We investigate the suppression of matter-wave Talbot interference under environmentally induced decoherence. The system is modeled as an atomic beam diffracted by a periodic grating whose transverse dynamics is described within the paraxial approximation. Environmental coupling is introduced through an effective open-system model that exponentially damps spatial coherences between diffracted components, allowing a continuous interpolation between the coherent Talbot regime and the incoherent far-field diffraction limit. In addition to the usual intensity and transverse-momentum distributions, we analyze the local probability flow associated with the diffracted matter wave. The corresponding Bohmian, or hydrodynamic, representation is used here as a diagnostic tool fully equivalent to the standard quantum description, with no additional assumptions beyond the probability current of the paraxial wave field. In the present Talbot geometry, this analysis shows how decoherence progressively suppresses the carpet structure and smooths the transverse-momentum distribution, while the flow may remain organized into channels determined by the grating periodicity. The results illustrate, in a periodic matter-wave Talbot geometry, that the loss of visible interference and the degradation of the grating-defined flow-domain organization need not occur simultaneously. In particular, flux-channel structures can persist in parameter regimes where multislit interference features have already been strongly reduced. This distinction provides a local characterization of decoherence in matter-wave Talbot interferometry and complements previous trajectory-based analyses of coherence loss in simpler interference and confined geometries.

We study one-dimensional quantum gases in continuous space with cavity-mediated infinite-range interactions using the Variational and the Diffusion Monte Carlo methods. Starting from the exact two-body solution, we construct a nontranslationally invariant Jastrow wave function that accurately captures the spatial structure induced by the cavity field and provides an efficient many-body ansatz for both bosonic and fermionic systems. We analyze properties of three characteristic quantum systems, subject to long-range interactions: (i) ideal Bose gas, (ii) interacting Bose gas, (iii) ideal Fermi gas. In the absence of short-range interactions, we identify a crossover from a stable, weakly modulated phase realized at finite particle number for repulsive interactions to a self-organized state for attractive interactions, marked by clustering, loss of superfluidity, and, at fixed interaction strength, the absence of a thermodynamic limit. Introducing short-range repulsion, either through contact interactions or fermionic statistics, leads to the formation of a mesoscopic gas-like regime that disappears in the thermodynamic limit. A qualitative phase diagram is proposed to illustrate the combined effects of short- and long-range interactions, highlighting the emergence of distinct regimes with characteristic structural properties. Applying the Kac prescription, we obtain a well-defined thermodynamic limit and show that the periodic modulation found for a finite number of particles in the repulsive regime is a finite-size artifact, while the self-organized state survives with its onset shifted to substantially stronger coupling.

Nonreciprocal conversion is essential for protecting sources and enabling unidirectional signal routing in photonic, phononic, electronic, and quantum systems, yet conventional implementations often rely on magnetic bias that can be difficult to integrate on chip. We propose a magnet-free scheme for frequency-domain nonreciprocity based on sequential, time-gated modulation in a three-mode system. By activating interactions in a fixed temporal order, the forward and reverse frequency-conversion pathways acquire unequal dwell times in a lossy intermediate mode, producing strong nonreciprocity without requiring nonlinearities or magnetic materials. Using harmonic-balance and Dyson-Born expansions, we derive an analytical expression for the isolation ratio and show that breaking time-reversal symmetry alone is insufficient to produce isolation in this scheme: Dissipation in the intermediate mode is necessary, and the isolation is maximized at a finite loss. The resulting framework identifies how duty cycles, modulation frequency, relative delay, coupling strength, and loss control the isolation, in agreement with direct time-domain simulations. The approach is general and applicable to integrated photonic, phononic, microwave, and superconducting-circuit platforms.

We investigate the role of magnetic sublevels in Autler-Townes spectra of Rydberg atoms driven by radio-frequency (rf) fields with arbitrary polarization. While conventional treatments predict two symmetric sidebands from independent $m_J$ transitions, experiments have reported additional unexplained spectral features. We show that these arise from elliptical rf polarization, which coherently couples multiple magnetic sublevels and requires a full multilevel treatment. We develop and diagonalize a Hamiltonian including all coupled $m_J$ sublevels, predicting polarization-dependent degeneracies that produce varying numbers of resolved peaks. Using long-wavelength transitions and an anechoic environment we realize homogeneous rf fields that enable complete resolution of the $m_J$-dependent dressed states. We observe excellent agreement with theory as the rf ellipticity is varied. These results demonstrate that rf polarization fundamentally modifies Autler-Townes spectra and provide a consistent framework for interpreting magnetic-sublevel structures, with implications for Rydberg-based rf electrometry and polarimetry.

Quantum annealing correction (QAC) models provide a promising approach for mitigating errors in quantum annealers. Previous studies have established that QAC models are crucial for ensuring the robustness of the ground state of the Ising model on hardware. In this work, the effects of QAC models incorporating replicas with additional interactions, specifically, the penalty spin model and the stacked model, are investigated for problems characterized by a small energy gap between the ground and first excited states during quantum annealing, a well-known bottleneck to reaching the ground state. The results demonstrate that these QAC models can obtain the optimal solution within short annealing times by exploiting diabatic transitions, even for problems with a small energy gap. These findings highlight the potential of QAC models as practical near-term algorithms for hardware subject to runtime limitations and control noise.

Simulating chemical reactions exhibits a pronounced unevenness in computational difficulty: While equilibrium reactant and product geometries are often tractable, transition-state (TS) geometries frequently display strong multireference character that challenges both classical solvers and coherent quantum state-preparation methods. We introduce a dissipative continuation protocol for preparing electronic ground states near TS geometries within a hybrid classical-quantum workflow. In the intended setting, classical electronic-structure methods supply an approximate TS geometry, a computationally motivated continuation path, and a locally compatible active-space representation along that path. Starting from a warm start at a tractable geometry on the same aligned path, the quantum routine transports the state toward the TS using orbital-gauge-aligned Hamiltonians and engineered dissipative cooling primitives that repeatedly contract population into the instantaneous low-energy sector. We prove that, for continuation paths satisfying a Lipschitz smoothness condition and a localized eigenstate thermalization hypothesis–motivated downward-drift condition within the relevant energy window, the ground state at the target geometry can be prepared to total energy error ${\varepsilon }_E$ with total ideal cooling-step complexity $\tilde{O}(C_{\mathrm{DK}}^2{N}_o^2/{\varepsilon }_E)$. Equivalently, for an intensive target error ${\varepsilon }_{\mathrm{int}}:={\varepsilon }_E/N_o$, the ideal cooling-step complexity is $\tilde{O}(C_{\mathrm{DK}}^2{N}_o/{\varepsilon }_{\mathrm{int}})$. Here $C_{\mathrm{DK}}$ quantifies ground-state rotation along the aligned path. The corresponding logical gate count is obtained by multiplying this primitive count by the cost of implementing one dissipative step, which is polynomial in the block-encoding size of the Lindbladian under standard Lindblad-simulation algorithms. This identifies a structured regime in which dissipative continuation provides a conditional route to ground-state preparation at strongly correlated TS geometries.

Nonadiabatic holonomic quantum computation (NHQC) offers intrinsic resilience to certain control imperfections. However, conventional nonadiabatic holonomic protocols are constrained by the fixed-pulse-area condition, which limits flexibility and prolongs duration of small-angle gates. Here we experimentally demonstrate a brachistochrone nonadiabatic holonomic single-qubit gate scheme in a trapped ${}^{40}\mathrm{Ca}^{+}$ ion and realize the construction of the $\sqrt{X}$ gate under the conventional NHQC, brachistochrone NHQC (BNHQC), and composite BNHQC (CBNHQC) protocols. By characterizing the performance of the gate in the presence of dissipation, Rabi-frequency errors and detuning errors, we show that BNHQC and CBNHQC outperform conventional NHQC, and BNHQC can offer a favorable balance between operation speed and robustness. It further shows that keeping high fidelity and strong robustness requires a reduction of the accumulated population of excited state in the evolution process. These results demonstrate the favorable balance between operation speed and robustness offered by time-optimal holonomic control, and they support further exploration of such schemes in trapped-ion platforms.

Rydberg atom arrays are a promising platform for quantum optimization, encoding computationally hard problems by reducing them to independent set problems with unit-disk graph topology. In the work of Nguyen et al., PRX Quantum 4, 010316 (2023), a systematic and efficient strategy was introduced to encode multiple problems into a special unit-disk graph: King's subgraph. However, King's subgraphs are not the optimal choice in two dimensions. Due to the power-law decay of Rydberg interaction strengths, the approximation to unit-disk graphs in real devices is poor, necessitating postprocessing that lacks physical interpretability. In this work we develop an encoding scheme that can universally encode computationally hard problems on triangular lattices, based on our innovative automated gadget search strategy. Numerical simulations demonstrate that, for a benchmark instance, quantum optimization on triangular lattices reduces independence-constraint violations by nearly two orders of magnitude compared to King's subgraphs, substantially alleviating the need for postprocessing in experiments.

We investigate charging dynamics in many-body quantum batteries by examining the relationship between instantaneous charging power and the emergence of bipartite, tripartite, and multipartite quantum correlations across different battery-charger configurations. We find that the charging power reaches its maximum before the correlation measures peak, revealing a temporal separation between rapid energy transfer and the buildup of quantum correlations. We further study the role of interaction structure using local and many-body charging Hamiltonians under both unconstrained and constrained charging Hamiltonians, in which the total available charging resources are fixed to scale proportionally with the number of spins, thereby isolating the influence of interaction geometry and particle participation on the charging dynamics. In the unconstrained case, the enhanced charging energy observed for higher-order interactions originates primarily from the larger energy scale of the charging Hamiltonian. Under constrained conditions, however, increasing the interaction order alone provides no advantage over parallel charging when interaction and local spin-flip contributions are balanced, whereas interaction-dominated protocols significantly enhance charging performance, highlighting the importance of collective many-body dynamics. Fully collective interactions are found to yield the largest enhancement in charging power together with stronger multipartite correlations, while partially collective interactions provide only limited improvements. Finally, extending the interaction range through next-nearest-neighbor couplings suppresses charging power, demonstrating that, under constrained energetic resources, charging performance is governed primarily by interaction structure, particle participation, and collective many-body dynamics rather than by interaction order alone.

While binary atomic Bose-Einstein condensates (BECs) are typically prone to collapse under strong interspecies attraction, it has been shown that higher-order fluctuation corrections, known as Lee-Huang-Yang corrections, can stabilize the mixture. In this work we demonstrate an alternative stabilization mechanism based on kinetic energy. Specifically, we consider a one-dimensional mixture of a quasi-BEC and a Tonks-Girardeau (TG) gas and show that the kinetic energy of the TG component can counteract the interspecies attraction, thereby preventing collapse. This balance leads to the formation of a self-bound quantum droplet, which exhibits two distinct regimes: a low-density droplet and a high-density droplet. We argue that these regimes are smoothly connected by a crossover. Furthermore, an analysis of the derivatives of the ground-state energy and bulk modulus reveals that the transition from a miscible mixture to the droplet phase is of third order. Our findings extend the theoretical understanding of quantum droplets in low-dimensional quantum gases, and the proposed system may be experimentally accessible within current ultracold-atom platforms.

We investigate hard-core bosons at half filling on a three-leg ladder under a uniform artificial gauge field. By analyzing current patterns and correlation functions, we uncover a rich quantum phase diagram containing multiple superfluid and insulating phases. In bosonic ladder systems, increasing the gauge flux typically destabilizes the Meissner phase and leads to vortex phases characterized by circulating currents. In the present system, however, we find that charge-density-wave (CDW) phases emerge precisely in such a flux regime despite the presence of only an on-site interaction, where vortex states are naturally expected and are indeed realized in nearby parameter regions. While part of this behavior can be qualitatively understood from a strong-coupling perspective, we also identify an isolated CDW region that cannot be connected to such limits. Furthermore, upon increasing the artificial gauge flux, we observe a reentrant sequence of quantum phase transitions, CDW $\to$ vortex-superfluid $\to$ CDW, revealing a strong competition between the vortex phase and the density-wave order.

We report the observation of a dimensional crossover of a $p$-wave Feshbach resonance in an ultracold, spin-polarized ${}^6\mathrm{Li}$ Fermi gas confined by a one-dimensional optical lattice. Using high-resolution atom-loss spectroscopy, we resolve the orbital doublet associated with the $m_{\ell }=0$ and $|m_{\ell }|=1$ scattering channels over a wide range of lattice depths. In the weak-confinement regime, the atom loss signal associated with the $|m_{\ell }|=1$ branch is stronger, consistent with the twofold orbital degeneracy of the three-dimensional system. As the lattice confinement increases, the relative loss weight of the two orbital branches evolves continuously toward the quasi-two-dimensional limit, indicating a progressive suppression of relative motion along the lattice direction. In addition, we observe a systematic confinement dependence of the orbital splitting between the two resonance branches. These results provide an experimental characterization of orbital-dependent $p$-wave scattering in reduced dimensions and motivate future microscopic studies of confined anisotropic scattering.

Higher-order exceptional points (EPs) are non-Hermitian degeneracies at which three or more eigenvalues and eigenvectors simultaneously coalesce. EPs typically require fine-tuning of multiple parameters, whereas symmetry protection can reduce the dimensionality of the parameter space required for their realization. Here, we show that gauge flux provides a route to symmetry-controlled higher-order EPs. Using a three-level loop-interaction system formed by coupling a single-mode waveguide to an orbital-angular-momentum (OAM) waveguide, we demonstrate that a gauge flux can be introduced through mode rotation induced by a trench in the OAM waveguide. In the absence of gauge flux, the system lacks the symmetry required to support higher-order EPs. By contrast, a gauge flux of $\pi /2$ induces a non-Hermitian chiral symmetry, giving rise to a third-order EP. By tuning the coupling strength, we further realize switching between third- and second-order EPs. Our results establish gauge flux as an alternative degree of freedom for realizing and manipulating higher-order non-Hermitian degeneracies.

We study two spatially separated boundary subsystems coupled to a common structured environment under relative motion within a Gaussian open-system framework. By integrating out the environment, we obtain an influence functional governed by a dressed environmental correlator evaluated at the boundary positions. Its retarded and Hadamard components govern coherent mediation and correlated fluctuations, respectively. Relative motion activates the leading resonant contribution to correlated decoherence through Doppler-shifted spectral overlap of the boundary excitations. For identical boundary dispersions, this contribution has an ideal narrow-linewidth onset at $v>2u_{\varphi }$. Below this value, no resonant momentum shell exists, whereas above it a finite shell opens and produces an enhanced correlated-decoherence contribution. Finite spectral linewidth generates subthreshold tails and rounds the ideal onset into a crossover centered on the same kinematic condition. The leading resonant contributions to motion-induced excitation production and correlated decoherence probe the same on-shell environmental structure. The proposed readout of this two-subsystem reduced-dynamics signature uses either differential-coherence measurements or a two-node noise cross-spectrum.

Dissipative phase transitions are strongly shaped by the symmetries of the Liouvillian, yet a clear understanding of the quantitative impact of weak and strong symmetries on critical behavior is presently lacking. We study a squeezed-photon model with single- and two-photon losses, realizing weak and strong symmetries in the simplest possible setting. The two symmetries exhibit identical Gaussian static fluctuations, whereas the order parameter and the asymptotic decay rate display distinct scaling behaviors. Our one-loop Keldysh analysis, together with cumulant-expansion numerics, reveals sharply different critical scaling with respect to the thermodynamic scaling parameter. This shows that weak and strong symmetries lead to distinct dynamical universality classes despite originating from the same symmetry group in the closed system. Our results provide a clear quantitative demonstration that strong symmetries fundamentally reshape dissipative criticality.