Quantum phase estimation is a core task in quantum technologies ranging from metrology to quantum computing, where it appears as a key subroutine in various algorithms. Here, we quantitatively connect the performance of phase estimation protocols with quantum coherence. To achieve this, we construct and characterize resource theories of quantum networks that cannot generate coherence. Given multiple copies of a unitary encoding an unknown phase and access to a fixed coherent state, we estimate the phase using such networks. For a unified and general approach, we assess the quality of the estimate using a generic cost function that penalizes deviations from the true value. We determine the minimal average cost that can be achieved in this manner and explicitly derive optimal protocols. From this, we construct a family of coherence measures that directly connect a state’s coherence with its value for phase estimation, demonstrating that every bit of coherence helps. This establishes coherence as a resource that quantifies the performance of phase estimation, and, thus, of any quantum technology relying on it as a subroutine.

We propose a time crystal based on a quantum black-hole laser, where the genuinely spontaneous character of the symmetry breaking stems from the self-amplification of spontaneous Hawking radiation. The resulting Hawking time crystal (HTC) is characterized by the periodic dependence of the out-of-time density-density correlation function, while equal-time observables are time independent because they embody averages over different realizations with a random oscillation phase. The HTC provides a nonlinear periodic analog of the Andreev-Hawking effect, exhibiting anticorrelation bands resulting from the spontaneous, quantum emission of pairs of dispersive waves and solitons into the upstream and downstream regions. Remarkably, we prove that any parametric amplifier has associated a time operator, which leads to a unique characterization of the time-crystal formation in terms of two time operators: one associated with the initial black-hole laser and another associated with the final spontaneous Floquet state.

Although light nuclear clusters are known to form abundantly in warm and dilute nuclear matter, their role in hot and dense nuclear matter remains unclear due to the lack of experimental indication for their modifications by the Mott effect under such conditions. To address this issue, we resort to intermediate-energy heavy-ion collisions, where light clusters are mainly produced in the transiently formed hot and dense matter. A kinetic approach, which includes dynamically the formation and dissociation of light clusters, is employed to deduce the strength of the Mott effect and the $\alpha$-particle fraction in hot and dense nuclear matter from the light-nuclei yields measured by the FOPI Collaboration in central $\mathrm{Au}+\mathrm{Au}$ collisions at energies of $0.25A$ to $0.6A\mathrm{GeV}$. We find an unexpectedly abundant $\alpha$ clustering in this environment, which will have profound implications for modeling the nuclear equation of state and describing supernovae and neutron star mergers.

The weak binding and spatially extended neutron densities characteristic of drip-line nuclei give rise to a distinctive low-energy dipole response. The drip-line nucleus ${}^8\mathrm{He}$ is the most neutron-rich bound nucleus with a mass-to-charge ratio of $A/Z=4$. We measure the dipole response of ${}^8\mathrm{He}$, including for the first time the four-neutron decay channel. A total dipole strength of $\sum B(E1)(E^{*}<15\mathrm{MeV})=0.95(16)e^2{\mathrm{fm}}^2$ and a dipole polarizability of ${\alpha }_D=0.61(1){\mathrm{fm}}^3$ are extracted from the differential Coulomb-excitation cross section and compared to state-of-the-art theoretical calculations employing coupled cluster and three-body approaches. We find that the dipole continuum is dominated, even at high excitation energies well above the $4n$ decay threshold, by two-neutron emission, pointing to a ${}^6\mathrm{He}+2n$ structure of the excited dipole mode. No indication was found for a $4n$ final-state correlation, while pronounced $nn$ and ${}^6\mathrm{He}\text{−}n$ final-state correlations are apparent.

Finding high-quality trial wave functions for quantum Monte Carlo calculations of light nuclei requires a strong intuition for modeling the interparticle correlations as well as large computational resources for exploring the space of variational parameters. Moreover, for systems with three-body interactions, the wave function should account for many-body effects beyond simple pairwise correlations. In this Letter, we design neural networks that efficiently incorporate these factors to generate expressive wave function Ansätze for light nuclei using variational Monte Carlo. Our neural-network approach for $A=3$ nuclei can capture, already at the level of variational Monte Carlo, the overwhelming majority of the ground-state energy estimated by Green’s function Monte Carlo (GFMC). It achieves a ground-state energy within 0.45% of the GFMC result for ${}^3\mathrm{H}$ using the softest chiral interaction, representing a substantial improvement over standard variational Monte Carlo, which exhibits a 3.7% deviation. The result indicates the potential of neural networks to construct effective trial wave functions for quantum Monte Carlo calculations.

The simultaneous emission of two $\alpha$ particles—double-$\alpha$ decay—represents a long-predicted but unobserved mode of nuclear radioactivity. Here, we formulate this process as a genuine three-body problem within the hyperspherical coordinate framework and evaluate decay probabilities by numerically solving the corresponding hyperradial Schrödinger equation combined with large-scale random sampling of the potential parameters. Inspired by this, we demonstrate that the decay width ratio between simultaneous and sequential $\alpha$ emission exhibits a strikingly linear dependence on $Z{Q}_{\alpha \alpha }^{-1/2}$, extending the barrier penetration dynamics into the correlated few-body regime. The nuclei ${}^{108}\mathrm{Xe}$, ${}^{218}\mathrm{Ra}$, ${}^{224}\mathrm{Pu}$, ${}^{222}\mathrm{U}$, ${}^{216}\mathrm{Rn}$, and ${}^{220}\mathrm{Th}$ are suggested as the most promising candidates for the observation of double-$\alpha$ decay, with predicted half-lives potentially accessible within present detection limits. Our results provide a unified framework for multi-$\alpha$ decay and open a pathway to probing nuclear clustering and few-body correlations in heavy nuclei.

Recent studies of rhombohedral multilayer graphene have revealed a variety of superconducting states that can be induced or enhanced by magnetic fields, reinforcing rhombohedral multilayer graphene as a powerful platform for investigating novel superconductivity. Here, we report an insulator-superconductor transition driven by in-plane magnetic fields $B_{\parallel }$ in rhombohedral hexalayer graphene. The upper critical field of $B_{\parallel }$ can reach 2 T and an analysis based on isospin symmetry breaking supports a spin-polarized superconductor. At $B_{\parallel }=0$, such spin-polarized superconductor transitions into an insulator, exhibiting a thermally activated gap of $\mathrm{\Delta }\approx 0.14\mathrm{meV}$. In addition, we observe four superconducting states in the hole-doped regime, which violate the Pauli limit, as well as phases with magnetoelectric hysteresis near charge neutrality point. These findings substantially enrich the phase diagram of rhombohedral graphene and provide new insight into the microscopic mechanisms of superconductivity.

Multiferroics are materials with coexisting electric and magnetic orders that are of central importance for fundamental research and technological applications. Unfortunately, intrinsic multiferroics that operate at room temperature remain rare due to an apparent incompatibility between magnetism and ferroelectricity. Here we predict that pure ferroelectrics may support multiferroic-like quasiparticles, termed “multiferrons,” that simultaneously carry static magnetic and electric dipoles. The electric dipole moment emerges from the parity-odd anharmonicity of the ferroelectric dynamics, while the magnetic moment has both paramagnetic and diamagnetic origins generated by circularly polarized transverse fluctuations of the ferroelectric polarization. In contrast to the established “dynamical multiferroicity” of circularly polarized phonons, which involves only oscillating electric dipoles, multiferrons exhibit or cause, apart from Zeeman and Einstein-de Haas effects, a linear dc Stark response, giant electric-field-tunable second-harmonic generation in the THz-frequency regime, and a magnetoelectric cross coupling. Multiferrons open a new route toward nonlinear THz optical applications and offer multiferroic functionalities with simple ferroelectrics.

Hyperbolic shear polaritons, recently discovered in infrared (IR) phononic systems, offer enhanced directionality and subwavelength confinement. This Letter proposes a strategy for realizing hyperbolic shear plasmon polaritons (HSPPs) in natural two-dimensional (2D) materials with time-reversal symmetry, thereby extending their operation beyond the IR range. We reveal that twisting a 2D material on an anisotropic substrate creates nondiagonalizable transverse conductivity components, leading to wave vector misalignment and the associated asymmetric loss in HSPPs. Furthermore, we highlight the tunability of these HSPPs through electrostatic doping and precise control of the twist angle. Our theoretical framework is validated using ${\mathrm{MoOCl}}_2$, paving the way for achieving visible-range HSPPs in natural, gate-tunable materials.

We investigate how isolated quantum many-body systems dynamically equilibrate under non-Abelian gauge-symmetry constraints. By encoding gauge superselection sectors into static SU(2) background charges, we map out the dynamical phase diagram of a $(1+1)\mathrm{D}$ SU(2) lattice gauge theory with dynamical matter. We uncover three distinct regimes: (i) an ergodic phase, (ii) a fragmented phase that is nonthermal but delocalized, and (iii) a disorder-free many-body localized regime. In the latter, a superposition of gauge superselection sectors preserves spatial matter inhomogeneities in time, as evidenced by distinct temporal scalings of entropy. We highlight the non-Abelian nature of these phases and argue for potential realizations on qudit processors.

We propose and demonstrate a fully passive discrete-state continuous-variable quantum key distribution (CV-QKD), which can eliminate all modulator side channels on the source side, using a local local oscillator. Using specially designed phase rotation and discretization methods, the CV-QKD system achieves a maximum fiber transmission length of 100 km at a repetition rate of 1 GHz in asymptotic security, with the corresponding secret key bit rate being 70.7 kbps. In composable security, secret keys are distributed at 25 km of fiber with a secret key bit rate of 1.66 Mbps. Our protocol significantly simplifies the architecture of CV-QKD system by eliminating the need for optical modulators and random number generators as well as presents robust practical security and superior performance, which is comparable to that of its active discrete-state counterpart. Overall, this protocol is expected to play an important role in quantum metropolitan area networks and quantum access networks requiring high realistic security.

Understanding whether primordial black holes form during strong first-order phase transition (FOPT) is a crucial open question in cosmology. We address this using a fully covariant formalism to study cosmological perturbations, highlighting previously overlooked gauge dependencies. We show that non-covariant treatments can overestimate primordial black holes and scalar-induced gravitational waves. Once gauge dependencies are accounted for, both signals are strongly suppressed, with direct implications for the FOPT interpretation of the Pulsar Timing Array signal.

The first search for the $B_s^0\to K^{-}{\pi }^{+}\gamma$ decay in the range $796<m(K^{-}{\pi }^{+})<1800\mathrm{MeV}/c^2$ is performed using data from proton-proton collisions collected by the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of $9{\mathrm{fb}}^{-1}$. The photons are reconstructed through their conversion into an electron-positron pair, which significantly improves the mass resolution of the reconstructed decays with respect to decays with an unconverted photon. A signal excess with a significance of 3.5 standard deviations is measured, constituting the first experimental evidence for this decay. In the range $796<m(K^{-}{\pi }^{+})<996\mathrm{MeV}/c^2$, the ratio $\mathcal{R}$ between the branching fractions of the signal decay and the favored ${\overline{B}}^0\to K^{-}{\pi }^{+}\gamma$ decay is measured to be $\mathcal{R}=(3.7\pm 1.2\pm 0.4)\times {10}^{-2}$ where the first uncertainty is statistical and the second is systematic. This measurement is consistent with the value predicted in the Standard Model. In the range $996<m(K^{-}{\pi }^{+})<1800\mathrm{MeV}/c^2$, the ratio $\mathcal{R}=(0.2\pm 2.7\pm 1.3)\times {10}^{-2}$ is measured.

In two-dimensional materials, strain provides effective means for tailoring electronic and optical properties. While uni- or biaxial strain has been widely implemented in monolayer semiconductors, deterministic control over atomic reconstruction and the resulting microscopic stacking textures in moiré heterostructures remains challenging. Here, we demonstrate the controlled formation of one-dimensional quantum wire arrays in ${\mathrm{MoSe}}_2\text{−}{\text{WSe}}_2$ heterobilayers through the interplay of uniaxial strain and atomic reconstruction. This process yields one-dimensional confinement of interlayer excitons within domain walls, producing near-unity linearly polarized emission due to confinement-induced symmetry breaking. The domain wall width and thereby the degree of exciton confinement can be precisely tuned via the interlayer twist angle. Under an out-of-plane electric field, the confined excitons exhibit Stark shifts exceeding 100 meV and fine-structure splitting modulations by up to a factor of 2. These findings establish strain tuning as a powerful route to realize designer moiré systems with programmable quantum properties, opening new opportunities for optoelectronic applications.

We investigate the response of the Rashba spin-orbit system to a time-periodic scalar potential, in order to determine whether an induced magnetization exists. We approach this by employing the Floquet Green’s function method within the Keldysh formalism, computing the nonequilibrium steady state of the system. We find that, even in the absence of an external magnetic field, the system evolves into a state with an oscillating magnetization density that is remarkably rich in structure. We provide a detailed physical interpretation of the results by performing a Fourier decomposition in nonlocal momentum space, which helps uncover the physical origin of the induced magnetic field in terms of Fermi surface spin polarization and the system’s dynamical character.