We investigate the laboratory-frame angular emission distribution of photoelectrons, ejected by circularly polarized light from chiral molecules, theoretically beyond the electric-dipole approximation. We demonstrate that the helicity-dependent forward-backward asymmetry, which is governed by the electric-dipole interaction and known as photoelectron circular dichroism (PECD), can be altered significantly by the helicity-independent asymmetry, which is induced by nondipole contributions. Our findings are exemplified by numerical calculations on the inner-shell photoionization of the bromine atom in the epibromohydrin molecule. The uncovered effect is expected to be omnipresent in the deep inner-shell ionization and needs to be taken into consideration in the interpretation of experiments on PECD in chiral molecules.

We present a novel method for mapping in situ the spatial distribution of photon momentum across a laser beam using a Bose-Einstein condensate (BEC) as a moving probe. By displacing the BEC, we measure the photon recoil by atom interferometry at different positions in the laser beam and thus reconstruct a two-dimensional map of the local intensity and effective dispersion of the $\vec{k}$ wave vector. Applied to a beam diffracted by a diaphragm, this method reveals a local extra recoil effect, which exceeds the magnitude $h\nu /c$ of the individual plane waves over which the beam can be decomposed. This method offers a new way to precisely characterize wavefront distortions and to evaluate one of the major systematic bias sources in quantum sensors based on atom interferometry.

Optical transitions in highly charged ions can be very sensitive to hypothetical beyond-the-standard-model phenomena. Those near the degeneracy due to the $5s\text{−}4f$ level crossing are especially promising. We present measurements of ${\mathrm{Os}}^{15,16,17+}$ ions at an electron beam ion trap and corresponding predictions of several transitions that show a high sensitivity to hypothetical fifth forces and possible violations of local Lorentz invariance. We found electric quadrupole transitions in ${\mathrm{Os}}^{16+}$, which are suitable for frequency metrology due to linewidths down to $44\mu \mathrm{Hz}$. Our calculations show the need for including enough inner-shell excitations to avoid an overestimation of interconfiguration transition rates, which were too faint for detection at the present signal-to-noise ratio.

Nonlinear Compton scattering holds great promise for creating powerful narrow-band sources of high-energy radiation. However, a spectral broadening of the harmonics arises for laser pulses with a realistic envelope due to inhomogeneous light pressure, reducing the source brightness. To effectively use the nonlinear Compton scattering, a rectangular laser pulse shape is more favorable. In this Letter, a pulse-stacking method is studied to obtain a close-to-rectangular envelope and a narrow-band Compton source in the nonlinear regime. The impact of stacking errors in amplitude, phase, and delay on the source brightness is investigated. A method is presented to obtain a multicolor gamma source.

In the realm of quantum information processing, the efficient characterization of entangled states poses an overwhelming challenge, rendering the traditional methods including quantum tomography unfeasible and impractical. To tackle this problem, we propose a new verification scheme using collective strategies, showcasing arbitrarily high efficiency that beats the optimal verification with global measurements. Our collective scheme can be implemented in various experimental platforms and scalable for large systems with a linear scaling on hardware requirement, and distributed operations are allowed. Notably, larger ensembles can always improve the efficiency further, but without increasing the quantum memory. More importantly, the approach consumes only a few copies of the entangled states, while ensuring the preservation of unmeasured ones, and even boosting their fidelity for any subsequent tasks. Furthermore, our protocol provides additional insight into the specific types of noise affecting the system, thereby facilitating potential targeted improvements. These advancements hold promise for a wide range of applications, offering a pathway towards more robust and efficient quantum information processing.

We investigate the photon statistics of an ensemble of coherently driven noninteracting two-level atoms in the weak driving regime. As it turns out, the system displays unique emission characteristics that are strongly in contrast to the emission of classical oscillating dipoles. By deriving the second-order autocorrelation function, we show that extraordinary two-photon correlations are obtained, ranging from strong antibunching to superbunching. These features are enhanced by disorder in the emitter positions, and the control parameter is the number of excitations in the system. We observe the appearance of bunching and antibunching when the light is scattered by the atoms predominantly coherently, i.e., mimicking classical Rayleigh scattering, whereas thermal photon statistics is obtained when the light is scattered via spontaneous decay, a well-known quantum effect. The underlying mechanism is the interplay between coherent scattering, which exhibits spatial fluctuations due to interference, and dissipation in the form of isotropic spontaneous decay.

We explore the task of learning about the dynamics of a Markovian open quantum system by monitoring the information it radiates into its environment. For an open system with Hilbert space dimension $D$, the quantum state of the emitted radiation can be described as a temporally ordered matrix-product state. We provide simple analytical expressions for the quantum Fisher information (QFI) of the radiation state, which asymptotically scales linearly with the sensing time unless the open system has multiple steady states. We characterize the crossovers in QFI near dynamical phase transitions, emphasizing the role of temporal correlations in setting the asymptotic rate at which QFI increases. We identify conditions under which information encoded in the mixed radiation state can be reliably accessed over both short and long timescales. We discuss when optimal sensing is possible with instantaneously measured radiation.

We introduce a systematic framework to derive the effective Hamiltonian governing the coherent dynamics of non-Markovian open quantum systems. By applying the minimal dissipation principle, we uniquely isolate the coherent contribution to the time-local generator of the reduced dynamics. We derive a general expression for the effective Hamiltonian and develop a recursive perturbative expansion that expresses it in terms of system-bath interaction terms and bath correlation functions. This expansion provides a systematic tool for analyzing energy renormalization effects across different coupling regimes. Applying our framework to paradigmatic spin systems, we reveal how environmental correlations influence energy shifts and eigenbasis rotations, offering insights into strong-coupling effects and non-Markovian quantum thermodynamics.

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.