Neutral-atom arrays offer a promising path for quantum simulation, yet the potential of fermionic ${}^{40}\mathrm{K}$ remains largely constrained by state-dependent light shifts that degrade cooling and detection fidelities. This problem can be resolved by working at a magic wavelength, where the differential light shift vanishes. We report the first experimental determination of the magic wavelength for the $D_1$ transition in fermionic ${}^{40}\mathrm{K}$ at 1227.54(4) nm. Using in-trap loss spectroscopy in a wavelength-tunable optical tweezer, we map the differential ac Stark shift across a range of trapping powers and wavelengths. By converting these shifts to differential scalar polarizabilities, we find excellent agreement with relativistic all-order calculations. Benchmark measurements at 1064.49 nm further quantify the intensity-sampling systematics inherent to standard trapping wavelengths, contrasting with the “mechanically clean” environment provided by the magic condition. Our results provide an important step toward high-fidelity in-trap $D_1$ cooling, fluorescence imaging, and light-assisted loading, establishing a robust path toward scaling fermionic neutral-atom arrays for quantum information science.

Common belief, confirmed by existing experiments, is that arbitrarily weak disorder should lead to spatial localization of eigenmodes of scalar wave equations when wave propagation is two dimensional (2D). We predict that, contrary to this belief, a localization-delocalization transition can take place for light scattered by two-level atoms placed at random positions in the middle plane of a parallel-plate 2D waveguide fed by its fundamental transverse-magnetic mode (electric field polarized perpendicular to the waveguide and to the atomic plane). This transition, driven by near-field dipole-dipole interactions between atoms, occurs upon increasing the areal number density of atoms beyond some critical value. A finite-size scaling analysis of the transition yields an estimate of its critical exponent $\nu =1.4\pm 0.2$.

Extending the high-harmonic cutoff with experimentally accessible fields is essential for advancing tabletop coherent extreme-ultraviolet (EUV) and soft-x-ray sources. Although terahertz (THz) assistance offers a promising route, cutoff extension at weak-to-moderate, laboratory-accessible THz strengths remains poorly understood. In this Letter, we investigate THz-assisted high-order harmonic generation (HHG) using time-dependent Schrödinger equation simulations supported by classical trajectory, quantum-orbit theory, and Bohmian dynamics. We demonstrate that even weak-to-moderate THz fields extend the cutoff, producing a pronounced “fish-fin” structure whose dominant branches saturate near $I_p+8U_p$. We attribute this extension to long electron excursions spanning multiple optical cycles before recombination. This cutoff-extension mechanism is robust across atomic species and driving parameters, indicating that laboratory-scale THz fields enable practical cutoff control and access to high-energy HHG.

We introduce the concept of optical coherence squeezing in double-slit interference. We construct Hermitian operators that characterize the coherence at the slits, leading to coherence uncertainty relations and a corresponding squeezing condition. We also analyze states exhibiting such squeezing and show its manifestations in the uncertainty of the magnitudes and positions of the intensity fringes. Our work suggests that coherence may be regarded as a degree of freedom for squeezing, complementing phase, amplitude, and polarization, which could benefit quantum-enhanced interferometry.

We propose to tune the ultracold collisions between alkali-metal dipolar diatomic molecules in nonadjacent rotational states with an electric field. The long-range intermolecular potential energy surface can be tuned with an electric field and a long-range potential well sufficient to support weakly bound tetratomic states can be induced. The origin of the potential well is interpreted based on perturbative analysis. Near the electric field at which the tetratomic state crosses the scattering threshold, the elastic cross section between molecules becomes highly tunable. We show that such tunability is applicable to diverse dipolar molecules.

Given the ability to apply an unknown quantum channel acting on a $d$-dimensional system, we develop a quantum algorithm for transforming its singular values. The spectrum of a quantum channel as a superoperator is naturally tied to its Liouville representation, which is in general non-Hermitian. Our key contribution is an approximate block-encoding scheme for this representation in a Hermitized form, given only black-box access to the channel; this immediately allows us to apply polynomial transformations to the channel's singular values by quantum singular value transformation (QSVT). We then demonstrate an $O(d^3/\delta )$ upper bound and an $\mathrm{\Omega }(d/\delta )$ lower bound for the query complexity of constructing a quantum channel that is $\delta$-close in diamond norm to a block encoding of the unnormalized Hermitized Liouville representation. We show that our method applies practically to the problem of learning the $q$-th singular value moments of unknown quantum channels for arbitrary $q>2,q\in \mathbb{R}$, which has implications for testing whether a quantum channel is entanglement breaking. Our results establish a general framework for manipulating black-box quantum channels with QSVT and related methods, enabling direct evaluation of the channel's spectral properties without tomography or significant classical postprocessing.

Precision, robustness, and efficiency are central requirements for quantum technologies. We show that genuine quantum features combined with non-Gaussianity enable the simultaneous optimization of these properties in a quantum battery-charging process. Using a generalized Jaynes-Cummings interaction as a paradigmatic light-matter interaction model, we apply the Full Counting Statistics to characterize stochastic energy exchanges between a stack of qubits and a single-mode bosonic field. We demonstrate that a sequential charging protocol driven by a non-Gaussian quantum field yields high performance in charging precision, which remains maximal even under suboptimal operating conditions. Our results establish the use of non-Gaussian quantum states in battery charging as a robust route to a quantum precision advantage over protocols based on Gaussian states, achieved through the suppression of detrimental quantum fluctuations.

We report on the realization of a quantum-degenerate Bose-Bose mixture of ${}^{162}\mathrm{Dy}$ and ${}^{164}\mathrm{Dy}$. Owing to the near-identical mass and polarizability of the two isotopes, the mixture thermalizes efficiently, with evaporation trajectories closely following those of the single-isotope case. Using a broad interspecies Feshbach resonance, we explore a miscible-immiscible transition between the two Bose-Einstein condensates. The tunability of the interspecies interaction, combined with the large magnetic dipole moment of Dy, makes this platform well suited for exploring dipolar effects in ultracold mixtures, including multicomponent supersolidity.

We report ab initio relativistic calculations on the complex open shell ${\mathrm{Sn}}^{12+}$ highly charged ion, a prototypical plasma ion relevant for extreme ultraviolet (EUV) nanolithography. Previous calculations of EUV emissivity in tin plasmas consistently generate a spectrum in which the region of peak emissivity is blueshifted relative to experiment. By optimizing our numerical methods to take full advantage of modern, high-performance CPU architectures, we are able to completely saturate the configuration interaction within the $n=4$ shell. Coupled with a thorough treatment of core-valence correlation we resolve the blueshift, finding a surprisingly large influence of highly excited states on the spectrum that is dominated by multiply excited states.

It has been shown for various systems that the decay rate of an unstable quantum system deviates from exponential behavior in short- and long-time regimes associated with memory effects. In particular, it is widely believed that in the short-time regime, the decay is quadratic, inducing the quantum Zeno effect, in which the decay is suppressed by rapidly repeated measurements. In our study, we find that when the environment of the unstable system has an energy spectrum with a lower bound but without an upper one, the decay rate in both regimes is scaled in terms of the spatial dimension and the exponent of the energy dispersion of the environment. Surprisingly, we find that in the short-time regime the decay exhibits fractional scaling, which leads to a quantum Zeno effect with a different scaling of the Zeno time.

Achieving ultrafast control over chirality, the fundamental handedness of matter and light, remains a pivotal challenge in chiral photochemistry and information science. Current chiroptical switches are limited to picosecond or nanosecond timescales, constrained by the slow structural rearrangement of molecules. Here, we propose a femtosecond chiroptical switch in a hydrogen atom by exploiting the typically ignored global phase of a Rabi-oscillating system, which we map directly onto the chirality of a bound-electron wave packet. We show that a resonant $2\pi$-area pulse induces chirality inversion primarily via a geometric phase, i.e., the Aharonov-Anandan phase, accumulated during cyclic evolution on the Bloch sphere. This geometric origin endows the switch with high robustness against pulse area errors. By optimizing the initial-state composition, we enhance the geometric phase contribution, thereby reinforcing the switching stability. Our work provides a robust route for ultrafast chirality control, with implications for geometric-phase-based quantum sensing and chiroptical information processing.

We demonstrate that the winding number of a toroidal Bose-Einstein condensate can be deterministically and robustly engineered by manipulating the motion of dark solitons via nonlinear coupling with the localized waves driven by external forces. As the soliton velocity relative to the background crosses zero, the emergence of a density zero, inducing the phase singularity, leads to a quantized jump in the winding number whose direction is determined by the direction of the velocity crossing. This approach enables the programmable manipulation of the winding number, and allows for versatile tailoring by accelerating multiple dark solitons. Our results are supported by full three-dimensional numerical simulations, while the experimental feasibility is discussed using state-of-the-art techniques. The explicit relation between the winding number and the persistent current in the ring geometry facilitates the design of compact rotation sensors, and opens new avenues for developing topological physics and advancing quantum technologies.

The Hawking effect—the amplification of fluctuations at the horizon—has been detected in quantum fluids through real-space density correlations. However, real-space observables integrate over frequency, mixing distinct scattering channels into a single interference pattern and obscuring the spectral and entanglement structure of the emission. Here, we numerically compute momentum-space two-point correlations in a transcritical quantum fluid, using the truncated Wigner approximation applied to a realistic, driven-dissipative polariton system. We spectrally resolve the Hawking-partner channel as well as graybody factor channels and find that both carry comparable correlation strength, demonstrating that the well-known real-space “moustache” is an interference between these spectrally distinct contributions. The Hawking-partner channel is dominated by negative correlations, a direct signature of quantum-vacuum pair creation. All features reach amplitudes detectable in state-of-the-art experiments. Our results establish that the full three-mode output state must be considered for entanglement characterization, and they provide a general framework applicable to any quantum fluid.

Chiroptical responses in atomic systems are usually weak, as they arise from the interference between electric- and much weaker magnetic-dipole transitions. We show that atoms arranged in chiral geometries can instead exhibit a strong collective chiroptical response mediated entirely by electric-dipole interactions. Using a coupled-dipole framework, we identify a regime of pronounced chiroptical response emerging at subwavelength interatomic separations, which can be tuned by the probe frequency. This enhancement is directly linked to the formation of subradiant collective modes. Our results establish a fundamental connection between geometric chirality and collective light-matter interactions, opening additional pathways for engineering and exploiting chiral optical responses in atomic systems.

Classical objectivity requires an environment to witness a pointer value, not merely to decohere it. We derive microscopic Hamiltonian laws for this distinction. Exact quantum nondemolition product monitoring yields a certified two-edge strong-Darwinism window: sufficient witnesses cross the optimal record-discrimination edge while retaining an unobserved complement that crosses the residual-coherence edge. Under additional regularity assumptions, the supplement gives converse bounds at the same logarithmic scale. For controlled-phase monitors, environmental asymmetry gives a single-fragment information bound, a redundancy converse, and, in efficient i.i.d. streams, an achievable block-capacity law for redundant witnesses. A finite-temperature spin-phase bath shows the physical separation: hot probes can decohere efficiently while losing the local asymmetry needed for objective witnesses.

We present a class of control pulses designed to transfer colocated ensembles without relying on frequency selectivity, thereby allowing much faster state transitions. A geometric approach allows us to construct sequences which are robust to changes in the background magnetic field along multiple axes, and errors in the pulse area. These pulses are extremely fast, with robustness to pulse area shown at half the quantum speed limit. We demonstrate these sequences on nuclear-dipole states, showing milliradian precision over several hours, 30-fold beyond the previous state of the art. This provides a path for extending the coherent integration time of ultralong-lived nuclear-spin states to the fundamental limit set by their $>10000$ s lifetimes, as the limiting self-interactions of the nuclei are suppressed in the symmetric superposition. The state-preparation quality demonstrated here directly opens up 30-fold improvements in next generation tests of the standard model, especially tests of the symmetries of QCD and searches for dark matter; it is also crucial for the development of nuclear-spin-based quantum memories and may be useful in other scenarios demanding extremely fast but robust transitions.

Releasing shell-shaped Bose-Einstein condensates from the external confinement produces a spherically symmetric density distribution characterized by concentric ripples surrounding a central peak. Here, we investigate how a vortex-antivortex dipole affects this dynamics, finding that increasing dipole separation progressively breaks the spherical symmetry. Correspondingly, the interplay of vortex physics and curvature produces a nonmonotonic behavior of the cloud aspect ratio with the vortex distance, and decreases the maximal central density achieved during the expansion. These features can be used for detecting vortex dipoles prepared in shell-shaped superfluids, as well as a basis for analyzing their signatures in other thin superfluids with more general curved geometries.

Quantized transport usually occurs in linear periodic systems with nontrivial topology. While nonlinearity can strongly influence this transport, particularly through the formation of solitons, it is still determined by the spatiotemporal Chern indices of the bands of the underlying linear potential. Here, we show that nonlinear quantized transport can be induced by a sliding nonlinear lattice, even when the latter is combined with a static linear lattice, whose bands are topologically trivial. In such a system, an effective topology emerges from characteristic features of stable Wannier solitons and can be described in terms of the transport of Wannier centers associated with a composite potential combining the stationary linear lattice and an effective moving nonlinear lattice. The phenomenon is generic, as confirmed by the analysis of the continuous Gross-Pitaevskii equation with mutually sliding nonlinear and linear lattices, as well as by the corresponding discrete model with spatially varying coefficients. By increasing the norm of the input state, i.e., the nonlinearity strength, one can observe the unique transition from the absence of transport, to the topological transport, and, eventually, to the nontopological dragging of the input state by the nonlinear lattice.

We present a microscopic calculation of spontaneous photon emission by twisted (paraxial) electrons propagating through inhomogeneous, axisymmetric magnetic fields. We construct exact electron states that incorporate transverse mode structure and wave-front curvature by combining the Foldy-Wouthuysen transformation with a geometric framework based on Lewis-Ermakov invariants and metaplectic transformations. We show that the evolution of such structured states corresponds to an open path in the space of quadratic forms, giving rise to a geometric contribution to the emission amplitude that cannot be eliminated by gauge choice or adiabatic arguments. The inverse radius of curvature of the electron wave front controls a finite-window boundary contribution to the emission amplitude in regions where the external magnetic field vanishes locally; this contribution vanishes when the observation window is extended to infinity. The mechanism presented generalizes Landau-level radiation to nonasymptotic, structured electron states and establishes a direct connection between noncyclic geometric evolution and photon emission.

We investigate a noncylindrically symmetric vector optical field constructed in the orthogonal dipolar coordinate system. This field generates a spin-dependent transverse wave-vector shift, enabling a controllable optical spin Hall effect in tightly focused fields. We demonstrate that the separation distance between opposite spins can be continuously tuned by varying the topological order of the dipolar vector optical field. Furthermore, the separated spins give rise to an extraordinary optical force governed by the Belinfante spin momentum, which manifests itself as a customizable spin-curl force and drives nanoparticles in opposite directions depending on their spin state. This work establishes a geometric degree of freedom for engineering spin-orbit interactions, providing a powerful platform for chiral nanoparticle sorting and advanced spin-photomechanical devices.