We analyze the effects of various forms of noise on one-dimensional systems of noninteracting fermions. In the strong noise limit, we demonstrate, under mild assumptions, that the statistics of the fermionic correlation matrix in the thermodynamic limit follow a universal form described by the recently introduced quantum simple symmetric exclusion process (QSSEP). For charge transport, we show that QSSEP, along with all models in its universality class, shares the same large deviation function for the transferred charge as the classical SSEP model. The method we introduce to derive this result relies on a gaugelike invariance associated with the choice of the bond where the current is measured. This approach enables the explicit calculation of the cumulant-generating function for both QSSEP and SSEP and establishes an exact correspondence between them. These analytical findings are validated by extensive numerical simulations. Our results establish that a wide range of noisy free-fermionic models share the same QSSEP universality class and show that their transport properties are essentially classical.

Studies of entanglement dynamics in quantum many-body systems have focused largely on initial product states. Here, we investigate the far richer dynamics from initial entangled states, uncovering universal patterns across diverse systems ranging from many-body localization (MBL) to random quantum circuits. Our central finding is that the growth of entanglement entropy can exhibit a counterintuitive nonmonotonic dependence on the initial entanglement in many nonergodic systems, peaking for moderately entangled initial states. To understand this phenomenon, we introduce a conceptual framework that decomposes entanglement growth into two mechanisms: “build” and “move.” The “build” mechanism creates new entanglement, while the “move” mechanism redistributes preexisting entanglement throughout the system. Specifically, we demonstrate that MBL dynamics are “move-dominated,” exhibiting a quantitative agreement with a random SWAP circuit that serves as a model of pure “move” dynamics by uniformly distributing preexisting entanglement. This implies that MBL acts as a redistributor of a hidden entanglement reservoir quantified by the bipartition-averaged entropy. This “build-move” framework offers a unified perspective for classifying diverse physical dynamics, deepening our understanding of entanglement propagation and information processing in quantum many-body systems.

We construct parametrized isometric tensor network states—referred to as “skeletons”—that allow us to explore phases of Abelian topological order and can be efficiently implemented on quantum processors. We obtain stable finite correlation length deformations of string-net fixed points, which are constructed both by conserving virtual symmetries of the tensor and by imposing local isometry constraints. They connect distinct topological phases via a shared critical point, thereby providing analytically tractable examples of phase transitions beyond anyon condensation. By mapping such classes of 2D tensor networks to 1D stochastic automata with local update rules, we show that expectation values of generalized Pauli strings of arbitrary weight can be efficiently computed using classical methods. Therefore these skeletons not only serve as an organizing principle for Abelian topological order but also provide a nontrivial test bed for quantum processors.

Efficient simulation of a quantum system generally relies on structural properties of the quantum state. Motivated by the recent results by Bakshi et al. on the sudden death of entanglement in high-temperature Gibbs states of quantum spin systems, we study the high-temperature Gibbs states of bounded-degree local fermionic Hamiltonians, which include the special case of geometrically local fermionic systems. We prove that, at a sufficiently high temperature that is independent of the system size, the Gibbs state is a probabilistic mixture of fermionic Gaussian states. This forms the basis of an efficient classical algorithm to prepare the Gibbs state by sampling from a distribution of fermionic Gaussian states.

Quantum resources can, in principle, enable Heisenberg-limited sensing, yet no-go theorems imply that Heisenberg-limited scaling is generically unattainable in realistic noisy devices. While quantum error correction (QEC) can suppress noise, its use in quantum sensing is constrained by stringent requirements, including prior noise characterization, restrictive signal-noise compatibility conditions, and measurement-based syndrome extraction with global control. Here we introduce a QEC protocol based on indefinite causal order (ICO), providing the first application of ICO to QEC. By coherently placing auxiliary controls and noisy evolution in an indefinite causal order, the resulting noncommutative interference enables an auxiliary system to herald and correct errors in real time, avoiding the entanglement encoding and entanglement readout required by traditional QEC. Furthermore, within the time-reversal regime of the Hamiltonian, our protocol extends correctability to parallel noises where traditional protocols may fail. We rigorously establish the protocol for single-noise and multinoise scenarios and demonstrate its performance in single-qubit, many-body, and continuous-variable platforms. We further identify regimes in which error correction can be implemented entirely by unitary control, without measurements. Our results reveal ICO as a powerful resource for metrological QEC and provide a broadly applicable framework for noise-resilient quantum information processing.

Generating non-Gaussian states and converting them into traveling wave packets is crucial yet challenging for scalable, fault-tolerant quantum computing. We present a hardware-efficient approach that simultaneously achieves both tasks by combining an engineered nonlinear dissipation with a linear transmission loss from a superconducting circuit to a waveguide. This combination of dissipative channels leverages low-order interactions to induce a high-order nonlinearity, enabling deterministic emission of a wide range of non-Gaussian, error-correctable states, such as Schrödinger cat states, Gottesman-Kitaev-Preskill states, and pair-cat states. We identify experimental superconducting-circuit platforms and realistic parameter regimes for our proposal.

Quantum networks and quantum repeaters represent the promising avenues for building large-scale quantum information systems, serving as foundational infrastructure for distributed quantum computing, long-distance quantum communication, and networked quantum sensing. A critical step in realizing a functional quantum network is the efficient and high-fidelity establishment of heralded entanglement between remote quantum nodes. A multimode entangling scheme offers a powerful strategy to accelerate remote entanglement distribution, particularly over long optical fibers. Here, we experimentally demonstrate multimode-enhanced heralded entanglement between two trapped-ion quantum network nodes. By harnessing ten temporal photonic modes, we achieve a 4.59-fold speedup in ion-ion entanglement generation and attain an entanglement fidelity of $95.9\%\pm 1.5\%$ over 1.2 km of fiber. Employing a dual-type architecture, our system is readily scalable to multiple nodes, thereby establishing a key building block for future large-scale quantum networks.

Gravitational-wave signals are typically interpreted under the vacuum hypothesis, i.e., assuming negligible influence from the astrophysical environment. This assumption is expected to break down for low-frequency sources such as extreme mass ratio inspirals (EMRIs), which are prime targets for the Laser Interferometer Space Antenna (LISA) and are expected to form, at least in part, in dense environments such as active galactic nuclei or dark-matter spikes or cores. Modeling environmental effects parametrically is challenging due to the large uncertainties in their underlying physics. We propose a nonparametric test for environmental effects in EMRIs, based on assessing the self-consistency of vacuum parameter posteriors inferred from different portions of the signal. Our results demonstrate that this test can reveal statistically significant inconsistencies from vacuum signals—arising from, e.g., incomplete modeling, environmental effects, or deviations from general relativity—without introducing additional parameters or assumptions about the underlying physics.

The active galactic nucleus (AGN) accretion disks are ideal sites for hierarchical black hole (BH) mergers. To robustly probe such a possibility, we analyze binary black hole mergers in the GWTC-4 with a flexible mixture population model for component masses, spin magnitudes, and spin tilt angles, and identify two distinct subpopulations. In the second subpopulation characterized by high spin magnitudes $\chi \sim 0.8$ as well as the broad mass distribution up to $\gtrsim 150M_{\odot }$, we find a pronounced preference for spins aligned with the orbital angular momentum: an isotropic tilt distribution is strongly disfavored (logarithmic Bayes factor $=4.5$). The aligned events account for $\sim 0.57_{-0.31}^{+0.23}$ of the second subpopulation, corresponding to a local rate of $\sim 0.25_{-0.16}^{+0.38}{\mathrm{Gpc}}^{-3}{\mathrm{yr}}^{-1}$ (all values reflect central 90% credible intervals). These notable features naturally arise from hierarchical mergers embedded in AGN disks, where gas torques may effectively align spins. Our results suggest that AGN-disk hierarchical assembly may be one important channel for the present gravitational-wave sample, and provide concrete, testable predictions for future detection.

We present a worldsheet action that reproduces a class of dual resonance amplitudes discussed in the literature, which generalize the Veneziano amplitude for open strings. Our proposal builds on the chiral composite linear dilaton introduced recently. We further compute higher-point extensions and closed-string analogs, which exhibit partial crossing symmetry.

We define a black hole state in a spin chain by studying thermal correlators in holography. Focusing on the Heisenberg model we investigate the thermal and complexity properties of the black hole state by evaluating its entanglement entropy, emptiness formation probability, and Krylov complexity. The entanglement entropy grows logarithmically with effective central charge $c\simeq 5.2$. We also find evidence for thermalization at infinite temperature.

In relativity, relaxation processes are often assumed to undergo time dilation under Lorentz boosts. We show that this intuition fails generically. Because of relativity of simultaneity, Lorentz boosts can split a single relaxation mode into a continuum of excitations, with a width set by the maximal signal propagation speed. Focusing on linearized relativistic (kinetic or rheological) theories with an Onsager-type symmetry, we derive rigorous bounds on relaxation spectra in arbitrary inertial frames, expressed solely in terms of rest-frame spectral data at zero wave number. As a consequence, nonhydrodynamic gaps, maximal relaxation rates, and the convergence radii of hydrodynamic modes obey nontrivial Lorentz-covariant constraints. These results provide a unified framework for understanding how relativity constrains relaxation dynamics in many-body systems.

Laser-cooled ions confined in electromagnetic traps provide a unique, tunable mesoscopic system where the interplay of the trapping potential, nonlinear Coulomb interactions, and laser-ion scattering generates rich, collective dynamics. In this work, we engineer thermally activated switching between two oppositely oriented, square-pyramidal configurations of five laser-cooled ions in a Paul trap. For identical ions (${{}^{40}\mathrm{Ca}}^{+}$), the inversions proceed via a Berry pseudorotation mechanism with a low activation barrier, enabled by the permutation symmetry, in contrast to the umbrella inversion observed in ammonia. The inversion rates obtained from experiments and the Langevin dynamics simulations are accurately captured by the multidimensional Kramers-Langer theory, enabling thermometry of the Doppler-cooled ion cluster at $1.86\pm 0.03\mathrm{mK}$. By substituting the apex ion with a heavier isotope (${{}^{44}\mathrm{Ca}}^{+}$), we break the permutation symmetry and observe a suppression of thermally activated inversions. Numerical analysis reveals that this symmetry breaking closes the low-barrier channel, forcing the system to invert through a high-barrier turnstile rotation. Thus, we demonstrate a structural analog of molecular kinetic isotope effects, establishing trapped ions as a versatile platform to explore symmetry-controlled collective dynamics.

Cavity quantum electrodynamics (cQED) harnesses light-matter interactions to produce nonclassical light states. However, a fundamental challenge lies in simultaneously achieving Purcell enhancement and tailored wave front control within a single cavity, due to conflicting resonator requirements. Here, we overcome this limitation by demonstrating triggered single-photon emission with customizable wave fronts from semiconductor quantum dots embedded in geometric-phase metacavities. These monolithic devices—only 200 nm thick—deliver Purcell-enhanced emission alongside spin-momentum-locked radiation, vortex beams, and holographic patterns depending on the design. The meta-atom lattice provides high-$Q$ optical confinement, while spatially modulated orientations of the elliptical holes enable efficient outcoupling of photons with designed states. This Letter establishes a new paradigm for intrinsically multiplexing metasurface-based wave front shaping with cQED, enabling high-performance quantum light sources from subwavelength-scale monolithic platforms.

Floquet engineering, customizing a system using periodic driving, offers a powerful tool to operate topological states of matter and even to create exotic nonequilibrium topological phenomena beyond static scenarios. Here, utilizing the idea of Floquet engineering, we theoretically predict and experimentally observe the fast driving tuned topologically distinct complex-energy braiding, which enables a new topological classification beyond conventional non-Hermitian band topology. Theoretical elucidation of our proposed Floquet engineering scheme is constructed via the Floquet theorem. To experimentally show that, we build a single-photon interferometric network. Distinct braiding topology is directly observed by different knots in the measured eigenspectrum, which is entirely consistent with our measured crossing patterns of the eigenvector loops on the Bloch sphere. We also experimentally show that transitions between Floquet topological phases with distinct knots can be identified by simply counting the total number of emergent exceptional points. Our Letter thus builds the Floquet engineering scheme as a general principle for studying the knot topology.

Microwave lasing carrying orbital angular momentum (OAM) holds significant potential for advanced applications in fields such as high-capacity communications, precision sensing, and radar imaging. However, conventional approaches to masers fail to produce emission with embedded OAM. The recent emergence of photonic time crystals (PTCs)—artificially structured media with periodically varying electromagnetic properties in time—offers a paradigm shift toward resonance-free lasing without the need for gain media. Yet, pioneering PTC designs have been based on three-dimensional bulk structures, which lack a surface-emitting configuration, and do not possess the capability to modulate OAM, thus hindering the realization of surface-emitted PTC masing that carries OAM. Here, we report the first experimental demonstration of surface-emitted microwave vortex beam lasing using ring-shaped PTCs, without the need for either a gain medium or a high-$Q$ cavity. By developing a multiplier-driven time-varying metamaterial that achieves over 100% equivalent permittivity modulation depth, we establish momentum band gaps ($k$ gaps) with sufficient bandwidth to overcome intrinsic losses and enable self-sustained coherent microwave amplification. Furthermore, space-time modulation induces nonreciprocity between clockwise and counterclockwise $k$-gap modes within the circularly symmetric PTC structure, facilitating the selective generation of microwave lasing carrying OAM, a functionality that is not readily accessible in conventional maser architectures. Our Letter bridges PTC physics with coherent OAM-carrying microwave emission, establishing a transformative platform for next-generation wireless communications, advanced sensing systems, and OAM-based technologies.

Continuous-variable (CV) quantum microcombs generated in high-$Q$ microresonators provide compact, frequency-multiplexed sources of entangled modes for integrated quantum information processing. Although deterministic Kerr-induced two-mode squeezing has been demonstrated on chip, achieving uniform squeezing across a large number of mode pairs remains a central challenge. Here we establish the conditions required for spectrally uniform squeezing and experimentally realize a vacuum-state CV quantum microcomb by combining a microresonator with an engineered single-family mode structure and optimized pump conditions. The device generates 14 independent two-mode squeezed states over a 0.7 THz bandwidth, each exhibiting more than 4 dB of raw squeezing, with a maximum of 4.3 dB. This uniform, high-performance quantum resource represents a key step toward scalable, integrated CV quantum technologies operating beyond classical limits.

Velocity circulation around closed loops is a fundamental quantity of central interest in the study of the energy cascade in turbulent flows. Recent theoretical and numerical studies have identified circulation as a geometric observable that captures intermittency through the area rule and a distinctive bifractal scaling of its moments in classical and quantum turbulence. One fundamental question is how these statistical characteristics of circulation are altered when an additional agent such as long-chain flexible polymer that can modify the turbulence energy cascade is added to the fluid. Here, through stereo particle image velocimetry measurements in high Reynolds number ($R_{\lambda }\approx 393$) turbulent flow of pure water and dilute polymer solution in a von Kármán swirling flow system, we provide the first experimental evidence that the area rule and the bifractality of the circulation hold for planar loops in both the 3D Newtonian and polymeric turbulence. These two statistical characteristics of circulation are robust despite strong modifications of the energy cascade and small-scale topology induced by polymer elasticity, except that the Hölder exponent in polymeric turbulence ($h\approx 1.55$) is significantly larger than in Newtonian turbulence ($h\approx 1.14$), suggesting that the flow is smoother in polymeric turbulence. Our results establish velocity circulation as a more universal and fundamental tool, compared to the very frequently used velocity increments, for unifying intermittency across different turbulent systems from Newtonian to polymeric to quantum turbulence.

We report the first experimental demonstration of directional and collimated electron acceleration in the direct laser acceleration regime using a relativistic hollow Laguerre-Gaussian (LG) laser. Electrons are confined within the hollow field distribution along the reflected laser direction, producing a collimated beam and overcoming the dispersed characteristic of Gaussian-laser-driven electrons. In particular, the left-circularly polarized LG laser generates a unique longitudinal resonant electric field on the axis, which, combined with transverse confinement, forms a stable acceleration structure. This leads to higher electron energies with improved stability and collimation compared with right-circularly polarized LG cases. The demonstrated LG-laser-driven collimating mechanism extends conventional direct laser acceleration into a stable and efficient regime, opening opportunities for particle collimation, high-flux particle sources, and coherent radiation generation in relativistic regimes.