This paper investigates the complex nonlinear dynamics of an optomechanical system featuring an optical cavity coupled to two mechanical resonators interconnected by a phase-dependent interaction. We specifically explore the role of this phase-dependent phonon hopping as a mechanism for generating synthetic gauge fields without relying on gain-loss or $\mathcal{P}\mathcal{T}$-symmetric elements, offering a potentially more robust approach to manipulating mechanical energy transfer. By deriving the semiclassical dynamical equations, we map out the system’s behavior across different parameter regimes. Our findings reveal a rich spectrum of dynamics, including bistability (the coexistence of two steady states) and the emergence of complex attractors such as self-excited oscillations, hidden attractors, and chaos. We demonstrate how controlling system parameters, particularly the mechanical coupling phase and optical drive, allows for tunability between these distinct dynamical states. The presence of tunable bistability and sensitive chaotic regimes offers significant potential for practical applications. Specifically, we discuss how these controlled dynamics could be leveraged for state switching in optical information processing and for enhancing sensitivity in advanced sensor technologies through chaos-based mechanisms. This work deepens our understanding of how synthetic gauge fields, generated via phase-dependent interactions, can sculpt the nonlinear dynamics of optomechanical systems, providing a pathway toward designing robust and tunable devices for signal processing, communication, and sensing.

High-fidelity quantum nondemolition qubit measurement is critical to error correction and rapid qubit feedback in large-scale quantum computing. Maximizing high-fidelity dispersive readout in superconducting qubits commonly requires passing a short and strong pulse through the qubit’s readout resonator, which is then processed by a sufficiently high bandwidth, high saturation power, and quantum-limited amplifier. We have developed an amplifier design pipeline that combines time-domain simulation of the untruncated device Hamiltonian, fabrication constraints, and maximization of saturation power. We have realized an amplifier based on a modified trilayer (Nb-Al-${\mathrm{Al}\mathrm{O}}_x$-Nb) fabrication suite at NIST, which utilizes an array of 25 rf superconducting quantum interference devices embedded within a low-$Q$ resonator powered by a high-power voltage pump delivered via a diplexer on the signal port. We show that, despite the intensity of the pump, the device is quantum efficient and capable of high-fidelity measurement limited by state transitions in the transmon. We present experimental data demonstrating up to $-91.2\mathrm{dBm}$ input saturation power with 20-$dB$ gain, up to 28-MHz instantaneous bandwidth, and phase-preserving qubit measurements with $62\mathrm{\%}$ quantum efficiency.

Double perovskites are regarded as promising candidates for the next generation of luminescent materials. However, a significant number of double perovskite luminescent materials (DPLMs) remain unexplored. This study integrates the atomistic line graph neural network model with the interpretable extreme gradient boosting model to explore DPLMs, thereby proposing a framework for the screening of high-quality DPLMs. The electronic band structures and the transition dipole moments (TDMs) of 2592 double perovskites are calculated using the Perdew-Burke-Ernzerhof functional to establish a database. The TDM at the direct band gap, experimentally validated, and the exciton binding energy ($E_b$) serve as the criteria for assessing the luminescent capabilities of materials, and the refractive indices serve as the criterion for assessing the application prospects of materials. Based on these conditions, this study identifies five materials with direct band gaps exhibiting luminescent properties and selects two materials with promising high-quality application potential for further validation. Furthermore, this study reveals that the average deviation of number of unfilled p orbital states of the constituent elements in a compound can serve as a preliminary criterion for assessing the luminescent capabilities of materials. This study leverages machine learning to reveal the link between material structure and luminescence, providing a foundation for designing double perovskite light-emitting diodes.

In quantum information processing, a tension between two different tasks occurs: while qubits’ states can be preserved by one isolating them, quantum gates can be realized only through qubit-qubit interactions. In arrays of qubits, weak coupling leads to states being spatially localized and strong coupling leads to delocalized states. Here we study the average energy level spacing and the relative entropy of the distribution of the level spacings (Kullback-Leibler divergence from Poisson distribution and Gaussian orthogonal ensemble) to analyze the crossover between localized and delocalized (chaotic) regimes in linear arrays of superconducting qubits. We consider both transmons and capacitively shunted flux qubits, which enables us to tune the qubit anharmonicity. Arrays with uniform anharmonicity, comprising only transmons or flux qubits, display remarkably similar dependencies of level statistics on the coupling strength. In systems with alternating anharmonicity, for typical disorder in the qubit frequencies the localized regime is found to be more resilient to the increase in qubit-qubit coupling strength in comparison with arrays with a single qubit type. Our results, which we also confirm using generalized Bose-Hubbard models, support the design of devices that incorporate different qubit types to achieve higher performances.

Nanomagnonic crystals are magnetic waveguides, the magnetic parameters of which are modulated at the nanoscale. The superlattice structure enables a band structure and magnonic band gaps. Here, we numerically investigate the field tunability of such a magnonic band gap. By subjecting different parts of the nanomagnonic crystal to a field, we realize a magnonic heterojunction. A numerical demonstration of an active modification of the band structure leads to magnonic amplitude modulation in the linear regime and magnonic frequency combs in the nonlinear regime. Our results will offer further opportunities for nanomagnonic crystals and inspire their experimental realization.

Chirality, a fundamental property of asymmetric structures, plays a crucial role in pharmaceutical, biological, and chemical systems, offering a powerful tool for selective screening of organic compounds. Although conventional optical chirality detectors are often bulky and cumbersome, due to their inherent chirality, topological insulators (TIs) offer a promising platform for developing compact yet sensitive devices; however, the complex interplay of photoresponses in TIs can limit the ultimate accuracy of their chirality detection. Here, we reveal that in ultrathin TI films, the overlap of the surface-state wave functions leads to their constructive interference and a strongly amplified photocurrent. By attentively analyzing the symmetries and behavior of competing photoresponses in a thin-film TI, we demonstrate that it is possible to effectively eliminate the unwanted contributions and isolate the helicity-dependent photocurrent (HDPC). Moreover, we show that the HDPC can be further enhanced by optimizing the illumination parameters, sensor strain, and/or back gating. Our findings provide a roadmap for design and optimization of miniaturized, high-performance TI chirality detectors, providing the potential to revolutionize chiral analysis in biomedical and material sciences.

The atom gravimeter, based on the principle of matter-wave interferometry, represents a new generation of high-precision gravity measurement instruments with significant application potential. We have successfully developed a high-precision atom gravimeter named USTC-AG12. To comprehensively evaluate its environmental adaptability and performance in long-term measurements, while effectively suppressing vibration noise and increasing system stability, we transported the device to a mountain 800 km away and conducted continuous gravity measurements using advanced vibration postcompensation techniques. The experimental results demonstrate that the atom gravimeter achieved stable operation for more than 150 days, with a measurement sensitivity of $18.6\text{μ}\mathrm{Gal}/\sqrt{\mathrm{Hz}}$ and stability of $0.6\text{μ}\mathrm{Gal}$ at 1000 s. Moreover, comparative observations with a superconducting gravimeter showed excellent consistency between the two instruments: the long-term measurements exhibited almost no drift. Additionally, we used the continuous observation data from the cold-atom gravimeter to thoroughly validate the reliability of gravity data in seismic analysis and research. Through comparative analysis with seismometer recordings, the two instruments demonstrated high consistency in extracting seismic surface wave dispersion velocities, confirming the application value of atom gravimeters in the field of seismic research.

Carrier transition is one of the major factors hindering the high-speed implementation of the Mølmer-Sørensen gates in trapped-ion quantum processors. We present an approach to design laser pulse shapes for the Mølmer-Sørensen gate in ion chains, which accounts for the effect of carrier transition on qubit-phonon dynamics. We show that the fast-oscillating carrier term effectively modifies the spin-dependent forces acting on ions, and this can be compensated by a simple nonlinear transformation of a laser pulse. Using numerical simulations for short ion chains and perturbation theory for longer chains up to 20 ions, we demonstrate that our approach allows suppression of the infidelity contribution from off-resonant carrier excitation from ${10}^{-3}$–${10}^{-2}$ to values below ${10}^{-4}$, whereas the gate duration remains of the order of tens of microseconds.

We demonstrate the efficient excitation of spin waves in the ultralow magnetic damping material yttrium iron garnet (YIG) by surface acoustic waves (SAWs). To this end, we use interdigital transducers fabricated on a piezoelectric zinc oxide (ZnO) thin film covering the YIG. This enables the excitation of coherent, propagating Rayleigh-type and Sezawa-type SAWs. We find that the ultralow magnetic damping of YIG is retained after the $\mathrm{Zn}\mathrm{O}$ deposition and we perform a comprehensive investigation of the magnetoelastic interaction due to the different SAW modes as a function of the external magnetic field magnitude and orientation. By measuring the SAW attenuation, our experiments reveal a highly anisotropic and nonreciprocal SAW–spin-wave interaction in agreement with our model calculation, while demonstrating that low-damping magnons can be efficiently excited by SAWs.

We present a cooling method that uses the phase separation and evaporative cooling of ${}^3$$\mathrm{He}$ to reach and continuously maintain subkelvin temperatures. While less complex than a dilution refrigerator, the system performs similarly to a continuous ${}^3$$\mathrm{He}$ cryostat but with a simpler design, a more efficient cooldown process, and a significantly smaller ${}^3$$\mathrm{He}$ requirement. Our prototype demonstrated a base temperature of 585 mK and 3 mW cooling power at 700 mK using just two gaseous liters of ${}^3$$\mathrm{He}$. Lower temperatures could be expected in systems with improved heat exchangers and pumping efficiency.

Using a focused ${\mathrm{He}}^{+}$ beam for nanopatterning and writing of Josephson barriers, we fabricated specially shaped Josephson junctions of in-line geometry in ${\mathrm{YBa}}_2{\mathrm{Cu}}_3{\mathrm{O}}_7$ thin film microbridges with an asymmetry ratio of critical currents of opposite polarities of approximately $7$ at the optimum magnetic field. Those Josephson diodes were subsequently used as ratchets to rectify an applied alternating current into a dc voltage. We also demonstrate the operation of such a ratchet in the loaded regime, where it produces a nonzero dc output power and yields a thermodynamic efficiency of up to 75%. The ratchet shows record figures of merit: an output dc voltage of up to $212\text{μ}\mathrm{V}$ and an output power of up to $0.2\mathrm{nW}$. The device has an essential area of approximately $1\text{μ}{\mathrm{m}}^2$. For rectification of quasistatic Gaussian noise, the figures of merit are more modest; however, the efficiency can be as high as for the deterministic ac drives within some regimes. Since the device is based on ${\mathrm{YBa}}_2{\mathrm{Cu}}_3{\mathrm{O}}_7$, it can operate at temperatures up to approximately $40\mathrm{K}$, where more noise is available for rectification.

Here we experimentally create a temporal waveguide doublet by introducing truncation boundaries in a synthetic temporal lattice, which is constructed using two fiber loops connected by a variable optical coupler. The optical pulses are confined to evolve and couple between the temporal lattice sites, akin to a directional waveguide coupler operating in the time dimension. Total energy transfer between the temporal waveguides is achieved only when the coupling ratio takes specific values. Nonlinearity is introduced into the temporal waveguides by incorporating an optoelectric conversion circuit into one of the fiber loops. We demonstrate a nonlinear Mach-Zehnder interferometer, where the output site of the optical pulse can be adjusted by varying the incident pulse intensity. The system has the potential to serve as a temporal switch and could find applications in optical pulse control and signal processing.

Photonic bound states in the continuum (BICs), possessing two unique properties of infinitely high quality ($Q$) factor and momentum-space polarization vortex, promise unprecedented opportunities for tailoring high-$Q$ resonances and enhancing light field manipulation. Recently, all-dielectric metasurfaces (MSs) underpinned by high refractive index and low intrinsic loss materials have unlocked the full potentials of BICs to realize ultrahigh-$Q$ resonances. However, experimental demonstrations of high-$Q$ terahertz BICs resonances in all-dielectric MSs with substrates remain a long-standing challenge. Here we propose and fabricate a paradigm of a crystalline silicon terahertz MS over a quartz substrate to demonstrate optical resonators with high-$Q$ quasi-BICs resonances. These resonators feature the simultaneous excitation of multiple topologically protected symmetry-protected BICs and accidental BICs. Under larger asymmetries, two additional BICs are observed in symmetry-broken terahertz MSs, thereby offering an extra degree of freedom for engineering BICs and easing fabrication. Our experimental results reveal two quasi-BICs modes characterized by sharp Fano resonances that boast an unparalleled $Q$ factor of up to 265, which is the highest reported experimental $Q$ factor in a terahertz MS with a substrate. We envision that these findings will not only hold enormous prospects for broadening the functional scope of terahertz metaphotonics but will also lay the groundwork for the realization of high-performance terahertz optoelectronic devices and metadevices.

In the traditional approach to controlling superconducting qubits using microwave pulses, the field of pulse shaping has emerged to assist in the removal of leakage and increase gate fidelity. However, the challenge of scaling microwave control electronics has created an opportunity to explore alternative methods such as single-flux quantum (SFQ) pulses. For qubits controlled by SFQ pulses, high fidelity gates can be achieved by optimization of the binary control sequence. We extend the notion of the derivative removal by adiabatic gate framework to a transmon qubit controlled by SFQ drivers. The proposed implementation of SFQ pulse sequences can be stored in 22 bits or fewer, with gate fidelities exceeding 99.99%. This modest memory requirement could help reduce the footprint of the SFQ coprocessors and power dissipation while preserving their inherent advantages of scalability and cost-effectiveness.

We present a metrological technique to characterize the thermodynamic state (temperature, pressure, and density) of gaseous molecules in a single spectroscopic measurement. We demonstrate the accuracy and precision of our approach by using a low-pressure (number density approximately $1.76\times {10}^{18}\mathrm{molecules}/{\mathrm{cm}}^3$) acetylene gas in a sealed glass cell over a temperature range of $-70{}^{\circ }\mathrm{C}$ up to $+60{}^{\circ }\mathrm{C}$. Under these experimental conditions the sample is in the gaseous state, displaying a behavior very close to that of an ideal gas. This allows us to predict the thermodynamic state with high accuracy, and thus rigorously test the performance of our approach. Our spectroscopic measurement uses a tunable wide-band optical frequency comb to acquire the full ro-vibrationally broadened acetylene spectrum between 1512 and 1538 nm with approximately $80$-kHz spectral resolution. Through nonlinear fitting of this entire spectrum we obtain high accuracy ($<1\mathrm{\%}$) and high-precision (approximately $0.1\mathrm{\%}$) estimates of the temperature, pressure, and density of the gas across the full examined temperature range. This combination of broadband probing and ultra-high-resolution spectrum ensures that we obtain reliable and precise measurements on the thermodynamic state.

Semiconductor components based on silicon carbide ($\mathrm{Si}\mathrm{C}$) are a key component for high-power electronics. Their behavior is determined by the interplay of charges and electric fields, which is typically described by modeling and simulations that are calibrated by nonlocal electric properties. So far, the 3D mapping of both the electric field and the concentrations of free charge carriers inside an electronic device remains a challenging task. To fulfill this information gap, we propose an operando method that utilizes single silicon vacancy ($V_{\mathrm{Si}}$) centers in $4\mathrm{H}$-$\mathrm{Si}\mathrm{C}$. The $V_{\mathrm{Si}}$ centers are at various positions in the intrinsic region of a p-i-n diode. To monitor the local static electric field, we perform Stark-shift measurements based on photoluminescence excitation, which allows us to infer the expansion of the depletion zone and therefore to determine the local concentration of dopants. Besides this, we show that our measurements allow us to additionally obtain the local concentration of free charge carriers. The method presented here therefore paves the way for a new quantum-enhanced electronic device technology, capable of mapping the interplay of mobile charges and electric fields in a working semiconductor device with nanometer precision.

We report relaxation oscillations in a one-dimensional array of Josephson junctions, wherein the array dynamically switches between low-current and high-current states. The oscillations are current-voltage dual to those ordinarily observed in single junctions. The current-voltage dual circuit quantitatively accounts for temporal dynamics of the array, including the dependence on biasing conditions. Injection locking of the oscillations results in well-developed current plateaux. A thermal model explains the self-consistent reduction of the superconducting gap due to overheating of the array in the high-current state. Our work suggests that overheating determines the switching from the high-current state to the low-current state.

Laser cooling is fundamental to quantum computation and metrology with trapped ions. In particular, quantum ground-state cooling required for many gate implementations can occupy a majority of runtime in current quantum computing systems. A key limitation to cooling arises from unwanted carrier excitation, which in typically used running-wave (RW) fields invariably accompanies the sideband excitations effecting cooling. Laser cooling in structured light profiles enables selective sideband excitation with nulled carrier drive; motivated by integrated photonic approaches’ passive phase and amplitude stability, we propose simple configurations realizable with waveguide addressing using either standing wave (SW) or first-order Hermite-Gauss modes. We quantify performance of Doppler cooling from beyond the Lamb-Dicke (LD) regime, and ground-state cooling using electromagnetically induced transparency (EIT) leveraging these field profiles. Carrier-free EIT offers significant benefits in cooling rate, motional frequency bandwidth, and final phonon numbers comparable to those achievable with resolved sideband cooling. Carrier-free Doppler cooling’s advantage is significantly compromised beyond the LD regime but continues to hold, indicating such configurations are applicable for highly excited ions. Our simulations focus on a level structure relevant to ${}^{40}{\mathrm{Ca}}^{+}$, though the carrier-free configurations can be generally applied to other species. We also quantify performance limitations due to polarization and modal impurities relevant to experimental implementation. Our results indicate potential for simple structured light profiles to alleviate bottlenecks in laser cooling, and for scalable photonic devices to improve basic operation quality in trapped-ion systems.