We report the first detection of coherent elastic neutrino-nucleus scattering (CEvNS) on natural germanium, measured at the Spallation Neutron Source at Oak Ridge National Laboratory. The Ge-Mini detector of the COHERENT collaboration employs large-mass, low-noise, high-purity germanium spectrometers, enabling excellent energy resolution, and an analysis threshold of 1.5 keV electron-equivalent ionization energy. We observe an on-beam excess of ${20.6}_{-6.3}^{+7.1}$ counts with a total exposure of 10.22 GWhkg, and we reject the no-CEvNS hypothesis with $3.9\sigma$ significance. The result agrees with the predicted standard model of particle physics signal rate within $2\sigma$.

The $Z_2$-gauged XY model is of long-standing interest both in the context of nematic order, and the study of fractionalization and superconductivity. This Letter presents heuristic arguments that no deconfinement of the XY field occurs in this model and presents results of a large-scale Monte Carlo simulations on a cubic lattice that are consistent with this conclusion. The correlation radius determining the confinement is found to be growing rapidly as a function of the parameters in the phase featuring the nematic order. Thus, mesoscopic properties of the system can mimic deconfinement with high accuracy in some part of the phase diagram.

Au(111) with its famous surface reconstruction has led to many studies, but its subsurface structure has never been determined. Here, we study the Au(677) surface which is a vicinal of Au(111) with steps and surface reconstruction, showing an array of surface dislocations. By using surface x-ray diffraction and atomistic simulations, we are able to quantitatively determine the complete structure and the strain fields associated with the surface reconstruction described in terms of surface dislocations, especially a stair-rod dislocation lying parallel to the surface step. The stair-rod dislocation strain field adds up to the one due to the step dipole, explaining the extraordinary regularity of the step array. We can also give new insights on the strain field associated with the Au(111) surface discommensuration lines ($22\times \sqrt{3}$ reconstruction) and find that it penetrates deeply into the bulk, in contrast with commonly used surface reconstruction models.

We characterize the possible moments of entropy production for overdamped stationary Markov processes. We find a general formulation of the problem, and derive a new necessary condition relating the second and third moments. We determine all possible first, second, and third moments of entropy production for a white noise process. As a consequence, we obtain a lower bound for the skewness of the current fluctuations in dissipative devices such as transistors, thereby demonstrating that the Gaussianity assumption widely used, e.g., in electronic engineering is thermodynamically inconsistent.

Unlike in crystals, it is difficult to trace emergent material properties of amorphous solids to their underlying structure. Nevertheless, one can tune features of a disordered spring network, ranging from bulk elastic constants to specific allosteric responses, through highly precise alterations of the structure. This has been understood through the notion of independent bond-level response—the observation that, in many cases, different springs have different effects on different properties. While this idea has motivated inverse design in numerous contexts, it has not been formalized and quantified in a general context that not just informs but enables and predicts inverse design. Here, we show how to quantify independent response by linearizing the simultaneous change in multiple emergent features, and introduce the much stronger notion of fully independent response. Remarkably, we find that the mechanical properties of disordered solids are always fully independent across a wide array of scenarios, regardless of the target features, tunable parameters, system size, dimensionality, and class of interactions. Furthermore, our formulation quantifies the susceptibility of features to parameter changes, which is correlated with the maximum linear tunability. We also demonstrate the implications for multifeature inverse design beyond the linear regime. These results formalize our understanding of a key fundamental difference between ordered and disordered solids while also creating a practical tool to both understand and perform inverse design.

Active nematics exhibit spontaneous flows through a well-known linear instability of the uniformly aligned quiescent state. Here, we show that even a linearly stable uniform state can experience a nonlinear instability, resulting in a discontinuous transition to spontaneous flows. In this case, quiescent and flowing states may coexist. Through a weakly nonlinear analysis and a numerical study, we trace the bifurcation diagram of striped patterns and show that the underlying pitchfork bifurcation switches from supercritical (continuous) to subcritical (discontinuous) by varying the flow-alignment parameter. We predict that the discontinuous spontaneous flow transition occurs for a wide range of parameters, including systems of contractile flow-aligning rods. Our predictions are relevant to active nematic turbulence and can potentially be tested in experiments on either cell layers or active cytoskeletal suspensions.

We report the experimental observation of spin and density modes in a binary mixture of superfluids of light. A miscible Bose-Bose mixture with repulsive interactions is realized by propagating the two circular polarization components of a laser through a nonlinear hot atomic vapor in the paraxial limit. By controlling the intensity and phase of both polarizations, we selectively excite the fundamental modes of the mixture. Using a Bragg-like spectroscopy technique, we measure the dispersion relation and identify two distinct branches with different sound velocities, corresponding to the spin and density modes. At high photon density, we observe a crossing of these branches, resulting from higher order nonlinear terms, linked to the saturation of the medium’s nonlinearity.

The relationship between antiferromagnetic (AFM) spin fluctuations (SF), nematic fluctuations, and superconductivity (SC) has been central to understanding the pairing mechanism in iron-based superconductors (IBSCs). Iron chalcogenides, which hold the simplest crystal structure in IBSCs, provide a good platform to investigate the relationship. Here, we report ${}^{77}\mathrm{Se}$ and ${}^{125}\mathrm{Te}$ nuclear magnetic resonance studies of ${\mathrm{FeSe}}_{0.47}{\mathrm{Te}}_{0.53}$, which is located close to a nematic quantum critical point (QCP), under pressures up to 1.35 GPa. Both the superconducting critical temperature and AFMSF were found to be enhanced under pressure, which suggests a correlation between SC and AFMSF in ${\mathrm{FeSe}}_{0.47}{\mathrm{Te}}_{0.53}$. However, the contribution of AFMSF to SC in ${\mathrm{FeSe}}_{0.47}{\mathrm{Te}}_{0.53}$ was found to be much less compared to that in ${\mathrm{FeSe}}_{1-x}{\mathrm{S}}_x$, suggesting that nematic fluctuations play a dominant role in the SC in ${\mathrm{FeSe}}_{1-x}{\mathrm{Te}}_x$ around the nematic QCP.

Anomalous thermal relaxation is ubiquitous in nonequilibrium statistical mechanics. An emblematic example of this is the Mpemba effect, where an initially “hot” system cools faster than an initially “cooler” one. This effect has recently been studied in a variety of different classical and quantum settings. In this Letter, we find a novel signature of the Mpemba effect in the context of quantum batteries. We identify situations where batteries in higher charge states can discharge faster than less charged states. Specifically, we consider a quantum battery encoded in a single bosonic mode that is charged using unitary Gaussian operations. We show that the ergotropy, used here as a dynamical indicator of the energy stored in the battery, can be recast as a phase space relative entropy between the system’s state and the unitarily connected passive state, at each time. Our formalism allows us to compute the ergotropy analytically under dissipative dynamics and allows us to understand the conditions which give rise to a Mpemba effect. We also find situations where two batteries charged to the same value using different operations can discharge at different rates.

Since its rediscovery in the twentieth century, the Mpemba effect, where a far-from-equilibrium state may relax faster than a state closer to equilibrium, has been extensively studied in classical systems and has recently received attention in quantum systems. Many theories explaining this counter-intuitive behavior in classical systems rely on memory effects. However, in quantum systems, the relation between the Mpemba effect and memory has remained unexplored. In this Letter, we consider general non-Markovian open quantum systems and reveal new classes of quantum Mpemba effects, with no analog in Markovian quantum dynamics. Generically, open quantum dynamics possess a finite memory time and a unique steady state. Because of non-Markovian dynamics, even if the system is initialized in the steady state it can take a long time to relax back. We find other initial states that reach the steady state much faster. Most notably, we demonstrate that there can be an initial state in which the system reaches the steady state within the finite memory time itself, giving the fastest possible relaxation to stationarity. We verify the effect for quantum dot systems coupled to electronic reservoirs in equilibrium and nonequilibrium setups at weak, intermediate and strong coupling. Our Letter provides new insights into the rich physics underlying accelerated relaxation in quantum systems.

We develop a method to calculate generic time-dependent correlation functions for inhomogeneous quantum quenches in ($1+1$)-dimensional conformal field theory (CFT) induced by sudden Hamiltonian deformations that modulate the energy density inhomogeneously. Our Letter particularly focuses on the effects of spatial boundaries, which have remained unresolved by previous analytical methods. For generic postquench Hamiltonian, we develop a generic method to calculate the correlations by mirroring the system, which otherwise are Euclidean path integrals in complicated spacetime geometries difficult to calculate. On the other hand, for a special class of inhomogeneous postquench Hamiltonians, including the Möbius and sine-square-deformation Hamiltonians, we show that the quantum quenches exhibit simple boundary effects calculable from Euclidean path integrals in a straightforward strip spacetime geometry. Applying our method to the time evolution of entanglement entropy, we find that, for generic cases, the entanglement entropy shows discontinuities (shockwave fronts) propagating from the boundaries. In contrast, such discontinuities are absent in cases with simple boundary effects. We verify that our generic CFT formula matches well with numerical calculations from free-fermion tight-binding models for various quench scenarios.

Encoding quantum information via time-bin entangled states has had a profound impact on the development of quantum communications. However, dispersive propagation limits their achievable transmission distances. Here we describe a regime for nonlocal dispersion cancellation where the sum of arrival times of photons undergoing identical dispersion remains highly correlated. We exploit this effect to mitigate dispersive effects in a quantum key distribution fiber link, allowing an increase in the secret key rate by over a factor of 5 after 80 km of optical fiber dispersion.

The Wineland parameter aims at detecting metrologically useful entangled states, called spin-squeezed states, from expectations and variances of total angular momenta. However, efficient strategies for estimating this parameter in practice have yet to be determined and, in particular, the effects of a finite number of measurements remain insufficiently addressed. We formulate the detection of spin squeezing as a hypothesis-testing problem, where the null hypothesis assumes that the experimental data can be explained by non-spin-squeezed states. Within this framework, we derive upper and lower bounds on the $p$ value to quantify the statistical evidence against the null hypothesis. By applying our statistical test to data obtained in multiple experiments, we are unable to reject the hypothesis that non-spin-squeezed states were measured with a $p$ value of 5% or less in most cases. We also find an explicit non-spin-squeezed state according to the Wineland parameter reproducing most of the observed results with a $p$ value exceeding 5%. More generally, our results provide a rigorous method to establish robust statistical evidence of spin squeezing from the Wineland parameter in future experiments, accounting for finite statistics.

I explore the limitations on the capacity of a relativistic channel to transmit power and information that arise because of the finiteness of the transverse speed of light. As a model system, I consider a rope constructed from a fundamental string, for which relativistic invariance is built in. By wiggling one end of the string, both power and information may be transmitted to the other end. I argue that even though an unbounded amount of power and information may be traveling down the string, there is a bound on how much may be transmitted. Further, I conjecture that the two kinds of channel capacity—power and information—interfere with each other, so that the only way to transmit the maximum amount of power is to send no information, and vice versa.

The current projected sensitivity on the electromagnetic coupling ${\alpha }_{\mathrm{em}}(m_Z^2)$ represents a bottleneck for the precision electroweak program at FCC-ee. We propose a novel methodology to extract this coupling directly from $Z$-pole data. By comparing the differential distribution of electrons, muons, and positrons in the forward region, the approach achieves a projected statistical sensitivity below the ${10}^{-5}$ level, representing a significant improvement over other methods. We assess the impact of leading parametric uncertainties including that of the top quark mass.

We accomplish for the first time the two-loop computation of the leading-twist contribution to the pion form factor by employing the effective field theory formalism rigorously. The next-to-next-to-leading-order hard function is determined by evaluating the appropriate five-point QCD amplitude with the modern multiloop technique and by implementing the ultraviolet renormalization and infrared subtractions in the presence of evanescent operators. The yielding two-loop correction to this fundamental quantity turns out to be numerically significant at experimentally accessible momentum transfers. We further demonstrate that the newly computed two-loop QCD correction is highly beneficial for an improved determination of the leading-twist pion distribution amplitude.

The neutron-neutron ($nn$) correlation function has been measured in $25\mathrm{MeV}/\mathrm{u}{}^{124}\mathrm{Sn}+{}^{124}\mathrm{Sn}$ reactions. Using the Lednický-Lyuboshitz approach, the $nn$ scattering length and effective range ($f_0^{nn}$, $d_0^{nn}$), as well as the reduced space-time size $R^{(0)}$ of the neutron emission source are simultaneously extracted as (${18.9}_{-1.2}^{+1.3}\mathrm{fm}$, ${1.9}_{-1.0}^{+1.3}\mathrm{fm}$) and $4.12\pm 0.12\mathrm{fm}$, respectively. The measured $nn$ scattering length is consistent with the results obtained in the low-energy scattering ${}^2\mathrm{H}({\pi }^{-},\gamma )2n$, indicating heavy-ion collisions can serve as an effective approach for measuring $nn$ interactions and further investigating the charge symmetry breaking of nuclear force. The space-time size extracted from momentum-gated correlation functions exhibits clear dependence on the pair momentum, with $R^{(0)}=2.8\pm 0.1\mathrm{fm}$ and $4.9\pm 0.2\mathrm{fm}$ being determined for the high and low momentum neutrons, respectively.

We report on the experimental observation of classical Brownian motion in momentum space by a Bose-Einstein condensate (BEC) of rubidium atoms prepared in a hexagonal optical lattice. Upon suddenly increasing the effective atomic mass, the BEC as a whole behaves as a classical rigid body with its center of mass receiving random momentum kicks by a Langevin force arising from atom loss and interactions with the surrounding thermal cloud. Physically, this amounts to selective heating of the BEC center-of-mass degree of freedom by a sudden quench, while with regard to the relative coordinates, the BEC is stabilized by repulsive atomic interactions, and its internal dynamics is suppressed by forced evaporative cooling induced by atom loss. A phenomenological theory is developed that well explains the experimental data quantitatively.

Generating and interfering nonclassical states of light is fundamental to optical quantum information science and technology. Quantum photonic integrated circuits provide one pathway towards scalability by combining nonlinear sources of nonclassical light and programmable circuits in centimeter-scale devices. The key requirements for quantum applications include efficient generation of indistinguishable photon-pairs and high-visibility programmable quantum interference. Here, we demonstrate a lithium niobate-on-insulator (LNOI) integrated photonic circuit that generates a two-photon path-entangled state, and a programmable interferometer for quantum interference. We generate entangled photons with $\sim 2.3\times {10}^8\mathrm{pairs}/\mathrm{s}/\mathrm{mW}$ brightness and perform quantum interference experiments on the chip with $96.8\pm 3.6\%$ visibility. LNOI is an emerging photonics technology that has revolutionized high-speed modulators and efficient frequency conversion. Our results provide a path towards large-scale integrated quantum photonics including efficient photon-pair generation and programmable circuits for applications such as boson sampling and quantum communications.