Entanglement between a single photon and a matter qubit is an indispensable resource for quantum repeater and quantum networks. With atomic ensembles, the entanglement creation probability is typically very low to inhibit high-order events. In this paper, we propose and experimentally realize a scheme that creates atom-photon entanglement with an intrinsic efficiency of 50%. We make use of Rydberg blockade to generate two collective excitations, lying in separate internal states. By introducing the momentum degree of freedom for the excitations, and interfering them via Raman coupling, we entangle the two excitations. Via retrieving one excitation, we create the entanglement between the polarization of a single photon and the momentum of the remaining atomic excitation, with a measured fidelity of 0.901(8). The retrieved optical field is verified to be genuine single photons. The realized entanglement may be employed to create entanglement between two distant nodes in a fully heralded way and with a much higher efficiency.

We elucidate the relation between out-of-time-order correlators (OTOCs) and quantum phase transitions via analytically studying the OTOC dynamics in a degenerate spectrum. Our method points to key ingredients to dynamically detect quantum phases via out-of-time-order correlators for a wide range of quantum phase transitions and explains the existing numerical results in the literature. We apply our method to a critical model, the $XXZ$ model that numerically confirms our predictions.

The dissipative dynamics of strongly interacting systems are often characterized by the timescale set by the inverse temperature ${\tau }_P\sim \hslash /(k_{B}T)$. We show that near a class of strongly interacting quantum critical points that arise in the infrared limit of translationally invariant holographic theories, there is a collective excitation (a quasinormal mode of the dual black hole spacetime) whose lifetime ${\tau }_{\mathrm{eq}}$ is parametrically longer than ${\tau }_P$: ${\tau }_{\mathrm{eq}}\gg T^{-1}$. The lifetime is enhanced due to its dependence on a dangerously irrelevant coupling that breaks the particle-hole symmetry and the invariance under Lorentz boosts of the quantum critical point. The thermal diffusivity (in units of the butterfly velocity) is anomalously large near the quantum critical point and is governed by ${\tau }_{\mathrm{eq}}$ rather than ${\tau }_P$. We conjecture that there exists a long-lived, propagating collective mode with velocity $v_s$, and in this case the relation $D=v_s^2{\tau }_{\mathrm{eq}}$ holds exactly in the limit $T{\tau }_{\mathrm{eq}}\gg 1$. While scale invariance is broken, a generalized scaling theory still holds provided that the dependence of observables on the dangerously irrelevant coupling is incorporated. Our work further underlines the connection between dangerously irrelevant deformations and slow equilibration.

We present the three-pion spectrum with maximal isospin in a finite volume determined from lattice QCD, including excited states in addition to the ground states across various irreducible representations at zero and nonzero total momentum. The required correlation functions, from which the spectrum is extracted, are computed using a newly implemented algorithm which speeds up the computation by more than an order of magnitude. On a subset of the data we extract a nonzero value of the three-pion threshold scattering amplitude using the $1/L$ expansion of the three-particle quantization condition, which consistently describes all states at zero total momentum. The finite-volume spectrum is publicly available to facilitate further explorations within the available three-particle finite-volume approaches.

We report results of a new technique to measure the electric dipole moment of ${}^{129}\mathrm{Xe}$ with ${}^3\mathrm{He}$ comagnetometry. Both species are polarized using spin-exchange optical pumping, transferred to a measurement cell, and transported into a magnetically shielded room, where SQUID magnetometers detect free precession in applied electric and magnetic fields. The result from a one week measurement campaign in 2017 and a 2.5 week campaign in 2018, combined with detailed study of systematic effects, is $d_A({}^{129}\mathrm{Xe})=(1.4\pm 6.6_{\mathrm{stat}}\pm 2.0_{\mathrm{syst}})\times {10}^{-28}e\mathrm{cm}$. This corresponds to an upper limit of $|d_A({}^{129}\mathrm{Xe})|<1.4\times {10}^{-27}e\mathrm{cm}$ (95% C.L.), a factor of 5 more sensitive than the limit set in 2001.

We numerically simulate two-dimensional, decaying elastoinertial turbulence using the finitely extensible, nonlinear, elastic spring model. We vary the polymer concentration over seven decades, and observe two turbulent elastoinertial regimes. In the weakly coupled regime only the small scale structures change, while in the strongly coupled regime all structures change. This regime is dominated by elastoinertial shock waves with drag reduction properties; i.e., the energy decay rate decreases when the polymer concentration increases.

Astrophysical jets are collimated, high-speed outflows observed to be natural features of celestial objects that spin and accrete matter. From protoplanetary nebula and young stellar objects to active galactic nuclei, common features suggest that universal mechanisms may lead to the remarkable straightness observed in many jets. Here we report observations from a new astrophysically relevant laboratory plasma jet experiment demonstrating the formation of long-lived, collimated, high aspect-ratio jets. The magnetized jets have strong helical shear flows and remain stable to instabilities over many growth times. These observations corroborate theoretical predictions that strong helical shear flows can stabilize current-driven instabilities in magnetically confined plasmas, solar prominences, and magnetically driven astrophysical jets in nature.

Surfaces enable useful functionalities for quantum systems, e.g., as interfaces to sensing targets, but often result in surface-induced decoherence where unpaired electron spins are common culprits. Here we show that the coherence time of a near-surface qubit is increased by coherent radio-frequency driving of surface electron spins, where we use a diamond nitrogen-vacancy (NV) center as a model qubit. This technique is complementary to other methods of suppressing decoherence and, importantly, requires no additional materials processing or control of the qubit. Further, by combining driving with the increased magnetic susceptibility of the double-quantum basis, we realize an overall fivefold sensitivity enhancement in NV magnetometry. Informed by our results, we discuss a path toward relaxation-limited coherence times for near-surface NV centers. The surface-spin driving technique presented here is broadly applicable to a wide variety of qubit platforms afflicted by surface-induced decoherence.

We identify a transient enhancement of the depolarizing field, leading to an unexpected quench of net polarization, during the growth of a prototypical metal-ferroelectric-metal epitaxial system made of ${\mathrm{BaTiO}}_3$ and ${\mathrm{SrRuO}}_3$. Reduced conductivity and, hence, charge screening efficiency in the early growth stage of the ${\mathrm{SrRuO}}_3$ top electrode promotes a breakdown of ferroelectric ${\mathrm{BaTiO}}_3$ into domains. We demonstrate how a thermal annealing procedure can recover the single-domain state. By tracking the polarization state in situ, using optical second harmonic generation, we bring new understanding to interface-related electrostatic effects in ferroelectric capacitors.

We experimentally and theoretically investigate the dynamics of inhibitory coupled self-driven oscillators on a star network in which a single central hub node is connected to $k$ peripheral arm nodes. The system consists of water-in-oil Belousov-Zhabotinsky $\sim 100\mu \mathrm{m}$ emulsion drops contained in storage wells etched in silicon wafers. We observed three dynamical attractors by varying the number of arms in the star graph and the coupling strength: (i) unlocked, uncorrelated phase shifts between all oscillators; (ii) locked, arm hubs synchronized in phase with a $k$-dependent phase shift between the arm and central hub; and (iii) center silent, a central hub stopped oscillating and the arm hubs oscillated without synchrony. We compare experiment to theory. For case (ii), we identified a logarithmic dependence of the phase shift on star degree, and were able to discriminate between contributions to the phase shift arising from star topology and oscillator chemistry.

We have studied topology and dynamics of quantum vortices in spin-2 Bose-Einstein condensates. By computationally modeling controllable braiding and fusion of these vortices, we have demonstrated that certain vortices in such spinor condensates behave as non-Abelian anyons. We identify these anyons as fluxon, chargeon, and dyon quasiparticles. The pertinent anyon models are defined by the quantum double of the underlying discrete non-Abelian symmetry group of the condensate ground state order parameter.

Modeling quantum devices is to find a model according to quantum theory that can explain the result of experiments in a quantum device. We find that usually we cannot correctly identify the model describing the actual physics of the device, regardless of the experimental effort, given a limited set of operations. According to sufficient conditions that we find, correctly reconstructing the model requires either a particular set of pure states and projective measurements or a set of evolution operators that can generate all unitary operators.

We present a method that allows the study of classical and quantum correlations in networks with causally independent parties, such as the scenario underlying entanglement swapping. By imposing relaxations of factorization constraints in a form compatible with semidefinite programing, it enables the use of the Navascués-Pironio-Acín hierarchy in complex quantum networks. We first show how the technique successfully identifies correlations not attainable in the entanglement-swapping scenario. Then we use it to show how the nonlocal power of measurements can be activated in a network: there exist measuring devices that, despite being unable to generate nonlocal correlations in the standard Bell scenario, provide a classical-quantum separation in an entanglement swapping configuration.

We introduce the idea of weakly coherent collisional models, where the elements of an environment interacting with a system of interest are prepared in states that are approximately thermal but have an amount of coherence proportional to a short system-environment interaction time in a scenario akin to well-known collisional models. We show that, in the continuous-time limit, the model allows for a clear formulation of the first and second laws of thermodynamics, which are modified to include a nontrivial contribution related to quantum coherence. Remarkably, we derive a bound showing that the degree of such coherence in the state of the elements of the environment represents a resource, which can be consumed to convert heat into an ordered (unitarylike) energy term in the system, even though no work is performed in the global dynamics. Our results therefore represent an instance where thermodynamics can be extended beyond thermal systems, opening the way for combining classical and quantum resources.

Among the prominent candidates for dark matter are bosonic fields with small scalar couplings to the standard-model particles. Several techniques are employed to search for such couplings, and the current best constraints are derived from tests of gravity or atomic probes. In experiments employing atoms, observables would arise from expected dark-matter-induced oscillations in the fundamental constants of nature. These studies are primarily sensitive to underlying particle masses below ${10}^{-14}\mathrm{eV}$. We present a method to search for fast oscillations of fundamental constants using atomic spectroscopy in cesium vapor. We demonstrate sensitivity to scalar interactions of dark matter associated with a particle mass in the range $8\times {10}^{-11}$ to $4\times {10}^{-7}\mathrm{eV}$. In this range our experiment yields constraints on such interactions, which within the framework of an astronomical-size dark matter structure are comparable with, or better than, those provided by experiments probing deviations from the law of gravity.

We propose a search strategy using the LHC as a photon collider to open sensitivity to scalar lepton (slepton $\tilde{\ell }$) production with masses around 15 to 60 GeV above that of neutralino dark matter ${\tilde{\chi }}_1^0$. This region is favored by relic abundance and muon $(g-2{)}_{\mu }$ arguments. However, conventional searches are hindered by the irreducible diboson background. We overcome this obstruction by measuring initial state kinematics and the missing momentum four-vector in proton-tagged ultraperipheral collisions using forward detectors. We demonstrate sensitivity beyond LEP for slepton masses of up to 200 GeV for $15\lesssim \mathrm{\Delta }m(\tilde{\ell },{\tilde{\chi }}_1^0)\lesssim 60\mathrm{GeV}$ with $100{\mathrm{fb}}^{-1}$ of 13 TeV proton collisions. We encourage the LHC collaborations to open this forward frontier for discovering new physics.

A recent experiment has observed the antiferromagnetic interaction between the ground state ${{}^{1}S}_0$ and the metastable state ${{}^{3}P}_0$ of ${}^{171}\mathrm{Yb}$ atoms, which are fermionic. This observation combined with the use of state-dependent optical lattices allows for quantum simulation of the Kondo model. We propose that in this Kondo simulator the anomalous temperature dependence of transport, namely, the Kondo effect, can be detected through quench dynamics triggered by the shift of a trap potential. For this purpose, we improve the numerical efficiency of the minimally entangled typical thermal states (METTSs) algorithm by applying additional Trotter gates. Using the improved METTSs algorithm, we compute the quench dynamics of the one-dimensional Kondo model at finite temperatures quasiexactly. We find that the center-of-mass motion exhibits a logarithmic suppression with a decrease in the temperature, which is a characteristic feature of the Kondo effect.