Scaling up cryogenic systems, like arrays of superconducting nanowire single-photon detectors (SNSPDs), requires developing cryogenic coprocessors to minimize the number of cables exiting the cryostat. This work addresses this challenge by demonstrating the ability to read out, process, encode, and store data from SNSPDs using integrated nanowire electronics. The authors design a digital counter based on nanocryotrons—three-terminal nanowire devices—to perform signal processing and digitization at low temperatures. These results suggest that nanowire coprocessors could be developed, which would benefit the application of SNSPD arrays and other superconducting platforms.

The cooling of levitated nanoparticles is a major step in optomechanics, aiming at both fundamental physics experiments and sensing applications, but using nonlinear cooling schemes and electro-optic modulation devices can significantly elevate the cost and complexity of the experiment. The authors implement a practical all-electrical controller capable of cooling the center-of-mass motion of a levitated nanoparticle to sub-Kelvin temperatures. When combined with improved vacuum and detection, this method can provide a simple and direct platform for three-dimensional near-ground-state cooling of the nanoparticle’s motional state.

Perovskite solar cell performance is affected by the rate of charge-carrier transfer into the charge transport layers (CTLs) and interfacial recombination, but these are difficult to distinguish. This study distinguishes them using ultrafast spectroscopy combined with a charge-carrier dynamics model that includes the Coulombic forces arising from the selective extraction of charge carriers. The authors obtain extraction and interface recombination rate constants for three common CTLs and determine the perovskite’s ambipolar diffusivity. These results identify the performance-limiting properties, and could inform the design of superior materials that can be characterized with this method.

Bulk acoustic wave (BAW) resonators that generate dynamic lattice strain are important for applications such as filters, sensors, and quantum control, but there is a lack of measurements available to quantify the strain directly. This study uses stroboscopic X-ray diffraction microscopy with correlated optical measurements on an ensemble of nitrogen-vacancy center defects to measure the dynamic strain in a diamond BAW resonator. This unique approach allows for directly imaging BAW resonator strain to improve fabrication and performance and for directly measuring important parameters of quantum defects to improve quantum control.

Nanomechanical resonators, nanoelectronic systems, amorphous solids, and dark matter searches have each been the subject of recent or proposed experiments at or below 1 mK, but achieving such low cryostat temperatures is challenging. The authors report the performance of an aluminum nuclear demagnetization refrigerator designed to facilitate access to microkelvin temperatures. They found the aluminum refrigerant is well-suited to continuous nuclear demagnetization refrigeration when its natural oxide layer is effectively removed in selected regions. These results will broaden the field of microkelvin physics, accelerating the rate of discovery and increasing its technological potential.

Triferroic multiferroicity, with ferroelectricity, ferromagnetism, and ferroelasticity coexisting in a single phase, is an intriguing phenomenon with promising device applications. Despite their great fundamental and technological importance, triferroic multiferroics remain substantially unexplored—especially those of semiconducting character. This computational study predicts semiconducting triferroic multiferroicity in the layered van der Waals material $T^{\prime }$-TiBr${}_2$, with ferroelastic control of magnetization orientation and ferroelectric control of the absolute values of spin-polarization-density distributions, which is quite exciting.

Laser-written optical waveguides in diamonds are a key technology to enhance coupling between defect centers and light, boosting applications in nanoscale sensing and quantum information processing. However, laser writing of photonic structures produces strain in the diamond lattice, modifying the properties of defect centers in poorly understood ways. This study demonstrates that optically detected magnetic resonance spectroscopy provides sufficient information to fully characterize the spatial distribution of strain in such a device, even without a constant magnetic field. The work yields an accessible tool that could be very useful for advancing diamond-based quantum technologies.

Interlayer exchange coupling (IEC) has been incorporated into almost all magnetic thin-film devices in the form of synthetic antiferromagnets, yet how such coupling is affected by the mixing of magnetic atoms into the nonmagnetic spacer layer is often overlooked. The authors show that antiferromagnetic IEC can be achieved and enhanced by spacer layers containing over 60 at.% of magnetic atoms, leading to huge antiferromagnetic bilinear coupling strength in multilayers deposited by magnetron sputtering. The magnetic atoms in these spacers exhibit a large magnetic moment, highlighting not only the importance of free electrons but also the role of magnetic moments in governing IEC.

High-quality, distributed entanglement forms the foundation for the unequaled level of security that can be assured in quantum key distribution (QKD), but its susceptibility to noise hinders practical implementations. This study experimentally demonstrates that enhancing quantum resources with quantum privacy amplification (QPA) increases the noise resilience of QKD beyond classical limits. Leveraging hyperentanglement in different field-tested degrees of freedom of a photon pair increases the efficiency of QPA, thereby unlocking its advantage for QKD. Here is a method to generate secure keys under noisy conditions, which was previously impossible, paving the way for robust QKD.

Harnessing spin waves for high-speed computing: In this work an innovative spin-wave reservoir chip, utilizing ferromagnetic permalloy thin films, demonstrates exceptional capabilities. By strategically manipulating spin-wave interference, the authors achieve a multi-input–multi-output reservoir capable of memory retention, nonlinearity enhancement, and accurate magnetic field estimation. This spintronic hardware paves the way for high-speed applications in reservoir computing and signal processing.

Arrays of single atoms trapped in optical tweezers have become a leading platform for quantum science and technology. A challenge at the frontier of the field is to scale up the number of atoms into the thousands. In addition, combining these arrays with a cryogenic environment would come with significant gains in lifetime and fidelity of quantum operations. This study successfully combines large-scale atomic arrays with a cryogenic environment, at a temperature of 6 K. The authors demonstrate the rearrangement of more than 800 atoms within a 2000-site array and discuss possible improvements of the setup, in a key step toward better, larger atom arrays for quantum technologies.

Quantum noise spectroscopy (QNS) is a powerful tool to characterize temporally correlated environmental noise, for noise-tailored control in noisy intermediate-scale quantum processors. However, QNS protocols have been limited by their vulnerability to state-preparation-and-measurement (SPAM) errors, and their inability to simultaneously characterize dephasing and relaxation effects. This work overcomes both of these challenges. The authors present a single-qubit QNS protocol utilizing continuous off-axis control for robust estimation of all multiaxis noise spectra, and show that SPAM errors can significantly alter or mask important features of the underlying native noise.

Silicon carbide MOSFETs are transforming power electronics by enabling higher switching frequencies and lower losses than their silicon-only counterparts. This study uses time-gated optical spectroscopy to investigate defect-assisted recombination in fully processed devices, specifically addressing their well-known hysteresis. The inquiry identifies a local vibrational mode with a very energy of 220 meV, indicating the presence of a carbon-cluster-like defect. This approach to characterizing interface states in MOSFETs reveals possibilities for enhancing device reliability and performance.

The ability to simulate XY models of classical spins is rather important, since e.g. it is related to solving NP-hard optimization problems. This study uses a photonic simulator to realize XY Hamiltonians with arbitrary spin connections and coupling strengths. The key unit is an optical system for vector-matrix multiplication that can perform arbitrary transformations of complex matrices. The Berezinskii-Kosterlitz-Thouless transition and ground-state search of several XY models are demonstrated experimentally. Thus this Letter provides an effective alternative approach for investigating such models and solving continuous quadratic optimization problems with optical systems.

Delving into the advancing realm of low-power, high-density magnetic memory, this research presents a Ta/(Pt/Ta)${}_4$/Pt/Co/Ta multilayered structure. Confronting challenges in conventional spin-orbit torque (SOT) magnetic random-access memory (MRAM), such as low spin Hall angles and elevated current densities, the authors achieve a reduction of 79% in critical-switching-current density, while enhancing torque efficiency and minimizing coercivity. Notably, a strong linear correlation among key parameters validates the domain-wall-depinning model, broadening its applicability to diverse metal dopants.

The cooling of levitated nanoparticles is a major step in optomechanics, aiming at both fundamental physics experiments and sensing applications, but using nonlinear cooling schemes and electro-optic modulation devices can significantly elevate the cost and complexity of the experiment. The authors implement a practical all-electrical controller capable of cooling the center-of-mass motion of a levitated nanoparticle to sub-Kelvin temperatures. When combined with improved vacuum and detection, this method can provide a simple and direct platform for three-dimensional near-ground-state cooling of the nanoparticle’s motional state.

Perovskite solar cell performance is affected by the rate of charge-carrier transfer into the charge transport layers (CTLs) and interfacial recombination, but these are difficult to distinguish. This study distinguishes them using ultrafast spectroscopy combined with a charge-carrier dynamics model that includes the Coulombic forces arising from the selective extraction of charge carriers. The authors obtain extraction and interface recombination rate constants for three common CTLs and determine the perovskite’s ambipolar diffusivity. These results identify the performance-limiting properties, and could inform the design of superior materials that can be characterized with this method.

Bulk acoustic wave (BAW) resonators that generate dynamic lattice strain are important for applications such as filters, sensors, and quantum control, but there is a lack of measurements available to quantify the strain directly. This study uses stroboscopic X-ray diffraction microscopy with correlated optical measurements on an ensemble of nitrogen-vacancy center defects to measure the dynamic strain in a diamond BAW resonator. This unique approach allows for directly imaging BAW resonator strain to improve fabrication and performance and for directly measuring important parameters of quantum defects to improve quantum control.

Scaling up cryogenic systems, like arrays of superconducting nanowire single-photon detectors (SNSPDs), requires developing cryogenic coprocessors to minimize the number of cables exiting the cryostat. This work addresses this challenge by demonstrating the ability to read out, process, encode, and store data from SNSPDs using integrated nanowire electronics. The authors design a digital counter based on nanocryotrons—three-terminal nanowire devices—to perform signal processing and digitization at low temperatures. These results suggest that nanowire coprocessors could be developed, which would benefit the application of SNSPD arrays and other superconducting platforms.

Nanomechanical resonators, nanoelectronic systems, amorphous solids, and dark matter searches have each been the subject of recent or proposed experiments at or below 1 mK, but achieving such low cryostat temperatures is challenging. The authors report the performance of an aluminum nuclear demagnetization refrigerator designed to facilitate access to microkelvin temperatures. They found the aluminum refrigerant is well-suited to continuous nuclear demagnetization refrigeration when its natural oxide layer is effectively removed in selected regions. These results will broaden the field of microkelvin physics, accelerating the rate of discovery and increasing its technological potential.

Triferroic multiferroicity, with ferroelectricity, ferromagnetism, and ferroelasticity coexisting in a single phase, is an intriguing phenomenon with promising device applications. Despite their great fundamental and technological importance, triferroic multiferroics remain substantially unexplored—especially those of semiconducting character. This computational study predicts semiconducting triferroic multiferroicity in the layered van der Waals material $T^{\prime }$-TiBr${}_2$, with ferroelastic control of magnetization orientation and ferroelectric control of the absolute values of spin-polarization-density distributions, which is quite exciting.

Laser-written optical waveguides in diamonds are a key technology to enhance coupling between defect centers and light, boosting applications in nanoscale sensing and quantum information processing. However, laser writing of photonic structures produces strain in the diamond lattice, modifying the properties of defect centers in poorly understood ways. This study demonstrates that optically detected magnetic resonance spectroscopy provides sufficient information to fully characterize the spatial distribution of strain in such a device, even without a constant magnetic field. The work yields an accessible tool that could be very useful for advancing diamond-based quantum technologies.

Interlayer exchange coupling (IEC) has been incorporated into almost all magnetic thin-film devices in the form of synthetic antiferromagnets, yet how such coupling is affected by the mixing of magnetic atoms into the nonmagnetic spacer layer is often overlooked. The authors show that antiferromagnetic IEC can be achieved and enhanced by spacer layers containing over 60 at.% of magnetic atoms, leading to huge antiferromagnetic bilinear coupling strength in multilayers deposited by magnetron sputtering. The magnetic atoms in these spacers exhibit a large magnetic moment, highlighting not only the importance of free electrons but also the role of magnetic moments in governing IEC.

High-quality, distributed entanglement forms the foundation for the unequaled level of security that can be assured in quantum key distribution (QKD), but its susceptibility to noise hinders practical implementations. This study experimentally demonstrates that enhancing quantum resources with quantum privacy amplification (QPA) increases the noise resilience of QKD beyond classical limits. Leveraging hyperentanglement in different field-tested degrees of freedom of a photon pair increases the efficiency of QPA, thereby unlocking its advantage for QKD. Here is a method to generate secure keys under noisy conditions, which was previously impossible, paving the way for robust QKD.

Harnessing spin waves for high-speed computing: In this work an innovative spin-wave reservoir chip, utilizing ferromagnetic permalloy thin films, demonstrates exceptional capabilities. By strategically manipulating spin-wave interference, the authors achieve a multi-input–multi-output reservoir capable of memory retention, nonlinearity enhancement, and accurate magnetic field estimation. This spintronic hardware paves the way for high-speed applications in reservoir computing and signal processing.

Arrays of single atoms trapped in optical tweezers have become a leading platform for quantum science and technology. A challenge at the frontier of the field is to scale up the number of atoms into the thousands. In addition, combining these arrays with a cryogenic environment would come with significant gains in lifetime and fidelity of quantum operations. This study successfully combines large-scale atomic arrays with a cryogenic environment, at a temperature of 6 K. The authors demonstrate the rearrangement of more than 800 atoms within a 2000-site array and discuss possible improvements of the setup, in a key step toward better, larger atom arrays for quantum technologies.

Quantum noise spectroscopy (QNS) is a powerful tool to characterize temporally correlated environmental noise, for noise-tailored control in noisy intermediate-scale quantum processors. However, QNS protocols have been limited by their vulnerability to state-preparation-and-measurement (SPAM) errors, and their inability to simultaneously characterize dephasing and relaxation effects. This work overcomes both of these challenges. The authors present a single-qubit QNS protocol utilizing continuous off-axis control for robust estimation of all multiaxis noise spectra, and show that SPAM errors can significantly alter or mask important features of the underlying native noise.

Silicon carbide MOSFETs are transforming power electronics by enabling higher switching frequencies and lower losses than their silicon-only counterparts. This study uses time-gated optical spectroscopy to investigate defect-assisted recombination in fully processed devices, specifically addressing their well-known hysteresis. The inquiry identifies a local vibrational mode with a very energy of 220 meV, indicating the presence of a carbon-cluster-like defect. This approach to characterizing interface states in MOSFETs reveals possibilities for enhancing device reliability and performance.