Quantum transduction between microwave and optical photons is essential for building scalable quantum networks, with electro-optics conversion emerging as a promising approach. Recent experiments, however, observe significant quality factor degradation in superconducting microwave cavities when realizing the electro-optics transducers. Here we identify the piezomechanical scattering, where there is microwave photon loss through phonon radiation into the substrate, as a universal dissipation mechanism in these hybrid quantum devices. By establishing a direct analogy to Rayleigh scattering theory, we derive the universal scaling laws governing the phononic dissipation process. Our analysis reveals a fundamental tradeoff where optimizing coherent transduction coupling inevitably increases dissipation, regardless of the configurations of microwave and optical cavities. We propose potential strategies to overcome this challenge. These findings establish piezomechanical scattering as a critical design constraint for quantum transducers and provide insights to optimize their performance toward practical quantum networking.

Scrambling, the delocalization of initially localized quantum information, is commonly characterized by the out-of-time-ordered correlator (OTOC). Employing the OTOC–Renyi-2 entropy theorem, we derive a quantum speed limit for the OTOC, which sets a lower bound for the rate with which information can be scrambled. This bound becomes particularly tractable by describing the scrambling of information in a closed quantum system as an effective decoherence process of an open system interacting with an environment. We prove that decay of the OTOC can be bounded by the strength of the system-environment coupling and two-point environmental correlation functions. We validate our analytic bound numerically using the nonintegrable transverse field Ising model. Our results provide a universal and model-agnostic quantitative framework for understanding the dynamical limits of information spreading across quantum many-body physics, condensed matter systems, and engineered quantum platforms.

Providing entanglement for the design of quantum technologies in the presence of noise constitutes today's main challenge in quantum information science. A framework is required that assesses the build-up of entanglement in realistic settings. In this work, we put forth a new class of nonlinear quantum master equations in Lindblad form that unambiguously identifies dynamical entanglement in open quantum systems via deviations from a separable evolution. This separability Lindblad equation restricts quantum trajectories to classically correlated states only. Unlike many conventional approaches, here the entangling capabilities of a process are not characterized by input-output relations, but separability is imposed at each instant of time. We solve these equations for crucial examples, thereby quantifying the dynamical impact of entanglement in nonequilibrium scenarios. Our results allow to benchmark the engineering of entangled states through dissipation. The separability Lindblad equation provides a unique path to characterizing quantum correlations caused by arbitrary system-bath interactions, specifically tailored for the noisy intermediate-scale quantum era.

Nonstabilizerness is a quantum property of states associated with the non-Clifford resources required for their preparation. As a resource, nonstabilizerness complements entanglement, and the interplay between these two concepts has garnered significant attention in recent years. In this work, we establish an exact correspondence between the generation of nonlocal nonstabilizerness and operator entanglement under unitary evolutions. Nonlocal nonstabilizerness refers to nonstabilizerness that cannot be erased via local operations, while operator entanglement generalizes entanglement to operator space, characterizing the complexity of operators across a bipartition. Specifically, we prove that a unitary map generates nonlocal nonstabilizerness if and only if it generates operator entanglement on Pauli strings. Guided by this result, we introduce an average measure of a unitary's Pauli-entangling power, serving as a proxy for nonlocal nonstabilizerness generation. We derive analytical formulas for this measure and examine its properties, including its typical value and upper bounds in terms of the nonstabilizerness properties of the evolution.

We explore the use of higher-order Hermite-Gauss modes for sensing optically induced transverse displacements. In the small-displacement regime, we show that projective measurements onto the two neighboring spatial modes yield optimal Fisher information, linearly scaling with the mode order $m$. We further extend the analysis to arbitrary displacement values and derive general expressions for the Fisher information, demonstrating that higher-order modes continue to outperform the fundamental Gaussian mode even at larger separations. This approach enables enhanced displacement sensitivity with only a minimal number of measurements, offering a simple and scalable alternative to conventional spatial mode demultiplexing schemes. We provide a proof-of-principle experimental demonstration using spatial light modulators, showing an order-of-magnitude reduction in estimation variance when employing Hermite-Gauss modes of order $m=8$ and $m=17$. These results highlight the potential of structured light for ultrasensitive displacement sensing and may enable new applications in birefringence measurements with broadband or low-coherence light sources.

Dual lattices such as honeycomb and hexagonal lattices typically obey Babinet's principle in optics, which states that the expected interference patterns of two complementary diffracting objects are identical and indistinguishable, except for their overall intensity. Here, we study Kapitza-Dirac diffraction of Bose-Einstein condensates in optical lattices and find that matter waves in dual lattices obey Babinet's principle only under the condition of weak-pulse Raman-Nath regime. In contrast, the Kapitza-Dirac matter-wave diffraction in the strong-pulse Raman-Nath regime, which generates subwavelength phase structures via phase wrapping, can break Babinet's principle and clearly resolve the distinct interference patterns of the dual honeycomb and hexagonal lattices. This method offers exceptional precision in characterizing lattice configurations and advance the study of symmetry-related phenomena, overcoming the limitations of real-space imaging.

We investigate topological features in the synthetic Fock-state lattice (FSL) of a single-atom system described by the quantum Rabi model. By diagonalizing the Hamiltonian, we identify a zero-energy defect state localized at a domain wall of the FSL, whose spin polarization is topologically protected. To address the challenge of applying band topology to the FSL, we introduce a physically motivated and directly measurable topological invariant based on phase-space geometry—the phase-space winding number. We show that the Zak phase, computed using a phase-space parameter, is related to the invariant. This quantized geometric phase reflects the spin polarization of the defect state, demonstrating a bulk-boundary correspondence. The resulting phase-space topology reveals the emergence of single-atom dressed states with contrasting properties—topologically protected spin states and driving-tunable bosonic states. Our results establish phase-space topology as a framework for exploring topological physics in single-atom synthetic dimensions, uncovering quantum-unique topological protection distinct from classical analogs.

The concept of compatibility originally emerged as a synonym for the commutativity of observables and later evolved into the notion of measurement compatibility. In any case, however, it has remained predominantly algebraic in nature, tied to the formalism of quantum mechanics. Recently, still within the quantum domain, the concept of context incompatibility has been proposed as a resource for detecting eavesdropping in quantum communication channels. Here, we propose a significant generalization of this concept by introducing the notion of theory-independent context compatibility, a concept that is trivially satisfied by classical statistical mechanics but is found in conflict with quantum mechanics. Moreover, we propose a figure of merit capable of quantifying the degree of violation of theory-independent context incompatibility, and we experimentally demonstrate, using a quantum optics platform, that quantum systems can exhibit pronounced degrees of violation. Besides yielding a concept that extends to generic probabilistic theories and retrieving the notion of measurement incompatibility in the quantum domain, our results offer a promising perspective on evaluating the role of incompatibility in the manifestation of nonlocal correlations.

Continuous-wave (cw) architectures provide a promising route to interface disparate quantum systems by relaxing the need for precise synchronization. While essential cw components, including microwave single-photon transistors and microwave–optical converters, have been explored, an all-optical cw single-photon transistor has remained a missing piece. We propose a high-efficiency, high-gain implementation using Rydberg atoms, in which a control photon disrupts the transmission of a continuous probe beam via the van der Waals interaction. This device completes the set of components required for cw processing of quantum signals and paves the way for all-optical processing at the quantum level.

The trapping and cooling of photon gases in microcavities has been used to create Bose-Einstein condensates. We investigate the conditions required for condensation in dye-filled microcavities, with photon populations created either by driving a transition of the dye, or by coupling the cavity modes to a thermal photon reservoir such as sunlight. We find that the threshold pump temperature, above which condensation appears, is determined by the second law of thermodynamics. The minimum achievable threshold is that of a reversible three-level heat engine, which we show arises in the dye-pumped case, and for pumping of the modes of a two-level cavity. For a many-level cavity condensation occurs at a similar but higher temperature. Our results show that photon condensates can be produced by pumping with incoherent thermal sources, opening possibilities for coherent light generation, energy harvesting, and experimental studies of quantum heat engines.

The Fraunhofer diffraction of quantum particles from materials with sharp electron-density edges or symmetric bond structures is ubiquitous. In contrast, diffraction from atoms with a characteristic asymptotically diffused electron distribution is far less intuitive, although known for many years. The current study unravels an unusual diffraction mechanism of elastic electrons from diffused atomic diffractors. Consequently, the fringe pattern converted to the Fourier reciprocal space maps out the effective scattering potential, which is not accessible in direct measurements. This may benefit large-volume and multiscale computational modeling of processes in materials where adopting the complex exact potentials is challenging and expensive. The study employs a relativistic partial-wave analysis with atoms modeled in the Dirac-Fock formalism and performs $e$-Cd measurements in absolute scale. Analysis for Mg, Ba, and Ra targets demonstrates the universality of the mechanism.

Recent experiments demonstrate that rapidly rotating Bose-Einstein condensates (BECs) near the lowest Landau level can self-organize into interaction-driven persistent quantum Hall droplet arrays. Inspired by this discovery, we investigate the formation and dynamics of single quantum Hall droplet and droplet arrays in rapidly rotating BECs. Guided by a rigorous theorem on localized many-body states for two-dimensional interacting systems in a magnetic field, we construct single quantum Hall droplet and droplet array states which are shown to be stationary solutions to the Gross-Pitaevskii equation in the rotating frame. The single quantum Hall droplet is shown to be dynamically stable, which underpins its role as the basic unit in a droplet array. The stability of the quantum Hall droplet arrays is demonstrated by their dynamic formation from a phase engineered initial condensate. Our study sheds light onto the nature of the quantum Hall droplet state in a rapidly rotating BEC and offers a new approach for generating and manipulating quantum Hall droplet arrays through designing the initial condensate phase.

Periodic driving of particles can create crystalline structures in their dynamics. Such systems can be used to study solid-state physics phenomena in the time domain. In addition, it is possible to realize photonic time crystals and to engineer the wave-number band structure of optical devices by periodic temporal modulation of the properties of light-propagating media. Here, we introduce a versatile approach which uses traveling-wave resonators to emulate various condensed matter phases in the time dimension. This is achieved by utilizing temporal modulation of the permittivity and the shape of small segments of the resonators. The required frequency and depth of the modulation are experimentally achievable which opens a pathway for the practical realization of crystalline structures in time in microwave and in optical systems.

We study the classical dynamics of a Paul-trapped ion in a low-density bath of atoms above $1\mu \mathrm{K}$. We find that lower-energy collisions with more massive atoms, especially at energies less than the initial micromotion heating, are more likely to form atom-ion complexes. These complexes evolve in a fractal structure for every scattering observable, showing nonhyperbolic chaotic dynamics. To explore the chaotic dynamics, we use a GPU-accelerated methodology allowing us to run over $3\times {10}^8$ trajectories of a ${}^{174}\mathrm{Yb}^{+}$ and different atoms. As a result, after analyzing the dynamics as a function of the atom species, collision energy, trap parameters, and ion-atom potential depth, we find a link between heating and the onset of chaos in the first atom-ion interaction that occurs when a low-density atomic bath is merged with a trapped ion.

We investigate the chiral dynamics of locally interacting bosons in a two-leg flux ladder, where on-site interactions, despite being fully isotropic, counterintuitively reverse the flux-induced chiral transport of density distribution. For a Bose-Einstein condensate (in the mean-field regime), this reversal arises from an interaction-driven dynamical band-occupation inversion, which selectively populates single-particle states of the opposing chirality. Strikingly, the chiral-transport inversion has a few-body, hence beyond-mean-field, origin, as the formation of two-body bound states with reversed chirality dominates the few-body dynamics. This dual pathway, that is, occupation inversion and bound-state formation, underlies the chiral-transport inversion, which challenges the conventional wisdom that isotropic interactions cannot bias density transport. Our work reveals the interplay between interactions and chirality and highlights how correlations engineer exotic quantum transport.

We demonstrate that dissipative state preparation protocols in many-body systems can be substantially accelerated via the quantum Mpemba effect. Our approach exploits weak symmetries to analytically identify a class of simple, experimentally realizable states that converge exponentially faster to the steady state than typical random initializations. In particular, we study the preparation of a lattice Bose-Einstein condensate (BEC), where the depletion can be controlled via the dissipation strength. We also show how to tune the momentum of the created high-fidelity BEC by combining superfluid immersion with lattice shaking. Our theoretical predictions are confirmed by numerical simulations of the dissipative dynamics. This protocol paves the way to unlock the enormous potential of the dissipative preparation of highly entangled states in analog quantum simulators.

A shell-shaped Bose-Einstein condensate released from its confinement expands radially both outward and inward, displaying a self-interference pattern characterized by a density peak surrounded by a halo. Here we analyze how an external imprinting or the thermal fluctuations of the condensate phase influence this expansion. In both cases we find that the curved geometry filters the imploding finite angular-momentum modes via a radial centrifugal potential, so that only the condensate state can reach the origin and form the central peak. As a consequence, we observe a pronounced dependence of the central density on the imprinting strength and on temperature. This geometric filtering effect characterizes the free expansion of curved atomic gases in contrast with flat counterparts, it is easily observable in the available experimental platforms and enables two-dimensional shells thermometry via simple absorption-imaging techniques.

A Hamiltonian with eigenenergy $E_n={\rho }_n(1-{\rho }_n)$ has been constructed, where ${\rho }_n$ denotes the $n\mathrm{th}$ nontrivial zero of the Riemann zeta function. To construct such a Hamiltonian, we generalize the Berry-Keating paradigm and encode number-theoretic information into the Hamiltonian using modular forms. Although our construction does not resolve the Hilbert-Pólya conjecture (since the eigenstates corresponding to $E_n$ are not normalizable), it provides a novel physical perspective on the Riemann Hypothesis (RH). In particular, we propose a physical interpretation of RH, which could offer a potential pathway toward its proof.

With an all-optical technique, we demonstrate the experimental feasibility to create a molecular ensemble with higher degrees of orientation ($|\langle cos{\theta }_{\text{2D}}\rangle |>0.23$) in a field-free space. In order to achieve higher degrees of orientation, two-color laser pulses with longer durations of $\sim 10\mathrm{ns}$ and carbonyl sulfide (OCS) molecules in the rotational ground state, which are selected by a molecular deflector, are employed. To prepare an oriented ensemble of OCS molecules in a field-free space, the 10-ns two-color pulses are rapidly turned off with a plasma shutter technique, in which the relative phase between the two wavelengths is stabilized with a feedback technique. The molecular orientation dynamics after the rapid turnoff of the two-color pulses is observed and well reproduced by numerical simulations.

We demonstrate a frequency-domain echo atom interferometer for measurements of gravitational acceleration $g$. The experiment relies on a sample of laser-cooled atoms at a temperature of approximately $10\mu \mathrm{K}$. Two composite running wave pulses with a relative detuning $\delta$, which are separated by a time $T$, are used to excite the sample and observe a grating echo at time $t=2T$. The echo is detected by coherently backscattering a traveling-wave readout pulse from the optical lattice that forms in the temporal vicinity of the echo time. The phase of the backscattered signal exhibits a linear dependence on $\delta$ for a fixed value of $T$ and the offset of this linear trend can be used to infer the value of $g$.