We experimentally demonstrate the suppression of self-excited thermoacoustic oscillations in a Sondhauss tube via genetic programming (GP). As a data-driven control strategy, GP optimizes both the control-law structure and its parameters based on a predefined cost function. We find that GP closed-loop control suppresses thermoacoustic limit-cycle oscillations through synchronous quenching, in contrast to the asynchronous quenching mechanism observed in conventionally controlled self-excited oscillators. Benchmark tests reveal that GP closed-loop control outperforms both GP open-loop and classic open-loop control, achieving a greater amplitude reduction while consuming an order of magnitude less actuation power. We then show that a Van der Pol oscillator model, driven by the optimal GP control law, faithfully reproduces the experimental dynamics, including synchronous quenching. These findings establish GP as an effective data-driven strategy for active control of thermoacoustic instabilities in propulsion and energy applications.

A three-dimensional magneto-optical trap (MOT), acting as an efficient method for producing cold atoms from room-temperature atomic vapor, has been widely used to develop atomic sensors. Various compact MOTs using a single laser beam have been reported, simplifying apparatuses and leading to miniaturized devices. Here, we propose single-beam MOTs based on back-to-back pyramidal and conical mirrors. In such back-to-back mirrors, a MOT trapping volume is formed by an incident laser beam, a retroreflected beam, and multiple reflections from the mirror surfaces. We present the design of back-to-back mirrors and a series of compact MOT configurations, with the potential of increasing access to the MOT and simultaneously creating multiple MOTs. We demonstrate a MOT in a back-to-back conical mirror, loading ∼1 × ${10}^7$ ${}^{87}\mathrm{Rb}$ atoms from background vapor and cooling the atoms to ∼7 µK using polarization gradients. Single-beam MOTs based on back-to-back mirrors contribute to building compact and scalable cold-atom-based sensors.

Three-color Rydberg electromagnetically induced transparency (EIT) of room-temperature $\mathrm{Rb}$ vapor in the presence of inert gases ($\mathrm{Ar}$, $\mathrm{Ne}$, and ${\mathrm{N}}_2$) at 50 and 500 mTorr is investigated. The observed EIT lines shift and develop blue-detuned satellite lines, dependent on inert-gas species and pressure. The separations of the satellite from the main EIT lines are approximately pressure-independent, while their strength increases with inert-gas pressure. The satellite lines are attributed to hyperfine collisions of the intermediate $5D_{3/2}$ state. Further, analyzing the Stark effect of Rydberg levels, it is found that the inert gases suppress static electric fields in the vapor cells, which we induce by photoillumination of the cell walls with an auxiliary 453-nm laser. In the work, we utilize Rydberg levels with principal quantum numbers $n=25$ and $50$ and angular momenta $\ell =3$ up to 6, excited by the EIT lasers and optional radio-frequency dressing fields. The work is of interest in the spectroscopic study of mixed-species warm vapors, in sensing applications of Rydberg atoms in vapor cells, and in noninvasive electric-field diagnostics of low-pressure discharge plasma.

We present a numerical framework that integrates a modified Langevin noise formalism into multimode Jaynes- and Tavis-Cummings models for first-principles, non-Markovian analysis of atom-field interactions in dissipative electromagnetic environments under weak coupling. This formalism enables the quantization of electric field operators in terms of boundary- and medium-assisted modes with real-valued eigenfrequencies, accounting for both radiative and absorptive losses. To efficiently handle the continuum nature of the boundary- and medium-assisted mode spectrum, we apply adaptive frequency refinement and mode-space coarse-graining based on finite-element simulations to obtain a tractable discrete set of field modes. These modes are then used to construct matrix representations of the Schrödinger equation, enabling direct computation of atomic observables and field quantities—such as single-photon amplitudes and higher-order correlation functions—beyond the Markovian approximation. Importantly, this framework does not rely on any phenomenologically designed memory kernel. Instead, the spectrum of boundary- and medium-assisted modes interacting with atoms inherently and rigorously captures memory effects arising from the open and dissipative electromagnetic environment. We present four numerical examples to validate the proposed framework and demonstrate its ability to model non-Markovian atomic dynamics in open and dissipative electromagnetic environments: (i) a two-level system near the surface of a perfect electric conductor, (ii) dissipative cavity quantum electrodynamics for a single two-level system, (iii) super- and subradiance in two-level system arrays, and (iv) entanglement sudden death between two two-level systems. This framework provides a versatile simulation tool for the design of quantum photonic devices, including nitrogen-vacancy center single-photon sources coupled to plasmonic structures, entangled photon-pair generation near lossy media, and decoherence modeling of solid-state quantum memories based on rare-earth ions and color centers. It is particularly well suited to dissipative quantum electrodynamics in photonic integrated circuits, where accurate modeling of scattering and diffraction is essential.

We present a scheme for high-sensitivity oscillators based on an exceptional point of degeneracy (EPD) in a circuit made of two $LC$ resonators coupled by a gyrator. The frequency of oscillation is very sensitive to perturbations of a circuit element, like a capacitor. We show conditions that lead to an EPD, assuming one of the two resonators is composed of an inductor and a capacitor of negative values. The EPD occurrence and sensitivity to perturbations in the linear case are demonstrated by finding that the eigenfrequency bifurcation around the EPD is described by the relevant Puiseux (fractional power) series expansion. We also investigate the effect of small losses in the system and show that they lead to instability. We fabricate the circuit and demonstrate its instability and nonlinearity, experimentally observing stable self-oscillations in the saturated regime. We measure the circuit’s sensitivity to a small capacitor perturbation. A shift in oscillation frequency after saturation in the order of 1 kHz is well detectable with very distinct spectral peaks with only 10-Hz linewidth, and with a clean spectrum down to $-70$ dB from the peak value. The sensitivity is (i) higher than the one of a comparable simple $LC$ linear resonator, (ii) comparable or better than other published EPD circuits, and (iii) applicable to both negative and positive values of the capacitance perturbation, contrary to what happens in $PT$-symmetric circuits. The proposed scheme can pave the way for an alternative generation of high-sensitive sensors to measure slight variations in physical, chemical, or biological quantities.

Superconductor-mediated exchange between two ferromagnetic insulators is predicted to result in an antiferromagnetic coupling between the two ferromagnetic insulating layers, thus locking the magnetization vectors in an antiparallel alignment. Such a scenario intuitively assumes the ferromagnetic magnetizations as macrospins lacking a magnetic microstructure. In order to test the validity of this assumption and to test the stability of the antiparallel alignment, we perform various switching experiments that attempt to either maintain or deliberately induce a domain structure in the ferromagnetic layers. Irrespective of the switching experiment we perform, we find a distinctive preference for the antiparallel alignment with increasing strength of superconductivity. We also achieve robust nonvolatile bistability of electronic states due to a pronounced macrospin behavior induced by superconducting exchange coupling.

Ideal spatial demultiplexing (SPADE) is proven to be a quantum-optimal tool for exoplanet detection, i.e., asymmetric source discrimination. However, recent investigations into the related problems of separation estimation and symmetric source discrimination showed its efficiency to be limited in the presence of noise. In this work, we use analytical tools to scrutinize the practical applicability of SPADE and derive the associated optimal decision strategy for exoplanet detection in the presence of experimental imperfections. On the one hand, we find that the probability of detection of noisy SPADE has the same scaling with planet-star separation and relative brightness as conventional techniques, such as direct imaging and coronagraphs. On the other hand, we prove that, due to a superior scaling coefficient under realistic noise conditions, SPADE remains the most efficient method for practical exoplanet detection in the sub-Rayleigh regime.

Material damage is a consideration for any applications where pressure fields may initiate cavitation. Histotripsy is a focused ultrasound therapy that exploits the destructive property of bubble clouds to disrupt viscoelastic tissue. The resulting effect achieves the same outcomes as surgery without the need for an invasive procedure. This study investigated the relationship between changes in bubble clouds throughout focused ultrasound exposure. Specifically, the dissolution period of bubbles generated in water and agarose gel was tracked with ultrafast ultrasound imaging. This imaging marker was found to increase in agarose during the initial stages of exposure, and maintained steady-state values after 555 ± 64 applied histotripsy pulses. The relative change in damage area of the gel and bubble-dissolution period with exposure duration were found to be equivalent (p > 0.05). Acoustic emissions tracked with passive acoustic imaging were also evaluated and were found to have a different functional form with exposure duration than the bubble-dissolution period or area of damage to the gel. In contrast, there were no noted changes in these imaging markers throughout histotripsy exposure when bubble clouds were generated in water. A previously validated bubble-dynamics model was extended to calculate the anticipated changes to bubble expansion during histotripsy exposure under the assumption that the agarose elastic modulus approached 0 kPa (i.e., total fractionation). The calculations predicted larger changes in the bubble dynamics than was observed, which might reflect complicated dynamics of the bubble cloud during the final stages of treatment.

The radiometric force arises when a body that is nonuniformly heated by radiation is immersed in a low-pressure gas. This phenomenon results from gas-surface interactions, which are characterized by accommodation coefficients. In turn, these coefficients depend on the gas species and surface properties such as roughness and chemical composition. When the accommodation coefficients are not constant over the body’s surface, the radiometric phenomenon arises even if the body temperature is uniform. In the present study, we calculate the force exerted on a thin membrane with different accommodation coefficients on its top and bottom surfaces. The temperature of the membrane is assumed to be higher than that of the surrounding gas. The direct simulation Monte Carlo method is used to span a wide range of Knudsen numbers, including the free-molecular, transitional, and viscous flow regimes. We show that perforations in the membrane increase the radiometric force in the viscous regime.

Regulating carrier transport at semiconductor interfaces using light is essential for optimizing optoelectronic devices. Recent advancements in ultrafast scanning electron microscopy and finite-element methods have provided deeper insights into photoinduced ballistic carrier dynamics in a silicon $p$-$n$ junction. In this work, we develop a finite-element model to further elucidate carrier-transport mechanisms across the junction and explore the use of dc bias to control hot carrier transport and the oscillatory behavior of plasma waves. Our results reveal that, at low laser fluence, applying a reverse bias to the $p$-$n$ junction significantly enhances carrier-transport efficiency. However, at higher laser fluence, the increased carrier density and Coulomb interactions induce terahertz plasma wave oscillations near the junction. The applied bias voltage plays a critical role in modulating these oscillations and their associated terahertz radiation. These findings suggest that dc bias offers an effective means to control photoinduced carrier transport and plasma wave dynamics in $p$-$n$ junctions, paving the way for high-efficiency, tunable terahertz radiation sources.

Topological phononic crystals (PnCs) offer innovative approaches for controlling acoustic waves, garnering significant attention owing to their potential for designing acoustic devices. In this work, we propose the topological PnC chains that achieve multimodal and broadband energy harvesting of acoustic waves through the synergistic effect of edge and bulk states. The phononic cavities support both the monopole- and quadrupolelike cavity modes that could be used for sound confinement and amplification. Based on Su-Schrieffer-Heeger model, the phononic cavity chain is designed, where the cavity coupling can be described by the tight-binding model with long-range couplings. By adjusting the coupling strength between phononic cavities, the system transitions from the topologically trivial phase to the nontrivial one, thereby generating topological edge states (TESs) and broadband bulk states (BSs). Two phononic chain configurations are constructed to generate TESs and BSs, which are validated by full-wave simulations and experimental measurements. The PVDF films are placed at the edge and bulk of the phononic cavity chain for piezoelectric energy harvesting. Compared with the reference harvester, both the TESs and BSs of the PnC structure exhibit much higher electrical outputs, achieving efficient broadband energy harvesting with a relative bandwidth exceeding 23%. The measured maximum area power density of the PnC structure reaches $0.00933\text{μ}\mathrm{W}/({\mathrm{cm}}^2{\mathrm{Pa}}^2)$, which is approximately 100 times higher than that of the reference structure. Furthermore, the experiments confirm the robustness of the TESs against structural disorders.

This study employs first-principles calculations to investigate functionalized ${\mathrm{Mo}}_2\mathrm{N}{T}_2$ (T = Ø, $\mathrm{H}$, $\mathrm{O}$, $\mathrm{F}$) MXenes as dual-functional materials for toxic gas capture and sensing applications. The surface of the pristine ${\mathrm{Mo}}_2\mathrm{N}$ surface is unsaturated, possesses dangling bonds, and exhibits a strong capability to capture various environmental gases. Surface functionalization significantly modulates this behavior: ${\mathrm{Mo}}_2{\mathrm{NH}}_2$ demonstrates remarkable selectivity toward ${\mathrm{NO}}_x$ capture, while ${\mathrm{Mo}}_2{\mathrm{NO}}_2$ emerges as a superior $\mathrm{NO}$ sensor due to its optimal adsorption strength (−0.342 eV), substantial charge transfer (−0.197 e), and 14%–18% current reduction in nanodevice measurements. Notably, investigations of mixed-terminated ${\mathrm{Mo}}_2{\mathrm{NO}}_x(\mathrm{OH})y$ systems reveal that hydroxyl concentration dictates $\mathrm{NO}$ reaction pathways: low $\mathrm{OH}$ triggers proton abstraction, forming $\mathrm{O}$-$\mathrm{N}$-$\mathrm{H}$ structures, whereas high $\mathrm{OH}$ induces direct $\mathrm{O}\text{−}\mathrm{H}$ cleavage, generating ${\mathrm{H}}_2\mathrm{N}\text{−}\mathrm{OH}$. Although water passivation mitigates these reactions, irreversible chemical transformations persist, underscoring that precise control of surface chemistry, particularly terminal-group engineering, is essential for achieving the selective capture capabilities and reversible sensing performance required for next-generation MXene-based gas management platforms.

Space-based gravitational wave detection plays a crucial role in advancing our understanding of the universe. One of its primary tasks is to release the test mass (TM) into free-fall state with high positional accuracy and extremely low residual velocity through a grabbing, positioning, and release mechanism (GPRM) after the satellite enters orbit, and then the TM is captured by an electrode housing. During the release process, hysteresis effects occur in the piezoelectric module of the release mechanism, and a hysteresis model must be fitted on the ground to achieve in-orbit control and compensation of the TM based on the model. However, when measuring the displacement signal from the GPRM on the ground, noise interferes with the signal collected, leading to inaccurate fitting of the hysteresis effect and impacting hysteresis control and compensation. In this work, we propose a hysteresis fitting and control method of the test-mass-release mechanism via adaptive stochastic resonance (ASR), which effectively denoises the noisy signals through numerical simulation. By simultaneously introducing a quantum particle swarm optimization algorithm and using cosine similarity as the optimization index, the method achieves optimal denoising output under different voltage excitations. Compared with other denoising methods and other particle swarm optimization algorithms, the proposed approach demonstrates a superior denoising performance. In terms of control, after ASR, the controlled displacement is free of interference, and the displacement curve is smooth. This method holds significant application value for hysteresis control in the GPRM.

Measurement-device-independent quantum key distribution (MDI QKD), which eliminates all the attacks from the eavesdropper to the measurement party, has been one of the most promising technologies for the implementation of end-to-end quantum networks. In practice, the asymmetry of both sources and channels is generally inevitable. Therefore, we propose a theory to analyze the performance when any two MDI users in networks communicate using asymmetric sources in distinct single or multiple temporal modes. As a specific application, we model to obtain the key rate of MDI QKD with a weak-coherent pulse source and a spontaneous parametric down-conversion source, and compare the performance to the cases with symmetric (i.e., identical) sources. The result demonstrates that the actual performance does not degrade due to the asymmetry of sources. On the contrary, it maintains at a good level over the entire distance we study. This work provides a theoretical basis for analyzing and optimizing MDI-QKD networks with asymmetric sources, thus paving the way for the practical deployment of completely asymmetric MDI-QKD networks.

This work presents a theoretical study of the electronic structure and transport properties of $\mathrm{Ni}$-$\mathrm{Au}$ alloys, recently identified as excellent thermoelectric metals with a power factor significantly exceeding that of conventional semiconductor thermoelectrics. Using first-principles calculations based on the Korringa-Kohn-Rostoker method combined with the coherent-potential approximation and the Kubo-Greenwood formalism, we demonstrate the key role of resonant scattering in determining the thermoelectric properties of these alloys. This is supported by calculated densities of states, Bloch spectral functions, electrical conductivity, and thermopower. Alloying $\mathrm{Ni}$ with $\mathrm{Au}$ not only induces resonant scattering but also leads to the formation of a flat band below the Fermi level. The combination of these two features results in high thermopower arising from a transition from resonant to weak scattering regimes near the Fermi level. Our findings are further compared with analogous calculations for constantan, a $\mathrm{Ni}$-$\mathrm{Cu}$ alloy long regarded as a reference thermoelectric metal. We show the key differences between the $\mathrm{Ni}$-$\mathrm{Au}$ and $\mathrm{Ni}$-$\mathrm{Cu}$ systems that explain why $\mathrm{Ni}$-$\mathrm{Au}$ exhibits nearly twice the thermopower of $\mathrm{Ni}$-$\mathrm{Cu}$. Finally, we simulate the effect of lattice parameter variation on the thermoelectric performance of $\mathrm{Ni}$-$\mathrm{Au}$ and suggest that this is a promising pathway for further enhancement, for example, through additional alloying or layer deposition.