture resistance and energy absorption. However, one material usually exhibits one specific Poisson ratio and a systematic tuning is highly desired. In this study, we design disordered networks with a wide tunable range of the Poisson ratio based on triangular analysis. By distorting the equilateral triangle lattice, the Poisson ratio can be systematically decreased due to the large area change in highly nonequilateral triangles. Analysis further shows that in a nonequilateral triangle, bonds with different lengths play distinct roles: the removal of short bonds can decrease the Poisson ratio, while the removal of long bonds does the opposite. Thus a negative Poisson ratio can be achieved by removing a small amount of short bonds. Moreover, such networks can serve as unit cells to build larger systems with a similar performance. Such auxetic networks are further experimentally realized in both spring and three-dimensionally printed systems, demonstrating the general validity of our analysis and its possible applications in building practical systems.

Metamaterials composed of asymmetric elements have been shown to break reciprocity; permitting the propagation of waves in one direction. The configuration of these metamaterials typically limits the propagation of the wave to a single direction, speed, or occurrence with little or no tunability. Here we present—theoretically, numerically, and experimentally—a simple design approach for reprogrammable metamaterials, which allows for all of these parameters to be tuned, enabled, disabled, or reset. We present a map of different geometries that allow for reciprocal and nonreciprocal wave propagation and attenuation. We show how a single design can be programmed on demand to support wave propagation and attenuation in both directions (reciprocal) or wave propagation in only one direction (nonreciprocal). In addition, we demonstrate real-time control of the wave velocity, both in amplitude and direction, as it propagates through the metamaterial. We show speeding up, slowing down, or complete reversal of the propagating wave direction. Furthermore, we show that the waves maintain a constant velocity regardless of the impulse magnitude, and even along a curved path. Our metamaterial could open exciting possibilities for designing nonlinear materials with exotic topological properties.

Photon-efficient imaging with the single-photon light detection and ranging captures the three-dimensional structure of a scene by only a few detected signal photons per pixel. However, the existing computational methods for photon-efficient imaging are pretuned on a restricted scenario or trained on simulated datasets. When applied to realistic scenarios whose signal-to-background ratios and other hardware-specific properties differ from those of the original task, the model performance often significantly deteriorates. In this paper, we present a domain adversarial adaptation design to alleviate this domain shift problem by exploiting unlabeled real-world data, with significant resource savings. This method demonstrates superior performance on simulated and real-world experiments using our home-built up-conversion single-photon imaging system, which provides an efficient approach to bypass the lack of ground-truth depth information in implementing computational imaging algorithms for realistic applications.

Speckle patterns generated in a disordered medium carry a lot of information despite the apparent complete randomness in the intensity pattern. When the medium possesses ${\chi }^{(2)}$ nonlinearity, the speckle is sensitive to the phase of the incident fundamental light, as well as the light generated within. Here, we examine the speckle decorrelation in the fundamental and second-harmonic transmitted light as a function of the varying power in the fundamental beam. At low incident powers, the speckle patterns produced by successive pulses exhibit strong correlations, which decrease with increasing power. The average correlation in the second-harmonic speckle decays faster than in the fundamental speckle. Next, we construct a theoretical model, backed up by numerical computations, to obtain deeper physical insights into the faster decorrelations in the second-harmonic light. While providing excellent qualitative agreement with the experiments, the model sheds light on the contribution of two effects in the correlations, namely, the generation of second-harmonic light and the propagation thereof.

Spin density waves (SDWs) are antiferromagnetic ground states characterized by real-space spin modulation. When an electronic system undergoes a paramagnetic-SDW transition, the translational symmetry is spontaneously broken and energy gaps are developed near the Fermi level, which offers potential for constructing various SDW components. Here we report a prototype resistive memory device based on a prototypical SDW metal, antiferromagnetic chromium. Transport and magnetic measurements show that the paramagnetic-SDW transition, i.e., the SDW antiferromagnetism, can be effectively suppressed by the electric-field-generated piezoelectric strain in epitaxial $\mathrm{Cr}/0.7\mathrm{Pb}({\mathrm{Mg}}_{1/3}{\mathrm{Nb}}_{2/3}){\mathrm{O}}_3$–$0.3{\mathrm{Pb}\mathrm{Ti}\mathrm{O}}_3$ (PMN-PT) heterostructures. This enables a large electroresistance effect for metallic systems as the SDW band gaps can be intentionally controlled to vanish or develop. Combining this electroresistance effect with the different remanent piezoelectric strain of PMN-PT after poling by electric-field pulses of opposite polarity, we obtain two nonvolatile resistance states differing by about 1.8% and stable against a magnetic field of 3 T at room temperature. Our work unveils the electric-field controllability of the SDW transitions in thin films and the consequent wide application prospects of SDW materials.

We solve robot-trajectory planning problems at industry-relevant scales. Our end-to-end solution integrates highly versatile random-key algorithms with model stacking and ensemble techniques, as well as path relinking for solution refinement. The core optimization module consists of a biased random-key genetic algorithm. Through a distinct separation of problem-independent and problem-dependent modules, we achieve an efficient problem representation, with a native encoding of constraints. We show that generalizations to alternative algorithmic paradigms such as simulated annealing are straightforward. We provide numerical benchmark results for industry-scale data sets. Our approach is found to consistently outperform greedy baseline results. To assess the capabilities of today’s quantum hardware, we complement the classical approach with results obtained on quantum annealing hardware, using qbsolv on Amazon Braket. Finally, we show how the latter can be integrated into our larger pipeline, providing a quantum-ready hybrid solution to the problem.

Active x-ray inspections have great potential for noninvasive detection of illicit materials. Dual-energy x-ray radiography, in particular, has been used to determine material composition by utilizing the energy-dependence of the x-ray attenuation coefficients. However, current implementations of this method are limited in their ability to determine the material composition of composite objects. Here we present an inverse algorithm that uses multienergy x-ray radiography data to noninvasively reconstruct the contents of a container. A critical feature of the current contribution is that material identification can be performed using conventional detectors and x-ray spectra with different endpoint energies produced by varying nothing more than the tube voltage. Adaptive regularization is used to increase the accuracy of material estimations from multienergy data sets. The utility of these methods is demonstrated with experimentally acquired radiographs obtained using a tunable x-ray source that produces spectra with endpoint energies of 100–450 keV. The object inspected is a scale model of a nuclear materials storage container composed of three-dimensional printed plastic and stainless-steel spheres inside a thin-walled steel container. Reconstructions of the steel sphere thicknesses are within a root-mean-square error of 0.37 cm.

The design for an inductive superconducting quantum interference proximity transistor with enhanced performance, the L-SQUIPT, is presented and analyzed. The interferometer is based on a double-loop structure, where each ring comprises a superconductor–normal-metal–superconductor mesoscopic Josephson weak link and the readout electrode is implemented in the form of a superconducting tunnel probe. Our design allows us to both improve the coupling of the transistor to the external magnetic field and increase the characteristic magnetic flux transfer functions, thereby leading to an improved ultrasensitive quantum limited magnetometer. The L-SQUIPT behavior is analyzed in both the dissipative and the dissipationless Josephson-like operation modes, in the latter case by exploiting both an inductive and a dispersive readout scheme. The improved performance makes the L-SQUIPT promising for magnetic flux detection as well as for specific applications in quantum technology, where a responsive dispersive magnetometry at millikelvin temperatures is required.

Midinfrared light is extensively used for identifying molecules because their characteristic vibrational modes commonly exist in the midinfrared spectral region. In this paper, a midinfrared quantum cascade laser is utilized for sorting silica particles with resonant enhancement of the optical force by exciting their vibrational mode. Silica particles on an evanescent wave drift rapidly along the prism surface, whereas identical-sized polystyrene particles drift at 7–10 times lower speed. We suggest the application of this principle for optical force chromatography in the midinfrared region.

We design an acoustic switch based on a spiral kirigami metasurface using numerical simulations and evaluate its performance experimentally. By etching an Archimedean spiral on a thin aluminum sheet, a band gap in out-of-plane vibration modes can be generated. The band gap is significantly suppressed by axially stretching the kirigami spiral structure, extending sound propagation to a broader frequency range. The kirigami metasurface is easily deformed and manipulated and can switch the energy transmission on and off in the desired operating-frequency range, providing an alternative design strategy for acoustic metasurfaces.

We demonstrate and study a microcell microwave atomic clock based on optical-microwave double resonance (DR) interrogation operated in a pulsed Ramsey scheme, called the μPOP clock, based on a microfabricated Rb vapor cell and a micro-loop-gap microwave resonator. For the mm-scale dimensions of this cell, the population and coherence relaxation rates of the Rb clock transition are on the order of 4–5 kHz, which puts constraints on the useful Ramsey times and overall pulse sequence in view of optimized clock performance. Our proof-of-principle demonstration of the μPOP clock shows that the pulsed DR approach is nevertheless feasible and results in a short-term clock stability of 1 × ${10}^{-11}$ τ${}^{-1/2}$ and reaching the ≤2 × ${10}^{-12}$ level at timescales of 1000 s to one day. The short-term instability budget established for the μPOP clock shows that the main limitation to the short-term stability arises from the detection noise. Thanks to the pulsed Ramsey scheme, light-shift effects are strongly reduced in the μPOP clock, which opens perspectives for further improvements of long-term clock stability, in view of future generations of miniature vapor-cell clocks with enhanced performances based on the DR scheme.