Today's most advanced ion-trap quantum computers have significant overhead due to the need for dual-species operation. Looking ahead, logical qubit register sizes will be limited by the encoding rate needed to correct generic Pauli errors. We address both of these issues by establishing high-fidelity control of metastable qubits, a key component of omg or dual-type architectures, which enables converting a significant fraction of gate errors to erasures. We first implement an erasure conversion scheme which enables detection of $\sim 94\%$ of spontaneous Raman scattering errors during logic gates and nearly all errors from qubit decay. Second, we perform a two-ion geometric phase gate using far-detuned (−44 THz) stimulated Raman transitions to produce an entangled state with a raw Bell-state fidelity of 97.73% and a state preparation and measurement-corrected Bell-state fidelity of 98.61%. When subtracting erasure errors, this fidelity becomes 99.16%. These results, along with projections based on our detailed error budget, demonstrate metastable trapped-ion qubits as a platform for low-overhead, fault-tolerant quantum computing.

When a metastable state decays into radiation, there must be entanglement between the radiation and the decaying system, as well as between radiation collected at late and early times. We study the interplay between these two types of entanglement in simple Gaussian models in the Markov approximation. We define, via a windowed Fourier transform, multimode quantum states associated with radiation fragments produced at different times and compute the corresponding entanglement entropy increments. On the basis of these results, we argue that such entropy increments are useful entanglement measures, especially in cases such as Hawking radiation, where one wishes to separate the radiation into “old” and “new.”

Absorption profiles of vector light upon interaction with atomic vapor carries distinct signatures of an external magnetic field vector. However, this signature becomes ambiguous for antiparallel magnetic field vectors of equal magnitude, which makes their absorption profiles visually indistinguishable. To resolve this ambiguity, we present a theoretical analysis of the interaction of vector light with optically polarized atoms immersed in reference and test magnetic fields. Furthermore, we demonstrate the complete characterization of the arbitrarily oriented test magnetic field via a Fourier analysis of the absorption profile. This analysis reveals a one-to-one correspondence between the magnetic field properties and the profile's contrast and rotational angle. Our findings open an avenue to design an optical vector atomic magnetometer based on structured light fields.

We investigate the Casimir effect in a system of two twisted photonic gratings made of uniaxially anisotropic materials. Two distinct configurations are explored: a stack of symmetric gratings and a stack of in-plane chiral grating, with the latter realized by choosing a specific orientation of the anisotropy axis relative to stripes. We apply the reflection-matrix-based Casimir-Lifshitz formalism to explore how twist angle, material anisotropy, and the separation between gratings influence Casimir energy, force, and torque. Our calculations reveal that the equilibrium orientation of the gratings is governed by the anisotropy rotation angles, leading to a chiral configuration where the anisotropy axes of the upper and lower gratings are mutually parallel. These findings demonstrate that material anisotropy provides a powerful mechanism for controlling rotational alignment forces in nanophotonic systems.

We investigate a two-color scheme for tabletop high-order harmonic generation (HHG) that combines a mid-infrared (MIR) driving field with an ultrashort ultraviolet (UV) pulse that could be generated via resonant dispersive wave emission in gas-filled hollow-core fibers. This configuration enables the generation of bright, isolated, and tunable attosecond x-ray pulses. In contrast to single-color driving schemes, which suffer from low conversion efficiency, unfavorable wavelength scaling, and limited spectral control, the $\mathrm{MIR}+\mathrm{UV}$ approach provides a practical and controllable route for advancing tabletop ultrafast spectroscopy and real-time molecular imaging within current experimental capabilities.

The interplay between nonlinear and topological physics has led to intriguing emergent phenomena, such as quantized and fractionally quantized Thouless pumping of solitons dictated by the topological invariants of the underlying band structure. Unlike linear Thouless pumping, which requires excitation of a Wannier function of a uniformly filled band, quantized soliton pumping is observed even with localized excitations that do not represent Wannier functions. Here, we show that similar solitonlike quantized pumping can be observed in the Aubry-André-Harper model by introducing a synthetic nonlinearity in the form of a cutoff on the coupling strengths between lattice sites. More importantly, we reveal that the localized excitations driving quantized soliton pumping are precisely the Wannier functions of the uniformly filled bands of the effectively nonlinear lattice, thus restoring consistency with linear Thouless pumping. We extend this approach to multiband systems and show that the nonlinearity introduces a degeneracy between bands, subsequently leading to the observation of fractionally quantized pumping. Our approach of introducing a synthetic nonlinearity is general and could be extended to reveal soliton dynamics in other nonlinear topological systems.

We investigate the fully quantum evolution of the population imbalance in a perfectly symmetric Bose-Josephson junction modeled by a two-mode Bose-Hubbard Hamiltonian, focusing on the validity of macroscopic quantum self-trapping beyond the mean-field theory. We show that for any finite number of particles, the exact quantum dynamics leads to the breakdown of macroscopic quantum self-trapping after a finite time, regardless of the initial state. Using the symmetries of the Bose-Hubbard Hamiltonian, we provide a mathematical demonstration of this result and analyze the spectral properties governing the dynamics. We identify a branching behavior in the eigenvalue differences and a nontrivial structure of the population-imbalance amplitudes. These features allow us to distinguish two clearly different dynamical regimes and to elucidate the mechanism leading to the emergence of a quasi–macroscopic quantum self-trapping regime for large particle numbers. These findings bridge the gap between mean-field predictions and exact quantum dynamics and provide insight into the emergence of classical nonlinear behavior from finite quantum many-body systems.

Typically, quantum phases of many-body systems fit either the Landau-Ginzburg paradigm or topological classifications, with the intertwined emergence of spontaneous symmetry breaking and topological order being experimentally challenging. We present an experimentally accessible spin-orbit-coupled Lieb lattice platform for magnetic topological states. Remarkably, we observe topological characteristics, quantified by Chern number and Bott index, coexisting with spontaneous symmetry-breaking orders (like ferrimagnetism) in the many-body ground states. Computational analyses reveal a pronounced parameter regime where magnetic topological insulators emerge even under weak interactions. This unconventional coexistence stems from the Lieb lattice's unique band structure, enabling synergy between interaction-driven symmetry breaking and spin-orbit coupling-induced band inversion. Crucially, spin polarization and spin winding coemerge as coupled phenomena originating from identical degrees of freedom. We propose an implementation using ultracold atoms with existing Raman lattice techniques. Our findings pave the way for exploring the interplay between symmetry-broken states and topological order in strongly correlated systems.

We provide the ultimate precision attainable in spectroscopy of a quantum emitter using single-photon pulses. We find that the maximum precision of linewidth estimation is independent of the details of the emitter's bare Hamiltonian, though this is not true for the detunings. We also identify optimal pulse shapes attaining these precisions.

We present a quantum averaging theory (QAT) for analytically modeling unitary gate dynamics in driven quantum systems beyond the rotating wave approximation. QAT addresses the simultaneous presence of distinct timescales by generating a rotating frame with a dynamical phase operator that toggles with the high-frequency dynamics and yields an effective Hamiltonian for the slow degree of freedom. By accounting for the fast-varying effects, we demonstrate that high-fidelity two-qubit gates in strongly driven systems are achievable by going beyond the validity of first-order approximations. The QAT results rapidly converge with numerical calculations of a fast-entangling Mølmer-Sørensen trapped-ion-qubit gate in the strong-coupling regime, illustrating QAT's ability to simultaneously provide both an intuitive, effective Hamiltonian model and high accuracy.

We consider coherently coupled bosonic mixtures scattering at low energies in the presence of an external confinement along either one or two directions. We exactly solve the two-body scattering problem, showing that for large Rabi coupling the confinement-induced resonance can be displaced towards scattering lengths much smaller than the oscillator length. Our results make the observation of confinement-induced resonances more tunable and accessible, offering yet another handle for the efficient control of strong interactions in ultracold quantum gases.

Supersolidity—the simultaneous superfluid flow and crystalline order—has been realized in quantum atomic systems, but remains widely unexplored in photonic platforms operating at weak light-matter coupling. We predict a supersolid phase of light in a plasma-filled optical microcavity, where photons acquire effective mass and interact via nonlocal, plasma-mediated nonlinearities. By deriving a Gross-Pitaevskii equation with a tunable photon-photon interaction kernel, we show that the light field can spontaneously crystallize into a supersolid lattice via modulational instability. Crucially, this supersolid arises from a weak photon-electron coupling enabled by virtual electronic transitions and it does not require hybrid polariton formation. Using doped semiconductor microcavities, we identify accessible conditions (electron densities $\sim {10}^{10}–{10}^{11}{\mathrm{cm}}^{-2}$ and optical intensities $\sim {10}^3–{10}^5\mathrm{W}/{\mathrm{cm}}^2$) for experimental realization. This work establishes plasmonic cavities as a platform for correlated photonic matter with emergent quantum order.

Area laws describe how entanglement entropy scales and thus provide important necessary conditions for efficient quantum many-body simulation, but they do not, by themselves, yield a direct measure of computational complexity. Here we introduce a complementary framework based on $p$-particle positivity conditions from reduced density matrix (RDM) theory. These conditions form a hierarchy of $N$-representability constraints for an RDM to correspond to a valid $N$-particle quantum system. We prove a general complexity bound: if a quantum system is solvable with level-$p$ positivity independent of its size, then its entanglement complexity scales polynomially with order $p$. We also show that locality provides one mechanism for satisfying this complexity bound, establishing connections to area laws. Positivity laws provide a rigorous framework for understanding entanglement complexity and certifying when many-body methods—including RDM approaches—can efficiently simulate correlated quantum matter and materials.

Starting from the interaction picture in quantum mechanics it is shown that perturbation theory for a weak static coupling of two subsystems in a natural way can be reformulated through integrals over products of imaginary time cross correlation functions. This inter alia leads to an expression for the London dispersion energy contribution of intermolecular interactions offering new ways to its numerical computation. The frequency-dependent charge susceptibility functions at imaginary frequencies appearing in the Casimir-Polder expression for the dispersion energy and the imaginary time density fluctuation cross correlation functions occuring in the equivalent alternative formula turn out to be Fourier cosine transform pairs.

Dipoles in triangular optical ladders constitute a flexible platform for the study of the interplay between geometric frustration and long-range anisotropic interactions, and in particular for the observation of the spontaneous onset of chirality. Frustration magnifies the effect of the dipolar interactions in itinerant polarized dipolar bosons. As a result, the dipole-induced transition between a chiral superfluid and a nonchiral two-component superfluid may be observed for current state-of-the-art temperatures even for the weak intersite interaction characterizing magnetic atoms in standard optical lattices. On the other hand, pinned spin-$1/2$ dipoles, which we discuss in the context of polar molecules in two rotational states, realize frustrated dipolar XXZ spin models. By controlling the external electric field strength and orientation, these systems can explore a rich ground-state landscape including chiral and nematic phases, as well as intriguing chiral dynamics.

We report a normal-mode induced synchronization blockade in coupled quantum van der Pol oscillators under the influence of external drive. In this mechanism, the coupling hybridizes the oscillator modes into spectrally split normal modes. The destructive interference between the transitions to these modes blocks synchronization. We find that this blockade can be controlled simply by tuning the coupling strength and detuning allowing dynamic manipulation of quantum synchronization through collective mode dynamics. We analyze the phase-locking behavior using perturbation analysis. Further, by deriving steady-state probability amplitudes we show how the energy redistribution and spectral splitting forms the basis of the blockade. Our results might provide new insights into how synchronization can be controlled in quantum systems.

We investigate the sensitivity of gravitational acceleration estimation using squeezed probe states in a quantum metrology framework. In particular, we analyze how the squeezing phase, beyond its amplitude, affects the attainable precision. We show that probes squeezed along the canonical phase-space quadratures can surpass the shot-noise limit only in specific time regimes, whereas position-momentum correlated input states can consistently overcome this limit across all interaction times. Furthermore, we demonstrate that optimal sensitivity can be achieved by combining projective momentum measurements with a time-dependent adjustment of the squeezing phase. Our results highlight the fundamental role of phase-engineered squeezing in quantum gravimetry protocols and provide new insights into the design of optimized sensing strategies.

We explore the effect of self-orthogonality at exceptional points (EPs) in non-Hermitian parity-time-symmetric systems. Using a driven three-band lattice model, we show that the Rabi frequency diverges as the system approaches an EP due to the coalescence of eigenstates. We demonstrate that this divergence manifests in experimentally accessible power oscillations, establishing a direct observable for self-orthogonality. Our results provide a pathway for probing EP physics in various metamaterial platforms.

We address the long-standing problem of determining accurate, time-resolved ionization rates for atoms in strong laser fields, a quantity that is fundamental to attosecond science. We show that it is possible to retrieve sub-optical-cycle dynamics of strong-field ionization from ionization probabilities obtained for a set of few-cycle laser pulses that covers a sufficiently broad parameter space. To this end, we introduce the general approximator for strong-field ionization rates, a retrieval tool that uses a few adjustable parameters to accurately reconstruct ab initio data. By imposing only essential physical constraints, our model provides a versatile framework for time-domain investigations of strong-field ionization and the role of ionization dynamics in attosecond metrology and lightwave electronics.

By employing singles, doubles, and triples excitations within the relativistic coupled-cluster framework, we perform comprehensive calculations of a wide range of atomic properties for the ${\mathrm{Th}}^{3+}$ ion. These properties are essential for advancing nuclear clock technology and probing fundamental physics. Combining our isotope shift parameters with experimental data, we estimate highly accurate values of the differential nuclear charge radii for ${}^{232,229}\mathrm{Th}$ and ${}^{229m,229}\mathrm{Th}$. Additionally, we determine the nuclear magnetic dipole and electric quadrupole moments for both the ground and isomeric states of ${}^{229}\mathrm{Th}$ by combining measured hyperfine-structure constants with our theoretical calculations. Our precise evaluations of electric dipole polarizabilities and hyperfine-induced quadrupole moments are critical for assessing systematic uncertainties in ${}^{229}\mathrm{Th}^{3+}$-based nuclear clocks. Notably, we observe unexpectedly significant contributions from higher-order relativistic effects and excitations involving orbitals with higher angular momentum, which markedly influence the energies of the ground state and its fine-structure partner. These results highlight the substantial challenges in achieving highly accurate predictions for these properties.