The exploration of many-body problems stands at the vanguard of modern physics, presenting profound challenges alongside compelling opportunities. Recently, the non-Hermiticity featured with complex spectra has significantly expanded the landscape of many-body phenomena beyond the Hermitian paradigm. Most existing studies focus on the interplay between non-Hermiticity and many-body interactions, with the latter being Hermitian in isolation. Here, by integrating nonreciprocity, a key mechanism inducing non-Hermiticity, into two-body interactions, we analytically demonstrate how such interactions govern correlated pair and experimentally confirm our prediction in a phononic crystal simulator. Resulting phenomena, including the non-Hermitian inverse skin effect where the particles undergo synchronous motion as a bound pair and accumulate opposite to the dominant hopping direction, as well as the time cluster effect where two initially separate particles tend to cluster and last as a bound pair in the time domain, are unambiguously captured in airborne sound measurements. These findings experimentally unveil the unique phenomena driven by nonreciprocal many-body interactions, opening new pathways for controlled engineering in correlated systems.

Driven-dissipative quantum systems can undergo transitions from stationary to dynamical phases, reflecting the emergence of collective nonequilibrium behavior. We study such a transition in a Bose-Einstein condensate coupled to an optical cavity and develop a cavity-assisted Bragg spectroscopy technique to resolve its collective modes. We observe dissipation-induced synchronization at the quasiparticle level, where two rotonlike modes coalesce at an exceptional point. This reveals how dissipation microscopically drives collective dynamics and signals a precursor to a dynamical phase transition.

The ability to control solid-state quantum emitters is fundamental to advancing quantum technologies. The performance of these systems is fundamentally governed by their spin-dependent photodynamics, yet conventional control methods using cavities offer limited access to key nonradiative processes. Here we demonstrate that anisotropic lattice strain serves as a powerful tool for manipulating spin dynamics in solid-state systems. Under high pressure, giant shear strain gradients trigger a complete reversal of the intrinsic spin polarization, redirecting ground-state population from $|0⟩$ to $|\pm 1⟩$ manifold. We show that this reprogramming arises from strain-induced mixing of the NV center’s excited states and dramatic alteration of intersystem crossing, which we quantify through a combination of optomagnetic spectroscopy and a theoretical model that disentangles symmetry-preserving and symmetry-breaking strain contributions. Furthermore, the polarization reversal is spatially mapped with a transition region below 120 nm, illustrating sub-diffraction-limit control. Our Letter establishes strain engineering as a powerful tool for tailoring quantum emitter properties, opening avenues for programmable quantum light sources, high-density spin-based memory, and hybrid quantum photonic devices.

Motivated by the importance of dispersive readout in quantum technology, we study a prototypical dispersive readout setup that is probed by a squeezed vacuum in a time-reversal-symmetric fashion. To this end, we develop a full-counting-statistics framework for dispersive readout and analyze its measurement information, accompanied by a generalized mean-field approach suitable to deal with nonunitary dynamics. Distinct from conventional input-output theory, our full-counting-statistics approach enables the direct calculation of arbitrary-order cumulants for the measured cumulative (i.e., time-integrated) photonic distribution while maintaining applicability to nonlinear systems. The corresponding Fisher information exhibits an exponential dependence on the squeezing parameter and a robustness against residual nonlinearity, which can even approach the quantum Fisher information, setting an upper limit. This Letter introduces a conceptually streamlined and computationally efficient framework for continuous quantum measurements, making it well suited for widespread adoption in quantum technologies.

Non-line-of-sight (NLOS) imaging aims to recover hidden scenes outside the direct line of sight, holding great promise for broad applications. Despite notable advancements, current methods are restricted to the manipulation of temporal or spatial degree of light. Here, we propose and demonstrate polarization-based scanning-free NLOS single-pixel imaging. By manipulating the polarization states of light incident on the visible relay wall, the interaction between a rough surface and different polarization light produces diverse speckle patterns to illuminate the hidden scenes. The reflected light is captured by a single-pixel detector, enabling the recovery of the details of the hidden object. Experimental results show that the polarization speckle diversity effectively encodes the hidden scene, achieving high-fidelity scanning-free NLOS imaging with millimeter spatial resolution through a keyhole. Furthermore, a noninvasive calibration method is developed by utilizing the angular memory effect of polarization speckles. These results not only offer new insights for single-pixel imaging and NLOS imaging techniques, but also open a new venue for the development of diverse light field modulation for optical imaging and relevant approaches to practical applications.

The classical field description of “phonon spin” relies on the invariance of a continuous elastic field under infinitesimal rotation. However, a local “medium element” in the continuous field may contain large numbers of vibrational particles at microscopic level, like for complex lattices with many atoms in a unit cell. We find this causes the phonon spin in real materials no longer a simple sum of each atom rotation, but a collective interference of many atoms, since phonons are phase-coherent vibrational modes across unit cells. We demonstrate the collective interference phonon spin manifested as the dipole moment rotation (DMR) of charge-polarized unit cell, by deriving the infrared circular dichroism (ICD) with phonon-photon interaction in complex lattices. We compare the DMR with the local atom rotation without interference, and exemplify their distinct ICD spectrum in a chiral lattice model and two realistic chiral materials. Detectable ICD measurements are proposed in $\alpha$ quartz with Weyl phonon near $\mathrm{\Gamma }$ point. Our study underlies the important role of collective interference and uncovers a deeper insight of phonon spin in real materials with complex lattices.

The interplay between topological materials and local symmetry breaking yields diverse topological quantum phenomena. A notable example is the parity-anomalous semimetal (PAS), which hosts a single unpaired gapless Dirac cone with a half-integer quantized Hall conductivity. Here, we realize this phase in a magnetic topological sandwich structure by applying an in-plane magnetic field. This configuration aligns the magnetization of one surface in plane while preserving a partially out-of-plane magnetization on the opposite surface, satisfying the condition for a gapless surface state near the Fermi level on only one surface. Our key evidence is a distinctive two-stage evolution of the conductivity tensor $({\sigma }_{xy},{\sigma }_{xx})$. The first stage culminates in the PAS at the fixed point $[(e^2/2h),m(e^2/h)]$, where $m\approx 0.6$ corresponds to the minimal longitudinal conductivity of a single gapless Dirac cone of fermions on a two-dimensional lattice. This PAS state remains stabilized and is superposed with a gapped band flow in the second stage. This observation demonstrates that this state stabilized by the in-plane field resists localization—in contrast to conventional expectation for two-dimensional electron systems with broken time-reversal symmetry. The dynamic transition from an integer quantized Hall insulator to a half-integer quantized Hall semimetal establishes this material system as a versatile platform for exploring the physics of the parity anomaly.

The kinetic theory of soliton gases (SG) is used to develop a solvable model for wave-mean field interaction in integrable turbulence. The waves are stochastic soliton ensembles that scatter off a critically dense SG or soliton condensate—the mean field. The derived two-fluid kinetic-hydrodynamic equations admit exact solutions predicting an induced mean field and SG filtering. The obtained SG statistical moments agree with ensemble averages of numerical simulations. The developed theory readily generalizes, with applications in fluids, nonlinear optics, and condensed matter.

A fundamental task in quantum information science is to measure nonlinear functionals of quantum states, such as $\mathrm{Tr}({\rho }^{k}O)$. Intuitively, one expects that computing a $k$th order quantity generally requires $\mathcal{O}(k)$ copies of the state $\rho$, and we rigorously establish this lower bound under sample access to $\rho$. Surprisingly, this limitation can be overcome when one has purified access via a unitary that prepares a purification of $\rho$, a scenario naturally arising in quantum simulation and computation. In this setting, we find a different lower bound of $\mathrm{\Theta }(\sqrt{k})$ and present a quantum algorithm that achieves this bound, demonstrating a quadratic advantage over sample-based methods. The key technical innovation lies in a designed quantum algorithm and optimal polynomial approximation theory—specifically, Chebyshev polynomial approximations tailored to the boundary behavior of power functions. Our results unveil a fundamental distinction between sample and purified access to quantum states, with broad implications for estimating quantum entropies and quantum Fisher information, realizing quantum virtual distillation and cooling and evaluating other multiple nonlinear quantum observables with classical shadows.

I propose a novel laboratory search for dark photons based on radiation-safety monitoring at synchrotron radiation facilities, including NanoTerasu, SPring-8, the KEK Photon Factory, and the European Synchrotron Radiation Facility. Dark photons can be produced parasitically in undulators or via photon-mirror interactions and subsequently traverse optical systems and shielding. Taking into account quantum effects and the internal structure of undulators, mirrors, and detectors, I show that even a simple Geiger-Müller counter routinely used for radiation-safety monitoring can detect such dark photons outside the shielding and set the strongest purely laboratory limits on the kinetic mixing parameter, $\chi \lesssim 5\times {10}^{-6}$, in the mass range 1–50 eV. Since radiation safety is strictly regulated, the resulting limits provide robust and realistic constraints.

Multiple cosmological observations hint at neutrino self-interactions beyond the standard model, yet such interactions face severe constraints from terrestrial experiments. We resolve this tension by introducing a model where active neutrinos resonantly convert to self-interacting dark radiation after BBN but before CMB epoch. This exploits the fact that cosmological observables cannot distinguish between neutrinos and dark radiation with the same abundance and free-streaming properties. Our mechanism, based on a simple type-I seesaw framework along with a keV scale scalar mediator, achieves two objectives: (i) it produces strongly self-interacting dark radiation that imitates neutrino self-interactions favored by cosmological data, and (ii) it depletes the active neutrino energy density, relaxing cosmological neutrino mass bounds and easing the tension with neutrino oscillation data. The model naturally evades laboratory constraints through suppression of the neutrino-mediator coupling by the squared mass ratio of active and sterile neutrinos. We show that this scenario is favored over $\mathrm{\Lambda }\mathrm{CDM}$ by the combined Planck and DESI data, while being consistent with all other constraints. Our mechanism is testable in future laboratory probes of absolute neutrino mass and searches for sterile neutrinos.

We propose nucleon energy correlators (NECs) as a novel framework to probe electroweak light-quark dipole operators in deep inelastic scattering with an unpolarized nucleon. These operators encode chirality-flipping interactions, whose effects are usually quadratically suppressed in unpolarized cross sections. We construct a chiral-odd quark NEC that accesses quark transverse spin via azimuthal angle asymmetries in the energy flow of the target fragmentation region. These asymmetries serve as clean and powerful observables, enabling linear constraints on the quark dipole couplings. Unlike existing methods, our approach requires neither polarized nucleon beams nor final-state hadron identification, relying instead on fully inclusive calorimetric measurements. This Letter establishes one of the first applications of energy correlator observables to new physics searches and opens a promising direction for precision studies of chirality-flipping effects at electron-ion colliders.

The use of nuclear spins as physical sensing systems is disadvantaged by their low signal responsivity, particularly when compared to sensing techniques based on electron spins. This primarily results from the small nuclear gyromagnetic ratio and the difficulties in achieving high spin polarization. Here we develop a new approach to investigating the response of hyperpolarized molecular nuclear spins to magnetic fields and demonstrate orders-of-magnitude enhanced magnetic responsivity over state-of-the-art proton and Overhauser magnetometers. Using hyperpolarized molecules with proton spins, we report the realization of magnetic amplification in linear and nonlinear types. We further extend this amplification to hyperpolarized scalar-coupled multispin molecules and observe substantial magnetic amplification exceeding 10%. Moreover, we observe an anomalous amplification with dispersive frequency dependence that originates from magnetic interference effects. Our Letter highlights the potential of hyperpolarized molecular nuclear spins for use in a new class of quantum sensors, with promising applications in both applied and fundamental physics, including highly accurate absolute magnetometry and the exploration of axion–nucleon exotic interactions.