The phase of spins in the quasi-two-dimensional (q2D) XY model has emerged as a topic of significant interest across multiple subfields of physics. Conventional wisdom, rooted in the Mermin-Wagner theorem and supported by existing paradigms, asserts that true long-range (LR) order is prohibited in q2D systems with continuous symmetries and short-range (SR) interactions. In this Letter, we propose a strictly SR q2D XY model defined on a plane perpendicularly intersected by a group of parallel planes, where each plane consists of XY spins coupled via nearest-neighbor interactions. Through large-scale Monte Carlo simulations complemented by finite-size scaling analysis, we establish the complete phase diagram of the setup. A LR ordered phase emerges in the q2D model when the spins on the parallel planes develop a Berezinskii-Kosterlitz-Thouless critical phase. The LR ordered phase is anisotropic: true LR correlations develop exclusively along the direction of the intersection lines, while the perpendicular direction exhibits quasi-long-range order. Furthermore, the LR order exhibits Goldstone-mode physics. Our findings reveal a mechanism for stabilizing LR order in low-dimensional systems with continuous symmetries, thereby establishing a new platform for studying exotic superfluidity.

Critical quantum field theories occupy a central position in modern theoretical physics for their inherent universality stemming from long-range correlations. As an example, the Tomonaga-Luttinger liquid (TLL) describes a wealth of one-dimensional quantum systems at low temperatures. Its behavior is deeply rooted in the emergence of an effective Fermi sea, leading to power-law correlations and Friedel oscillations. A promising direction to realize systems exhibiting novel universal behavior beyond TLL is through the generalization of the underlying Fermi sea. In this Letter, we show that fractional Fermi seas with reduced occupancy arise in an integrable Bose gas driven out of equilibrium by cyclic changes in interactions across the full range of repulsive and attractive regimes. The correlation functions feature signatures of criticality incompatible with a conventional TLL, suggesting a novel critical phase. Our predictions, based on generalized hydrodynamics, are directly relevant to cold atoms.

We present a real-time quantum Monte Carlo algorithm that simulates the dynamics of open quantum systems by stochastically compressing and evolving the density matrix under both Markovian and non-Markovian master equations. Our algorithm uses population dynamics to continuously suppress the sign problem, preventing its accumulation throughout the evolution for a broad class of noisy-circuit Liouvillians of practical and experimental interest. We apply it to a variety of quantum circuits and demonstrate significant speedups and scaling improvements over state-of-the-art quantum trajectory methods and convergence to exact solutions even in non-Markovian regimes where trajectory methods fail. Our approach improves the efficiency of classical simulation of gate-based quantum computing, quantum annealing, and general open system dynamics.

Single nuclear spins in silicon are a promising resource for quantum technologies due to their long coherence times and excellent control fidelities. Qubits and qudits have been encoded on donor nuclei, with successful demonstrations of Bell states and quantum memories on the spin-${}^1{/}_2$ ${}^{31}\mathrm{P}$ and cat-qubits on the spin-${}^7{/}_2$ ${}^{123}\mathrm{Sb}$ nuclei. Isoelectronic nuclear spins coupled to gate-defined quantum dots, such as the naturally occurring ${}^{29}\mathrm{Si}$ isotope, possess no additional charge and allow for the coupled electron to be shuttled without destroying the nuclear spin coherence. Here, we demonstrate the coupling of a spin-${}^9{/}_2$ ${}^{73}\mathrm{Ge}$ nuclear spin to a gate-defined quantum dot in SiMOS via Pauli spin blockade readout using rf reflectometry. We observe the hyperfine interaction (HFI) to the coupled quantum dot electron and are able to tune it from 180 to 350 kHz, through the voltages applied to the lateral gate electrodes. This smaller HFI combined with the faster readout enable easier quantum nondemolition readout of the nuclear spin state. Thus, this work lays the foundation for future spin control experiments on the spin-${}^9{/}_2$ qudit as well as more advanced experiments such as entanglement distribution between distant nuclear spins or repeated weak measurements.

Fast coherent state transport is essential to quantum computation and quantum information processing. While an adiabatic transport of atomic qubits guarantees a high fidelity of the state preparation, it requires a long timescale that defies efficient quantum operations. Here, we propose an adaptable and fast bang-bang-bang protocol, utilizing a combination of forward- and backward-moving trap potentials, to expedite the coherent state transport. We further showcase the advantage of applying squeezed coherent state evolution under a deeper potential followed by a weaker one, where a design of symmetric squeezing potential transports promotes an even shorter timescale for genuine state preparation. Our protocols outperform conventional forward-moving-only methods, providing new insights and opportunities for rapid state transport and preparation, ultimately advancing the capabilities of quantum control and quantum operations.

It is shown that the Kerr metric represents the nonlinear superposition of self-dual and anti-self-dual Taub-Newman-Unti-Tamburino (NUT) instantons. This promotes the Newman-Janis algorithm to a rigorous derivation of the Kerr metric with a definite physical origin. In the same way, the Kerr-Newman and charged Kerr-Taub-NUT solutions are systems of Taub-NUT instantons and chiral dyons.

Directly probing light-quark Yukawa couplings and their flavor structure remains a major challenge due to their smallness and overwhelming QCD backgrounds. In this Letter, we propose a theoretical framework to access these couplings at lepton colliders through transverse spin dependent azimuthal modulations in dihadron fragmentation. These modulations arise from the interference between Higgs mediated and standard model amplitudes in $e^{-}{e}^{+}\to q\overline{q}Z$, producing angular structures that are linearly sensitive to the Yukawa couplings $y_q$, in contrast to conventional observables that scale as $y_q^2$. By combining channels with an identified accompanying single hadron, $h^{\prime }={\pi }^{\pm },K^{\pm }$, and $p/\overline{p}$, this approach cleanly disentangles the up- and down-quark Yukawa contributions, yielding typical limits at the $\mathcal{O}({10}^{-4}–{10}^{-3})$ level and establishing fragmentation dynamics as a novel and complementary probe of the Higgs flavor structure.

Nuclear mass is a key indicator of how the nuclear shell structure evolves. The recent mass measurement study of neutron-rich lanthanum isotopes [Jaries et al., Phys. Rev. Lett. 134, 042501 (2025)] reveals the presence of a distinct prominence in their two-neutron separation energies. However, its presence has been called into question based on the results of another mass determination [Liu, Ph.D. thesis, University of Notre Dame, 2025, 10.7274/28766600.v1.]. In this Letter, we report an effort to clarify these contradictory results through the use of the simultaneous mass-lifetime measurement of the neutron-rich lanthanum isotope ${}^{149}\mathrm{La}$ using a multireflection time-of-flight mass spectrograph combined with a $\beta$-TOF detector. The peak corresponding to a $\beta$-decaying state was observed in the time-of-flight spectra at a position of $221(6)\mathrm{keV}/{\mathrm{c}}^2$ lighter than the reported ${}^{149}\mathrm{La}$ mass in Jaries et al., but our measured result is in excellent agreement with the mass value reported in Liu. We have concluded that this peak is the ground state of ${}^{149}\mathrm{La}$. With this, the previously reported distinct prominence in the two-neutron separation energies disappears, while a new kink structure, similar to that in the cerium isotopes, appears. Comparison with theoretical models suggests that a nuclear shape transition from octupole deformation to another type of deformation occurs around $N=91$ and is likely the cause of this kink structure.

EXO-200 was a leading double beta decay experiment consisting of a single-phase, enriched liquid xenon time projection chamber filled with an admixture of 80.672% ${}^{136}\mathrm{Xe}$ and 19.098% ${}^{134}\mathrm{Xe}$. The detector operated at the Waste Isolation Pilot Plant between 2010 and 2018 and was designed to search for double beta decay of ${}^{136}\mathrm{Xe}$. Data were acquired in two phases separated by a period of detector upgrades. We report on the search for $0\nu \beta \beta$ and $2\nu \beta \beta$ decay of ${}^{134}\mathrm{Xe}$ with Phase II EXO-200 data, with median 90% CL exclusion sensitivity to half-life $T_{1/2}^{0\nu }\ge 3.7\times {10}^{23}\mathrm{yr}$ and $T_{1/2}^{2\nu }\ge 2.6\times {10}^{21}\mathrm{yr}$, respectively. No statistically significant signal is observed for either decay mode. We set a world-leading lower limit on the half-life of the neutrinoless decay mode of ${}^{134}\mathrm{Xe}$ of $T_{1/2}^{0\nu }\ge 8.7\times {10}^{23}$ (90% CL) and the second strongest constraint on the two-neutrino decay of $T_{1/2}^{2\nu }\ge 2.9\times {10}^{21}$ (90% CL), a threefold improvement over the EXO-200 Phase I measurement. New constraints are also set for the $2\nu \beta \beta$ and $0\nu \beta \beta$ decays of ${}^{134}\mathrm{Xe}$ to the lowest excited state of ${}^{134}\mathrm{Ba}$.

Emergent collective excitations constitute a hallmark of interacting quantum many-body systems, yet in solid-state platforms their study has been largely limited by the constraints of linear-response probes and by finite momentum resolution. We propose to overcome these limitations by combining the spatial resolution of ultracold atomic systems with the nonlinear probing capabilities of two-dimensional spectroscopy (2DS). As a concrete illustration, we analyze momentum-resolved 2DS of the quantum sine-Gordon model describing the low-energy dynamics of two weakly coupled one-dimensional Bose-Einstein condensates. This approach reveals distinctive many-body signatures, most notably asymmetric cross-peaks reflecting the interplay between isolated ($B_2$ breather) and continuum ($B_1$ pair) modes. The protocol further enables direct characterization of anharmonicity and disorder, establishing momentum-resolved 2DS as both a powerful diagnostic for quantum simulators and a versatile probe of correlated quantum matter.

A quantum-mechanical description is presented for the three-body physics of shielded dipolar molecules, including a prediction of observable Efimov physics. Despite the anisotropic and long-range nature of the interaction, shielding enables a regime in which universality emerges already at the two-body level and extends to the three-body sector, where Efimov physics emerges. On the negative side of the scattering-length resonance, computed trimer binding energies display the characteristic scaling expected for Efimov states. Finally, the sudden approximation can be used to create trimer bound states, starting from positive energy trap states as a way to create or detect these molecular trimers. Moreover, the three-body parameter expressed in dipolar units is found to be universal.

Scaling quantum computers to large sizes requires the implementation of many parallel qubit readouts. Here we present an ultrastable superconducting-qubit readout method using the multitone self-phase-referenced Pound-Drever-Hall (PDH) technique, originally developed for use with optical cavities. In this work, we benchmark PDH readout of a single transmon qubit, using room-temperature heterodyne detection of all tones to reconstruct the PDH signal. We demonstrate that PDH qubit readout is insensitive to microwave phase drift, displaying 0.73° phase stability over 2 hours, and capable of single-shot readout in the presence of phase errors exceeding the phase shift induced by the qubit state. We show that the PDH sideband tones do not cause unwanted measurement-induced state transitions for a transmon qubit, leading to a potential signal enhancement of at least 14 dB.

Although strain gradients hold great promise for tailoring emergent functionalities, their flexible global control remains a fundamental challenge. Here, we address this concern in ${\mathrm{PbTiO}}_3$ under biaxial tensile strain by uncovering the spontaneous appearance of strain gradients and 90° ferroelectric domain walls and demonstrating their electric control. Combining symmetry analysis and first-principles calculations, we reveal hidden polar-acoustic instabilities within conventionally assumed ground states. We further demonstrate that the trilinear coupling among the modulated polar mode, acoustic mode with modulated strain, and uniform polar mode spontaneously stabilizes a lower-energy $a_1/a_2$ 90° domain structure with $Pmc{2}_1$ symmetry and intrinsic strain gradients. Remarkably, we discover similar polar-acoustic coupling that governs both the $c/a$ domain patterns and their dramatic piezoelectric enhancement. Leveraging these strong lattice couplings, we develop a unified framework for describing and electrically switching spatially varying strain and polarization fields. Our Letter resolves long-standing cross-scale discrepancies in the strain phase diagrams of ${\mathrm{PbTiO}}_3$, reveals a new phonon-mediated mechanism for giant piezoelectricity, and provides the atomistic foundation for the electrical control of strain gradients and domain walls.

The orbital motion of chargeless bosons, unlike that of electrons, does not generate a magnetic moment and thus cannot directly interact with magnetic fields. To formulate the orbital angular momentum (OAM) of magnons, we first identify its proper conjugate variable by considering the Aharonov-Casher effect, which gives rise to a virtual perturbation to the equilibrium state, allowing us to calculate the magnon OAM as a virtual response to an infinitesimal electric field divergence. At finite temperatures, both self-rotation and topological contributions to the magnon OAM are explicitly derived, analogous to their electronic counterpart but with the correct bosonic statistics. In a two-dimensional honeycomb lattice, we show that the Dzyaloshinskii-Moriya interaction induces a large magnon OAM in both the ferromagnetic and antiferromagnetic phases. Our formalism can be generalized to other chargeless bosons with intrinsic spin.

We predict an anomalous thermally activated superradiance in molecular aggregates within polaritonic environments. In contrast to free space, the collective emission is enhanced when either the exciton-phonon coupling or the temperature increases. This counterintuitive phenomenon is captured by a microscopic theory that combines macroscopic quantum electrodynamics with a modified polaron quantum master equation approach, revealing a nontrivial interplay among excitons, phonons, and polaritons.

Fission and fusion of lipid membranes are ubiquitous shape transformations in living cells, necessary for maintaining the shape of organelles and enabling a host of transport processes between them. These topology-changing events involve curvature-elastic free energy changes proportional to the Gaussian curvature modulus, $\overline{\kappa }$. However, precisely because of its topological nature, the value of this modulus is exceptionally hard to determine. Here we propose a novel method to computationally determine $\overline{\kappa }$ that involves simulating triply periodic minimal surfaces. We measure their excess curvature energy $E$ and infer the associated free energy $F$ via a thermodynamic argument that rests on the strong temperature dependence of $E$ and the relatively weak temperature dependence of $E/F$. Our approach is unique in that it circumvents the complications arising in alternative procedures that require an open membrane edge to break the constraints of the Gauss-Bonnet theorem. As an illustration, we determine $\overline{\kappa }$ for a coarse-grained lipid model over a range of temperatures and lipid shapes. We show that the observed changes of both the Gaussian curvature modulus as well as its ratio to the ordinary bending modulus follow widely held expectations.

Extended, localized, and critical states form the three elementary classes of eigenstates underlying Anderson localization. While phases involving extended and localized states are widely studied, experimental realization of critical phases, particularly those where critical states coexist with others, remains a challenge. Here, we report to realize five distinct localization phases: extended, localized, critical, extended-localized mixed, and critical-localized mixed, in a one-dimensional Floquet lattice with quasiperiodic hopping amplitudes and on-site potentials. These phases are identified through characteristic spatiotemporal dynamics, supported by mutually consistent experimental observations and theoretical analysis. Our findings establish a unified experimental framework for systematic studies of localization transitions, mobility edges, and criticality in driven quasiperiodic systems.

We show that general relativity and other geometrical theories can be viewed as a degenerate Otto cycle with only heat-exchange legs in emergent gravity. Including work-producing legs yields controlled violations of local Lorentz invariance and energy-momentum conservation, which produce late-time cosmological acceleration. Implications for the cosmological constant problem, structure formation, and local observations are discussed.