Designing the amplitude and range of couplings in quantum systems is a fundamental tool for exploring a large variety of quantum mechanical effects. Here, we consider off-resonant photon scattering processes on a geometrically shaped molecular cloud. Our analysis shows that such a setup is properly modeled by a Bose-Hubbard Hamiltonian where the range, amplitude, and sign of the tunneling processes of the scattered photonic modes can be accurately tuned. Specifically, by varying the molecular distribution, we demonstrate that different configurations characterized by geometrical frustration, long-range power law hopping processes, and nonlocal gauge fields can be achieved. Our results thus represent a powerful and alternative approach to perform an accurate Hamiltonian engineering of quantum systems with nontrivial coupling structures.

The year 2024 was the hottest in the modern era, followed by 2023. Do these temperatures signal unexpected changes in the climate system? Writing the global annual mean temperature as the sum of two terms, greenhouse-gas driven climate change and fluctuations due to internal and external variability, we model the first term by extending the logarithmic dependance of the temperature anomaly to non-equilibrium conditions. We validate the method using the illustrative scenarios considered by the IPCC. Fitting the data, we find that the residuals for 2023 and 2024 are consistent with past fluctuations. We comment on how putative changes in the climate regime will manifest themselves in coming years.

We use the self-consistent harmonic approximation with machine learning interatomic potentials to calculate the effect of ${}^{18}\mathrm{O}$ substitution on the properties of quantum paraelectric ${\mathrm{SrTiO}}_3$ (STO). We find that calculations including both quantum and anharmonic effects are able to reproduce the experimentally observed isotope effect, in which the replacement of ${}^{16}\mathrm{O}$ by ${}^{18}\mathrm{O}$ induces the ferroelectric state, and we demonstrate that the ferroelectric phase transition in $\mathrm{ST}{}^{18}\mathrm{O}$ can be reproduced in a purely displacive description. We calculate the ferroelectric soft mode frequency as a function of volume, lattice parameters, and temperature for $\mathrm{ST}{}^{16}\mathrm{O}$ and $\mathrm{ST}{}^{18}\mathrm{O}$ and find that the phase space in which $\mathrm{ST}{}^{16}\mathrm{O}$ shows quantum paraelectric behavior, while $\mathrm{ST}{}^{18}\mathrm{O}$ becomes ferroelectric, is narrow. Our Letter shows that machine learning interatomic potentials enable temperature-dependent simulations that include quantum and anharmonic phonon effects and that quantitative prediction of the phase diagram in the case of STO is limited by the accuracy of the underlying electronic structure method.

The easy implementation of gain and loss provides a fertile ground for the experimental exploration of non-Hermitian (NH) physics. This raises the question of whether NH effects can be realized in a Hermitian system without gain and loss. The interface between coupled Hermitian subsystems naturally lends itself to NH phenomena due to the nonconservative processes occurring there. Nonetheless, endowing such interfaces with rich NH physics remains a significant challenge. Here, we study a junction between a topological model and a conductor model, where the interface can be effectively described by an NH Hamiltonian. Such an NH nature is attributed to the self-energy of the conductor, which functions as a reservoir. Consequently, we demonstrate that the wave propagation along this interface exhibits dissipative nonreciprocity (termed non-Bloch transport), which was previously considered exclusive to NH systems. Moreover, the metamaterialization of tight-binding models is also studied by identifying their equivalent connectivity, thereby enabling the experimental observation of the aforementioned exotic NH interface behavior. Our Letter establishes a conceptually profound framework for engineering NH effects, with broad applicability across both optical and electronic platforms.

Non-Hermitian systems generally host complex spectra that bring unique spectral topologies, leading to spectral braiding and the non-Hermitian skin effect. The experimental exploration of non-Hermitian physics is mainly concentrated in artificial systems, due to the flexibility in the introduction of the non-Hermiticity, but to date has focused only on the systems without gauge fields or with Abelian gauge fields. Here, we propose a non-Abelian Hatano-Nelson model with a nonreciprocal U(2) gauge field. The gauge field induces two non-Hermitian phenomena: the first is the Hopf-link-shaped complex energy braiding, and the second is the bipolar skin effect arising under the non-Abelian condition. The non-Abelian Hatano-Nelson model is implemented in electric circuits, and the Hopf-link-shaped admittance spectra and bipolar skin admittance modes are observed. Our Letter enriches the experimental non-Hermitian physics and provides an approach to designing multifunctional non-Hermitian devices.

We study the stochastic dynamics of a symmetric self-chemotactic particle and determine the long-time behavior of its mean squared displacement (MSD). The attractive or repulsive interaction of the particle with the chemical field that it generates induces a nonlinear, non-Markovian effective dynamics, which results in anomalous diffusion for spatial dimensions $d\le 2$. In one spatial dimension, we map the case of repulsive chemotaxis onto a run-and-tumble-like dynamics, leading to an MSD which, as a function of the elapsed time $t$, grows superdiffusively with exponent $4/3$. In the presence of attractive chemotaxis, instead, the particle exhibits a slowdown, with the MSD growing logarithmically with time. In $d=2$, we find logarithmic aging of the diffusion coefficient, while in $d=3$ the motion reverts to standard diffusive behavior with a renormalized diffusion coefficient.

Mutual information is a theoretically grounded metric for quantifying cellular signaling pathways. However, its measurement demands characterization of both input and output distributions, limiting practical applications. Here, we present alternative method that alleviates this requirement using dual reporter systems. By extending extrinsic-intrinsic noise analysis, we derive a mutual information estimator that eliminates the need to measure input distribution. We demonstrate our method by analyzing the bacterial chemotactic pathway, regarding multiple flagellar motors as natural dual reporters. We show the biological relevance of the measured information flow by comparing it with theoretical bounds on sensory information. This framework opens new directions for quantifying information flow in cellular signaling pathways.

Sequential sharing of quantum nonlocality enables multiparty collaborative information processing, which is typically realized through unsharp measurements in previous studies. By contrast, we experimentally demonstrate that the sequential sharing of quantum nonlocality can be observed using only projective measurements, with the introduction of classical randomness. We achieve sequential violations of the Clauser-Horne-Shimony-Holt inequality in a bipartite quantum system by sharing classical randomness or using a probabilistic projective measurement. Extending the first protocol to a tripartite quantum system, sequential tripartite nonlocality is observed with the Greenberger-Horne-Zeilinger state, where violations of the Mermin inequality are observed in sequential measurements. We experimentally demonstrate these phenomena through the preparation and measurement of a three-photon entangled state. Our work reveals the key role of projective measurements in the sequential sharing of quantum nonlocality, providing a new experimental complement for measuring quantum nonlocality and opening new technological pathways for distributed utilization nonlocality in quantum networks.

Various exotic phenomena emerge in nonequilibrium quantum many-body systems. The Mpemba effect, denoting the situation where a hot system freezes faster than a colder one, is a counterintuitive nonequilibrium phenomenon that has attracted enduring interest for more than half a century. In this Letter, we unveil a novel phenomenon of the Mpemba effect in the imaginary-time relaxation dynamics in quantum many-body systems, termed as the imaginary-time Mpemba effect (ITME). We propose a mechanism for the ITME rooted in the initial state’s eigenbasis expansion, and we demonstrate its emergence in representative quantum lattice models. Using sign-free quantum Monte Carlo (QMC) simulations, we unequivocally establish the existence of the ITME across diverse interacting quantum systems. Crucially, given the widespread use of imaginary-time dynamics for ground-state calculations, the discovery of the ITME potentially provides a new pathway to accelerate quantum many-body simulations, particularly for QMC methods hindered by the sign problem.

We test screened dark energy with near-Earth, space-based measurements. In a post-Newtonian framework, we compute leading corrections to geodetic precession (Gravity Probe B), LAGEOS-2 pericenter advance, and the Sagnac delay in a prospective orbital configuration, yielding bounds on chameleon, symmetron, and dilaton models. LAGEOS-2 sets the strongest Earth-orbit limits on symmetron and dilaton, while a Sagnac setup at the projected sensitivity of state-of-the-art space clocks gives the tightest chameleon constraint. These results show that low-density, space-based experiments sensitively probe screened dark energy and exclude previously allowed parameter space. Notably, at nuclear-clock precision $\mathcal{O}({10}^{-19})$, a Sagnac test would exclude the entire chameleon parameter space considered.

We report the first measurement of the Hubble constant $H_0$ using the stochastic gravitational-wave background arising from binary black hole mergers. This astrophysical background is sensitive to the expansion history of the Universe and, thus, can be used for cosmological parameter inference independently of not only electromagnetic methods, but also gravitational-wave standard siren approaches. We describe the background’s cosmological dependence and show how it can be used as a “stochastic siren” to measure $H_0$. By analyzing existing resolved binary black hole mergers and the current nondetection of the background, we find that $H_0$ can be measured more accurately relative to using resolved mergers alone. We also note that the stochastic siren may serve a unique role in the Hubble tension in that the lower bound of the $H_0$ measurement would progressively increase with continued nondetection of the background.

We present a neural network wave function framework for solving non-Abelian lattice gauge theories in a continuous group representation. Using a combination of SU(2) equivariant neural networks alongside an SU(2) invariant, physics-inspired ansatz, we learn a parametrization of the ground state wave function of SU(2) lattice gauge theory in $2+1$ and $3+1$ dimensions. Our method, performed in the Hamiltonian formulation, has a straightforward generalization to $\mathrm{SU}(N)$. We benchmark our approach against a solely invariant ansatz by computing the ground state energy, demonstrating the need for bespoke gauge equivariant transformations. We evaluate the Creutz ratio and average Wilson loop, and obtain results in strong agreement with perturbative expansions. Our method opens up an avenue for studying lattice gauge theories beyond one dimension, with efficient scaling to larger systems, and in a way that avoids both the sign problem and any discretization of the gauge group.

A reliable calculation of radiative corrections to $\tau \to \pi \pi {\nu }_{\tau }$ decays is an important prerequisite for using hadronic $\tau$ decays for a data-driven evaluation of the hadronic-vacuum-polarization (HVP) contribution to the anomalous magnetic moment of the muon, $a_{\mu }^{\mathrm{HVP},\mathrm{LO}}[\pi \pi ,\tau ]$. In this Letter, we present an improved model-independent analysis of these radiative corrections, including, for the first time, effects beyond pointlike pions in the evaluation of the loop diagrams. These structure-dependent corrections, implemented via a dispersive representation of the pion form factor, lead to significant changes compared to previous calculations due to enhancements near the $\rho (770)$ resonance. We also devise strategies for the matching to chiral perturbation theory and a stable implementation of the real corrections down to the two-pion threshold, which shows that some higher-order isospin-breaking corrections need to be kept due to a strong threshold enhancement. Finally, we perform dispersive fits to the currently available $\tau \to \pi \pi {\nu }_{\tau }$ spectra and discuss the consequences for isospin-breaking corrections in the evaluation of $a_{\mu }^{\mathrm{HVP},\mathrm{LO}}[\pi \pi ,\tau ]$.

We present a novel multimessenger approach to extract the effective radial flow of the quark-gluon plasma (QGP) by jointly analyzing thermal photon and dilepton spectra in heavy-ion collisions. A key feature of this method is that it circumvents the need for a directly unmeasurable reference—the photon temperature in the absence of flow—by establishing, within a calibrated model framework, a stable, approximately linear correlation with the dilepton-inferred temperature. This construction defines an experimentally constructible quantity, $v_r^{\mathrm{eff}}$, which reflects early-time collectivity and exhibits a strong correlation with the spacetime-averaged radial velocity of the QGP. Together with previous results linking dilepton slopes to the initial QGP temperature, our work establishes a consistent framework for electromagnetic tomography of the QGP. Our framework quantifies the experimental precision target, thereby providing a concrete road map for future measurements at RHIC and the LHC and opening a new avenue to probe the early-time dynamics of hot QCD matter.

We investigate the dynamical phase evolution of Coulomb-focused electrons in strong-field ionization. We diffract the electrons with an ultrashort standing light wave to track their time-dependent phase. Our findings show that low-energy electrons exhibit a unique chromosome-shaped diffraction pattern, distinct from higher-energy electrons. Our numerical model quantitatively reproduces the experimental results, confirming this pattern maps the electron’s time-dependent phase evolution as it escapes from a Coulomb potential. Our pulsed diffraction grating technique offers a new way to sense an electron’s quantum phase at very large distances without interfering its release mechanism.

Hydrodynamic attractors characterize hydrodynamiclike evolution in strongly interacting systems, independent of initial conditions or microscopic details, outside the conventional hydrodynamic regime. They explain why hydrodynamic models apply to high-energy nuclear collisions, but so far have only been explored for monotonic expansion, such as Bjorken flow. We demonstrate that a system undergoing periodic expansion and contraction exhibits a novel cyclic attractor behavior. We employ Müller-Israel-Stewart theory to a driven ultracold Fermi gas to predict the shape of the attractor, which does not converge to Navier-Stokes dynamics at late times. This phenomenon can be measured in real time in ultracold quantum gases with externally modulated scattering length, offering a new avenue for the experimental discovery of hydrodynamic attractors.

The infamous weakness of molecular chiroptical responses challenges the all-optical realization of crucial applications such as enantio-selective sorting of chiral molecules, or biasing chiral chemical reactions. Chiral optical cavities are a natural choice for confronting this challenge. Ideally, the dissymmetry between the two helicities inside such cavities is maximized. Here, we propose a chiral infrared optical cavity formed by planar mirrors made of diffracting lattices of silver helices with almost maximum electromagnetic chirality. It combines the strong helicity selectivity of the helices with the helicity-preserving reflectivity that planar systems show at large incidence angles. For the manifold of cavity modes that have a component with zero in-plane momentum, we demonstrate an unprecedented dissymmetry of 95% inside the cavity at the target frequency, making it a compelling candidate for enantio-selective applications.