While invariant measures are widely employed to analyze physical systems when a direct study of pointwise trajectories is intractable, e.g., due to chaos or noise, they cannot uniquely identify the underlying dynamics. Our first result shows that, in contrast to invariant measures in state coordinates, e.g., $[x(t),y(t),z(t)]$, the invariant measure expressed in time-delay coordinates, e.g., $[x(t),x(t-\tau ),\dots ,x(t-(m-1)\tau )]$, can identify the dynamics up to a topological conjugacy. Our second result resolves the remaining ambiguity: by combining invariant measures constructed from multiple delay frames with distinct observables, the system is uniquely identifiable, provided that a suitable initial condition is satisfied. These guarantees require informative observables and appropriate delay parameters ($m$, $\tau$), which can be limiting in certain settings. We support our theoretical contributions through a series of physical examples demonstrating how invariant measures expressed in delay coordinates can be used to perform robust system identification in practice.

Magic states and magic gates are crucial for achieving universal quantum computation, but important questions about how magic resources should be implemented to attain maximal quantum advantage have remained unexplored, especially in the context of measurement-based quantum computation (MQC). This Letter bridges the gap between MQC and the resource theory of magic by introducing the key concepts of “invested” and “potential” magic resources. The former quantifies the magic cost associated with MQC, serving as both a resource witness and a feasible upper bound for the practical realization, and is gate-order independent; the latter represents the maximal achievable magic resource in a given graph structure defining MQC. We utilize both concepts to analyze the quantum Fourier transform (QFT) and provide a fresh perspective on the universality of MQC, highlighting the crucial role of non-Pauli measurements in injecting magic. In particular, we theoretically prove that high-dimensional graphs can generate an exponential advantage of MQC compared to classical computing. We demonstrate experimentally our theoretical findings in a high-fidelity four-photon setup, surpassing conventional magic state injection methods in both qubit efficiency and resource utilization. Our findings pave the way for future research exploring magic resource optimization and novel distillation schemes within the MQC framework, advancing fault-tolerant universal quantum computation.

Long-range nonstabilizerness can be defined as the amount of nonstabilizerness that cannot be removed by shallow local quantum circuits. We study long-range nonstabilizerness in the context of many-body quantum physics, a task with possible implications for quantum-state preparation protocols and implementation of quantum-error correcting codes. After presenting a simple argument showing that long-range nonstabilizerness is a generic property of many-body states, we restrict to the class of ground states of gapped local Hamiltonians. We focus on one-dimensional (1D) systems and present rigorous results in the context of translation-invariant matrix product states (MPSs), with our analysis extending to all gapped 1D phases under widely accepted physical assumptions. By analyzing the fixed points of the MPS renormalization-group flow, we provide a sufficient condition for long-range nonstabilizerness, which depends entirely on the local MPS tensors. Physically, our condition captures the fact that the mutual information between distant regions of stabilizer fixed points is quantized and remains so after applying shallow quantum circuits.

We consider a broad class of strongly interacting quantum lattice gases, including the Fermi-Hubbard and Bose-Hubbard models. We focus on macroscopic particle clusters of size $\theta N$, with $\theta \in (0,1)$ and $N$ the total particle number, and we study the quantum probability that such a cluster is transported across a distance $r$ within time $t$. Conventional effective light cone arguments yield a bound of the form $\exp (vt-r)$. We report a substantially stronger bound $\exp [\theta N(vt-r)]$, which provides exponential suppression that scales with system size. Our result establishes a universal dynamical large deviation principle: macroscopic suppression of supersonic macroscopic transport (MASSMAT).

The coupling of two-level quantum systems to the thermal environment is a fundamental problem with applications of such usually single-particle or fermionic systems ranging from qubit state preparation to spin models. The present Letter studies the elementary problem of the thermodynamics of an ensemble of bosons populating a two-level system. Using an optical dye microcavity platform, we thermalize photons in a two-mode system at conditions of tunable chemical potential, demonstrating the statistical mechanical problem of $N$ bosons populating a two-level system, coupled to a heat bath. Under pulsed excitation, we observe Josephson oscillations between the two quantum states, which verifies the possibility for coherent manipulation. In contrast, under stationary conditions, the thermalization of the two-mode system is observed, arising from radiative coupling of photons to the dye. As the energetic splitting between eigenstates is 2 orders of magnitude smaller than thermal energy, at low occupations, an almost equal distribution of the occupation of the modes is observed, as expected from Boltzmann statistics. For larger occupation, we observe efficient population of the ground state and saturation of the upper level at high filling, expected from quantum statistics. Our experiment holds promise for state preparation in quantum technologies as well as for quantum thermodynamics studies.

We explore a roughening phase transition that occurs in the entanglement dynamics of certain quantum circuits. Viewing entanglement as the free energy of a membrane in a circuit-defined random environment, there is a competition between membrane smoothing due to lattice pinning and roughening due to disorder in the circuit. In particular, we investigate the randomness-induced roughening transition of the entanglement membrane in a ($3+1$)-dimensional Clifford circuit model by calculating the entanglement entropy for various bipartitions. We further construct a scaling theory for membranes tilted away from lattice planes, uncovering new scaling forms and a crossover to a previously unexplored critical “tilted regime.”

The strongest experimental evidence for dark matter is the Galactic Center gamma-ray excess observed by the Fermi telescope and even predicted prior to discovery as a potential dark matter signature via weakly interacting massive particle dark matter self-annihilations. However, an equally compelling explanation of the excess gamma-ray flux refers to a population of old millisecond pulsars that also accounts for the observed boxy morphology inferred from the bulge old star population. We employ a set of Milky Way-like galaxies found in the hestia constrained simulations of the local universe to explore the rich morphology of the central dark matter distribution, motivated by the GAIA discovery of a vigorous early merging history of the Milky Way galaxy. We predict a significantly nonspherical gamma-ray morphology from the weakly interacting massive particle interpretation. Future experiments, such as the Cherenkov Telescope Array, that extend to higher energies, should distinguish between the competing interpretations.

A recent covariant formulation, that includes nonperturbative effects from loop quantum gravity (LQG) as self-consistent effective models, has revealed the possibility of nonsingular black hole solutions. The new framework makes it possible to couple scalar matter to such LQG black holes and derive Hawking radiation in the presence of quantum spacetime effects while respecting general covariance. Standard methods to derive particle production both within the geometric optics approximation and the Parikh–Wilczek tunnelling approach are therefore available and confirm the thermal nature of Hawking radiation. The covariant description of scale-dependent decreasing holonomy corrections maintains Hawking temperature as well as universality of the low-energy transmission coefficients, stating that the absorption rates are proportional to the horizon area at leading order. Quantum-geometry effects enter the thermal distribution only through subleading corrections in the graybody factors. Nevertheless, they do impact energy emission of the black hole and its final state in a crucial way regarding one of the main questions of black-hole evaporation: whether a black-to-white-hole transition, or a stable remnant, is preferred. For the first time, a first-principles derivation, based on a discussion of backreaction, finds evidence that points to the former outcome.

We present a first principles calculation within quantum chromodynamics (QCD) of the radiative decays of the $J/\psi$ into the light pseudoscalar mesons $\eta$ and ${\eta }^{\prime }$. Within a lattice computation we obtain the transition form factors as a function of photon virtuality from the timelike region, accessible experimentally via the “Dalitz” decay $J/\psi \to e^{+}{e}^{-}{\eta }^{(\prime )}$, through to the real photon point corresponding to $J/\psi \to \gamma {\eta }^{(\prime )}$. This is the first calculation in lattice QCD with two (heavier than physical) degenerate flavors of light quark and a heavier strange quark, in which the ${\eta }^{\prime }$ appears as the first excited state with pseudoscalar isoscalar quantum numbers. We access it reliably by using variationally optimized operators, the use of which also improves the purity of the $J/\psi$ and $\eta$ signals, reducing systematic uncertainties. High quality results at a large number of kinematic points are obtained in a typically noisy disconnected process by using a novel correlator averaging procedure. Our results show the expected enhanced production of the ${\eta }^{\prime }$ over the $\eta$ in this process, and suggest that the demonstrated lattice technology is suitable for future calculations considering processes in which light meson resonances are produced.

Nonequilibrium, strongly interacting systems exhibit rich dynamics even in the presence of strong dissipation. For example, periodic dynamics, such as discrete time crystalline (DTC) phases, can appear. The DTC phase structure can be further enriched using external periodic driving—Floquet driving. In this Letter, we study a photoionization-induced Floquet driving of a DTC phase in a thermal Rydberg gas. We add an additional laser to induce photoelectrons from the cell wall. These electrons are rotated around the magnetic-field vector and collide with the Rydberg atoms, generating a plasma with large electric fields that perturb further Rydberg excitation. This results in a photoionization-induced Floquet driving of the DTC phase. Importantly, we demonstrate experimentally how the DTC phase relies on the emergence of bistability. Simulations of the mean-field Floquet-driven system reproduce the experimental observations. Our Letter fills an experimental gap in our understanding of the relation of multistability and dissipative discrete time crystals, and in this regard, it constitutes a highly controlled platform for exploring exotic nonequilibrium physics in dissipative interacting systems.

When submerged in a chiral active bath, a passive object becomes a spinning ratchet imbued with odd transport properties. We present the most general Langevin dynamics for a rigid body in a chiral active bath, in the adiabatic limit of large object mass. For rotationally symmetric objects, odd diffusion and odd mobility are connected by an Einstein relation, that we show numerically to break down outside the adiabatic limit. As the object symmetry decreases, its dynamics becomes increasingly irreversible: A massive disk exhibits an effective equilibrium dynamics, while a rod admits distinct translational and rotational temperatures, and a wedge is fully irreversible. Conversely, this departure from equilibrium can be read in universal far-field currents and density modulations of the bath, which we measure numerically and derive analytically.

We investigate a generic non-phase-invariant Hamiltonian model that governs the dynamics of nonlinear dispersive waves. We give evidence that initial data characterized by random phases naturally evolve into phase correlations between positive and negative wave numbers, leading to the emergence of nonzero anomalous correlators and negative frequencies. Using analytical techniques, we show that anomalous correlators develop on a timescale of $\mathcal{O}(1/\epsilon )$, earlier than the kinetic timescale. Our theoretical predictions are validated through direct numerical simulations of the deterministic system.

We numerically investigate the steady shear rheology of mixtures of active and passive Brownian particles, with varying fractions of active components. We find that even a small fraction of active dopants triggers fluidization with comparable efficiency to fully active systems. A combined parameter, active energy, given by the dopant fraction multiplied by the propulsion speed squared controls the steady shear rheology and glass transition of the active-passive mixtures. These results together provide a quantitative strategy for fine-tuning the mechanical properties of a soft material with small amounts of active dopants.

Indefinite causal order (ICO), a striking feature of quantum mechanics, has attracted broad theoretical and experimental interest. While ICO holds promise for quantum information processing, akin to quantum entanglement, its experimental realization and rigorous verification remain fundamental challenges. Here, we demonstrate and certify generalized multidimensional multipartite ICOs using a programmable integrated-photonic quantum chip implementing a generalized quantum switch. By violating definite causal order bounds with high statistical significance, we experimentally characterize and verify these generalized ICOs. Furthermore, we explore a resource theory of causal nonseparability by implementing a single-copy distillation protocol. Our Letter constitutes a major step toward a generalized framework for quantum causality.

Quantum computers promise efficient simulation of Lindbladian dynamics in open quantum systems, with broad applications in quantum chemistry, quantum error correction, and quantum state preparation. However, simulating open systems is more challenging than simulating closed systems, inherently requiring nonunitary operations. Existing approaches face unique challenges: methods with higher theoretical efficiency demand numerous ancillae and multiqubit operations that are experimentally challenging, while more experimentally feasible methods incur deep quantum circuits to control simulation errors. Here, we introduce a powerful framework, the linear combinations of superoperators, to systematically compensate for simulation errors and overcome these challenges. Utilizing simple gates and experimentally accessible Trotter decompositions, our approach achieves an exponential reduction in circuit depth with respect to the simulation precision, if only two ancillas are allowed to be used. We further extend the approach to time-dependent Lindbladians, achieving for the first time logarithmic depth in precision. Numerical simulations demonstrate significant performance advantages, establishing our method as a practical and scalable solution for simulating open quantum systems on near-term quantum hardware.

We present results of a search for spin-independent dark matter-nucleus interactions in a $1{\mathrm{cm}}^2$ by 1 mm thick (0.233 g) high-resolution silicon athermal phonon detector operated above ground. For interactions in the substrate, this detector achieves an rms baseline energy resolution of $361.5(4)\mathrm{m}\mathrm{eV}$ (statistical error), the best for any athermal phonon detector to date. With an exposure of $0.233\mathrm{g}\times 12$ hours, we place the most stringent constraints on dark matter masses between 44 and $87\mathrm{M}\mathrm{eV}/{\mathrm{c}}^2$, with the lowest unexplored cross section of $4\times {10}^{-32}{\mathrm{c}\mathrm{m}}^2$ at $87\mathrm{M}\mathrm{eV}/{\mathrm{c}}^2$. We employ a conservative salting technique to reach the lowest dark matter mass ever probed via direct detection experiment. This constraint is enabled by two-channel rejection of low energy backgrounds that are coupled to individual sensors.

In the context of fuzzy dark matter (FDM) we study the core formation in the presence of an ideal gas (IG). Our analysis is based on the solution of the Schrödinger-Poisson-Euler system of equations that drives the evolution of FDM together with a compressible IG, both coupled through the gravitational potential they produce. Starting from random initial conditions for both FDM and IG, we study the evolution of the system until it forms a nearly relaxed, virialized, and close to hydrostatic equilibrium core, surrounded by an envelope of the two components. We find that the core corresponds to Newtonian fermion-boson stars (FBS). If the IG is used to model luminous matter, our results indicate that FBS behave as attractor core solutions of structure formation of FDM along with visible matter.

The recent measurement of baryonic acoustic oscillations by the Dark Energy Spectroscopic Instrument reveals a mild tension with observations of the cosmic microwave background (CMB) within the standard $\mathrm{\Lambda }$ cold dark matter ($\mathrm{\Lambda }\mathrm{CDM}$) cosmological model. This discrepancy leads to a preference for a total neutrino mass that is lower than the minimum value inferred from neutrino oscillation experiments. Alternatively, this tension can be eased within $\mathrm{\Lambda }\mathrm{CDM}$ by assuming a higher optical depth ($\tau \simeq 0.09$), but such a value conflicts with large-scale CMB polarization data. We point out that cosmic birefringence, as suggested by recent Planck reanalyses, resolves this discrepancy if the birefringence angle varies significantly during reionization. Specifically, we consider the fact that the measured cosmic birefringence angle ${\beta }_0=0.34\pm 0.09(1\sigma )\mathrm{deg}$ has the phase ambiguity, i.e., the measured rotation angle is described by $\beta ={\beta }_0+180n\mathrm{deg}$ ($n\in \mathbb{Z}$). We show that cosmic birefringence induced by axionlike particles with nonzero $n$ suppresses the reionization bump, allowing a higher $\tau$ consistent with data. We provide a viable parameter space where the birefringence effect simultaneously accounts for the low-$\ell$ polarization spectra, the Planck $EB$ correlations, and the elevated value of $\tau$, suggesting a key role for cosmic birefringence in current cosmological tensions.