Arrays of optical tweezers form the backbone of neutral-atom analog and digital quantum processors. However, the intertrap distance remains generally much larger than the size of the tweezers to avoid interference-induced trap distortions, limiting the trap density. Here, we report single-atom trapping in four superresolved tweezers, meaning with a separation below the Sparrow diffraction limit. The optical pattern is generated using a superoscillatory phenomenon leading to subwavelength traps with full control of the trap relative phases. We investigate two sets of relative phases that impede or allow the hopping and the reshuffling of atoms. We envision that superoscillatory light structuring will bridge the gap between large-distance traps generated by tweezer arrays and short-distance traps formed with optical lattices.

Nonstabilizerness is a fundamental resource for quantum computation, enabling quantum algorithms to surpass classical capabilities. Despite its importance, characterizing this resource remains challenging due to the intricate geometry of stabilizer polytopes and the difficulty of simulating nonstabilizer states. In this work, through device-independent considerations, we reveal an unexpected connection between nonstabilizerness and Bell inequalities. Although certain stabilizer states can already achieve maximal violations of specific Bell inequalities, we demonstrate that appropriately constructed Bell inequalities can nevertheless serve as witnesses of nonstabilizerness, revealing when a state lies beyond the stabilizer set. This result bridges two key quantum resources, uncovering a novel relationship between the device-independent framework and resource-theoretic properties of quantum computation.

Quantum vortices are commonly described as funnel-like objects around which the superfluid swirls, and their motion is typically modeled in terms of massless particles. Here, we show that in Fermi superfluids the normal component confined in the vortex core provides the vortex with a finite inertial mass. This inertia imparts an unambiguous signature to the dynamic behavior of vortices, specifically manifesting as small-amplitude transverse oscillations which remarkably follow the prediction of a simple pointlike model supplemented by an effective mass. We demonstrate this phenomenon through large-scale time-dependent simulations of Fermi superfluids across a wide range of interaction parameters, at both zero and finite temperatures, and for various initial conditions. Our findings pave the way for the exploration of inertial effects in superfluid vortex dynamics.

Time delays in photoemission are on the order of attoseconds and have been experimentally determined in atoms, molecules, and solids. Their magnitude and energy dependence are expected to yield fundamental insights into the properties of the systems in which they are measured. In a recent study Biswas et al. [Nat. Phys. 16, 778 (2020)] determined the absolute photoemission time of the $\mathrm{I}4d$ level in iodoethane via attosecond streaking spectroscopy, finding the presence of a functional group to increase the photoemission time delay, suggesting a correlation between the size of the functional group and time delay based on a semiclassical calculation. Here we experimentally study the dependence of the $\mathrm{I}4d$ photoemission time on the functional group in the iodoalkanes from iodomethane up to 2-iodobutane at three photon energies across the giant resonance in the $\mathrm{I}4d\to \varepsilon f$ photoemission channel, finding that the presence alone of a functional group does not necessarily increase the photoemission delay, and that overall no clear correlation between its size and the photoemission time delay can be established.

By examining rotating ferromagnetic spinor condensates through the perspective of large spin, we identify an atypical type of topological point defects in the magnetization texture. These defects are not predicted by conventional homotopy analysis but rather by the Riemann-Hurwitz formula. The magnetization texture in the system is described by an equal-area mapping from the plane to the sphere of magnetization, forming a lattice of uniformly charged skyrmions. This lattice contains doublyquantized (winding number $=2$) point defects arranged on the sphere in a tetrahedral configuration. The fluid is found to be rotating rigidly, except at the point defects, where the vorticity vanishes. This vorticity structure describes an unconventional “unvortex” lattice, which contrasts with the well-known vortex lattice in scalar rotating superfluids, where vorticity is concentrated exclusively within defect points. Numerical results are presented, confirming these predictions and demonstrating their persistence in smaller-spin condensates.

We study strong-field ionization by quantum lights with emphasis on high-order above-threshold ionization and the intensity-dependent enhancements in the photoelectron spectra. We find that the length of the plateau in the photoelectron energy spectrum generated by such quantum lights can be extended by an order of magnitude in comparison with that generated by the classical coherent laser light and that within this plateau resonantly enhanced groups of sharp peaks appear at energies which are integer multiple of the photon energy. We relate the observed intensity-dependent enhancements to the channel closing effect. Our results are particularly interesting in the context of the recent interplay and merging of quantum optics with strong-field physics and attoscience.

Quantum gas mixtures offer a wide field of research, ranging from few-body physics of impurities to many-body physics with emergent long-range interactions and ultracold molecular gases. Achieving precision control of mixtures is much harder than for single-component gases, and consequently, the respective techniques are less developed. Here we report on a decisive step forward in this direction by realizing dissipationless and fully differential optical control of the motional degrees of freedom of one of the species without affecting the other. This is achieved with ${}^{166}\mathrm{Er}$ and ${}^6\mathrm{Li}$ in a novel dual-species experiment, where the measurements are performed on each species separately. Our experiments pave the way to a new generation of precision many-body experiments with quantum gas mixtures with unprecedented long lifetimes and low temperatures.

We study the temporal dynamics of light interacting with a one-dimensional lattice of cold atoms. In such a system, a photonic band gap opens up, yielding an efficient Bragg reflection for an incident field incoming with the right angle and detuning. Here, we report two new effects appearing in the Bragg reflection. First, for some detunings, there is a “flash,” i.e., a transient increase of the reflected intensity when the incident field is switched off. Second, the subsequent extinction of the reflected field is clearly superradiant, with decay rates up to eight times the natural decay rate of the atomic excited state. Numerical simulations are in qualitative agreement with the observations, which can be explained by a classical photonic model. Our results are a step towards exploiting this photonic band gap in atomic systems for quantum-optical applications.

The emission of a photon by an electron in an intense laser field is one of the most fundamental processes in electrodynamics and underlies the many applications that utilize high-energy photon beams. This process is typically studied for electrons colliding head-on with a stationary-focus laser pulse. Here, we show that the energy lost by electrons in the quantum regime and the yield of emitted photons can be substantially increased by replacing a stationary-focus pulse with an equal-energy flying-focus pulse whose focus copropagates with the electrons. These advantages of the flying focus result from the energy loss and the photon yield scaling more favorably with the interaction time than the laser intensity in the quantum regime, with the latter also holding in the classical regime. Monte Carlo simulations of electrons colliding with equal-energy stationary and flying-focus laser pulses demonstrate these advantages.

We perform unbiased quantum Monte Carlo simulations of quantum Ising models defined on amorphous arrays of Rydberg atoms, motivated by a recent proposal for their experimental realization using engineered configurations of the optical tweezers. In contrast to previous studies focusing on periodic geometries, our models are designed to possess well-controlled local structural properties while lacking long-range order. We identify a quantum phase transition from a paramagnetic to a spin-glass phase, characterized via the Edwards-Anderson order parameter computed from the replica overlap. The magnetic structure factor reveals short-range, isotropic antiferromagnetic correlations, and the spin-overlap distribution exhibits a nontrivial form with two broad peaks and significant weight at zero overlap. A comparison with the clean kagome lattice, which shares similar local geometry, underscores the critical role of amorphous structure in stabilizing the spin-glass phase. Our results suggest a promising pathway for the experimental realization of quantum spin glasses using programmable Rydberg atom arrays.

Qubit measurements in quantum devices involve various types of errors, including erroneous state determination, correlated preparation errors, and measurement-induced leakage from the computational states. We propose a feedforward protocol to reduce readout-induced faults, applicable for qubits with errors biased between the different states, in settings like quantum error correction with repeated measurement cycles. The method consists of an adaptive readout sequence conditioned on each check qubit's readout result from the previous cycle, which is optimized for the expected measured state. Focusing on a simple realization of conditionally flipping (by an $X$ gate) the state of check qubits before their measurement, we investigate the effect of such state-dependent errors using simulations in the setup of a low-density parity check code. We show that the suggested protocol can reduce both logical errors and decoding time, two important aspects of fault-tolerant quantum computations.

Topologically nontrivial band structure of a material may give rise to special states that are confined to the material's boundary and protected against disorder and scattering. Quantum spin Hall effect (QSHE) is a paradigmatic example of phenomenon in which such states appear in the presence of time-reversal symmetry in two dimensions. Whereas the spatial structure of these helical edge states has been largely studied, their dynamic properties are much less understood. We design a microwave experiment mimicking QSHE and explore the spatiotemporal dynamics of unidirectional transport of optical angular momentum (or pseudospin) by edge states. Pseudospin-polarized signal propagation is shown to be immune to scattering by defects introduced along the edge. Its velocity is 2 to 3 orders of magnitude slower than the speed of light in the free space, which may have important consequences for practical applications of topological edge states in modern optical and quantum-information technologies.

In this work, we show that a counterfactual account of Lüders' rule—which we argue is naturally implied by the mathematical structure of the rule itself—rules out underlying-state models of quantum mechanics (a type of hidden-variable model, typically used in the contextuality and nonlocality literature, where quantum states are treated as probability measures over “better-defined states”). This incompatibility arises because the counterfactual update requires ontological models to update their states according to conditional probability, which in turn establishes an equivalence between compatibility and the existence of such models.

For arbitrary reciprocal single-mode structures, regardless of their geometric shapes or constituent materials, there must exist incident directions of plane waves for which they are optically achiral.

We report resonant inelastic x-ray scattering (RIXS) spectra of neon atoms interacting with intense x-ray pulses generated using an x-ray free-electron laser (XFEL). We find that an unexpected peak emerges near the $K\alpha$ line of Ne, which does not coincide with any physical resonances of neon ions. We perform theoretical calculations based on a quantum-state-resolved rate-equation approach with x-ray-induced processes including possible resonant excitations. Our dynamics simulations demonstrate that a sequence of multiple resonant photoabsorption events are involved and the interplay of those multiple resonances in combination with the relatively large spectral bandwidth of XFEL radiation leads to the emergent resonance-like structure at a position where no resonances exist. Our finding offers critical guidance for future applications of high-intensity RIXS at XFEL facilities.

Autonomous quantum thermal machines are particularly suited to understand how correlations between thermal baths, a load, and a thermal machine affect the overall thermodynamic functioning of the setup. Here, we show that by tuning the operating temperatures and the magnitude of the coupling between machine and load, the thermal machine can operate in four modes: engine, accelerator, heater, or refrigerator. In particular, we show that as we increase the coupling strength, the engine mode is suppressed and the refrigerator mode is no longer attainable, leaving the heater as the most pronounced functioning modality, followed by the accelerator. This regime switching can be amplified by quantum effects, such as the bosonic enhancement factor for a harmonic oscillator load, which effectively modifies the machine-load coupling, making the thermodynamic functioning sensitive to the initial preparation of the load.

Quantum logic operations between physically distinct qubits is an essential aspect of large-scale quantum information processing. We propose an approach to high-speed mixed-species entangling operations in trapped-ion quantum computers, based on mechanical excitation of spin-dependent ion motion by ultrafast pulsed lasers. We develop the theory and machine design of pulse sequences that realize megahertz-speed "fast gates" between a range of mixed-isotope and mixed-species ion pairings with experimentally realistic laser controls. We demonstrate the robustness of the gate mechanism against expected experimental errors, and identify errors in ultrafast single-qubit control as the primary technical limitation. The proposed mixed-species gate mechanism can be used for fast transfer of quantum information between specialized qubits and quantum memories, which we show enables the protection of matter-photon interfaces against rapid spin dephasing in optical networks of trapped-ion processors.

We investigate the magnetic-field dependence of the interaction between two Rydberg atoms, $|n{S}_{1/2},m_J\rangle$ and $|(n+1)S_{1/2},m_J\rangle$. In this setting, the effective spin-1/2 Hamiltonian takes the form of an XXZ model. We show that the anisotropy parameter of the XXZ model can be tuned by applying a magnetic field and, in particular, that it changes drastically near the Förster resonance points. Based on this result, we propose experimental realizations of spin-1/2 and spin-1 Heisenberg-type quantum spin models in Rydberg atom quantum simulators, without relying on Floquet engineering. Our results provide guidance for future experiments of Rydberg atom quantum simulators and offer insight into quantum many-body phenomena emerging in the Heisenberg model.

The Josephson effect characterizes superfluids and superconductors separated by a weak link, the so-called Josephson junction. A recent experiment has shown that Josephson oscillations can also be observed in a supersolid, where the weak link is not due to an external barrier, but is self-induced by interparticle interactions. Here we show theoretically that supersolids—despite their self-induced character—feature key properties of bosonic Josephson junction arrays, including macroscopic quantum self-trapping. We focus on the harmonically trapped dipolar supersolids of interest for current experiments and show that they can be described with a generalized Josephson model that takes into account spatial inhomogeneities. Our work sheds new light on the dynamics of supersolids and opens the way to the study of a novel class of Josephson junctions.

We propose physically realizable exceptional point degeneracies (EPDs) corresponding to synthetic reflectionless modes (SRMs). These are solutions of an auxiliary wave operator that is defined in synthetic frequency dimensions and describe incoming reflectionless waves onto a Floquet-driven cavity. The SRM-EPD emerges as a consequence of a local $\mathcal{PT}$ symmetry imposed on the auxiliary operator via appropriate Floquet driving. Its presence signifies the possibility to design wavefronts and time-modulated schemes with up or down targeted frequency conversion and flat transmission spectra. The theory is validated via simulations with driven RF resonators.