Recent nonmagnetized studies of binary neutron star mergers have indicated the possibility of identifying equation-of-state features, such as a phase transition or a quark-hadron crossover, based on the frequency shift of the main peak in the postmerger gravitational wave spectrum. By performing a series of general relativistic, magnetohydrodynamic simulations we show that similar frequency shifts can be obtained due to the effect of the magnetic field. The existing degeneracy can either mask or nullify a shift due to a specific equation-of-state feature, and therefore the interpretation of observational data is more complicated than previously thought, requiring a more complete treatment that would necessarily include the neutron star’s magnetic field.

Conformal boundary conditions in two-dimensional conformal field theories are still mostly an uncharted territory. Even less is known about the relevant boundary deformations that connect them. A natural approach to the problem is via conformal perturbation theory, which, however, becomes quickly intractable. Using the formalism of open string field theory, we construct the corresponding classical solution, from which we can easily extract the boundary theory data. As a simple illustration we calculate the boundary degeneracy $g$ to next-to-leading order for a generic theory.

Neutrino-nucleus elastic scattering ($\nu A_{\mathrm{el}}$) with partial quantum-mechanical coherency has been observed in several nuclei with neutrinos from decay-at-rest pions. This interaction with reactor neutrinos where coherency is $>95\%$ has not yet been experimentally observed. We present new results on the studies of the $\nu A_{\mathrm{el}}$ cross section with an electrocooled $p$-type point-contact germanium detector at the Kuo-Sheng Reactor Neutrino Laboratory. A total of 242(357) kg-days of Reactor ON(OFF) data at a detector threshold of 200 eV in ionization energy are analyzed. The Lindhard model parametrized by a single variable $k$ which characterizes the quenching function was used. A limit at 90% confidence level of $\rho <4.7$ at the predicted value of $k=0.162$ is derived, where $\rho$ is the ratio of the measured to standard model (SM) cross section. Conversely, $k<0.288$ at the SM value of $\rho =1$.

Lepton flavor universality in rare $b\to s$ transitions is tested for the first time using $B_s^0$ meson decays. The measurements are performed using $pp$ collision data collected by the LHCb experiment between 2011 and 2018, corresponding to a total integrated luminosity of $9{\mathrm{fb}}^{-1}$. Branching fraction ratios between the $B_s^0\to \varphi e^{+}{e}^{-}$ and $B_s^0\to \varphi {\mu }^{+}{\mu }^{-}$ decays are measured in three regions of dilepton mass squared, $q^2$, with $0.1<q^2<1.1$, $1.1<q^2<6.0$, and $15<q^2<19{\mathrm{GeV}}^2/c^4$. The results agree with the standard model expectation of lepton flavor universality.

The two-loop self-energy correction to the bound-electron $g$ factor in hydrogenlike ions is investigated, taking into account the electron-nucleus interaction exactly. This all-order calculation is required to improve the total theoretical uncertainty of the $g$ factor, which is limited by the fact that two-loop self-energy corrections have only been calculated so far in the form of an expansion in $Z\alpha$. Here, $Z$ is the nuclear charge number and $\alpha$ is the fine-structure constant. In this work, we report calculations of the last missing parts of the total two-loop self-energy correction, exactly in $Z\alpha$. We apply our theory to the recently measured $g$ factor of the hydrogenlike ${{}^{118}\mathrm{Sn}}^{49+}$ ion [J. Morgner et al., Nature (London) 622, 53 (2023)] and, with a factor of 8, improve the accuracy of its state-of-the-art theoretical value by almost one order of magnitude, enabling more detailed tests of quantum electrodynamics and new physics in strong fields.

The amplitude and phase of a photoionization channel provide deep insights into the nature of ionization dynamics. Here, we propose a novel experimental approach to retrieve these parameters from the photoelectron momentum distribution (PMD), where a 400 nm femtosecond laser is used to ionize polarized Rb atoms prepared in the $5p$ state. The magnetic quantum numbers of polarized atoms are well controlled by breaking down the symmetry of the cooling laser in a magneto-optical trap reaction microscope. From the tilt angle of the PMD and the interference structure of $\epsilon s$ and $\epsilon d$ ionization channels, we are able to extract their relative amplitude and phase shift, in good agreement with ab initio calculations. This exhibits a benchmark one-photon single ionization study of the hydrogen-like atom, providing a complete measurement with full characterizations of intermediate and final state wave functions.

Experimental control over the strength and angular dependence of interactions between atoms is a key capability for advancing quantum technologies. Here, we use microwave dressing to manipulate and enhance Rydberg-Rydberg interactions in an atomic ensemble. By varying the cloud length relative to the blockade radius and measuring the statistics of the light retrieved from the ensemble, we demonstrate a clear enhancement of the interaction strength due to microwave dressing. These results are successfully captured by a theoretical model that accounts for the excitation dynamics, atomic density distribution, and phase-matched retrieval efficiency. Our approach offers a versatile platform for further engineering interactions by exploiting additional features of the microwave fields, such as polarization and detuning, opening pathways for new quantum control strategies.

Topological concepts have been employed to understand a wide range of phenomena in physics. While a plethora of ground states are known to have topological underpinning, it is still quite unclear if and how topology manifests itself in the relaxation dynamics of strongly correlated many-body systems. In this Letter, we study time evolution of interacting bosons in a finite one-dimensional superlattice and uncover surprising emergent topological phenomena in the long-time stationary states. Beginning with simple product states, the system evolves into stationary states with high energy whose string correlation and entanglement are investigated. Based on extensive numerical simulations and effective-model analysis, it is demonstrated that the stationary states are nonthermal for a wide range of parameters, and they exhibit certain features that are characteristic of the symmetry-protected topological ground state of the Hamiltonian. In contrast, no topological feature is found in the stationary state as long as the system thermalizes. This difference is further corroborated by the distinct behavior of quantum entanglement and edge states of the system. Our theoretical prediction can be examined by current experimental techniques and paves the way for a more comprehensive understanding of topological phases in nonequilibrium settings.

We present 4D topological textures in (quasi)monochromatic nonparaxial optical lattices that contain all possible polarization ellipses with every combination of ellipticity and orientation in 3D space. These fields span the nonparaxial polarization space (a complex projective plane) and a 4-sphere within specific spatiotemporal regions, forming 4D skyrmionic structures. Constructed from five plane waves with adiabatically varying relative amplitudes, they are experimentally realizable in free space by focusing a temporally variant beam with a high numerical aperture lens.

Attosecond dynamics of electron transmission through atomically thin crystalline films is studied with an ab initio scattering theory. The temporal character of the electron propagation through graphene multilayers is traced to the band structure of bulk graphite: In the forbidden gaps the wave packet transit time ${\tau }_{\mathrm{T}}$ saturates with thickness and in the allowed bands ${\tau }_{\mathrm{T}}$ oscillates following transmission resonances. Hitherto unknown negative transit time due to in-plane scattering is discovered in monolayers of graphene, h-BN, and oxygen. Moreover, Wigner time delay is found to diverge at the scattering resonances caused by the emergence of secondary diffracted beams. This offers a way to manipulate the propagation timing of the wave packet without sacrificing the transmitted intensity. The spatial reshaping of the wave packet at the resonances may help elucidate details of the streaking by an inhomogeneous field at the surface.

${\mathrm{YbNi}}_4{\mathrm{P}}_2$ is the first known ferromagnetic metal showing a second-order quantum phase transition. Current theoretical understanding rules out second-order ferromagnetic quantum criticality in centrosymmetric two- and three-dimensional (2D and 3D) metals. Thus, studying the electronic structure of ${\mathrm{YbNi}}_4{\mathrm{P}}_2$ is of prime fundamental importance. Using angle-resolved photoemission spectroscopy, we experimentally prove the existence of 1D Fermi surface contours. In addition, our results demonstrate that part of the electronic structure of ${\mathrm{YbNi}}_4{\mathrm{P}}_2$ is made of states of higher dimensionality, thereby bringing into question the fact that ferromagnetic quantum criticality in centrosymmetric crystals is exclusively found in 1D systems. Our experimental data show that the electronic structure of ${\mathrm{YbNi}}_4{\mathrm{P}}_2$ is a playground of mixed dimensionality, electron correlations, strong hybridization, and spin-orbit coupling, all of them providing new insights in understanding the origin of ferromagnetic quantum criticality.

Quasi-long-ranged order is the hallmark of two-dimensional liquid crystals. At equilibrium, this property implies that the correlation function of the local orientational order parameter decays with distance as a power law: i.e., $\sim |\mathit{r}{|}^{-{\eta }_p}$, with ${\eta }_p$ a temperature-dependent exponent. While in general nonuniversal, ${\eta }_p=1/4$ universally at the Berezinskii-Kosterlitz-Thouless transition, where orientational order is lost because of the unbinding of disclinations. Here, we demonstrate that, in active liquid crystals, the notion of quasi-long-ranged order fundamentally differs from its equilibrium counterpart, and the exponent ${\eta }_p$ is allowed to vary in the range $0<{\eta }_p\le 2$, with the upper bound corresponding to the isotropic phase. Our theoretical predictions are supported by a survey of a variety of experimental realizations of two-dimensional active liquid crystals.

The emergence of classical behavior in quantum theory is often ascribed to the interaction of a quantum system with its environment, which can be interpreted as environmental monitoring of the system. As a result, off-diagonal elements of the density matrix of the system are damped in the basis of a preferred observable, often taken to be the position, leading to the phenomenon of decoherence. This effect can be modeled dynamically in terms of a Lindblad equation driven by the position operator. Here the question of decoherence resulting from a monitoring of position and momentum, i.e., a phase-space measurement, by the environment is addressed. There is no standard quantum observable corresponding to the detection of phase-space points, which is forbidden by Heisenberg’s uncertainty principle. This issue is addressed by use of a coherent-state-based positive operator-valued measure for modeling phase-space monitoring by the environment. In this scheme, decoherence in phase space implies the diagonalization of the density matrix in both position and momentum representations. This is shown to be linked to a Lindblad equation where position and momentum appear as two independent Lindblad operators.

We propose and demonstrate experimentally continuous phased dynamical decoupling (CPDD), where we apply a continuous field with discrete phase changes for quantum sensing and robust compensation of environmental and amplitude noise. CPDD does not use short pulses, making it particularly suitable for experiments with limited driving power or nuclear magnetic resonance at high magnetic fields. It requires control of the timing of the phase changes, offering much greater precision than the Rabi frequency control needed in standard continuous sensing schemes. We successfully apply our method to nanoscale nuclear magnetic resonance and combine it with quantum heterodyne detection, achieving microhertz uncertainty in the estimated signal frequency for a 120 s measurement. Our Letter expands significantly the applicability of dynamical decoupling and opens the door for a wide range of experiments, e.g., in nitrogen-vacancy centers, trapped ions, or trapped atoms.

A search is performed for dark matter particles produced in association with a resonantly produced pair of $b$-quarks with $30<m_{bb}<150\mathrm{GeV}$ using $140{\mathrm{fb}}^{-1}$ of proton-proton collisions at a center-of-mass energy of 13 TeV recorded by the ATLAS detector at the LHC. This signature is expected in extensions of the standard model predicting the production of dark matter particles, in particular those containing a dark Higgs boson $s$ that decays into $b\overline{b}$. The highly boosted $s\to b\overline{b}$ topology is reconstructed using jet reclustering and a new identification algorithm. This search places stringent constraints across regions of the dark Higgs model parameter space that satisfy the observed relic density, excluding dark Higgs bosons with masses between 30 and 150 GeV in benchmark scenarios with $Z^{\prime }$ mediator masses up to 4.8 TeV at 95% confidence level.

Quantum light—specifically light in noncoherent quantum states—can now be generated with intensities high enough to induce nonlinear responses in atoms, marking the emergence of a new “quantum era” in strong-field atomic physics. In this Letter, we explore the influence of quantum states of light on one of the key processes in this field: atomic double ionization. We develop a theoretical framework to model the interaction between a two-electron atom and light in arbitrary quantum states, such as phase-squeezed coherent states or bright squeezed vacuum states. Our results reveal that the quantum state of light significantly impacts the atomic double ionization process, leading to substantial changes in ionization probability and correlated electron momentum distribution.

By employing two-color counterrotating circularly polarized laser fields, we investigate the dynamics of electron recapture into Rydberg states under strong, ultrashort laser pulses, probed via coherent extreme-ultraviolet free-induction decay (XFID). Our study reveals significant distinctions between XFID and above-threshold high-order harmonic generation in terms of their ellipticity dependence on the driving-laser waveforms, yield variations with the laser-intensity ratios, and sensitivity to the driving-laser ellipticity. All these differences arise from the fundamentally distinct electron trajectories underlying the two processes. More importantly, our findings provide compelling evidence that Rydberg-electron recapture predominantly occurs at the end of the driving laser field, offering the first direct experimental confirmation of this long-proposed mechanism.

We demonstrate the existence and stability of one-dimensional (1D) topological kink configurations immersed in higher-dimensional bosonic gases and nonlinear optical setups. Our analysis pertains, in particular, to the two- and three-dimensional extended Gross-Pitaevskii models with quantum fluctuations describing droplet-bearing environments but also to the two-dimensional cubic-quintic nonlinear Schrödinger equation containing higher-order corrections to the nonlinear refractive index. Contrary to the generic dark soliton transverse instability, the kink structures are generically robust under the interplay of low-amplitude attractive and high-amplitude repulsive interactions. A quasi-1D effective potential picture dictates the existence of these defects, while their stability is obtained numerically and analytically through linearization analysis and direct dynamics in the presence of external fluctuations showcasing their unprecedented resilience. These “generic” (across different models) findings should be detectable in current cold atom and optics experiments, offering insights toward controlling topological excitations.

Superpositions of handed molecular states give rise to achiral eigenstates, delocalized across a double-well potential via tunneling. A coherent superposition of these energy eigenstates could dynamically relocalize the molecules into chiral states, which has only been addressed theoretically. Here, we present a microwave pump-probe study to create and probe coherent chiral tunneling dynamics in a given rotational state. Through a time-resolved scheme, we uncover the periodic time evolution of the induced chiral wave packet under field-free conditions. Moreover, we demonstrate precise phase control of this coherence via phase modulation during pump excitation.