We study an extended model to describe the spin-lattice coupling, incorporating individual vibrations of bonds and atomic sites alongside distance-dependent exchange interactions. The proposed spin Hamiltonian can be effectively considered as an interpolation between two well-established minimum models, the bond-phonon model and the site-phonon model. The extended model, which treats bond phonons and site phonons on comparable footing, well reproduces successive field-induced phase transitions as well as the thermodynamic properties of a three-up–one-down state in the pyrochlore-lattice Heisenberg antiferromagnet, including negative thermal expansion, an enhanced magnetocaloric effect, and a sharp specific-heat peak. The present approach is broadly applicable to various spin models, providing a framework for identifying the primary phonon modes responsible for spin-lattice coupling and for understanding complex magnetic phase diagrams.

It is well established that light can control magnetism in matter, e.g. via the inverse Faraday effect or ultrafast demagnetization. However, such control is typically limited to magnetization transverse to light’s polarization plane or out-of-plane magnetism in two-dimensional (2D) materials, while in-plane magnetic moments have remained largely unexplored. This is due to the difficulty of generating electronic orbital angular momentum components within light’s polarization plane. Here we overcome this limitation, demonstrating complete three-dimensional all-optical control of magnetism in 2D materials. Using first-principles simulations, we show that a tailored two-color laser field can induce and steer magnetic moments in any direction with the relative angle between the laser polarizations playing a key parameter in coherent control. We analyze the physical mechanism of this process and show that it arises from a simultaneous breaking of time-reversal and spatial-inversion symmetries in the two-color laser. In-plane orbital moments are introduced via nonzero out-of-plane longitudinal photogalvanic currents enabled by broken-inversion and mirror symmetries, while time-reversal symmetry breaking enables buildup of spin-flip and rotation processes through spin-orbit coupling, translating the orbital moments to transient magnetism. Our findings demonstrate a full 3D coherent control scheme for transient magnetic states on femtosecond timescales driven by tailored lasers, and can be used to develop novel spectroscopies for magnetism, all-optical magnetic switching for ultrafast spintronics, and novel information storage capabilities.

Quantum droplets are dilute self-bound configurations of bosons that result from the balance between a mean-field attraction and a repulsion induced by quantum fluctuations. Such droplets have been successfully realized in cold atomic gases and represent a signature of their quantum nature. Here, we predict the existence of a similar droplet phase in a solid-state system, involving polaritons formed from the strong coupling between excitons (bound electron-hole pairs) and photons in a semiconductor microcavity. We consider a spin mixture of exciton-polaritons near a biexciton Feshbach resonance, which allows one to tune the interspecies interactions to be attractive and comparable in magnitude to the intraspecies repulsion. We find that self-bound quantum droplets are achievable for realistic parameters in atomically thin semiconductors, and that they can be detected via their excitation spectrum and spatial profile. This exotic phase could potentially lead to polariton condensation at lower thresholds and it opens an alternative avenue to achieve the long-sought quantum polaritonic regime.

Qubit readout schemes often deviate from ideal projective measurements, introducing critical issues that limit quantum computing performance. In this Letter, we model charge-sensing-based readout for semiconductor spin qubits in double quantum dots, and identify key error mechanisms caused by the backaction of the charge sensor. We quantify how the charge noise of the sensor, residual tunneling, and $g$-tensor modulation degrade readout fidelity, induce a mixed postmeasurement state, and cause leakage from the computational subspace. For state-of-the-art systems with strong spin-orbit interaction and electrically tunable $g$ tensors, we identify a readout sweet spot, that is, a special device configuration where readout is closest to projective. Our framework provides a foundation for developing effective readout error mitigation strategies, with broad applications for optimizing readout performance for a variety of charge-sensing techniques, advancing quantum protocols, and improving adaptive circuits for error correction.

Large thermal fluctuations of the liquid phase obscure the weak macroscopic electric field that drives electrochemical reactions, rendering the extraction of reliable interfacial charge distributions from ab initio molecular dynamics extremely challenging. We introduce SMILE (Scalar Macro-dipole Integrated LEarning) charge partition, a macro-dipole-constrained scheme that infers atomic charges using only the instantaneous atomic coordinates and the total dipole moment of the simulation cell—quantities routinely available from standard density functional theory calculations. SMILE preserves both the global electrostatic field and the local potential without invoking any explicit charge-partitioning scheme. Benchmarks on three representative electrochemical interfaces—nanoconfined water, ${\mathrm{Mg}}^{2+}$ dissolution in water, and a kinked Mg vicinal surface under anodic bias—show that SMILE eliminates the qualitative errors observed for unconstrained charge decompositions. The method is computationally inexpensive and data-efficient, opening the door to charge-aware machine-learning potentials capable of bias-controlled, nanosecond-scale simulations of realistic electrochemical systems.

We report cross-validated measurements of the isotope effect on dielectric relaxation for four isotopologues of ice and water, including the $1–{10}^5\mathrm{Hz}$ region, in which only sporadic and inconsistent measurements were previously available. In ice, the relaxation rates exhibit an activated temperature dependence with an isotope-independent activation energy. Across 248–273 K, the ${\mathrm{H}}_2\mathrm{O}$-to-${\mathrm{D}}_2\mathrm{O}$ relaxation rate ratio remains constant at $2.0\pm 0.1$. This scaling agrees with Kramers’ theory in the high-friction limit if the moving mass is the proton or deuteron, indicating that dielectric relaxation is governed by a classic proton transfer over an energy barrier rather than molecular reorientation.

Efficient estimation of nonlinear properties is a significant yet challenging task in quantum information processing and many-body physics. Current methodologies often suffer from an exponential sample complexity or require auxiliary qubits and deep quantum circuits. To address these limitations, we propose an efficient auxiliary-free replica shadow (AFRS) framework, which leverages the power of joint entangling operations on a few input replicas while integrating the mindset of shadow estimation. We rigorously prove that AFRS can offer exponential improvements in estimation accuracy compared with the conventional shadow method and facilitate the simultaneous estimation of various nonlinear properties, unlike the destructive swap test. Additionally, we introduce an advanced local-AFRS variant tailored to estimating local observables with constant-depth quantum circuits, significantly simplifying the experimental implementation. Our Letter paves the way for efficient and practical estimation of nonlinear properties on near-term quantum devices.

The Forbush decrease of cosmic rays is an important probe of the interplanetary environment disturbed by solar activities. In this Letter, we study the properties of eight Forbush decreases’ electrons (including positrons) between 2 and 20 GeV from January 2016 to March 2024 with the Dark Matter Particle Explorer. The maximum decrease amplitudes of these events are about 30%–15%, and the amplitudes reduce with energy. The recovery time of these events shows diverse behaviors of their energy dependence. Some of them show strong energy dependence, while some have a nearly constant recovery time. It has been shown that such diverse behaviors could be related to the geometry of the regions of the interplanetary space disturbed by coronal mass ejections, which can be characterized by the combined effect of the coronal mass ejection velocity, angular spread, and ejection direction.

The relaxation of many physical systems is constrained by collisions. However, most space and astrophysical plasmas are nearly collisionless, leaving open questions about the pathways of energy transfer and dissipation. In many turbulent plasmas, the electric field takes on the role of energy transfer leading to dissipation. Using measurements from the Magnetospheric Multiscale Mission, we study the statistical properties of the electric field spectrum in the kinetic range of strong turbulence generated by magnetic reconnection in the Earth’s magnetotail. From the inertial to the kinetic range (often called the dissipation range) of scales, we find that turbulent fluctuations develop increasingly non-Gaussian features. The kinetic range contains two regimes with distinct behaviors in the power spectrum and measures of non-Gaussianity. In the subelectron kinetic regime (smaller than the electron gyroradius), the turbulence becomes isotropic and exhibits energy equipartition between the electric field and magnetic field. Our analyses indicate (1) a growing presence of intermittent structures that are expected to lead to enhanced energy dissipation, (2) changes in the electric field dynamics at the transitions between turbulence regimes, and (3) an asymptotic relaxation to a state of energy equipartition in the electromagnetic field in the subelectron kinetic range, where the energy transfer between the magnetic and electric fields appears to be near complete. These results reveal the importance of the electric field in mediating turbulence dissipation and relaxation in collisionless plasmas.

The $\beta$-pyrochlore ${\mathrm{CsNiCrF}}_6$ is a charge ice—each tetrahedron of the pyrochlore lattice is occupied by two ${\mathrm{Ni}}^{2+}$ and two ${\mathrm{Cr}}^{3+}$ according to an ice rule, resulting in fully packed same-species loops with power-law length distribution. Using inelastic neutron scattering and numerical simulations, we show that the spin dynamics can be well described by a model with three antiferromagnetic interaction strengths, one for Ni–Ni, Cr–Ni, and Cr–Cr interactions. Because the strengths of the two intraloop interactions are quite different, the fluctuations of each type of loop can be identified in the spectrum. ${\mathrm{CsNiCrF}}_6$ therefore forms an algebraic loop liquid in which power-law cation correlations control the spin dynamics. Our parameters predict a transition to spin nematic order with associated arrest of dynamics at $T_n\approx 0.55\mathrm{K}$, while we observe a freezing transition at $T_f=2.3\mathrm{K}$. Measurements of magnetization, ac, and nonlinear susceptibility show that this is not a canonical spin glass transition so we associate it with the development of slow dynamics due to interloop nematic correlations.

The bulk photovoltaic effect, which occurs in single-phase, noncentrosymmetric materials, is characterized by two primary mechanisms—the ballistic current and the shift current—that each generate dc current during carrier excitation. The excitation shift current in particular has intriguing properties, including ultrafast time evolution, a deep connection to wave function quantum geometry, and a well-established sensitivity to light frequency, optical polarization, material strain and strain gradients, coexisting dc electric fields, and more. Shift photocurrent from excitation has been explored in a variety of real materials using ab initio calculations, but shift current from carrier recombination, while predicted in model systems, has not been explored in real materials. To address this gap, we present a method to calculate the shift current due to carrier recombination under steady-state illumination using first-principles calculations. We then model the response of GaN and several other wurtzite semiconductors under realistic experimental conditions. These results show that recombination current may be comparable in magnitude to excitation shift current and demonstrate that even simple materials exhibit significant variations in recombination shift current that are jointly controlled by material properties and illumination conditions. As relaxation processes may depend on spin and valley degrees of freedom, this Letter enables new possibilities to understand and control the interplay between excitation and recombination shift currents that respond sensitively to electronic, magnetic, structural, and topological factors.

Conductivity is one of the most direct probes of electronic systems, yet its theoretical description remains challenging in the presence of strong nonlocal correlations. In this Letter, we analyze the conductivity of the half-filled single-band Hubbard model and identify the role of spatial correlations across the Mott transition. We show that in the correlated metallic regime, an accurate description of the conductivity requires not only the correct spectral function but also the inclusion of complex multielectron processes encoded in vertex corrections. The crossover to the Mott insulating regime is marked by a vanishing contribution of vertex corrections to the dc conductivity. However, in the Mott insulating case vertex corrections remain significant for the optical conductivity.

We show that finding the classical bound of broad families of Bell inequalities can be naturally framed as the contraction of an associated tensor network, but in tropical algebra, where the sum is replaced by the minimum and the product is replaced by the arithmetic addition. We illustrate our method with paradigmatic examples both in the multipartite scenario and the bipartite scenario with multiple outcomes. We showcase how the method extends into the thermodynamic limit for some translationally invariant systems and establish a connection between the notions of tropical eigenvalue and the classical bound per particle as a fixed point of a tropical renormalization procedure.

Periodically driven quantum systems can host nonequilibrium phenomena without static analogs, including in their entanglement dynamics. Here, we discover temporal entanglement transitions (TETs) in a Floquet spin chain, which correspond to a quantum phase transition in the spectrum of the entanglement Hamiltonian and are signaled by dynamical spontaneous symmetry breaking. We identify the symmetry principles underlying these transitions: they appear when the driven Hamiltonian preserves global symmetry (here, ${\mathbb{Z}}_2$), the initial state respects this symmetry, and the reduced density matrix carries weight in both subsystem-parity sectors, with TETs occurring precisely when the sector weights become equal (given the previous two conditions are also satisfied). Intriguingly, we find these transitions across a broad range of driving frequencies (from adiabatic to high-frequency regime) and independent of drive details, where they manifest as periodic, sharp entanglement spectrum reorganizations marked by the Schmidt-gap closure, a vanishing entanglement echo, and symmetry-quantum-number flips, while remaining invisible to conventional local observables. At high frequencies, the entanglement Hamiltonian acquires an intrinsic timescale decoupled from the drive period, rendering the transitions genuine steady-state features. Finite-size scaling reveals universal critical behavior with correlation-length exponent $\nu =1$, matching equilibrium Ising universality despite its emergence from purely dynamical mechanisms decoupled from static criticality. Our Letter establishes TETs as novel features in Floquet quantum matter.

As demand for quantum technologies increases, so does the need to generate and classify nonclassical correlations in complex many-body systems. We introduce a simple and versatile method for creating and certifying entanglement and many-body Bell correlations. This method relies on a single qubit interacting with an $N$-qubit system. We demonstrate that (i) such pairwise interaction is sufficient to induce many-body quantum correlations, and (ii) the qubit can serve as a probe to extract all information about these correlations. Thus, single-qubit measurements reveal multipartite entanglement and $N$-body Bell correlations, enabling the rapid and efficient certification of nonclassicality in complex systems.

We report a phase transition in the projected ensemble—the collection of postmeasurement wave functions of a local subsystem obtained by measuring its complement. The transition emerges in systems undergoing random permutation dynamics, a type of quantum time evolution wherein computational basis states are shuffled without creating superpositions. It separates a phase exhibiting deep thermalization, where the projected ensemble is distributed over Hilbert space in a maximally entropic fashion (Haar random), from a phase where it is minimally entropic (“classical bit-string ensemble”). Crucially, this deep thermalization transition is invisible to the subsystem’s density matrix, which always exhibits thermalization to infinite temperature across the phase diagram. Through a combination of analytical arguments and numerical simulations, we show that the transition is tuned by the total amount of coherence injected by the input state and the measurement basis, and is exhibited robustly across different microscopic models. Our findings represent a novel form of ergodicity-breaking universality in quantum many-body dynamics, characterized not by a failure of regular thermalization, but rather by a failure of deep thermalization.

Estimating partition functions of Ising spin glasses is a cornerstone of statistical physics and computational science, yet it remains classically challenging due to its #$P$-hard complexity. While Jarzynski’s equality offers a theoretical pathway, its practical application is crippled at low temperatures by rare, divergent statistical fluctuations. Here, we introduce a quantum protocol that overcomes this fundamental limitation by synergizing reverse quantum annealing with optimized nonequilibrium initial distributions. Our method dramatically suppresses the estimator variance, achieving saturation in the low-temperature regime where existing methods fail. Numerical benchmarks on the Sherrington-Kirkpatrick spin glass and the 3-SAT problem demonstrate that our protocol reduces computational scaling exponents by over an order of magnitude (e.g., from $\sim 8.5$ to $\sim 0.5$), despite retaining exponential system-size dependence. Crucially, our protocol circumvents stringent adiabatic constraints, making it feasible for near-term quantum devices like superconducting qubits, trapped ions, and Rydberg atom arrays. This Letter provides a methodological framework for quantum-enhanced estimation in spin glass thermodynamics and beyond by harnessing nonadiabatic quantum dynamics to address a classically difficult problem.

We use concepts from quantum cryptography to relate the entanglement in many-body mixed states to standard correlation functions. If a system can be used as a resource for distilling private keys—random classical bits that are shared by spatially separated observers but hidden from an eavesdropper having access to the environment—we can infer that the state of the system is entangled. For thermal states, we derive a simple relation between the information accessible to the eavesdropper and the linear response of the system. This relation allows us to determine which spatial correlations can be used to detect entanglement across wide varieties of physical systems, and provides a new experimental probe of entanglement. We also show that strong symmetries of a density matrix imply the existence of correlations that are always hidden from the environment. This result implies that, although grand canonical ensembles are separable above a finite temperature, canonical ensembles are generically entangled at all finite temperatures.