Superconducting qubits are building blocks for quantum processors, but they suffer from frequency collisions, which hinder the construction of large qubit lattices. This study introduces weakly tunable qubits, whose frequency can be tuned over a small range via external magnetic flux. Through theoretical derivation and experimental demonstration, the authors show that these transmonlike qubits—without losing the desired key properties—can be used to avoid frequency collisions in large qubit systems while minimizing the sensitivity to flux noise. They can also be applied to operate flux-tuned qubit gates.

A sensor containing thumbnail-sized interferometers might help astronomers detect gravitational waves emitted from certain black hole mergers.

Even though silicon is widely used in superconducting quantum processors as the substrate upon which qubits are fabricated, the effect of silicon on the performance of the qubits is not fully understood. Using ultrahigh-quality microwave cavities to measure dielectric loss with parts-per-billion precision, the authors clearly show that using silicon is detrimental to qubit coherence time. The loss tangent found here is an order of magnitude worse than previously measured. This study sheds light on the physical mechanisms behind dissipation in silicon, and highlights the need for further work to fully understand the origin of these losses, and how to mitigate them.

Infrared quantum absorption spectroscopy (IRQAS) enables the estimation of a sample’s optical properties in the infrared region, using only a visible light source and detectors, which is technologically favorable. So far, spectral coverage of IRQAS systems has been limited to less than 1 µm. This work reports a wavelength-tunable IRQAS system and an efficient measurement scheme to achieve broadband spectroscopy in a short acquisition time. The successful demonstration of rapid spectral measurement over a wide midinfrared window (1.9–5.2 µm) exhibits the great potential of this technique and paves the way for the use of IRQAS in real-world applications.

Qubit measurement is an essential step in any quantum computation. In circuit quantum electrodynamics, a leading quantum computer architecture, qubit readout is commonly one of the longest and lowest-fidelity processes. The authors numerically explore the dynamics of a driven transmon-resonator system under strong, nearly resonant measurement drives to better understand this issue. They find clear signs of transmon “ionization”, in which the qubit escapes its confining potential under the influence of the drive, and semiclassical methods then reveal the mechanism. This approach can be used to optimize circuit parameters, suppress these spurious effects, and increase readout fidelity.

Already a building block of modern life, silicon is also poised to power the next leap in information technology, in which the quantum mechanical properties of single impurities located just beneath its surface can be used to create vastly more powerful computers. Here a multinational team presents a specialized microscope to better understand the inner workings of such silicon chips, by scanning a finely focused beam of ultralow-energy ions across the surface. The tiny “click” that each ion makes when it hits the chip is detected and mapped, enabling the identification of manufacturing defects; these results can then be fed back to improve the fabrication process.

Tunable couplers, which turn on and off the interaction between qubits, have emerged as a key means to achieve low error rates in superconducting quantum computers. Conventional devices using one transmon qubit exhibit unwanted residual coupling, though, especially at the high detuning that is desirable for suppressing crosstalk errors. To solve this critical problem, the author proposes a tunable coupler based on two transmons that satisfies the ideal conditions of no residual coupling and fast two-qubit gate operations at high detuning. This double-transmon coupler is expected to become standard for superconducting architectures by eliminating unwanted coupling during idle time.

Reconfigurable metamaterials have attracted significant attention due to their cross-disciplinary importance, with applications from deployable space structures to soft robots. These applications might benefit from high-dimensional stable deformations under minimal actuation, which known structures have not demonstrated. The authors present a comprehensive dynamical model and experiments based on pressurized strawlike elements, which are lattices of ungrounded unit cells with high-order multistability. These elements can maintain a myriad of complex stable configurations and exhibit complex dynamical transitions—properties that pave the way toward significant engineering advances.

Ultrasensitive nanomechanical sensors are envisioned to enable nanoscale magnetic resonance imaging (nano-MRI) and other scanning force microscopy applications. However, their sensitivity to very small forces makes such sensors susceptible to unwanted tip-surface interactions that cause bending and instability. This study shows how these noncontact interactions affect scanning force measurements. The authors present strategies to overcome the challenges of overcoupling, which lead to the successful demonstration of faithful nano-MRI reconstruction of individual influenza viruses.

Quantum sensing of low-frequency fields is important for nuclear magnetic resonance (NMR) due to its rich structure and narrow line widths, both at low fields focusing on $J$ couplings and at high fields for down-converted frequencies from conventional NMR. However, the most sensitive and coherent quantum sensing methods work at dc and high-frequency fields only. This study utilizes a quantum oscilloscope approach to bridge this gap. The resulting algorithm has a frequency-independent sensitivity and is able to work in the zero-field region. This approach would have an impact on designing low-frequency measurements where the high sensitivities of quantum sensors are an indispensable treat.

Light may be manipulated not only in space, but also in time. This study uses a nonreciprocal temporal-loop-based phase shifter to construct a low-noise, low-profile, and linear nonmagnetic circulator. In contrast to conventional magnet-based circulators, such a temporal circulator is controllable, compatible with integrated-circuit technology, and suitable for high frequencies. The experimental demonstration at microwave frequencies seems very promising.

Tin halide perovskites present outstanding optoelectronic properties and great application potential, without the toxicity of lead. Here a systematic first-principles investigation reveals that a high-density defect complex, consisting of a tin vacancy plus a hydrogen molecule ($V_{\mathrm{Sn}}$–H${}_2$), is a highly effective center for nonradiative recombination of electrons and holes in this semiconductor. That would explain the experimentally observed significant nonradiative loss in devices based on formamidinium tin triiodide. Therefore, the passivation of this defect complex is expected to improve the performance of tin-based perovskite solar cells and other optoelectronic devices.

Plasmonic antennas as polariton launchers are crucial for light manipulation down to the nanoscale. However, unlike their well-established radio-frequency counterparts, these nanoantennas lack a roadmap for their purpose-driven design. This study offers a framework based on rf concepts for approaching directional polariton launchers in two-dimensional systems. By offering several guidelines applied to simulations and near-field experiments, the work promises to accelerate the engineering of polariton launchers for tomorrow’s nanophotonic devices.

The Josephson effect has enabled many applications in superconducting electronics. Meanwhile, spin-orbit coupling (SOC) is crucial for many normal-state spin-based devices. Our respective advances in understanding these two phenomena have been largely decoupled, though, with the implications from their interplay left unexplored. The authors address this disconnect and discover fascinating opportunities in Josephson junctions that can be strongly tuned and dynamically driven by time-dependent SOC. Their transparent findings, supported by recent experiments, are directly related to superconducting electronics and spintronics, improving qubits, and controlling Majorana states.

The ability to generate structured light in different media is important for various applications, such as optical trapping, imaging, and data communication, but is technically difficult. This study uses ideas from the calculus of variations to develop a simplified, consistent framework that can be used to generate the required customized optical fields. The proposed approach is easily generalized, extending its applicability beyond optics to other wave-related phenomena and subjects, such as acoustics.

Even though silicon is widely used in superconducting quantum processors as the substrate upon which qubits are fabricated, the effect of silicon on the performance of the qubits is not fully understood. Using ultrahigh-quality microwave cavities to measure dielectric loss with parts-per-billion precision, the authors clearly show that using silicon is detrimental to qubit coherence time. The loss tangent found here is an order of magnitude worse than previously measured. This study sheds light on the physical mechanisms behind dissipation in silicon, and highlights the need for further work to fully understand the origin of these losses, and how to mitigate them.

Infrared quantum absorption spectroscopy (IRQAS) enables the estimation of a sample’s optical properties in the infrared region, using only a visible light source and detectors, which is technologically favorable. So far, spectral coverage of IRQAS systems has been limited to less than 1 µm. This work reports a wavelength-tunable IRQAS system and an efficient measurement scheme to achieve broadband spectroscopy in a short acquisition time. The successful demonstration of rapid spectral measurement over a wide midinfrared window (1.9–5.2 µm) exhibits the great potential of this technique and paves the way for the use of IRQAS in real-world applications.

Qubit measurement is an essential step in any quantum computation. In circuit quantum electrodynamics, a leading quantum computer architecture, qubit readout is commonly one of the longest and lowest-fidelity processes. The authors numerically explore the dynamics of a driven transmon-resonator system under strong, nearly resonant measurement drives to better understand this issue. They find clear signs of transmon “ionization”, in which the qubit escapes its confining potential under the influence of the drive, and semiclassical methods then reveal the mechanism. This approach can be used to optimize circuit parameters, suppress these spurious effects, and increase readout fidelity.

Already a building block of modern life, silicon is also poised to power the next leap in information technology, in which the quantum mechanical properties of single impurities located just beneath its surface can be used to create vastly more powerful computers. Here a multinational team presents a specialized microscope to better understand the inner workings of such silicon chips, by scanning a finely focused beam of ultralow-energy ions across the surface. The tiny “click” that each ion makes when it hits the chip is detected and mapped, enabling the identification of manufacturing defects; these results can then be fed back to improve the fabrication process.

Tunable couplers, which turn on and off the interaction between qubits, have emerged as a key means to achieve low error rates in superconducting quantum computers. Conventional devices using one transmon qubit exhibit unwanted residual coupling, though, especially at the high detuning that is desirable for suppressing crosstalk errors. To solve this critical problem, the author proposes a tunable coupler based on two transmons that satisfies the ideal conditions of no residual coupling and fast two-qubit gate operations at high detuning. This double-transmon coupler is expected to become standard for superconducting architectures by eliminating unwanted coupling during idle time.

A sensor containing thumbnail-sized interferometers might help astronomers detect gravitational waves emitted from certain black hole mergers.

Reconfigurable metamaterials have attracted significant attention due to their cross-disciplinary importance, with applications from deployable space structures to soft robots. These applications might benefit from high-dimensional stable deformations under minimal actuation, which known structures have not demonstrated. The authors present a comprehensive dynamical model and experiments based on pressurized strawlike elements, which are lattices of ungrounded unit cells with high-order multistability. These elements can maintain a myriad of complex stable configurations and exhibit complex dynamical transitions—properties that pave the way toward significant engineering advances.

Ultrasensitive nanomechanical sensors are envisioned to enable nanoscale magnetic resonance imaging (nano-MRI) and other scanning force microscopy applications. However, their sensitivity to very small forces makes such sensors susceptible to unwanted tip-surface interactions that cause bending and instability. This study shows how these noncontact interactions affect scanning force measurements. The authors present strategies to overcome the challenges of overcoupling, which lead to the successful demonstration of faithful nano-MRI reconstruction of individual influenza viruses.

Superconducting qubits are building blocks for quantum processors, but they suffer from frequency collisions, which hinder the construction of large qubit lattices. This study introduces weakly tunable qubits, whose frequency can be tuned over a small range via external magnetic flux. Through theoretical derivation and experimental demonstration, the authors show that these transmonlike qubits—without losing the desired key properties—can be used to avoid frequency collisions in large qubit systems while minimizing the sensitivity to flux noise. They can also be applied to operate flux-tuned qubit gates.

Quantum sensing of low-frequency fields is important for nuclear magnetic resonance (NMR) due to its rich structure and narrow line widths, both at low fields focusing on $J$ couplings and at high fields for down-converted frequencies from conventional NMR. However, the most sensitive and coherent quantum sensing methods work at dc and high-frequency fields only. This study utilizes a quantum oscilloscope approach to bridge this gap. The resulting algorithm has a frequency-independent sensitivity and is able to work in the zero-field region. This approach would have an impact on designing low-frequency measurements where the high sensitivities of quantum sensors are an indispensable treat.

Light may be manipulated not only in space, but also in time. This study uses a nonreciprocal temporal-loop-based phase shifter to construct a low-noise, low-profile, and linear nonmagnetic circulator. In contrast to conventional magnet-based circulators, such a temporal circulator is controllable, compatible with integrated-circuit technology, and suitable for high frequencies. The experimental demonstration at microwave frequencies seems very promising.

Compared to traditional solar cells, solar thermophotovoltaic (STPV) systems have the advantage of utilizing the full spectrum of solar radiation, but their thermodynamic efficiency is still far lower than the ultimate limit. This study shows that the efficiency deficit is caused by back emission from the intermediate layer toward the sun, resulting from the reciprocity of the system. The authors therefore propose using an intermediate layer with nonreciprocal radiative properties, which would suppress back emission and funnel more photons toward the cell, for a significant efficiency boost.

Tin halide perovskites present outstanding optoelectronic properties and great application potential, without the toxicity of lead. Here a systematic first-principles investigation reveals that a high-density defect complex, consisting of a tin vacancy plus a hydrogen molecule ($V_{\mathrm{Sn}}$–H${}_2$), is a highly effective center for nonradiative recombination of electrons and holes in this semiconductor. That would explain the experimentally observed significant nonradiative loss in devices based on formamidinium tin triiodide. Therefore, the passivation of this defect complex is expected to improve the performance of tin-based perovskite solar cells and other optoelectronic devices.

Plasmonic antennas as polariton launchers are crucial for light manipulation down to the nanoscale. However, unlike their well-established radio-frequency counterparts, these nanoantennas lack a roadmap for their purpose-driven design. This study offers a framework based on rf concepts for approaching directional polariton launchers in two-dimensional systems. By offering several guidelines applied to simulations and near-field experiments, the work promises to accelerate the engineering of polariton launchers for tomorrow’s nanophotonic devices.