In previous work we introduced a formalism that maps classical networks of nonlinear oscillators onto a quantumlike Hilbert space. We demonstrated that specific network transformations correspond to quantum gates, underscoring the potential of classical many-body systems as platforms for quantum-inspired information processing. In this paper we extend this framework by systematically identifying the classical dynamics best suited for this purpose. Specifically, we address the following question: Can the collective steady state of a classical network encode signatures of quantum information? We prove that the answer is affirmative for a special class of synchronizing many-body systems, namely, a complex-field extension of the Kuramoto model of nonlinearly coupled classical oscillators. Through this approach, we investigate how quantumlike entangled states can emerge from classical synchronization dynamics.

In this work, we introduce a unified method to characterize and measure multipartite entanglement using the framework of thermodynamics. A family of entanglement measures is proposed: ergotropic-gap concentratable entanglement. Furthermore, we establish that ergotropic-gap concentratable entanglement constitutes a well-defined entanglement measure within a specific parameter regime, satisfying key properties including continuity, majorization monotonicity, and monogamy. We demonstrate the utility of this measure by showing it effectively distinguishes between multiqubit Greenberger-Horne-Zeilinger states and W states. It also proves effective in detecting entanglement in specific classes of four-partite star quantum network states.

The computation of dynamical response functions is central to many problems in condensed matter physics. Owing to the rapid growth of quantum correlations following a quench, classical methods face significant challenges even if an efficient description of the equilibrium state is available. Quantum computing offers a promising alternative. However, existing approaches often assume access to the equilibrium state, which may be difficult to prepare in practice. In this work, we present a method that circumvents this by using energy filter techniques, enabling the computation of response functions and other dynamical properties in both microcanonical and canonical ensembles. Our approach only requires the preparation of states that have significant weight at the desired energy. The dynamical response functions are then reconstructed from measurements after quenches of varying duration by classical postprocessing. We illustrate the algorithm numerically by applying it to compute the dynamical conductivity of a free-fermion model, which unveils the energy-dependent localization properties of the model.

The fully differential cross section is the most detailed quantity that can be measured or calculated to study ionization in few-body systems. For 75 keV proton collisions with helium, various experimental data are available. However, previous theoretical calculations found significant discrepancies across the entire range of data. In this work the wave-packet convergent close-coupling method is extended to calculating these cross sections for electrons ejected with energies from 1 to 75.4 eV. The approach utilizes a two-center expansion and correlated two-electron helium wave functions to describe the four-body proton-helium system. While there is good agreement with the experiment for electrons ejected with energies near the matching-velocity point, elsewhere, the results overall do not support the picture provided by the available measurements. Hence, further investigations, both theoretical and experimental, are necessary to resolve the intermediate-energy proton-helium differential ionization problem.

Metastable qubits in atomic systems can enable large-scale quantum computing by simplifying hardware requirements and adding efficient erasure conversion to the preexisting toolbox of high-fidelity laser-based control. For trapped atomic ions, the fundamental error floor of this control is given by spontaneous Raman and Rayleigh scattering from short-lived excited states. We measure spontaneous Raman scattering rates out of a metastable $D_{5/2}$ qubit manifold of a single trapped ${}^{40}\mathrm{Ca}^{+}$ ion illuminated by 976 nm light that is $-44$ THz detuned from the dipole-allowed transition to the $P_{3/2}$ manifold. This supports the calculation of error rates from both types of scattering during one- and two-qubit gates on this platform, thus demonstrating that infidelities less than ${10}^{-4}$ are possible.

Quantum logic gates performed via two-photon stimulated Raman transitions in ions and atoms are fundamentally limited by spontaneous scattering errors. Recent theoretical treatment of these processes has predicted no lower bound on the scattering-induced error rate of such gates when implemented with far-detuned lasers, while also providing an extension to metastable qubits. To validate this theoretical model, we provide experimental measurements of Raman scattering rates due to near- and far-detuned lasers for initial states in the metastable $D_{5/2}$ level of ${}^{137}\mathrm{Ba}^{+}$. The measured spontaneous Raman scattering rate is consistent with the theoretical prediction and suggests that metastable-level two-qubit gates with an error rate approximately equal to ${10}^{-4}$ are possible with laser excitation detuned by tens of terahertz or more.

The spin polarization of electrons in strong laser fields, an important phenomenon predicted by strong-field quantum electrodynamics, has garnered considerable attention in recent years due to its broad potential applications. In the present work we investigate the collision dynamics between multi-GeV electrons and circularly polarized laser pulses with relativistic intensity and duration of tens of femtoseconds by employing a density-matrix method. Numerical results demonstrate that the energy of outgoing electrons significantly influences their longitudinal spin polarization (LSP). Notably, for an incident electron energy of 80 GeV and a laser intensity parameter of 0.4, the LSP exceeds $60\%$ around the energy corresponding to the peak of the scattering energy spectrum. Our findings provide a promising avenue for experimentally generating ultrarelativistic longitudinally spin-polarized electron beams.

The advent of ultracold alkaline-earth atoms in optical lattices has established a platform for investigating correlated quantum matter with $\mathrm{SU}\left(N\right)$ symmetry, offering highly tunable model parameters that allow experiments to access phenomena that are unavailable in conventional materials. Understanding the ground-state physics of $\mathrm{SU}\left(N\right)$ Fermi-Hubbard models away from the Heisenberg limit and from the spin-flavor balanced setting is important, as examining the flavor imbalance reveals new physics in Fermi-Hubbard models and shows how $\mathrm{SU}\left(N\right)$ phases react to practical experimental imperfections in optical lattices. In this study, mean-field phase diagrams are presented for the unit-density SU(3) Fermi-Hubbard model at two sets of flavor densities, $(\frac{1}{3}-\delta ,\frac{1}{3}+\delta ,\frac{1}{3})$ and $(\frac{1}{4}-\delta ,\frac{1}{4}+\delta ,\frac{1}{2})$, with the flavor imbalance introduced as $\delta$. Novel phases are identified at moderate interaction strengths for both densities, and their robustness is investigated in the presence of flavor imbalance. Furthermore, we provide microscopic explanations of the phases found and their stability. Analysis of thermal ensembles of random mean-field solutions indicate that, at temperatures accessible in state-of-the-art cold atom experiments, some spin orders are hard for conventional scattering or local observable measurements to detect, but can be more accessible with quantum gas microscopy in optical lattice experiments. This work also shows that nesting and Mottness, intertwined in the usual SU(2) Hubbard model in stark contrast to generic materials, can be tuned in the SU(3) model and play distinct roles. The resulting phase diagrams not only deepen our understanding of $\mathrm{SU}\left(N\right)$ Fermi-Hubbard models but also inform future experimental search for new phases.

The sensitive axis of an atom gravimeter is defined by the direction of the Raman lasers. Any tilt of the Raman lasers with respect to the vertical direction introduces systematic errors in gravity measurements. In this work, we report a determination of the tilt of Raman lasers, where the fringe of the atom interferometer is scanned by varying the tilt, rather than the phase, of the Raman lasers. Unlike the periodic cosine fringes typically used in atom interferometers, the fringe obtained by changing the tilt, referred to as the tilt-scanned fringe, is aperiodic in tilt and exhibits a shift due to the presence of a nonzero tilt. The tilt-scanned fringe is highly sensitive to the tilt-caused shift, enabling convenient and precise determination of the Raman laser tilt in atom gravimeters. We demonstrate that one tilt-scanned fringe, corresponding to a tilt measurement sampling time of 13 s, can determine the tilt with a typical precision of about $30\mu \mathrm{rad}$ in our developed atom gravimeter. The short-term sensitivity and measurement accuracy of the tilt-scanned fringe method were evaluated, demonstrating performance comparable to conventional tilt determination techniques. We expect this method to offer a convenient solution for Raman laser alignment in atom gravimeters and enhance the efficiency of absolute gravity surveys.

We explore quantum phase transitions in the multiphoton Jaynes-Cummings-Hubbard model (JCHM). Using the mean-field approximation, we demonstrate that the multiphoton JCHM exhibits quantum phase transitions between the Mott insulator (MI) phase, the superfluid phase, and an additional phase we refer to as the forbidden phase. The multiphoton JCHM MI phases are classified according to a conserved quantity associated with the total number of excited atoms and photons. When this conserved quantity diverges toward positive infinity, this system enters the forbidden phase. By analyzing the system, we observe MI, superfluid, and forbidden phases in both the single- and two-photon JCHMs, although the MI phases in the two-photon case are confined to subspaces with small values of the conserved quantity. In contrast, only the superfluid and forbidden phases appear in the three- and four-photon JCHMs, with no MI phase observed.

The average energy and energy spread of a quantum system are two important factors that affect a system's evolution speed, which is usually defined as the changing rate of the distance between a quantum state and the state during its evolution. Alternatively, the evolution speed of a quantum system could also be studied based on its evolution path. It is found that if we define the evolution speed of a quantum unitary system as the changing rate of the path distance between a quantum state and the state during its evolution, the instantaneous evolution speed is determined by the Hamiltonian's eigenvalues, rather than its expectation value or variance imposed on any quantum state. More specifically, the range of the Hamiltonian's eigenvalues determines the evolution speed of a quantum system through the relation ${\omega }_H=\frac{1}{2}({\lambda }_{max}-{\lambda }_{min})$, which is independent of the quantum state. Given an initial state ${\rho }_0$ in a quantum unitary system, the minimum time required to evolve it to a target state ${\rho }_{\tau }$ is ${\tau }_{min}=\frac{{\mathcal{L}}_{min}({\rho }_0,{\rho }_{\tau })}{{\omega }_H}$, where ${\mathcal{L}}_{min}({\rho }_0,{\rho }_{\tau })$ is the path distance contained in the shortest evolution from ${\rho }_0$ to ${\rho }_{\tau }$. This lower bound of the evolution time is tight and achievable in a finite-energy system.

We demonstrate the generation of counterpropagating, twin-photon pairs in the optical communication band, utilizing periodically poled Rb-doped ${\mathrm{KTiOPO}}_4$. The spectral and polarization indistinguishability of the photon pairs is confirmed through a Hong-Ou-Mandel interference measurement. At degeneracy, the photon-pair generation exhibits a broad angular distribution. Notably, the forward-propagating photon tunes with the pump frequency while the backward-propagating photon frequency remains nearly independent of the pump wavelength.

Resolving high-contrast targets is a fundamental, yet highly challenging, task in astronomy. Using quantum estimation theory, we demonstrate that the ultimate limit for estimating the separation between two unequal-brightness thermal sources via interferometry remains constant, enabling the potential for superresolution. We give a comparative analysis of two primary stellar interferometric schemes: amplitude interferometry and intensity interferometry. Notably, the nulling strategy employed in amplitude interferometry, a configuration specifically proposed for exoplanet detection by leveraging destructive interference to suppress the brighter source, is quantum optimal for separation estimation. While intensity interferometry is less effective than amplitude interferometry in lossless scenarios and fails to achieve superresolution, it becomes competitive when optical loss in large-scale interferometry is considered. By applying these methodologies to modern stellar interferometry, we highlight the promise of large-scale interferometry for advancing high-resolution astronomical observation.

We benchmark ionization and excitation energies of transition-metal atoms Sc–Zn with a transcorrelated Hamiltonian combined with pseudopotentials. The similarity transformed Hamiltonian provides compact transcorrelation (TC) wave functions in affordable aug-cc-pVTZ and aug-cc-pVQZ Gaussian bases and eliminates the need for complete basis set extrapolations. The use of Douglas-Kroll-Hess theory is omitted because scalar relativistic effects are included in the pseudopotentials. Treating the full semicore ($3s3p$) valence and freezing only $1s$–$2p$ shells, we reach chemical accuracy for all atoms and properties with coupled cluster and full configuration interaction quantum Monte Carlo. Consistent total energies across disparate orbital sets and correlation solvers highlight the robustness of the TC workflow. Our study pushes benchmark-quality quantum chemistry into the $3d$ block without large-scale basis sets and opens a practical route for transcorrelation to strongly correlated molecules and materials hosting heavier transition metals.

Accurate determination of the temperature of trapped ion Coulomb crystals (ICCs) is critical for advancing quantum technologies. We present a deep learning approach to classify ICC temperature states from fluorescence images. A high-fidelity dataset was generated using the (py)LIon molecular dynamics toolkit, simulating ICCs containing 100–268 ions over a temperature range of 5–20 mK. In the initial 16-class problem (each class a 1-mK interval), a ConvNeXt convolutional network achieved a peak accuracy of 57%, demonstrating its ability to capture fine-grained structural features. To overcome low distinguishability among similar temperature classes, we redefined the task into four broader temperature intervals and applied a vision transformer (ViT). The ViT model achieved a test accuracy of 84%, indicating substantially improved generalization. These results highlight the complementarity of convolutional neural network and transformer architectures for noninvasive temperature diagnostics. We discuss limitations due to dataset diversity and outline future work on larger-scale simulations and physics-guided network designs to further improve ICC temperature estimation in quantum applications.

The most sensitive direct neutrino mass searches today are based on measurement of the end point of the $\beta$ spectrum of tritium to infer limits on the mass of the unobserved neutrino. To avoid the smearing associated with the distribution of molecular final states in the T-He molecule, the next generation of these experiments will need to employ atomic (T) rather than molecular $\left({\mathrm{T}}_2\right)$ tritium sources, at currents of at least ${10}^{15}$ atoms per second. Following production, atomic T can be trapped in gravitational and/or magnetic bottles for $\beta$ spectrum experiments, if and only if it can first be cooled to millikelvin temperatures. Accomplishing this cooling presents substantial technological challenges. The Project 8 collaboration is developing a technique based on magnetic evaporative cooling along a beamline (MECB) for the purpose of cooling T to feed a magnetogravitational trap that also serves as a cyclotron radiation emission spectroscope. Initial tests of the approach are planned in a pathfinder apparatus using atomic Li. This paper presents a method for analyzing the dynamics of the MECB technique and applies these calculations to the design of systems for cooling and slowing of atomic Li and T. A scheme is outlined that could provide a current of T at the millikelvin temperatures required for the Project 8 neutrino mass search.

We investigate three kinds of instabilities in binary immiscible homogeneous Bose-Einstein condensate, considering rubidium isotopes ${}^{85}\mathrm{Rb}$ and ${}^{87}\mathrm{Rb}$ confined in two-dimensional circular box. Rayleigh-Taylor and Kelvin-Helmholtz (KH) instability types are studied under strong perturbations. Without external perturbation, instabilities are also probed by immiscible-to-miscible quenching transition, under two different initial configurations. Our numerical simulations show that all such instability dynamics are dominated by large vortex production and sound-wave (phonon) propagation. For long-term propagation, vortex dynamics become dominant over sound waves in the KH instability, while sound-wave excitations predominate in the other cases. For all the dynamical simulations, the emergence of possible scaling laws are investigated for the compressible and incompressible parts of the kinetic energy spectra, in terms of the wave number $k$. The corresponding results are compared with the classical Kolmogorov scalings, $k^{-5/3}$ and $k^{-3}$, for turbulence, which are observed in the kinetic energy spectra at some specific time intervals.