Understanding mechanisms of quantum ordering in strongly correlated systems remains a central challenge in condensed matter physics, with implications for designing novel quantum materials. Here, we investigate kinetic antiferromagnetism on a triangular lattice under an applied magnetic field, where spin polarons emerge as charge-magnon bound states with mutual attraction. Using large-scale diagrammatic Monte Carlo simulations, we show that this interaction drives high-temperature phase separation into charge- and magnon-rich regions, bordered by polarized Mott insulating voids. Spectral function analysis reveals a substantial energy correction from magnon interactions, indicating that these carrier-rich regions form a strongly bound charge-magnon liquid. These findings shed new light on recent experiments on ${\mathrm{MoTe}}_2/{\text{WSe}}_2$ moiré bilayers, underscoring kinetic magnetism as a unique pathway for strong intercarrier attraction and high-temperature quantum ordering, with potential applications in quantum materials.

We theoretically study dynamical excitonic condensates occurring in bilayers with an imposed chemical potential difference and in photodoped semiconductors. We show that optical spectroscopy can experimentally identify phase-trapped and phase-delocalized dynamical regimes of condensation. In the weak-bias regime, the trapped dynamics of the order parameter’s phase lead to an in-gap absorption line at a frequency almost independent of the bias voltage, while, for larger biases, the frequency of the spectral feature increases approximately linearly with bias. In both cases, there is a pronounced second-harmonic response. Close to the transition between the trapped and freely oscillating states, we find a strong response upon application of a weak electric probe field, compare the results to those found in a minimal model description for the dynamics of the order parameter’s phase, and analyze the limitations of the latter.

We investigate the measurement incompatibility of continuous-variable systems with infinite-dimensional Hilbert spaces under the influence of pure losses, a fundamental noise source in quantum optics, and a significant challenge for long-distance quantum communication. We show that loss channels with transmissivities less than $1/n$ make any set of $n$ measurements compatible. Additionally, we design a set of measurements that remains incompatible even under extreme losses, where the number of measurements in the set increases with the amount of loss. These measurements rely on on-off photodetectors and linear optics, making them feasible for implementation under realistic laboratory conditions. Furthermore, we demonstrate that no loss channel can break the incompatibility of all measurements. As a result, quantum steering remains achievable in the presence of pure loss.

Virtual excitations, inherent to ultrastrongly coupled light-matter systems, induce measurable modifications in system properties, offering a novel resource for quantum technologies. In this Letter, we demonstrate how these virtual excitations and their correlations can be harnessed to enhance precision measurements, without the need to extract them. Building on the paradigmatic Dicke model, which describes the interaction between an ensemble of two-level atoms and a single radiation mode, we propose a method to harness hybridized light-matter modes whose renormalized frequencies encode the effects of virtual excitations for quantum metrology. Remarkably, we find that, for a fixed squeezing parameter $\xi$, exploiting virtual squeezing through oscillator frequency shifts yields a quadratic enhancement in estimation precision—scaling as $\exp (4\xi )$—compared to the conventional $\exp (2\xi )$ scaling of real squeezed states. These results show that virtual excitations, though unobservable, can drive metrological performance beyond the standard quantum limit. Our approach establishes a broadly applicable framework for high-precision measurements across a wide class of ultrastrongly coupled quantum systems.

In the well-studied genus zero case, bases of d log integrands with integer leading singularities define Feynman integrals that automatically satisfy differential equations in canonical form. Such integrand bases can be constructed without input from the differential equations and without explicit involvement of dimensional regularization parameter $\epsilon$. We propose a generalization of this construction to genus one geometry arising from the appearance of elliptic curves. We argue that a particular choice of algebraic 1-forms of the second kind that avoids derivatives is crucial. We observe that the corresponding Feynman integrals satisfy a special form of differential equations that has not been previously reported, and that their solutions order by order in $\epsilon$ yield pure functions. We conjecture that our integrand-level construction universally leads to such differential equations.

The phase diagram of QCD probably exhibits a moat regime over a large region of temperature $T$ and chemical potential $\mu \ne 0$. A moat regime is characterized by quasiparticle moatons (pions) whose energy is minimal at nonzero spatial momentum. At $\mu \ne 0$, higher mass dimension operators play a critical role in a moat regime. At dimension six, there are nine possible gauge-invariant couplings between scalars and photons. For back-to-back dilepton production, only one operator contributes, which significantly enhances production near a moat threshold. This enhancement is an experimental signature of moatons.

Spinel oxides (${\mathrm{AB}}_2{\mathrm{O}}_4$) are promising optoelectronic materials due to their structural stability and tunable electronic properties. However, conventional strategies like doping, element substitution, and thermal treatment have achieved limited success in optimizing their performance. Here, we demonstrate that pressure-induced polyhedral reorganization triggers an indirect-to-direct band-gap transition driven by the enhanced hybridization of $\mathrm{O}\text{−}{p}_y$ orbitals in ${\mathrm{AB}}_2{\mathrm{O}}_4$ systems. The pressure-induced polyhedral reorganization also causes a connectivity shift from corner-sharing tetrahedra (${\mathrm{GaO}}_4$) to edge-sharing octahedra (${\mathrm{GaO}}_6$) in single-phase ${\mathrm{CaGa}}_2{\mathrm{O}}_4:{\mathrm{Bi}}^{3+}$ crystals, which tailors the electronic redistribution from isolated to quasi-1D ladderlike configurations. The optimized electronic structure leads to a concurrent enhancement in the photoresponsivity by $\sim 200\%$ and the emergence of an exotic white-light emission, which can be quenched to ambient conditions. These findings reveal how ${\mathrm{GaO}}_{\mathrm{x}}$ polyhedral reorganization directly governs electronic evolution in ${\mathrm{CaGa}}_2{\mathrm{O}}_4:{\mathrm{Bi}}^{3+}$, providing a new pathway to tailor electronic structures and optoelectronic properties through pressure-driven design that bypasses the limitations of traditional approaches.

We propose a singlet-only always-on gapless exchange (SAGE) spin qubit that encodes a single qubit in the spins of four electrons while allowing universal baseband control. While conventional exchange-only qubits suffer from magnetic-field-gradient-induced leakage and coherent errors due to local nuclear environments and variations in the $g$-factor, the SAGE qubit subspace is protected from coherent errors due to local magnetic field gradients, and leakage out of the computational subspace is energetically suppressed due to the exchange interactions between electrons being always on. Consequently, we find that when magnetic gradient noise dominates over charge noise, coherence times and single-qubit gate infidelities of the SAGE qubit improve by an order of magnitude compared to conventional exchange-only qubits. Moreover, using realistic parameters, two-qubit gates can be performed with a single interqubit exchange pulse with times comparable in duration to conventional exchange-only qubits but with a significantly simplified pulse sequence.

Quantum tunneling experiments have provided deep insights into basic excitations occurring as Green’s function poles in the realm of complex quantum matter. However, strongly correlated quantum materials also allow for Green’s functions zeros (GFZs) that may be seen as an antidote to the familiar poles and have so far largely eluded direct experimental study. Here, we propose and investigate theoretically how cotunneling through Mott insulators enables direct access to the shadow band structure of GFZs. In particular, we derive an effective Hamiltonian for the GFZ that is shown to govern the cotunneling amplitude and reveal fingerprints of many-body correlations clearly distinguishing the GFZ structure from the underlying free Bloch band structure of the system. Our perturbative analytical results are corroborated by numerical data in the framework of both exact diagonalization and matrix product state simulations for a one-dimensional model system consisting of a Su-Schrieffer-Heeger-Hubbard model coupled to two single-level quantum dots.

Electronic ferroelectrics, with polarization $\mathit{P}$ induced by strongly correlated charges, are expected to show ultrafast, huge, and flexible responses required in future optoelectronics. Although the challenges for ultrafast manipulation of such a polarization are ongoing, the expected advantages have been unclear. In this Letter, we demonstrate an unprecedentedly large increase by a factor of 2.7 in optical second harmonic generation at room temperature in the prototypical electronic ferroelectrics, the rare-earth ferrite ${\mathrm{LuFe}}_2{\mathrm{O}}_4$, by applying a terahertz field of $260\mathrm{kV}/\mathrm{cm}$. The transient anisotropy indicates that the direction of macroscopic polarization can be controlled three dimensionally on subpicosecond timescales, offering additional degrees of freedom in controlling polarization. Although the polarization response is in phase concerning the terahertz field, its sensitivity increased with delay, indicating that cooperative interactions among microscopic domains play an important role in the unprecedented response.

We develop a general formalism of the phonon magnetic moment by including the relaxation processes. We then identify the skew-scattering and side-jump contributions to the phonon magnetic moment originating from the nonadiabaticity, both of which are related to the nonlocal phonon Berry curvature and are in close analogy to those in the electronic Hall effect. All contributions of the phonon magnetic moment are exemplified in a honeycomb lattice, showing that the extrinsic contribution can be as important as the intrinsic one and that the resulting phonon angular momentum varies significantly across the Brillouin zone. Our Letter offers a systematic framework of the phonon chirality and paves the way for tuning the phonon magnetic moment through the nonadiabaticity.

Balanced network theory describes the dynamic state of randomly connected systems with intrinsic negative feedback, predicting the suppression of correlations as connectivity increases. We show that this weak-correlation universality holds broadly but breaks down in power-law networks where the largest out-degrees scale with system size. In such networks, residual correlations cross over to a regime that retains macroscopic fluctuations in the thermodynamic limit. Unlike Erdös-Rényi networks, the degree heterogeneity of power-law topologies amplifies coherent population-level fluctuations. Our results provide a theoretical foundation for the strong correlations observed in real-world networks with sparse and heterogeneous connectivity.

We propose a numerical method to efficiently compute quantum generating functions for a wide class of observables in one-dimensional quantum systems at high temperature. We obtain high-accuracy estimates for the cumulants and reconstruct full counting statistics from the quantum generating functions. We demonstrate its potential on spin $S=1/2$ anisotropic Heisenberg chain, where we can reach timescales hitherto inaccessible to state-of-the-art classical and quantum simulations. Our results challenge the conjecture of the Kardar-Parisi-Zhang universality for isotropic integrable quantum spin chains.

In this Letter, we motivate the fact that couplings between a scalar field and the standard model with strengths ${10}^{-6}(m_{\varphi }/\mathrm{eV}{)}^{-1/4}$ relative to gravity yield the total measured cosmological dark matter abundance over a broad mass range of ${10}^{-12}$ to ${10}^{14}\mathrm{eV}$. Remarkably, this result holds with minimal sensitivity to whether the scalar couples to electrons, photons, hadrons, or other particles at laboratory energy scales, thereby linking fifth force experiments to the search for dark matter.

The Quantum-Enhanced Space-Time (QUEST) experiment consists of a pair of colocated power recycled Michelson interferometers, each designed to have a broadband, shot-noise-limited displacement sensitivity of $2\times {10}^{-19}\mathrm{m}/\sqrt{\mathrm{Hz}}$ from 1 to 200 MHz. Here, we present the first results of QUEST, with a search up to 80 MHz, that set new upper limits on correlated length fluctuations from 13 to 80 MHz, constituting the first broadband constraints for a stochastic gravitational wave background at these frequencies. In a coincident observing run of ${10}^4\mathrm{s}$, the averaging of the cross-correlation spectra between the two interferometer signals resulted in a strain sensitivity of $3\times {10}^{-20}1/\sqrt{\mathrm{Hz}}$, making QUEST the most sensitive table-top interferometric system to date.