Atomic interferometers offer extraordinary inertial sensitivity, yet their intrinsically periodic response has long prevented continuous operation over a wide dynamic range. The authors demonstrate a dual-channel closed-loop atomic beam interferometer, enabling simultaneous quantum feedback for rotation and acceleration. By converting periodic matter-wave interference into continuously tracked control parameters, the scheme overcomes the conventional half-fringe limitation while preserving precision. This advance brings practical quantum inertial navigation a significant step closer.

What happens when a photon is absorbed by a superconductor? Although vortex-antivortex pairs have long been suspected to play a central role in superconducting photon detection, their dynamics following photon absorption have eluded direct observation. By monitoring quantized voltage signals generated by photon-induced vortices, the authors reveal their generation statistics and demonstrate photon-number resolution. This work provides a rare microscopic view of photon detection in superconductors, and opens a route toward fast superconducting photon-number-resolving detectors.

Quantum topological structured light offers a promising route to robust information encoding, but its practical realization is limited by the challenge of generating high-quality states in a reconfigurable manner. The authors demonstrate an interferometric approach that generates high-fidelity topological structured light by mapping spatial-mode entanglement onto hybrid spatial-polarization entangled states, with the interferometer implementing a reconfigurable controlled-unitary operation through programmable spatial modulation. This versatile platform for generating high-quality topological quantum states enables adaptable architectures for photonic quantum information processing.

Spin manipulation by hopping has emerged as an attractive approach for efficient spin control in arrays of germanium hole-spin qubits. The physical mechanism relies on disorder-induced differences in the axes of spin precession in neighboring quantum dots, though, and thus is ineffective in the absence of disorder. This work proposes electrostatic squeezing of the quantum dots to engineer the spin-precession axis deterministically, which would render spin manipulation independent of any disorder. Remarkably, the protocol remains robust even under moderate disorder, offering a promising pathway for spin manipulation in large, sparse spin-qubit arrays.

Computers can now autonomously design intricate electromagnetic devices for communication, sensing, and quantum technologies, but optimizers routinely get trapped by locally optimal designs that are still far from the best. This work temporarily reshapes the governing physics into a smooth problem that can be solved exactly. The reshaped problem delivers not only a blueprint for the device but also a map of its own uncertainty, showing where to trust the blueprint and where to keep exploring. Across eight distinct photonic and microwave design tasks, this convex preoptimization consistently beats conventional stop-and-restart sweeps while using a fraction of the computing time.

Fault-tolerant quantum computing depends on ancilla qubits that can extract error syndromes from data qubits, but ancilla errors can propagate back to the data qubits, contaminating the very information they are meant to protect. The Kerr-cat qubit has been proposed as a better ancilla, but a suitable interaction between Kerr-cat and transmon qubits needs to be experimentally verified. This study finds a beam-splitter interaction between a Kerr-cat and a transmon, producing an effective ẐX̂ coupling suitable for parity readout, and confirms expected behavior across different cat sizes and drive strengths.

Artificial spin ices are promising for reconfigurable magnonics and unconventional computing because their magnetic states and spin-wave spectra can be tailored, but available control mechanisms are limited. The authors pattern an exchange-coupled Co-Fe/Ru/Ni-Fe synthetic ferrimagnet into an artificial spin lattice and study its static and dynamic behavior. They show that quadratic and biquadratic interlayer exchange coupling can stabilize orthogonal layer magnetizations, drive hard-axis alignment, and reshape the spin-wave spectrum. This additional degree of freedom may enable field-reconfigurable magnonic crystals, spin-wave filters, and artificial-spin-ice metamaterials.

Semiconductor quantum dots are excellent deterministic sources of single photons. One of the best routes to generate pure single photons is through the biexciton-exciton cascade, but achieving high Hong-Ou-Mandel visibility (or photon indistinguishability) is fundamentally hindered by the finite ratio of radiative lifetimes of the two excited electronic states in that cascade. This study reduces the biexciton lifetime by selective cavity enhancement, and uses the single photon from the biexciton-to-exciton transition. This approach is a powerful path to achieving excellent single-photon indistinguishability and purity, plus high brightness.

Producing narrow-band, high-spectral-density pulses from an x-ray free-electron laser (XFEL) is important for demanding applications at extreme photon energies, such as high-resolution spectroscopy and studies of structural dynamics, but conventional hard-x-ray self-seeding becomes increasingly limited as photon energy increases. This study extends hard-x-ray self-seeding at the European XFEL to 18 keV, and explores second-harmonic-generation self-seeding as a route toward even higher photon energies. Experiments demonstrate coherent amplification of the second harmonic at 15 and 18 keV, while simulations show the potential for narrowband operation at 30 keV.

Millimeter waves sit at the energy scale of many collective excitations in quantum materials, but probing microscopic samples at these frequencies is difficult: Spectroscopic alignment is hard in a cryostat, and superconducting cavities stop working in high magnetic fields. This Letter reports an all-silicon (no metal or superconductor) photonic crystal cavity functioning as a chip-scale conductivity sensor near 100 GHz, reaching a quality factor above ${10}^5$ at 4.3 K. The all-dielectric platform should work at the strong fields and low temperatures where quantum Hall edge modes, magnetoplasmons, and field-tuned correlated phases exist, and it may be scalable to terahertz frequencies.

Magnon-phonon hybridization enables coupled control of spin and mechanical excitations, but the limited frequency tunability of conventional surface-acoustic-wave (SAW) devices is restrictive. The authors develop a SAW platform with a fundamental frequency of 193 MHz, enabling quasicontinuous mapping of magnon-phonon resonances up to 5.6 GHz in an epitaxial Co${}_2$FeSi film. Magnon-induced SAW absorption is enhanced near the transition between monostable and bistable magnetization states; even so, the two regimes exhibit distinct frequency scalings. This approach provides a route toward tunable, potentially energy-efficient magnonic devices and dynamic spin control in hybrid systems.

Light emission via inelastic electron tunneling (LEIT) is an ultrabroadband light source with potential impact in visible-light communication, intelligent optical sensing, and on-chip optoelectronics. Its low efficiency is typically addressed using plasmonic tunneling junctions, but their subwavelength size results in omnidirectional radiation with poor collimation. The authors combine a plasmonic tunneling junction with a metasurface to collimate LEIT to a narrow divergence angle across a broad spectral window. The supported hybrid plasmon-photon modes both enhance the local density of states and extend spatial coherence, mitigating the trade-off between response speed and collimation.

Transition-edge sensors (TESs) have already been proven to detect electrons with kinetic energy of about 100 eV, with a Gaussian energy resolution of 1 eV, comparable to the photon energy resolution of the same device. This study investigates how changes in the experimental setup influence the energy resolution of TES devices, for electrons produced by a ‘cold’ source of vertically aligned carbon nanotubes. Decreasing the size of both TES and electron source, the energy resolution for electrons significantly improves by a factor of more than 21. These results open up possibilities for the high-resolution spectroscopy of low-energy electrons, for e.g. the measurement of neutrino mass.

Superconducting qubits must be initialized in their ground state with very high fidelity, for quantum computing and sensing. Conventional reset schemes are limited, as they operate the qubit within the same noisy electromagnetic environment used for its everyday control. This study couples a transmon qubit to a high-overtone bulk acoustic resonator, a physically distinct bath that is intrinsically colder than its electromagnetic surroundings. The authors use its multimode structure to repeatedly extract entropy from the qubit. This simple, feedback-free protocol yields residual excited-state populations one to two orders of magnitude lower than for typical schemes.

Arrays of Josephson junctions can generate highly accurate voltage waveforms at cryogenic temperatures, and when optically driven are promising for low-dissipation control of superconducting quantum circuits. Their use in quantum computing has been limited, though, by the frequency at which control data can be delivered to the arrays. Combining externally shunted junctions of high characteristic frequency and low critical current, fast optical pulses, and a high-bandwidth photodiode, this study demonstrates data transfer at frequencies up to 60 GHz, about four times as high as usual for Josephson arbitrary-waveform synthesizers—and even higher frequencies may be attainable.

Narrow superconducting strips are key elements of photodetectors, resonators, and quantum circuits, in which magnetic vortices can degrade device performance. The lower critical field (above which a vortex-containing state is favorable) for such strips is usually estimated using Pearl-London theory, which cannot yield the vortex core’s temperature dependence microscopically. By solving the two-dimensional Usadel equations self-consistently, this study provides a microscopic calculation of the lower critical field at any temperature below the superconducting critical temperature, giving a quantitative basis for predicting the vortex-free field tolerance of superconducting thin-film devices.

Atomic interferometers offer extraordinary inertial sensitivity, yet their intrinsically periodic response has long prevented continuous operation over a wide dynamic range. The authors demonstrate a dual-channel closed-loop atomic beam interferometer, enabling simultaneous quantum feedback for rotation and acceleration. By converting periodic matter-wave interference into continuously tracked control parameters, the scheme overcomes the conventional half-fringe limitation while preserving precision. This advance brings practical quantum inertial navigation a significant step closer.

What happens when a photon is absorbed by a superconductor? Although vortex-antivortex pairs have long been suspected to play a central role in superconducting photon detection, their dynamics following photon absorption have eluded direct observation. By monitoring quantized voltage signals generated by photon-induced vortices, the authors reveal their generation statistics and demonstrate photon-number resolution. This work provides a rare microscopic view of photon detection in superconductors, and opens a route toward fast superconducting photon-number-resolving detectors.

Quantum topological structured light offers a promising route to robust information encoding, but its practical realization is limited by the challenge of generating high-quality states in a reconfigurable manner. The authors demonstrate an interferometric approach that generates high-fidelity topological structured light by mapping spatial-mode entanglement onto hybrid spatial-polarization entangled states, with the interferometer implementing a reconfigurable controlled-unitary operation through programmable spatial modulation. This versatile platform for generating high-quality topological quantum states enables adaptable architectures for photonic quantum information processing.

Spin manipulation by hopping has emerged as an attractive approach for efficient spin control in arrays of germanium hole-spin qubits. The physical mechanism relies on disorder-induced differences in the axes of spin precession in neighboring quantum dots, though, and thus is ineffective in the absence of disorder. This work proposes electrostatic squeezing of the quantum dots to engineer the spin-precession axis deterministically, which would render spin manipulation independent of any disorder. Remarkably, the protocol remains robust even under moderate disorder, offering a promising pathway for spin manipulation in large, sparse spin-qubit arrays.

Computers can now autonomously design intricate electromagnetic devices for communication, sensing, and quantum technologies, but optimizers routinely get trapped by locally optimal designs that are still far from the best. This work temporarily reshapes the governing physics into a smooth problem that can be solved exactly. The reshaped problem delivers not only a blueprint for the device but also a map of its own uncertainty, showing where to trust the blueprint and where to keep exploring. Across eight distinct photonic and microwave design tasks, this convex preoptimization consistently beats conventional stop-and-restart sweeps while using a fraction of the computing time.

Fault-tolerant quantum computing depends on ancilla qubits that can extract error syndromes from data qubits, but ancilla errors can propagate back to the data qubits, contaminating the very information they are meant to protect. The Kerr-cat qubit has been proposed as a better ancilla, but a suitable interaction between Kerr-cat and transmon qubits needs to be experimentally verified. This study finds a beam-splitter interaction between a Kerr-cat and a transmon, producing an effective ẐX̂ coupling suitable for parity readout, and confirms expected behavior across different cat sizes and drive strengths.

Artificial spin ices are promising for reconfigurable magnonics and unconventional computing because their magnetic states and spin-wave spectra can be tailored, but available control mechanisms are limited. The authors pattern an exchange-coupled Co-Fe/Ru/Ni-Fe synthetic ferrimagnet into an artificial spin lattice and study its static and dynamic behavior. They show that quadratic and biquadratic interlayer exchange coupling can stabilize orthogonal layer magnetizations, drive hard-axis alignment, and reshape the spin-wave spectrum. This additional degree of freedom may enable field-reconfigurable magnonic crystals, spin-wave filters, and artificial-spin-ice metamaterials.

Semiconductor quantum dots are excellent deterministic sources of single photons. One of the best routes to generate pure single photons is through the biexciton-exciton cascade, but achieving high Hong-Ou-Mandel visibility (or photon indistinguishability) is fundamentally hindered by the finite ratio of radiative lifetimes of the two excited electronic states in that cascade. This study reduces the biexciton lifetime by selective cavity enhancement, and uses the single photon from the biexciton-to-exciton transition. This approach is a powerful path to achieving excellent single-photon indistinguishability and purity, plus high brightness.

Producing narrow-band, high-spectral-density pulses from an x-ray free-electron laser (XFEL) is important for demanding applications at extreme photon energies, such as high-resolution spectroscopy and studies of structural dynamics, but conventional hard-x-ray self-seeding becomes increasingly limited as photon energy increases. This study extends hard-x-ray self-seeding at the European XFEL to 18 keV, and explores second-harmonic-generation self-seeding as a route toward even higher photon energies. Experiments demonstrate coherent amplification of the second harmonic at 15 and 18 keV, while simulations show the potential for narrowband operation at 30 keV.