The integration of cold atoms with nanophotonic chips is a promising approach for realizing scalable quantum technologies, yet stable trapping of single atoms near chip surfaces remains an outstanding challenge. Here we study the dynamics of single ${}^{87}\mathrm{Rb}$ atoms near the surface of a photonic chip by deterministically delivering single atoms to sub-10-$\text{μ}\mathrm{m}$ distances from the chip surface using optical tweezers. We use a translatable tweezer to transport atoms to the chip surface, revealing that atom loss is dominated by surface-induced evaporation as atoms at temperatures of approximately $0.1\mathrm{mK}$ collide with the 300 K surface. To overcome this loss mechanism, we implement an optical conveyor belt technique that transfers atoms in a standing-wave tweezer, preventing direct surface collisions. This approach enables single-atom lifetimes of up to 4 s in close proximity to the chip without the assistance of additional laser cooling. Our results demonstrate the viability of long-lived atomic qubits when they are integrated with photonic circuits and provide design insights for hybrid quantum systems. These advancements pave the way for the creation of scalable atom-photon interfaces, which could find applications in quantum networking, computation, simulation, and sensing.

A photonic heat amplifier designed for cryogenic operations is introduced and analyzed. This device comprises two variable-range-hopping reservoirs connected by lossless lines, which allow them to exchange heat through photonic modes. This configuration enables negative differential thermal conductance, which can be harnessed to amplify thermal signals. To achieve this, one reservoir is maintained at a high temperature, serving as the source terminal of a thermal transistor. Concurrently, in the other reservoir, we establish tunnel contacts to metallic reservoirs, which function as the gate and drain terminals. With this arrangement, it is possible to control the heat flux exchange between the source and the drain by adjustment of the gate temperature. We present two different parameter choices that yield different performances: the first emphasizes modulation of the source-drain heat current, while the second focuses on the modulation of the lower-temperature variable-range-hopping reservoir. Lastly, we present a potential design variation in which all electronic reservoirs are thermally connected through only photonic modes, allowing interactions between distant elements. The proposed photonic heat amplifier addresses the lack of thermal transistors and amplifiers in the millikelvin range, while being compatible with the rich toolbox of circuit quantum electrodynamics. It can be adapted to various applications, including sensing and the development of thermal circuits and control devices at subkelvin temperatures, which are relevant to quantum technologies.

Waveguide quantum electrodynamics—the study of atomic systems interacting with propagating electromagnetic fields—is a powerful platform for understanding the complex interplay between light and matter. Qubit control is an indispensable tool in this field, and most experiments thus far have used narrowband control pulses to interact with qubits at specific frequencies. Dynamics can change significantly with fast, broadband pulses, since waveguide properties such as dispersion affect the pulse evolution and its impact on the qubit. Here we use dispersion to achieve spatial addressing of superconducting qubits separated by a subwavelength distance within a microwave waveguide. This approach relies on a self-focusing effect to create a position-dependent interaction between a chirped pulse and an individual qubit. This method emphasizes the importance of dispersion in the design and analysis of quantum experiments, and offers avenues for the rapid control of quantum states.

We simultaneously cool $\gtrsim 100$ mechanical modes of a membrane with a photothermally modified optical cavity driven by a single blue-detuned laser. In contrast to radiation pressure and bolometric forces applied directly to the mechanical system, this cooling effect does not depend on the sign of the detuning, allowing for single-laser stabilization (i.e., simultaneous positive optical spring and damping) that is especially effective at room temperature and high laser power. We also provide intuition about the competing thermal processes and propose two simple modifications to the mirror coatings that can strongly enhance this effect.

Superconducting traveling-wave parametric amplifiers (TWPAs) are increasingly used in various applications, including quantum computing, quantum sensing, and dark-matter detection. However, one characteristic of these amplifiers, gain compression, has not received much attention. As a result, there is a lack of comprehensive experimental exploration of this phenomenon in the existing literature. In this study, we present an experimental investigation of gain compression in a Josephson traveling-wave parametric amplifier based on a four-wave mixing process. We have implemented an alternative setup to monitor the complex transmission of both the pump and signal tones, which allows us to simultaneously track pump depletion and signal amplification as functions of signal power and frequency across the entire bandwidth of the device. Our findings indicate that, while pump depletion occurs during gain compression, it is not the only mechanism involved in the saturation of a TWPA. Power-induced phase-matching processes also take place within the device. This study provides valuable insights for optimizing TWPAs for applications that require high total input power, such as multiplexed qubit readout or broadband photon emission.

The separation of physical forces acting on the tip of a magnetic force microscope (MFM) is essential for correct magnetic imaging. Electrostatic forces can be modulated by varying the tip-sample potential and minimized to map the local Kelvin potential. However, distinguishing magnetic forces from van der Waals forces typically requires two measurements with opposite tip magnetizations under otherwise identical measurement conditions. Here, we present an inverted magnetic force microscope where the sample is mounted on a flat cantilever for force sensing, and the magnetic tip is attached to a miniaturized electromagnet that periodically flips the tip’s magnetization. This setup enables the extraction of magnetic tip-sample interactions from the sidebands occurring at the switching rate in the cantilever oscillation spectrum. Our method achieves the separation of magnetic signals from other force contributions in a single-scan mode. Future iterations of this setup may incorporate membrane, trampoline, or string resonators with ultrahigh quality factors, potentially improving measurement sensitivity by up to 3 orders of magnitude compared to the state-of-the-art MFM systems using cantilevers.

Vacuum-gap capacitors have recently attracted significant interest in superconducting circuit platforms due to their compact design and exceptionally low dielectric losses in the microwave regime. Their intrinsic ability to support mechanical vibrational modes makes them well suited for circuit optomechanics. However, precise control over the gap size and the realization of high-coherence mechanical modes remain longstanding challenges. Here, we present a detailed and scalable fabrication process for vacuum-gap capacitors that support ultrahigh-coherence mechanical motion, exhibit low microwave loss, and occupy a significantly smaller footprint compared to conventional planar geometries. By employing a planarized ${\mathrm{Si}\mathrm{O}}_2$ sacrificial layer, we achieve vacuum gaps on the order of 150 nm. Using this platform, we have recently demonstrated ground-state cooling and motion squeezing of a mechanical oscillator with a quality factor of 40 million—a 100-fold improvement compared to prior works—as well as a single-photon optomechanical coupling rate of approximately 15 Hz [Youssefi et al., Nat. Phys. 19, 1697 (2023)]. Additional achievements include the realization of an optomechanical topological lattice with 24 sites [Youssefi et al., Nature 612, 666 (2022)] and the observation of quantum collective dynamics in a mechanical hexamer [Chegnizadeh et al., Science 386, 1383 (2024)]. Collectively, these results underscore the potential of vacuum-gap capacitors as a platform for coupling superconducting qubits to mechanical systems, enabling quantum storage, and probing gravitational effects in quantum mechanics.

Pressure is a key parameter for tuning or revealing superconductivity in materials and compounds. Many measurements of superconducting phase transition temperatures have been conducted using diamond anvil cells (DACs), which provide a wide pressure range and enable concomitant microscopic structural characterization of the sample. However, the inherently small sample volumes in DACs complicate the unambiguous detection of the Meissner effect, the hallmark of superconductivity. Recently, the Meissner effect in superconductors within a DAC was successfully demonstrated using diamond nitrogen-vacancy (N-$V$) widefield magnetometry, a noninvasive optical technique. In this work, we show that N-$V$ magnetometry can also map superconductivity with micrometer resolution. We apply this technique to a microcrystal of ${\mathrm{Hg}\mathrm{Ba}}_2{\mathrm{Ca}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{8+\delta }$ ($\mathrm{Hg}$-1223) mercury-based cuprate superconductor under 4 GPa of pressure. The method is capable of mapping the magnetic field expulsion and the critical temperature $T_c$ of the sample, allowing to determine its heterogeneities. Flux pinning zones are identified through flux trapping maps. This approach could enable detailed investigations of superconductivity of a broad range of materials under high-pressure conditions.

We present a high-power continuous-wave (cw) lunar laser ranging (LLR) technique that has the potential to significantly improve Earth-Moon distance measurements. Using a 1-kW cw laser at 1064 nm and a 1-m-aperture telescope as an example, we develop a detailed link budget and analyze the prevailing noise sources to assess system performance when ranging to next-generation $\sim 10$-cm corner-cube retroreflectors (CCRs). Unlike legacy arrays, these smaller CCRs are designed to yield lower intrinsic range errors, yet their reduced reflective area results in lower photon return rates, posing challenges for pulsed LLR systems. The photon-rich cw approach, by providing continuous high-power illumination, overcomes this limitation, reducing shot noise and enabling sustained millimeter-level ranging with a pathway to sub-0.1-mm precision. Furthermore, by alternating measurements between widely separated lunar reflectors, differential LLR mitigates common-mode station errors to achieve tens-of-micrometer precision, limited primarily by uncorrelated atmospheric turbulence. This scalable approach—integrating high-power cw lasers, narrowband filtering, and rapid atmospheric turbulence averaging—enables next-generation gravitational tests, precision lunar geodesy, and improved lunar reference frames in support of planetary exploration.

We propose a numerical approach to design highly efficient adiabatic schedules for analog quantum computing, focusing on the maximum-independent-set problem and neutral atom platforms. On the basis of a representative dataset of small graphs, we present numerical evidence that the optimum schedules depend principally on the hardness of the problem rather than on its size. These schedules perform better than the benchmark protocols and admit a straightforward implementation in the hardware. This allows us to extrapolate the results to larger graphs and to successfully solve moderately hard problems using QuEra’s 256-qubit Aquila computer. We believe that extending our approach to hybrid algorithms could be the key to solving the hardest instances with the current technology, making yet another step toward real-world applications.

Biomolecular condensates in cells underpin cellular organization but have also been implicated in disease progression. As a result, modulation of condensate formation is becoming a path of interest to ameliorate biological malfunction. However, identifying the mechanism of action of a modulator is particularly challenging. This is because condensates are typically highly multicomponent, rendering it difficult to delineate which molecular interactions a modulator is influencing to drive or oppose condensate formation. Here, we extend the theoretical framework of energy dominance to include modulation effects, allowing us to uncover mechanisms of action of small molecular modulators through measuring species energetics. Using this approach, we experimentally investigate the effect of the small molecule suramin on condensates formed by the RNA-binding protein G3BP1 and RNA. We show that suramin specifically disrupts G3BP1-RNA interactions, as independently confirmed though orthogonal binding assays. Together, this work paves the way for systematic studies of condensate modulators in the future.

Hybrid quantum systems are highly promising platforms for addressing important challenges in quantum information science and quantum sensing. Their implementation, however, is technologically nontrivial since each component typically has unique experimental requirements. Here, we work toward a hybrid system consisting of a superconducting on-chip microwave circuit in a dilution refrigerator and optically trapped ultracold atoms. Specifically, we focus on the design optimization of a suitable superconducting chip and on the corresponding challenges and limitations. We present detailed microwave-cavity engineering strategies for maximized and tunable coupling rates to atomic Rydberg-Rydberg transitions in ${}^{87}\mathrm{Rb}$ atoms while respecting the boundary conditions due to the presence of a laser beam near the surface of the chip. Finally, we present an experimental implementation of the superconducting microwave chip and discuss the cavity characteristics as a function of temperature and applied dc voltage. Our results highlight the considerations required for realizing a flexible, tunable superconductor-atom hybrid system and lay the groundwork for realizing this exciting platform in a dilution refrigerator with vacuum Rabi frequencies approaching the strong-coupling regime.

Electron-energy-loss spectroscopy (EELS) with an electron microscope and X-ray absorption spectroscopy (XAS) with a synchrotron are techniques for material characterization, both of which are based on exciting core electrons. Both techniques have a similar energy resolution, but while the spatial resolution of EELS can drop to atomic scales, the spatial resolution of XAS is typically limited to micrometer scales. Yet, XAS is commonly the preferred technique for analysis of the extended fine structure of ionization edges, mainly thanks to the excellent signal-to-noise ratio and the large range of ionization energies (from ∼5 to ∼40 keV) that can be probed at synchrotron end stations. In contrast, EELS is traditionally limited to ionization energies of $\lesssim$2 keV because electrons in the beam that lose more than 2 keV will be too distant from the operating energy of the electron microscope. Chromatic effects in the postsample lenses allow only some of such energy-loss electrons to reach the EELS detector, as the latter electrons will either suffer from being strongly defocused or will not make it to the detector at all. In this paper, we present results from our novel Iliad EELS spectrometer, which offers a greatly increased range of ionization energies up to 30 keV. We achieve this vast increase by carefully controlling the optics of our electron microscope and carefully matching the optics of our EELS spectrometer to it, such that all the chromatic effects are removed or compensated. We exemplify its performance by recording EELS near-edge fine structure (ELNES) of the $\mathrm{Zr}$ L-edges at 2.3 keV, extended fine structure EELS (EXELFS) of $\mathrm{Cu}$ K-edge at ∼9 keV, and EELS of the Mo K-edge at 20 keV and $\mathrm{Sb}$ K-edge at ∼30 keV. We benchmark our data against near-edge and extended fine structure X-ray absorption (XANES and EXAFS) data, and we quantitatively analyze the $\mathrm{Cu}$ K-edge EXELFS, demonstrating the capability to determine element-specific bond lengths and to distinguish different oxidation states such as metallic $\mathrm{Cu}$, ${\mathrm{Cu}}_2\mathrm{O}$, or $\mathrm{Cu}\mathrm{O}$ on a submicrometer scale.

As a point defect with unique spin and optical properties, nitrogen-vacancy ($\mathrm{N}\text{−}$V) centers in diamond have attracted considerable attention in the fields of quantum sensing, quantum simulation, and quantum networks. The optical properties of an $\mathrm{N}\text{−}$V center are crucial for all these quantum applications. However, $\mathrm{N}\text{−}$V centers fabricated by destructive methods, such as electron irradiation or ion implantation, usually exhibit poor optical coherence. In this work, we demonstrate a nondestructive method to fabricate optically coherent $\mathrm{N}\text{−}$V centers. High-purity single-crystal diamonds are annealed under high-pressure and high-temperature conditions (≥1750 °C, 5.5 GPa), and individually resolvable $\mathrm{N}\text{−}$V centers with narrow PLE linewidth (<100 MHz) are produced. These $\mathrm{N}\text{−}$V centers have excellent spin coherence and charge environment and are suitable for the most advanced quantum applications. The high-pressure condition prevents the conversion of diamond to graphite during high-temperature annealing, significantly expanding the parameter space for creating high-performance artificial defects. These findings deepen our understanding of $\mathrm{N}\text{−}$V center formation in diamond and have implications for the optimization of color centers in solids, including silicon carbide and other wide-band-gap semiconductors.

Physical reservoir computing has emerged as a powerful framework for exploiting the inherent nonlinear dynamics of physical systems to perform computational tasks. Recently, we presented the magnon-scattering reservoir, whose internal nodes are given by the fundamental wavelike excitations of ferromagnets called magnons. These excitations can be geometrically quantized and, in response to an external stimulus, show transient nonlinear scattering dynamics that can be harnessed to perform memory and nonlinear transformation tasks. Here, we test a magnon-scattering reservoir in a single magnetic disk in the vortex state against two key performance indicators for physical reservoir computing: the short-term memory and parity-check tasks. Using time-resolved Brillouin light scattering microscopy, we measure the evolution of the reservoir’s spectral response to an input sequence consisting of random binary inputs encoded in microwave pulses with two distinct frequencies. Two different output spaces of the reservoir are defined: one based on the time-averaged frequency spectra and another based on temporal multiplexing. Our results demonstrate that the memory and nonlinear transformation capability do not depend on the chosen readout scheme, provided that the dimension of the output space is large enough to capture all nonlinear features provided by the magnon-magnon interactions. This further shows that it is solely the nonlinear magnons in the physical system—not the readout—that determine the reservoir’s capacity.

Achieving densely connected hardware graphs is a challenge for most quantum computing platforms today, and a particularly crucial one for the case of quantum annealing applications. In this context, we present a scalable architecture for quantum annealers to realize effective Ising Hamiltonians of arbitrary connectivity. Our proposal consists of a resource-efficient configuration based on a hardware graph where physical qubits are connected to at most three others and containing exclusively 2-local interactions. We derive this configuration based on chains of qubits encoding logical variables by describing the problem graph in terms of triangles. We thus present a promising route to scale up devices dedicated to classical optimization tasks within the quantum annealing paradigm.

Josephson parametric amplifiers (JPAs) typically require rf pump power that is several orders of magnitude stronger than the maximum signal power they can handle. The low power efficiency and strong pump leakage into the signal circuitry could be critical concerns in practical applications. In this work, we discuss how to optimize the pump coupling scheme for a three-wave mixing JPA by employing microwave filtering techniques, with the goal of maximizing pump power efficiency and minimizing pump leakage without sacrificing other properties of interest. We implement the corresponding filter design in a superconducting nonlinear asymmetric inductive element (SNAIL)-based JPA and demonstrate an improvement of more than 3 orders of magnitude in both power efficiency and pump-leakage suppression compared to a similar device with conventional capacitive coupling, while maintaining state-of-the-art dynamic range and near-quantum-limited noise performance. Furthermore, we show experimentally that the filter-coupled JPA is more robust against noise input from the pump port, exhibiting no significant change in added noise performance with up to 4 K of effective noise temperature at the pump port.

Lumped-element inductors are an integral component in the circuit QED toolbox. However, it is challenging to build inductors that are simultaneously compact, linear, and low-loss with standard approaches that either rely on the geometric inductance of superconducting thin films or on the kinetic inductance of Josephson-junction arrays. In this work, we overcome this challenge by utilizing the high kinetic inductance offered by superconducting granular aluminum (grAl). We demonstrate lumped-element inductors with a few nH of inductance that are up to $100$ times shorter than inductors built from pure aluminum (Al). To characterize the properties of these linear inductors, we first report on the performance of lumped-element resonators built entirely out of grAl with sheet inductances varying from $30$–$320$ pH/sq and self-Kerr nonlinearities of $0.2$–$20\mathrm{Hz}/\mathrm{photon}$. Further, we demonstrate ex situ integration of these grAl inductors into hybrid resonators with $\mathrm{Al}$ or tantalum ($\mathrm{Ta}$) capacitor electrodes without increasing total internal losses. Interestingly, the measured internal quality factors systematically decrease with increasing room-temperature resistivity of the grAl film for all devices, indicating a trade-off between compactness and internal loss. For our lowest resistivity grAl films, we measure quality factors reaching $3.5\times {10}^6$ for the all-grAl devices and $4.5\times {10}^6$ for the hybrid grAl/$\mathrm{Ta}$ devices, similar to state-of-the-art quantum circuits. Our loss analysis suggests that the surface-loss factor of grAl is similar to that of pure $\mathrm{Al}$ for our lowest resistivity films, while the increasing losses with resistivity could be explained by increasing inductor loss in the grAl film.

Since the 1950s, soft ionic devices have evolved from individual components to an expanding library of sensors, actuators, signal transmitters, and processors. However, integrating these components into complex, multifunctional systems remains challenging due to the nonintuitive and nonlinear interactions between ionic elements. In this work, we address these fundamental challenges by developing a lumped element model that enables interrogation of the physics that governs ionic circuits, as well as rapid design and optimization. Our model captures features specific to ionic charge carriers, while preserving the hierarchical design flexibility and computational efficiency of traditional circuit modeling. We demonstrate that our model can not only fit individual device behavior but also accurately predict the behavior of larger circuits formed by combining those devices. Additionally, we show how our tool utilizes the intrinsic nonlinearities of ionic systems to enable extended functionality, revealing how factors such as ion enrichment, ion leakage, and polymer charge density influence performance. Finally, we present a fully ionic power supply, sensor, control system, and actuator for a soft robot that adapts its motion in response to environmental salt, illustrating the tool’s potential to accelerate advancements in chemical sensing, biointerfacing, biomimetic systems, and adaptive materials.

Brain-inspired learning in physical hardware has enormous potential for rapid learning with minimal energy expenditure. One of the characteristics of biological learning systems is their ability to learn in the presence of various noise sources. Inspired by this observation, we introduce a noise-based learning approach for physical systems implementing multilayer neural networks. Simulation results show that our approach allows for effective learning with a performance approaching that of the conventional backpropagation algorithm, which is effective but has a high energy cost. Using a spintronics hardware implementation, we demonstrate experimentally that learning can be achieved in a small network composed of physical stochastic magnetic tunnel junctions. These results provide a path toward efficient learning in general physical systems that embraces rather than mitigates the noise inherent in physical devices.