This study highlights efforts to develop an accurate, simple methodology to assess the electromechanical response in thin-film heterostructures, using laser Doppler vibrometry to measuring surface displacements smaller than 1 nm. The work demonstrates how to use the measured values to extract the piezoelectric coefficient $d_{33}$ for a generic thin-film system by means of finite-element modeling. Finally, the work shows how to assess the electromechanical figure of merit for thin films, and offers a procedure for how to compare them to their bulk counterparts via the electromechanical coupling coefficient $k_{33}$.

A phonon (quantized vibration of a crystalline medium) is much shorter in wavelength than a photon of the same frequency. This length-scale reduction offers an opportunity to achieve higher density of quantum information storage, and may open a path to scalable implementations of superconducting quantum processors. However, the smallness of the acoustic wavelength also poses a challenge: It may result in fast qubit decoherence via an unintentional emission of phonons. The authors demonstrate how to circumvent such spontaneous emission and attain quantum coherent coupling of a qubit to an isolated phonon mode.

Despite the fundamental differences between quantum and classical topological material systems, recent studies have shown remarkable similarities in their underlying mathematical structure. This study discusses the classical analogue of the well-known second-quantization formalism, and uses it to analyze a dimerized mechanical chain. The formalism reveals a striking resemblance between the Hamiltonians of the classical dimerized chain and the Kitaev chain, a toy model renowned for bound-state solutions akin to Majorana zero modes. This formulation provides a powerful tool to discover and design classical mechanical mimics of topological quantum systems.

Antiferromagnetic (AFM) spin-orbitronics and data storage rely on the motion of AFM solitons (domain walls and skyrmions) in thin films consisting of nanocrystalline grains. The design of high-performance antiferromagnet-based memory and logic devices has been limited by a lack of knowledge about the interaction of AFM solitons with grain boundaries. The authors develop a model of a nanocrystalline AFM material (e.g. magnetoelectric Cr${}_2$O${}_3$), including proper intergrain exchange. Their approach provides design rules for granular AFM memory devices, and should stimulate further research on ultrafast magnetization dynamics of the order parameter in insulating granular AFM thin films.

The challenge of predicting protein folding—a pivotal task in biology, chemistry, and drug design—has yet to be fully surmounted, due to the complexity of finding the lowest-energy configuration of the constituent amino acids. The current study provides a hybrid classical-quantum digitized counterdiabatic approach that enhances the performance of existing quantum algorithms, producing remarkable results even in the NISQ era. This innovative solution opens up possibilities for tackling complex problems in biology and chemistry, pushing the boundaries of what is achievable with quantum computing.

An ongoing line of inquiry in cavity optomechanics consists of increasing the strength of the light-oscillator interaction to explore various dynamical regimes. By combining a high-finesse microcavity with an ultrasensitive force sensor (a suspended SiC nanowire), one can reach the regime where a single photon in the cavity has a measurable impact on the nanoresonator. The internal optical resonances of the nanowire strongly structure and possibly enhance the light-nanowire interaction, which can be fine-tuned through careful positioning of the subwavelength-sized nanowire within the standing wave inside the cavity.

All electronics are subject to thermal noise, which sets a minimum power to distinguish a signal from ambient background. Here quantum systems—in particular the nitrogen-vacancy center in diamond—show a path forward, as they can be laser-cooled to a quantum mechanical ground state while a device remains at ambient conditions. By placing an ensemble of N-$V$ centers inside a low-loss microwave cavity in which their spins strongly interact with gigahertz magnetic fields, the cold spins extract more energy than can leak in from the hot environment. The output voltage shows vastly reduced fluctuations at the cavity frequency; the effective temperature is lowered by 150 K.

This article reports experiments on the mass partitioning of a fragmenting liquid sheet, formed after the impact of a nanosecond laser pulse on a tin microdroplet, to help in optimizing mass utilization of the liquid tin that is key to extreme-ultraviolet nanolithography. The authors apply machine learning to analyze subresolution fragments in the temporal evolution of the sheet and its bounding rim, ligaments protruding from the rim, and droplets shed by the ligaments. A full accounting includes the further contributions unique to laser-droplet impact: the mass ablated by the laser, and a surprising, centrally located mass remnant.

Magnetism has played an increasingly important role in thermal technologies over the past century, including solid-state magnetic refrigerators and magneto-optical thermal switches. In this study, modeling shows that a two-pronged approach enables a thermal switch with two tuning “knobs”: a magnetocaloric knob to tune the temperature gradient, and a magneto-optical knob to fine-tune the effective thermal resistance. This enables additional modes of operation, such as reversing the flow of heat. This work highlights the utility of combining various “-caloric” effects with complementary modes of heat transfer for fresh ways of controlling thermal energy.

Spintronic devices have attracted strong interest in neuromorphic computing, because of their inherent nonlinear behavior and synchronization capabilities. To build magnon-based networks between spintronic oscillators acting as neurons, control mechanisms are the key to adjusting their interactions. This study uses spin-orbit torque to reduce damping and enable magnon scattering in ultrathin waveguides. Microwave power and frequency, as well as spin-current magnitude, can be used as control parameters for nonlinear generation of additional magnon modes at distinct frequencies. Field-dependent time- and space-resolved measurements expose the underlying physical process.

Research on space-time-modulated systems has recently attracted interest due to their fascinating properties, such as nonreciprocity and frequency mixing. However, the scarcity of commercial full-wave solutions limits their study at present. Here mathematical tools are presented to shed light on the physics of moving and space-time metallic gratings, for direct application in engineering.

This study reports a significant result in atom interferometry, specifically for gravity measurements: an achieved sensitivity of $2.2\times {10}^{-8}$ m/s${}^2$ per shot, which advances the state of the art by about a factor of two. Integrating for 2000 s, the resolution here is $8\times {10}^{-10}$ m/s${}^2$, which is equivalent to the effect produced by a 60-kg person 2 m away. Based on such extremely sensitive and stable gravity measurements, a test of local Lorentz invariance in the gravity sector is performed, where the accuracy of the upper bound on the space-space component is improved by a factor of four—a milestone result in testing fundamental physics with such metrology.

Sound-absorbing materials (SAMs) are important for extensive acoustic applications, due to widespread demand for constructing tailored acoustic environments. This Perspective introduces the conservation qualities of SAMs that fundamentally govern their absorption potentials. Based on these conservation qualities, the authors offer an overview of the progress in SAMs from single-resonant to coupled-resonant systems, and outline significant results, advanced modulation techniques, and innovative design concepts. Finally, they provide an outlook on future directions for the development and application of SAMs, such as multifunctional materials and metaliners.

Non-Hermitian photonics, in which energy is not conserved, has attracted growing interest lately due to its potential for realizing innovative optical functionalities. Devices in this paradigm typically utilize material-absorption loss, though, which inevitably reduces efficiency. To overcome this issue, this study demonstrates a non-Hermitian waveguide based solely on vertical radiation from a photonic crystal. This device exhibits perfect transmission when light comes from one side, yet perfect reflection from the opposite side, and offers further degrees of freedom in photonics design to accelerate real-world applications.

The stochastic magnetic tunnel junction is an emerging device in neuromorphic computing, but controlling such a random system with high energy efficiency and flexibility remains a challenge. The authors propose a spintronic neuron with stochastic switching behavior that is modulated by a microwave signal. Their approach improves the training speed and performance of the system for the benchmark task of recognizing handwritten digits, compared to a conventional software-based sigmoidal neural network. This study advances the quest to create flexible, inexpensive neuromorphic computing systems.

Symmetry-protected bound states in the continuum (BICs) possessing nontrivial physical properties have facilitated the development of wave systems in various fields. However, limited by leakage from a finite photonic structure, the asymptotic behavior of the quality factor $Q$ for $N$ resonators is proportional to $N^2$. This Letter demonstrates a super quasibound state in the continuum, to manipulate the asymptotic behavior. Coordinating the avoided crossing of BICs in parameter space with the merging of BICs in momentum space can switch the asymptotic behavior from $N^2$ to $N^3$ proportionality, for applications such as lasing and optical sensing.

This study highlights efforts to develop an accurate, simple methodology to assess the electromechanical response in thin-film heterostructures, using laser Doppler vibrometry to measuring surface displacements smaller than 1 nm. The work demonstrates how to use the measured values to extract the piezoelectric coefficient $d_{33}$ for a generic thin-film system by means of finite-element modeling. Finally, the work shows how to assess the electromechanical figure of merit for thin films, and offers a procedure for how to compare them to their bulk counterparts via the electromechanical coupling coefficient $k_{33}$.

A phonon (quantized vibration of a crystalline medium) is much shorter in wavelength than a photon of the same frequency. This length-scale reduction offers an opportunity to achieve higher density of quantum information storage, and may open a path to scalable implementations of superconducting quantum processors. However, the smallness of the acoustic wavelength also poses a challenge: It may result in fast qubit decoherence via an unintentional emission of phonons. The authors demonstrate how to circumvent such spontaneous emission and attain quantum coherent coupling of a qubit to an isolated phonon mode.

Despite the fundamental differences between quantum and classical topological material systems, recent studies have shown remarkable similarities in their underlying mathematical structure. This study discusses the classical analogue of the well-known second-quantization formalism, and uses it to analyze a dimerized mechanical chain. The formalism reveals a striking resemblance between the Hamiltonians of the classical dimerized chain and the Kitaev chain, a toy model renowned for bound-state solutions akin to Majorana zero modes. This formulation provides a powerful tool to discover and design classical mechanical mimics of topological quantum systems.

Antiferromagnetic (AFM) spin-orbitronics and data storage rely on the motion of AFM solitons (domain walls and skyrmions) in thin films consisting of nanocrystalline grains. The design of high-performance antiferromagnet-based memory and logic devices has been limited by a lack of knowledge about the interaction of AFM solitons with grain boundaries. The authors develop a model of a nanocrystalline AFM material (e.g. magnetoelectric Cr${}_2$O${}_3$), including proper intergrain exchange. Their approach provides design rules for granular AFM memory devices, and should stimulate further research on ultrafast magnetization dynamics of the order parameter in insulating granular AFM thin films.

The challenge of predicting protein folding—a pivotal task in biology, chemistry, and drug design—has yet to be fully surmounted, due to the complexity of finding the lowest-energy configuration of the constituent amino acids. The current study provides a hybrid classical-quantum digitized counterdiabatic approach that enhances the performance of existing quantum algorithms, producing remarkable results even in the NISQ era. This innovative solution opens up possibilities for tackling complex problems in biology and chemistry, pushing the boundaries of what is achievable with quantum computing.

An ongoing line of inquiry in cavity optomechanics consists of increasing the strength of the light-oscillator interaction to explore various dynamical regimes. By combining a high-finesse microcavity with an ultrasensitive force sensor (a suspended SiC nanowire), one can reach the regime where a single photon in the cavity has a measurable impact on the nanoresonator. The internal optical resonances of the nanowire strongly structure and possibly enhance the light-nanowire interaction, which can be fine-tuned through careful positioning of the subwavelength-sized nanowire within the standing wave inside the cavity.

All electronics are subject to thermal noise, which sets a minimum power to distinguish a signal from ambient background. Here quantum systems—in particular the nitrogen-vacancy center in diamond—show a path forward, as they can be laser-cooled to a quantum mechanical ground state while a device remains at ambient conditions. By placing an ensemble of N-$V$ centers inside a low-loss microwave cavity in which their spins strongly interact with gigahertz magnetic fields, the cold spins extract more energy than can leak in from the hot environment. The output voltage shows vastly reduced fluctuations at the cavity frequency; the effective temperature is lowered by 150 K.

This article reports experiments on the mass partitioning of a fragmenting liquid sheet, formed after the impact of a nanosecond laser pulse on a tin microdroplet, to help in optimizing mass utilization of the liquid tin that is key to extreme-ultraviolet nanolithography. The authors apply machine learning to analyze subresolution fragments in the temporal evolution of the sheet and its bounding rim, ligaments protruding from the rim, and droplets shed by the ligaments. A full accounting includes the further contributions unique to laser-droplet impact: the mass ablated by the laser, and a surprising, centrally located mass remnant.

Magnetism has played an increasingly important role in thermal technologies over the past century, including solid-state magnetic refrigerators and magneto-optical thermal switches. In this study, modeling shows that a two-pronged approach enables a thermal switch with two tuning “knobs”: a magnetocaloric knob to tune the temperature gradient, and a magneto-optical knob to fine-tune the effective thermal resistance. This enables additional modes of operation, such as reversing the flow of heat. This work highlights the utility of combining various “-caloric” effects with complementary modes of heat transfer for fresh ways of controlling thermal energy.

Spintronic devices have attracted strong interest in neuromorphic computing, because of their inherent nonlinear behavior and synchronization capabilities. To build magnon-based networks between spintronic oscillators acting as neurons, control mechanisms are the key to adjusting their interactions. This study uses spin-orbit torque to reduce damping and enable magnon scattering in ultrathin waveguides. Microwave power and frequency, as well as spin-current magnitude, can be used as control parameters for nonlinear generation of additional magnon modes at distinct frequencies. Field-dependent time- and space-resolved measurements expose the underlying physical process.

Research on space-time-modulated systems has recently attracted interest due to their fascinating properties, such as nonreciprocity and frequency mixing. However, the scarcity of commercial full-wave solutions limits their study at present. Here mathematical tools are presented to shed light on the physics of moving and space-time metallic gratings, for direct application in engineering.

This study reports a significant result in atom interferometry, specifically for gravity measurements: an achieved sensitivity of $2.2\times {10}^{-8}$ m/s${}^2$ per shot, which advances the state of the art by about a factor of two. Integrating for 2000 s, the resolution here is $8\times {10}^{-10}$ m/s${}^2$, which is equivalent to the effect produced by a 60-kg person 2 m away. Based on such extremely sensitive and stable gravity measurements, a test of local Lorentz invariance in the gravity sector is performed, where the accuracy of the upper bound on the space-space component is improved by a factor of four—a milestone result in testing fundamental physics with such metrology.