We develop a comprehensive theoretical framework that unifies quantum emission dynamics in one-dimensional Lieb lattices, bridging the gap between ideal flat-band coherence and realistic narrow-band dissipation. By coupling an emitter to sublattices with finite flat-band wave-function overlap, we activate a collective, size-independent interaction fundamentally distinct from dispersive-band processes. Controllably breaking lattice symmetry transforms the flat band into a narrow dispersive band, enabling a continuous crossover from non-Markovian to Markovian dynamics governed by the competition between coupling strength and engineered bandwidth. Crucially, we derive explicit scaling laws that provide a quantitative blueprint for tuning spontaneous emission from coherent trapping to Markovian decay. Our work provides a unified framework that connects idealized flat-band physics to emerging narrow-band platforms such as $\mathrm{moir}\acute{\mathrm{e}}$ photonic crystals, offering a practical toolkit for interpreting experiments and engineering quantum emission in structured photonic environments.

Recently, interest has surged in eigenvalue nonlinearity-based topological transport governed by the equation of auxiliary eigenvalues $H\mathrm{\Psi }=\omega S\left(\omega \right)\mathrm{\Psi }$ [Isobe et al., Phys. Rev. Lett. 132, 126601 (2024); Bai and Liang, Phys. Rev. A 111, 042201 (2025); Bai and Liang, Phys. Rev. A 112, 052207 (2025)] rather than the conventional Schrödinger equation $H\mathrm{\Psi }=E\mathrm{\Psi }$ in conservative settings, bit non-Hermitian generalizations remain uncharted. In this work, we are motivated to investigate the nonlinear Thouless pumping in a non-Hermitian and nonlinear Rice-Mele model. In particular, we uncover how non-Hermiticity parameters can induce fractional topological phases—even in the presence of quantized topological invariants as predicted by conventional linear approaches. Crucially, these fractional phases are naturally explained within the framework of the equation of auxiliary eigenvalues, directly linking nonlinear spectral characteristics to the bulk-boundary correspondence. Our findings reveal emergent phenomena arising from the interplay between nonlinearity and non-Hermiticity, providing key insights for the design of topological insulators and the controlled manipulation of quantum edge states in the real world.

Mesoscopic spin ensembles provide an experimentally accessible setting in which collective dipolar dynamics are easier to realize than architectures based on individually controlled spins, yet remain too large for exact many-spin treatments. We develop a spin coherent-state closed-time-path theory for coarse-grained spin packets that yields loop-dressed real-time dynamics together with a controlled Gaussian fluctuation sector. Within this treatment, the relevant reduced subsystem is the Gaussian state of the canonical tangent-plane packet modes. On the Jeener cube, the exact classical invariant manifold provides an exact null control, while away from that manifold the native packet dynamics generate pairwise entanglement together with positive full-inseparability scores in the retained Gaussian packet-mode description. Coherent loop dressing enhances these observables in a channel-dependent way, whereas dissipative dressing suppresses them. These results show that coarse packet theories can support emergent mesoscopic Gaussian entanglement and can identify which dressing channels strengthen or weaken it.

As a crucial resource in the field of quantum metrology, spin squeezing can facilitate highly precise measurements that surpass the limitations imposed by classical physics. However, the quantum advantage of spin squeezing is significantly compromised by decoherence, thus impeding its practical implementation. Here, by investigating the influence of local dissipative environment on spin squeezing beyond the conventional Born-Markov approximation, we find a mechanism to protect spin squeezing from decoherence and show that robust spin squeezing can be achieved in the steady state. We outline an experimental proposal to verify our prediction in a trapped-ion platform. Overcoming the challenges set by decoherence in spin squeezing, our work provides guidance to realize high-precision sensing in realistic environments and sheds light on the effect of non-Markovian environment on quantum systems.

Controlled and multicontrolled quantum gates whose action on a target qubit depends on the state of multiple control qubits, represent a fundamental logical building block for complex quantum algorithms. We propose a scheme for realizing this class of gates based on non-abelian holonomies in modulated photonic waveguide networks. Our approach relies on linear photonic cicuits formed by two star networks coupled via a two-path circuit. A star network with $M$ peripheral waveguides coupled to a single central site, or $M$ pod, naturally generalizes the tripod structure used in non-abelian Thouless pumping and stimulated Raman adiabatic passage. In the present work, we first analyze the minimal case of two connected tripods and design adiabatic driving loops that implement single-qubit, cnot, and swap gates. We then show how extending the approach to larger $M$-pod structures enables the realization of multiply controlled operations, which we exemplify by designing toffoli and the or gate on two coupled pentapods. Finally, we demonstrate that networks of connected tripods can implement the Deutsch quantum query algorithm.

We investigate the dynamics of two trapped ions interacting with a common thermal reservoir, focusing on how cross-correlated dissipation influences heating, steady-state behavior, and parameter sensitivity. Starting from a microscopic system-reservoir model, we derive the corresponding Heisenberg-Langevin equations and show that reservoir-induced correlations generate collective decay channels and, when the cross-damping rate matches the local damping, a decoherence-free normal mode that preserves memory of the initial excitations. Using the Fisher information associated with motional population measurements, we identify the parameter regimes in which cross-damping enhances the estimability of both system and reservoir properties. For nonclassical initial states, we also show that reservoir-mediated correlations can generate or maintain entanglement, with the strongest effects occurring near the decoherence-free condition.

We consider two 2-level quantum emitters (QEs) chirally coupled to a one-dimensional waveguide; the separations of QEs are comparable to or larger than the wavelength of its emitted photon and the electromagnetic field in a waveguide has a direction-dependent velocity. The chiral coupling induces the propagation phases acquired by the resonant photon in the waveguide and unequal emission rates of the QEs. It is found that the collective radiative decay could be enhanced for both QEs, inhibited for both QEs, enhanced for one while inhibited for the other, completely suppressed for both QEs, enhanced or inhibited for one QE while unchanged for the other, and unchanged for both QEs for appropriate parameters. In particular, the mechanism for radiation completely suppressed is the presence of a QE-photon bound state, which is superposition of the QE's dark state and the photon trapped in the region between QEs.

One-dimensional quantum systems that undergo spontaneous symmetry breaking, having a symmetric (nondegenerate) and a broken-symmetry (doubly degenerate) phase, have been intensely studied in different branches of physics. In most cases, the spontaneously broken symmetry is parity. However, it is possible to obtain similar phases in systems without parity symmetry, through an antiunitary symmetry that implies a twofold symmetry either on momentum or coordinate in the system's classical limit. To illustrate this phenomenon, we use a Kerr parametric oscillator (KPO) with one- and two-photon drives that, despite the breaking of parity symmetry, may have doubly degenerate levels. Different realizations of squeezed KPOs convey a great deal of attention, as effective Hamiltonians for driven superconducting circuits and the occurrence of degeneracy in such systems could be of practical interest in their application to obtain protected qubits in parity-breaking setups. In addition to this, the reported spectral features strongly indicate the existence of additional symmetries in the system.

We explore the evolution of a strongly interacting dissipative quantum Ising spin chain that is driven by a slowly varying time-dependent transverse field. This system possesses an extensive number of instantaneous (adiabatic) stationary states that are coupled through nonadiabatic transitions. We analytically calculate the generator of the ensuing slow dynamics and analyze the creation of coherences through nonadiabatic processes. For a certain choice of the transverse field shape, we show that the system solely undergoes transitions among classical basis states after each pulse. The concatenation of many of such pulses leads to an evolution of the spin chain under a many-body dynamics that features kinetic constraints. Our setting not only allows for a quantitative investigation of adiabatic theorems and nonadiabatic corrections in a many-body scenario. It also directly connects to many-body systems in the focus of current research, such as ensembles of interacting Rydberg atoms that are resonantly excited by a slowly varying laser pulse and subject to dephasing noise.

Quantum communication offers many applications, with teleportation and superdense coding being two of the most fundamental. In these protocols, preshared entanglement enables either the faithful transfer of quantum states or the transmission of more information than is possible classically. However, channel losses degrade the shared states, reducing teleportation fidelity and the information advantage in superdense coding. Here, we investigate how to mitigate these effects by optimizing the measurements applied by the communicating parties. We formulate the problem as an optimization over general positive operator-valued measures (POVMs) and compare the results with physically realizable noiseless attenuation (NA) and noiseless linear amplification (NLA) circuits. For teleportation, NLA or NA and optimized POVMs improve the average fidelity by up to $78\%$ while maintaining feasible success probabilities. For superdense coding, they enhance the quantum advantage over the classical channel capacity by more than $100\%$ in some regimes and shift the break-even point, thereby extending the tolerable range of losses. Notably, the optimal POVMs effectively reduce to NA or NLA, showing that simple, experimentally accessible operations already capture the essential performance gains.

In this work, we introduce a method to express the stabilizer of a $\mathbf{k}$-uniform complete hypergraph state as a linear combination of local operators. Quantum hypergraph states generalize graph states and exhibit properties that are not shared by their graph counterparts—most notably, their stabilizers are intrinsically nonlocal, as hyperedges can involve arbitrary subsets of vertices. Our formulation provides an explicit description of the stabilizers for $\mathbf{k}$-uniform complete hypergraphs and may offer insights for exploring these states within the stabilizer formalism. In particular, this approach could facilitate the construction of new Bell inequalities or find applications in quantum error correction.

The electron scattering from the nested fullerene system ${\text{C}}_{60}@{\text{C}}_{240}$, the smallest stable carbon nano-onion, is investigated in the present work. Resonance features appearing in the total cross sections of nested fullerenes are analyzed by comparing those from the individual cages. It reveals the emergence of a window resonance, unique to the hybrid system. The impact of resonances on the differential cross section is also examined. To further elucidate the scattering dynamics, the studies are extended to the time domain by calculating the Eisenbud-Wigner-Smith and angular time delays. The studies, therefore, provide a qualitative analysis of the scattering process of a nested system and serve as a basis for understanding and controlling the dynamics of electron scattering from complex fullerene systems.

We report high-precision calculations of the $1s^{2}2s2p\left(2{}^{3}P^o\right)$, $1s^{2}2s3s\left(3{}^{3}S^e\right)$, and $1s^{2}2s4s\left(4{}^{3}S^e\right)$ states of the ${}^9\mathrm{Be}$ isotope and beryllium with infinite nuclear mass $\left({}^{\infty }\mathrm{Be}\right)$. For each state, the nonrelativistic wave function is obtained in an independent variational calculation by expanding it in a large basis of all-electron explicitly correlated Gaussian (ECG) functions, with up to 15 000 ECGs employed. In our calculations, the electrons and the nucleus are treated on an equal footing, which allows the direct inclusion of all relevant nuclear recoil effects. Leading relativistic and quantum electrodynamics corrections to the energy levels are subsequently evaluated within perturbation theory, using the variational nonrelativistic wave functions as zeroth-order states. These highly accurate nonrelativistic wave functions are also used to compute the fine-structure splittings for ${}^9\mathrm{Be}$ and ${}^{\infty }\mathrm{Be}$. The employed approach accounts for the leading-order spin–orbit and electron spin–spin interactions $(\propto {\alpha }^2)$, contribution from the electron anomalous magnetic moment $(\propto {\alpha }^3)$, and the most significant couplings between the target states and nearby electronic states $(\propto {\alpha }^4)$. Our results show a notable improvement in accuracy compared with previous theoretical calculations and are in good agreement with the best available experimental data.

Optical Kerr nonlinearity is important for various applications in both classical and quantum regimes. It has been shown that Kerr nonlinearity can be considerably enhanced based on electromagnetically induced transparency in cold atoms. However, in a hot atomic ensemble the Kerr nonlinearity is usually weakened by the Doppler effect. Here we show that the Kerr nonlinearity can be enhanced by tuning the wave-number mismatch between the probe and control fields in hot atoms. When the wave number of the control field, denoted by $k_c$, is larger than that of the probe field, denoted by $k_p$, the transition strength for the probe field from the ground to two dressed states created by the control field becomes stronger, leading to an increased nonlinear dispersion and absorption. Upon increasing the ratio $k_c/k_p$ further, the effective number of atoms contributing to the interaction decreases such that the nonlinear dispersion and absorption are eventually reduced. Nevertheless, the peak nonlinear dispersion and absorption are enhanced by factors of up to 3 and 2, respectively, for $k_c/k_p>1$ in comparison to the case of $k_c/k_p=1$. Our results may be beneficial for a variety of applications where the Kerr nonlinearity is crucial.

Atomtronic quantum sensors based on trapped superfluids offer a promising platform for high-precision inertial measurements where the dynamics of quantized vortices can serve as sensitive probes of external forces. We analytically investigate the persistent current oscillations between two density-coupled Bose-Einstein condensate rings of equal radius and show that the vortex dynamics is governed by low-energy acoustic excitations circulating through the condensate bulk. The oscillation frequency and damping rate are quantitatively predicted by a simplified hydrodynamic model, in agreement with Bogoliubov–de Gennes analysis and Gross-Pitaevskii simulations. We identify the critical dissipation separating persistent oscillations from overdamped vortex localization. Furthermore, we demonstrate that periodic modulation of the interring barrier at resonant frequencies enables controlled vortex transfer even when the condensates are well separated in density. These results clarify the role of collective hydrodynamic modes in circulation transfer and establish a framework for employing vortex dynamics in atomtronic quantum technologies.

We identify the steerable exponentially localized in-gap mode in a quasiperiodic non-Hermitian Aubry-André-Harper chain with a spatially fluctuating, zero-mean imaginary gauge field. Under open boundary conditions, the system is exactly related to the Hermitian Aubry-André-Harper model by a nonunitary gauge transformation: the open boundary conditions spectrum and Lyapunov exponents are unchanged, while eigenstates acquire a gauge-dependent envelope. In a parameter region with spectrally isolated in-gap boundary modes, we find two exponentially localized in-gap modes with sharply different responses to the imaginary gauge field. One remains boundary pinned, but the other is gauge steerable: it stays exponentially localized while its probability maximum shifts as the gauge field is changed, with its eigenenergy unchanged. We further show that weak on-site gain, applied at a single site chosen once and then kept fixed, can dynamically prepare this steerable mode from a generic bulk wave packet. Changing the gauge field then yields exponentially localized states at different locations.

In optical non-Hermitian systems, exceptional points (EPs) are singularities in the parameter space where at least two eigenvalues and their eigenmodes coalesce simultaneously. Recently, research on the interaction between EPs and bound states in the continuum (BICs) has attracted considerable attention. However, coupling a BIC with leaky Mie resonant modes to form an EP has not yet been explored. Here, we propose coupling a BIC) and toroidal dipole modes to form an EP. By controlling the relative position between the two modes, the BIC is converted into a quasi-BIC while adjusting the coupling strength. Simulations show that the resulting EP exhibits stronger field enhancement and boosts second-harmonic conversion efficiency (CE) by approximately 5.6 times compared to only the toroidal dipole mode alone. Furthermore, unlike quasi-BICs, which require precise control over structural defects, the CE of the proposed model can be further enhanced to 0.35 by structural perturbations. Our research enriches the configurations of EPs and paves the way for their application in high-efficiency harmonic generation.

Correlation imaging (CI) is an emerging approach to imaging aimed at overcoming the limitations of conventional, intensity-based imaging modalities. In this paper, we focus on a peculiarity of chaotic-light-based CI: the strict link between image properties, and source size and geometry. We will show that the light source acts as a limiting aperture, whose geometrical properties significantly affect image formation, hence, the defocused resolution and depth of field. In ghost imaging, the image quality is typically associated with the speckle size, namely, with wave-optics effects; here, we evaluate the second-order correlation function of an out-of-focus CI system and demonstrate that the out-of-focus point-spread function is governed by a geometrical circle of confusion determined by the illumination numerical aperture. Both analytical results and numerical simulations indicate that this geometrical effect dominates the optical response of CI systems both in out-of-focus conditions and when large sources are employed. Even more, in correlation plenoptic imaging, the axial resolution is found to be directly linked to the illumination geometry, as the source size is found to constrain both the quality of the refocused images and the axial sectioning capability. The presented analysis applies to all CI architectures, thus providing a comprehensive framework for understanding and optimizing source-dependent effects in CI.