The increasing number of control lines connecting quantum processors to external electronics constitutes a major bottleneck in the realization of large-scale quantum computers. Frequency-division multiplexing is expected to enable control of multiple qubits through a single microwave cable; however, interference from off-resonant microwave tones hinders precise qubit control. Here, we propose an active interference suppression method for frequency-division-multiplexed simultaneous gates on microwave-controlled qubits. We demonstrate that the deliberate incorporation of off-resonant microwave tones improves single-qubit gate fidelity. In particular, the gate infidelity scales inversely with the square of the number of microwave tones when off-resonant orthogonal or quasi-orthogonal tones are incorporated. Furthermore, we show that fast oscillations, neglected under the rotating wave approximation, degrade the gate fidelity, and that this degradation can be mitigated through optimized frequency allocation. The proposed approach is simple and effective for improving the performance of frequency-division-multiplexed quantum gates.

We study the electronic structure and dynamical correlations in antiferromagnetic ${\mathrm{BiFeO}}_3$, a prototypical room-temperature multiferroic, using a variety of static and dynamical first-principles methods. Conventional static Hubbard corrections ($\mathrm{DFT}+U, \mathrm{DFT}+U+V$) incorrectly predict a deep-valence Fe $3d$ peak (around $-7\text{eV}$) in antiferromagnetic ${\mathrm{BiFeO}}_3$, in contradiction with hard x-ray photoemission. We resolve this failure by using a recent generalization of $\mathrm{DFT}+U$ to include a frequency-dependent screening—$\mathrm{DFT}+U\left(\omega \right)$—or using a dynamical Hubbard functional. The screened Coulomb interaction $U\left(\omega \right)$, computed with spin-polarized random-phase approximation and projected onto maximally localized Fe $3d$ Wannier orbitals, is expressed as a sum over poles, yielding a self-energy that augments the Kohn-Sham Hamiltonian. This $\mathrm{DFT}+U\left(\omega \right)$ approach predicts a fundamental band gap of $1.53\text{eV}$, consistent with experiments, and completely eliminates the unphysical deep-valence peak. The resulting simulated hard x-ray photoelectron spectroscopy spectrum reproduces the experimental line shape with an accuracy comparable to state-of-the-art approaches. Our work highlights the critical nature of dynamical screening in complex oxides and of $\mathrm{DFT}+U\left(\omega \right)$ as a predictive and computationally efficient approach to address the electronic structure of correlated materials.

Receptor-mediated ligand endocytosis underlies essential homeostatic functions and in signaling contexts it is often regarded as a mechanism for signal attenuation. Here, we show that ligand removal can paradoxically enhance directional information in autonomous cell-cell attraction. Many cell systems migrate toward one another in the absence of externally imposed gradients, implying that secretion, diffusion, and uptake must themselves generate usable directional cues. We develop a surface-resolved theory of a finite-sized detector exposed to a nearby source and derive analytical expressions for the steady-state ligand field. The resulting concentration profiles are governed by a single dimensionless Damköhler number that compares receptor-mediated endocytosis to diffusive ligand transport. Increasing ligand removal lowers extracellular ligand concentrations and reduces absolute concentration differences across the detector surface, but preferentially enhances relative surface anisotropy. Thus, destroying the signal can increase the usable information encoded in relative gradients. Incorporating nonlinear downstream processing reveals a trade-off between contrast enhancement and signal depletion, with the directional response greatest within a joint regime of endocytosis and downstream sensing that overlaps the measured range of receptor internalization rates. These results recast receptor-mediated endocytosis as an extracellular information-processing mechanism that reshapes the surrounding ligand gradient to enhance directional information.

We use spin dynamics simulations to determine the origin of the unusual correlated diffuse scattering, characterized by half-moon shapes bridging the magnetic Bragg peaks, observed in the polarized elastic neutron scattering from manganese tungstate, ${\mathrm{MnWO}}_4$. We first fit a Heisenberg Hamiltonian with 12 nearest-neighbor exchange interactions and single-ion anisotropy to the experimental ground-state magnon dispersion. We then show via spin dynamics simulations that our model Hamiltonian both reproduces the experimentally observed half-moon features and captures their persistence into the paramagnetic regime. Moreover, we identify the three-dimensional, competing antiferromagnetic interactions driving this behavior. Our work complements earlier studies of half-moon-shaped signatures in pyrochlore and triangular structures, by providing insight into their origin and showing that the half moons in ${\mathrm{MnWO}}_4$ result from three-dimensional competing exchange interactions, in the absence of the spin-liquid behavior with which they are usually associated.

Characterizing the temperature of materials in high-energy-density (HED) experiments is a major gap in the benchmarking of HED matter, such as matter in the deep interiors of planets and low-mass stars. Extended x-ray absorption fine structure (EXAFS) spectroscopy is one of the few techniques capable of determining temperature at HED conditions, but the inferred EXAFS temperature depends upon the atomic potential, which itself is not measured. This work compares simultaneous EXAFS and self-emission temperature measurements [S. Boccato et al., J. Geophys. Res.: Solid Earth, 122, 9921 (2017)], to quantify the impact of atomic potentials implicit in the EXAFS temperature analysis. Traditional EXAFS analysis employing a harmonic potential produces systematically lower temperatures than from self-emission ($\sim 35\%$ at 100 GPa and 3000 K), while a sixth-order distortion to the pair potential recovers agreement between the two measurements. These results highlight and quantify the need and complexity of distortions or anharmonic corrections to atomic potentials at HED conditions.

Multipartite quantum entanglement plays a crucial role in the emergence of quantum phases and their transitions in quantum many-body systems. It is of general interest to know what sort of analysis on quantum entanglement can bring us a profound insight to understand the rich dynamics of quantum many-body systems. In this work, we study the characteristics of quantum entanglement in relation to ${\mathbb{Z}}_n$-ordered phases emerging under a varied strength of one-dimensional Rydberg interaction via numerical investigation. We propose an approach based on the structure of pairwise entanglement across the Rydberg chain using two-qubit concurrence as an entanglement measure. We define an entanglement-structure factor via Fourier analysis of total concurrence at each site and address ${\mathbb{Z}}_n$ phase transitions in comparison with the conventional order parameter based on local density, i.e., magnetization. We also discuss how the required two-qubit concurrence can be measured in analog Rydberg atom arrays using site-selective erasure and parametrized laser pulses. Our numerical investigation suggests that an entanglement-structure-based approach can provide a powerful tool in analyzing symmetry breaking in quantum phase transitions.

We obtain an exact solution for the spectral function for one-dimensional Bose-Bose and Fermi-Fermi mixtures with strong repulsive interactions, valid in arbitrary confining potentials and at all frequency scales. For the case of harmonic confinement, we show that, on top of the ladder structure of the density excitations imposed by the external confinement, spin excitations emerge as sideband peaks, with dispersion related to the one of ferromagnetic or antiferromagnetic spin chains and a width fundamentally larger for fermionic mixtures than for bosonic ones, as determined by the different symmetry of spin-excited states. The observation of spin excitation branches can provide a univocal probe of interaction-induced magnetism in ultracold atoms.

We investigate proton acceleration in the relativistic transparency regime using ultrathin foils irradiated by petawatt-class laser pulses, achieving proton energies exceeding $80\mathrm{MeV}$. Shot-resolved analysis of transmitted spectra reveals that temporal gating at the onset of relativistically induced transparency shapes the pulse, producing either smooth or modulated spectra. A spectral smoothness metric, benchmarked against particle-in-cell simulations and a semianalytical gating model, demonstrates that different transmission levels correspond to distinct transparency onset times. We find that maximum proton energies are consistent with transparency occurring near the laser pulse peak, while later or absent onset can also drive efficient acceleration. These spectral diagnostics establish a powerful probe of acceleration cascades and a route to understanding and controlling shot-to-shot fluctuations in laser-ion interactions.

This article is part of a Physical Review Collection on the Physics of Changing Climate.

Tipping elements are large-scale components of the Earth system that may undergo abrupt and potentially irreversible transitions once critical thresholds are crossed. How these elements interact and coevolve under anthropogenic forcing remains poorly understood. Here, we introduce a Bayesian framework to quantify interdependence among tipping element regions based on lagged correlations, yielding a probabilistic measure of their connectivity that rigorously accounts for observational and sampling uncertainty. Using the preindustrial period as a baseline, we show that connectivity patterns among tipping elements are substantially weakened under high anthropogenic forcing, whereas the loss of coherence remains comparatively limited under low-forcing scenarios. This decorrelation is particularly pronounced in the Northern Hemisphere. We further identify the Atlantic meridional overturning circulation as a key contributor to the observed loss of connectivity, in line with recent evidence that it may be approaching a tipping point. In addition, we propose a simple toy model where tipping elements are seen as an adaptive dynamical system, losing coherence as a reaction to external perturbations. The results are robust across past decades and across different climate models, with deviations from the baseline strengthening into the future, especially under high-emission pathways.

We report the observation of the magnetic-field-induced $\left(5d^{10}6s^2\right){}^1\mathrm{S}_0\text{−}\left(5d^{10}6s6p\right){}^3\mathrm{P}_0$ transition in a bosonic isotope of mercury, ${}^{198}\mathrm{Hg}$, realized in an optical lattice clock. We characterize this ${}^{198}\mathrm{Hg}$ clock transition at 265.6 nm, determining key features such as the quadratic Zeeman shift, the probe light shift, and the magic frequency. We also report a comparison between the ${}^{198}\mathrm{Hg}$ optical lattice clock and ${}^{87}\mathrm{Sr}$. In this comparison, the ${}^{198}\mathrm{Hg}$ clock has a relative frequency stability of $6\times {10}^{-16}/\sqrt{\tau /\text{s}}$ and a total relative systematic uncertainty of $6.9\times {10}^{-16}$. This comparison yields the first direct determination of the ${}^{198}\mathrm{Hg}/{}^{87}\mathrm{Sr}$ optical frequency ratio: ${}^{198}\mathrm{Hg}/{}^{87}\mathrm{Sr}=2.6293157346841181$, with the same relative uncertainty.

In this article, we propose a squeezing-enhanced protocol for the efficient readout of bosonic qubits, whose encoding states can be first mapped onto a multilevel atom and then read out via dispersive coupling. We demonstrate that by simultaneously applying intracavity and external squeezing for the readout of this multilevel atom, the measurement signal-to-noise ratio between adjacent energy levels can be exponentially enhanced. We begin by examining this enhancement in a three-level system and subsequently extend the framework to multilevel systems, proving that the signal-to-noise ratio between any adjacent energy levels can achieve a similar exponential improvement. This dual-squeezing approach leads to an exponential enhancement in both the dispersive coupling strength and the signal-to-noise ratio. As a result, the single-shot readout time is exponentially shortened and the single-shot measurement error is exponentially reduced, ultimately improving the single-shot readout fidelity of bosonic qubits by more than an order of magnitude. This method provides an effective pathway for high-fidelity readout based on bosonic encoding.

Laser wakefield accelerators (LWFAs) provide extremely large accelerating gradients for compact electron accelerators and photon sources but are limited by dephasing, where trapped electrons outrun the accelerating phase of the wakefield. Flying-focus pulses can eliminate dephasing by driving a wake at the vacuum speed of light, but these pulses involve trade-offs, such as varying spot size, long duration, or large plasma volume. Here, we show that a spatiotemporally structured laser pulse propagating in a plasma waveguide can drive a wakefield at the vacuum speed of light while maintaining a constant spot size and ultrashort duration. The pulse is formed by superposing plasma-waveguide modes with appropriately selected frequencies. Compared with flying-focus approaches, the waveguide substantially reduces the required plasma volume. Scaling laws and quasi-three-dimensional particle-in-cell simulations show that the single-stage energy gain increases linearly with the number of modes used to construct the pulse, enabling larger energy gains or shorter stages than standard LWFA.

Long-range interactions can fundamentally reshape the low-energy properties of low-dimensional quantum matter, altering both continuous-symmetry breaking (CSB) and topological phenomena. However, their impact on the quantum criticality separating these regimes remains poorly understood. We determine the ground-state phase diagram and critical properties of the spin-one Heisenberg chain with single-ion anisotropy and staggered antiferromagnetic power-law interactions, using matrix-product state calculations complemented by high-order series expansions (perturbative continuous unitary transformations + Monte Carlo). Such long-range, nonfrustrated interactions circumvent the Hohenberg-Mermin-Wagner theorem, thereby stabilizing CSB phases in direct competition with the Haldane phase. We map out the resulting phase diagram and analyze the entanglement entropy scaling behavior in the U(1) and SU(2) CSB phases, finding logarithmic corrections beyond the short-range, universal contributions expected from linearly dispersed Goldstone modes. We further characterize all critical boundaries through finite-size scaling of either the entanglement entropy or the staggered magnetization. In particular, the large-$D$-to-U(1)-CSB transition exhibits unconventional, continuously varying critical exponents as a function of the long-range decay exponent with a strong dependence on the imposed boundary conditions leading to distinct finite-size scalings for sufficiently long-range potentials. Remarkably, the Haldane-to-U(1)-CSB transition likewise displays unconventional quantum criticality with distinct continuously varying critical exponents. Our work positions this model as a target for near-term atomic platforms with tunable long-range couplings and exhibiting natural single-ion anisotropy, offering a minimal playground for exploring the interplay between long-range interactions, continuous symmetry breaking, and topology.

High-precision quasisimultaneous collinear/anticollinear laser spectroscopy was performed to measure the $5s{}^2{S}_{1/2}\to 5p{}^2{P}_{1/2}$ ($D1$), the $5s{}^2{S}_{1/2}\to 5p{}^2{P}_{3/2}$ ($D2$), and the three $4d\to 5p$ transitions in naturally abundant ${\mathrm{Sr}}^{+}$ isotopes. For absolute transition frequencies, an uncertainty as low as $600\mathrm{k}\mathrm{Hz}$ was achieved, while common-mode rejection allowed us to extract isotope shifts with uncertainties down to a level of $200\mathrm{k}\mathrm{Hz}$, 1 order of magnitude better than previously achieved. Similarly, the uncertainties of the hyperfine-structure coefficients for ${}^{87}\mathrm{Sr}$ of the $5p$ states and the $4d{}^2{D}_{3/2}$ levels are improved. A King-plot analysis yielded a field-shift ratio of the $D2$ and $D1$ lines of $F_{\mathit{\text{D}}\text{2}}/F_{\mathit{\text{D}}\text{1}}=1.004\left(5\right)$, which lies within the theoretically allowed region and can be used as a benchmark for atomic structure theory calculations. We use the information from all stable isotopes in the investigated transitions to compare field-shift and mass-shift constants obtained by various techniques regularly used in the literature, ranging from King plots with purely experimental input to ab initio atomic structure calculations by state-of-the-art theory. We show that in the region above $N=50$, the charge radii are strongly dependent on the approach being used.

We propose a simple scalable scheme for the dissipative generation of entangled states of multiple emitters coupled to a waveguide. Our approach exploits collective interactions arising from the formation of subradiant and superradiant excited states, combined with the quantum Zeno effect. We show that, starting from an arbitrary initial state, the system deterministically evolves toward a W-type entangled steady state, with an infidelity that scales inversely with the cooperativity. The protocol is scalable to an arbitrary number of emitters. We further analyze the impact of additional experimental imperfections and present a detailed implementation based on trapped ${}^{133}\mathrm{Cs}$ atoms.

Scalable trapped-ion quantum computing is commonly realized with modular chips that feature distinct zones with specific functionalities, such as storage, state preparation, and gate execution. To execute a quantum circuit, the ions must be transported between these zones. This process is called ion shuttling. To achieve reliable computation results, the shuttling process must be optimized. However, as the number of ions increases, this becomes a high-dimensional optimization problem where optimal solutions cannot be computed efficiently. We demonstrate, to the best of our knowledge, the first use of reinforcement learning (RL) for the optimization of ion shuttling. RL is well suited for such scenarios, as it enables learning a strategy through direct interaction with the problem. We show that our RL approach outperforms current state-of-the-art heuristic techniques, yielding a reduction in shuttling operations of up to $36.3\%$. Furthermore, we show that our method is easily applicable to various chip architectures. Our approach offers a versatile method to study shuttling efficiency during chip design and, therefore, a highly relevant tool for future, more complex architectures.

Altermagnets are a novel class of magnetic systems characterized by their momentum-dependent spin splitting without net magnetization. In this work, we extend established Euclidean tight-binding models of altermagnets to regular hyperbolic lattices in two spatial dimensions defined on a discretized Poincaré disk. Using hyperbolic crystallography and Abelian hyperbolic band theory, we show that the inclusion of next-nearest-neighbor hopping is sufficient to induce spin splitting in minimal tight-binding models of bipartite hyperbolic lattices. While certain families and special cases of hyperbolic lattices remain antiferromagnetic, we identify an entire family and a special case that generically permit spin splitting in this framework. Hence, altermagnetism is inherent to certain hyperbolic lattices. Since Abelian hyperbolic band theory yields a momentum space that is at least four dimensional, we classify the leading spin-splitting harmonics using four-dimensional atomic orbitals. As an outlook, we apply non-Abelian hyperbolic band theory to the $\{10,5\}$ lattice. Although its Abelian spectrum is spin degenerate, two selected higher-genus supercells exhibit spin splitting. This finding suggests that spin degeneracy does not necessarily persist within all translation representation sectors.

Time materials are materials with acoustic, electromagnetic, or elastic properties that change while waves are propagating through them. Waves can scatter from such temporal inhomogeneities, but due to causality, they cannot reflect back in time. As a result, time-scattered wave fields do not resemble space-scattered wave fields—which are spatially mirrored—but instead look like copies of the original signal traveling back in time. Consequently, they can form an ingredient for physical solvers of inverse problems that rely on time-reversal transformations. Here, we investigate the use of time reflections for calculating so-called focusing wave fields. We establish a one-to-one mapping between focusing wave fields and the transmitted wave fields produced by time scattering. This mapping is then used to construct a space-time medium where the time scattering anticipates the space scattering and “computes” the exact inverse transmission response for the space scattering. We demonstrate the construction with a simple numerical example of a single pulse encountering a series of time boundaries before reaching a spatial inhomogeneity. The time boundaries scatter the single pulse into a focusing wave field that subsequently focuses through the spatial inhomogeneity. With certain mild assumptions, the transmitted wave has both the same wave shape and amplitude as the original pulse, yielding a transmission coefficient of unity.

Discrete nonlinear systems support a rich variety of localized and extended wave phenomena, with their dynamics sensitively dependent on the symmetries of the underlying interaction forces within the lattice. Odd elasticity, emerging in effective models of active materials, breaks the action-reaction symmetry of the local interactions and gives rise to new wave behavior. We investigate the existence and stability of traveling waves in a nonlinear lattice with odd elasticity, where the coupling force between adjacent units depends asymmetrically on the deformations of the coupled units (nonreciprocal or asymmetric elastic coupling). We demonstrate the existence of periodic and quasiperiodic traveling waves and analyze their spectral stability using the master stability framework. In particular, we identify the onset of Eckhaus instability based on the curvature of the associated master stability curve. This approach enables a quantitative analysis of size effects, specifically the bounds on lattice sizes for which a given traveling wave is stable. The stability analysis for quasiperiodic waves is based on an effective description of the envelope of the response through a rotating-wave approximation, which agrees well with direct numerical simulations. Our findings establish a unified framework for understanding wave propagation characteristics in nonlinear lattices, for both periodic and quasiperiodic wave profiles. We highlight, qualitatively and quantitatively, the role of odd elasticity on the existence and stability of nonlinear traveling waves in dissipative systems, and discuss how localization and stability depend on the interplay between nonlinearity, dissipation, and nonreciprocity.