You might hear an echo in the mountains, but can you hear your voice reflecting from the mug on your desk? Probably not: The intensity of that reflected sound is negligible, compared to the other reflections in your office…and what if we put out more mugs? Acoustic cloning, a form of holography, allows us to study acoustic wave propagation and reflection from a physical scatterer, even with modifications to that object. This study presents both theoretical framework and experimental implementation. The method is expected to be widely applicable in all domains of acoustic scattering, such as material characterization, active metamaterials, and virtual-acoustics applications.

Far-off-resonant couplings are useful in quantum computing because they do not require special tunings of device components, but still await further exploration. The authors use a “flip-chip” coupling geometry to unequivocally demonstrate the presence of a far-off-resonant longitudinal coupling between a quantum-dot charge qubit and a microwave cavity, which can be turned on or off at will. This work provides a powerful and versatile tool for reading out and coupling quantum-dot qubits over large distances.

Magnetic sensors generally exhibit a trade-off between spatial resolution and field sensitivity: As sensor size decreases, resolution improves but sensitivity deteriorates. This study reveals that the field distribution in a superconducting Josephson junction can be inferred by analyzing the diffractionlike magnetic field modulation of the critical current $I_c$. Here the spatial resolution is constrained solely by the field range of the $I_c(H)$ pattern and is unrelated to the junction’s size. A remarkable feature of this detection method is that high spatial resolution accompanies high field sensitivity.

This work demonstrates that triplet-triplet annihilation (TTA) is the predominant mechanism of intrinsic photogeneration of charge-carrier pairs via autoionization, in a single-component disordered organic system with no heavy atoms. The findings challenge established beliefs by revealing efficient carrier generation via TTA upon excitation near the absorption edge. Photocurrent measurements, optical spectroscopy, and spin-sensitive techniques support this model of bimolecular charge generation. Such mechanisms in organic semiconductors are relevant not just for OLEDs, but also for long-persistent luminescence, photovoltaics, and potentially for photocatalytic water splitting.

Internal modifications of transparent solid-state materials by intense, ultrashort laser pulses enable numerous applications in micromachining, photonics, and medicine. Understanding the highly nonlinear propagation of the laser beam through the interaction zone is important in developing these technologies. Here a comprehensive propagation model reveals that even under extremely tight focusing, the key physical quantities are rigidly clamped by plasma shielding, at values up to two orders of magnitude lower than those inferred from earlier studies. Potential routes to overcome the clamping limits are discussed.

Aligning suspended optics in gravitational-wave observatories is crucial for detecting astrophysical phenomena⏤and it is also challenging, due to several environmental factors. This research implements neural-network-based sensing and control deployed at the GEO600 detector, utilizing a sensor with a convolutional neural network and long- and short-term memory, plus a deep-reinforcement-learning-based agent for enhanced alignment. The method demonstrates sensitivity improvement over traditional schemes, thus offering a practical approach for AI-based real-time control of gravitational-wave interferometers, to aid the detection of cosmic events like merging compact neutron-star binaries.

While charge carriers in electronics are fundamental to device operation, little is empirically known about their spatial distribution under standard operating conditions. The authors develop a technique for self-emissive electron microscopy that allows them to image electrons close to their point of generation in operando. Increased electron emission, and thus carrier density, is observed at the ridges of V-shaped defects in a green LED, confirming that the sidewalls of these defects allow lateral carrier injection⏤a necessity for increasing efficiency. Measuring the spatial distribution of carriers with this technique can inform the design of superior devices.

The integration of magnetic soft actuators and printed magnetic field sensors presents a compelling strategy for advancing soft robotics, with transformative implications for interactivity. This Perspective discusses the synergy between these technologies, which combined will provide mechanically conformal feedback systems to tracking complex dynamics at high speeds and increase environmental compatibility. These insights are meant to guide the field toward a future where multifunctional magnetic composites with printable, transparent, healable, and biocompatible properties operate seamlessly in parallel, reshaping the possibilities of soft robotics.

Laser-driven plasma accelerators (LPAs) can generate particle beams with high peak current in a short acceleration distance, making them a promising radiation source in compact setups. However, minimizing beam divergence at the exit of an LPA is crucial for effective beam transport, particularly in free-electron lasers (FELs). The authors implement an integrated plasma lens just a centimeter behind the LPA, effectively collimating the electron beam in a straightforward setup. This technique is essential for generating LPA-driven seeded FELs, and has potential for creating specific density profiles for adiabatic focusing, or for the staging of accelerators.

In the rapidly developing cold-atom-qubit platform, off-resonant modulated driving (ORMD) allows us to realize good two-qubit entangling gates. To achieve high fidelities with Rydberg-blockade gates under practical conditions, the high-frequency components in a modulation pattern must be dealt with. This study’s filtering approach is applicable to constructing entangling gates that work at finite Rydberg-blockade strength, and to overcome the residual thermal motion of qubit atoms. These results are expected to provide an essential upgrade for such gates.

Heat engines capable of delivering both high power output and high efficiency are earnestly sought after, but a fundamental trade-off generally exists between the two metrics. This study highlights the exact nature of this trade-off for engines that exchange heat radiatively with a hot source. The authors also show that this trade-off is less restrictive compared to linear heat engines, especially at high temperatures. This work is particularly relevant for thermophotovoltaics, offering a complete characterization of their performance bounds.

The self-calibration of rf sensors using Rydberg-atom vapor cells is a major advantage over conventional rf antennas, but has been limited by Doppler broadening. In this study, ultranarrow linewidths comparable to those in ultracold gases are obtained in a room-temperature vapor cell, by overcoming Doppler shifts via a three-photon scheme to reduce the spectral linewidth to less than 200 kHz. This narrow linewidth extends the self-calibrated regime of such sensors by over an order of magnitude, compared to what has been achieved in standard two-photon schemes.

Far-off-resonant couplings are useful in quantum computing because they do not require special tunings of device components, but still await further exploration. The authors use a “flip-chip” coupling geometry to unequivocally demonstrate the presence of a far-off-resonant longitudinal coupling between a quantum-dot charge qubit and a microwave cavity, which can be turned on or off at will. This work provides a powerful and versatile tool for reading out and coupling quantum-dot qubits over large distances.

Magnetic sensors generally exhibit a trade-off between spatial resolution and field sensitivity: As sensor size decreases, resolution improves but sensitivity deteriorates. This study reveals that the field distribution in a superconducting Josephson junction can be inferred by analyzing the diffractionlike magnetic field modulation of the critical current $I_c$. Here the spatial resolution is constrained solely by the field range of the $I_c(H)$ pattern and is unrelated to the junction’s size. A remarkable feature of this detection method is that high spatial resolution accompanies high field sensitivity.

You might hear an echo in the mountains, but can you hear your voice reflecting from the mug on your desk? Probably not: The intensity of that reflected sound is negligible, compared to the other reflections in your office…and what if we put out more mugs? Acoustic cloning, a form of holography, allows us to study acoustic wave propagation and reflection from a physical scatterer, even with modifications to that object. This study presents both theoretical framework and experimental implementation. The method is expected to be widely applicable in all domains of acoustic scattering, such as material characterization, active metamaterials, and virtual-acoustics applications.

This work demonstrates that triplet-triplet annihilation (TTA) is the predominant mechanism of intrinsic photogeneration of charge-carrier pairs via autoionization, in a single-component disordered organic system with no heavy atoms. The findings challenge established beliefs by revealing efficient carrier generation via TTA upon excitation near the absorption edge. Photocurrent measurements, optical spectroscopy, and spin-sensitive techniques support this model of bimolecular charge generation. Such mechanisms in organic semiconductors are relevant not just for OLEDs, but also for long-persistent luminescence, photovoltaics, and potentially for photocatalytic water splitting.

Internal modifications of transparent solid-state materials by intense, ultrashort laser pulses enable numerous applications in micromachining, photonics, and medicine. Understanding the highly nonlinear propagation of the laser beam through the interaction zone is important in developing these technologies. Here a comprehensive propagation model reveals that even under extremely tight focusing, the key physical quantities are rigidly clamped by plasma shielding, at values up to two orders of magnitude lower than those inferred from earlier studies. Potential routes to overcome the clamping limits are discussed.

Aligning suspended optics in gravitational-wave observatories is crucial for detecting astrophysical phenomena⏤and it is also challenging, due to several environmental factors. This research implements neural-network-based sensing and control deployed at the GEO600 detector, utilizing a sensor with a convolutional neural network and long- and short-term memory, plus a deep-reinforcement-learning-based agent for enhanced alignment. The method demonstrates sensitivity improvement over traditional schemes, thus offering a practical approach for AI-based real-time control of gravitational-wave interferometers, to aid the detection of cosmic events like merging compact neutron-star binaries.

While charge carriers in electronics are fundamental to device operation, little is empirically known about their spatial distribution under standard operating conditions. The authors develop a technique for self-emissive electron microscopy that allows them to image electrons close to their point of generation in operando. Increased electron emission, and thus carrier density, is observed at the ridges of V-shaped defects in a green LED, confirming that the sidewalls of these defects allow lateral carrier injection⏤a necessity for increasing efficiency. Measuring the spatial distribution of carriers with this technique can inform the design of superior devices.