Similar to an electron in a solid, an impurity in an atomic Bose-Einstein condensate (BEC) is dressed by excitations from the medium, forming a polaron quasiparticle with modified properties. This impurity can also undergo chemical recombination with atoms from the BEC, a process resonantly enhanced when universal three-body Efimov bound states cross the continuum. To study the interplay between these phenomena, we use a Gaussian state variational method able to describe both Efimov physics and arbitrarily many excitations of the BEC. We show that the polaron cloud contributes to bound state formation, leading to a shift of the Efimov resonance to smaller interaction strengths. This shifted scattering resonance marks the onset of a polaronic instability towards the decay into large Efimov clusters and fast recombination, offering a remarkable example of chemistry in a quantum medium.

We use single photon detectors to probe the motional state of a superfluid ${}^4\mathrm{He}$ resonator of mass $\sim 1\mathrm{ng}$. The arrival times of Stokes and anti-Stokes photons (scattered by the resonator’s acoustic mode) are used to measure the resonator’s phonon coherences up to the fourth order. By postselecting on photon detection events, we also measure coherences in the resonator when $\le 3$ phonons have been added or subtracted. These measurements are found to be consistent with predictions that assume the acoustic mode to be in thermal equilibrium with a bath through a Markovian coupling.

The striking nonlinear effects exhibited by cavity QED systems make them a powerful tool in modern condensed matter and atomic physics. A recently discovered example is the quantized pumping of energy into a cavity by a strongly coupled, periodically driven spin. We uncover a remarkable feature of these energy pumps: they coherently translate, or boost, a quantum state of the cavity in the Fock basis. Current optical cavity and circuit QED experiments can realize the required Hamiltonian in a rotating frame. Boosting thus enables the preparation of highly excited nonclassical cavity states in near-term experiments.

Coordinate transformations are a versatile tool to mold the flow of light, enabling a host of astonishing phenomena such as optical cloaking with metamaterials. Moving away from the usual restriction that links isotropic materials with conformal transformations, we show how nonconformal distortions of optical space are intimately connected to the complex refractive index distribution of an isotropic non-Hermitian medium. Remarkably, this insight can be used to circumvent the material requirement of working with refractive indices below unity, which limits the applications of transformation optics. We apply our approach to design a broadband unidirectional dielectric cloak, which relies on nonconformal coordinate transformations to tailor the non-Hermitian refractive index profile around a cloaked object. Our insights bridge the fields of two-dimensional transformation optics and non-Hermitian photonics.

Nonlinear integrable equations serve as a foundation for nonlinear dynamics, and fractional equations are well known in anomalous diffusion. We connect these two fields by presenting the discovery of a new class of integrable fractional nonlinear evolution equations describing dispersive transport in fractional media. These equations can be constructed from nonlinear integrable equations using a widely generalizable mathematical process utilizing completeness relations, dispersion relations, and inverse scattering transform techniques. As examples, this general method is used to characterize fractional extensions to two physically relevant, pervasive integrable nonlinear equations: the Korteweg–deVries and nonlinear Schrödinger equations. These equations are shown to predict superdispersive transport of nondissipative solitons in fractional media.

Global gyrokinetic simulations of mesoscale reversed shear Alfven eigenmodes (RSAE) excited by energetic particles (EP) in fusion plasmas find that RSAE amplitude and EP transport are much higher than experimental levels at nonlinear saturation, but quickly diminish to very low levels after the saturation if background microturbulence is artificially suppressed. In contrast, in simulations coupling micro-meso scales, the RSAE amplitude and EP transport decrease drastically at the initial saturation but later increases to the experimental levels in the quasisteady state with bursty dynamics due to regulation by thermal ion temperature gradient (ITG) microturbulence. The quasisteady state EP transport is larger for a stronger microturbulence. The RSAE amplitude in the quasisteady state ITG-RSAE turbulence from gyrokinetic simulations, for the first time, agrees very well with experimental measurements.

We introduce a new class of out-of-equilibrium noninteracting topological phases: the topological space-time crystals. These are time-dependent quantum systems that do not have discrete spatial translation symmetries but instead are invariant under discrete space-time translations. Similar to the Floquet-Bloch systems, the space-time crystals can be described by a frequency-domain-enlarged Hamiltonian, which is used to classify topologically distinct space-time crystals. We show that these space-time crystals can be engineered from conventional crystals with an additional time-dependent drive that behaves like a traveling wave moving across the crystal. Interestingly, we are able to construct 1D and 2D examples of topological space-time crystals based on tight-binding models that involve only one orbital, in contrast to the two-orbital minimal models for any previously discovered static or Floquet topological phases with crystalline structures.

The Mn-based superconductor is rare owing to the strong magnetic pair-breaking effect. Here we report on the discovery of pressure-induced superconductivity in ${\mathrm{KMn}}_6{\mathrm{Bi}}_5$, which becomes the first ternary Mn-based superconductor. At ambient pressure, the quasi-one-dimensional ${\mathrm{KMn}}_6{\mathrm{Bi}}_5$ is an antiferromagnetic metal with $T_N\approx 75\mathrm{K}$. By measuring resistance and ac magnetic susceptibility under hydrostatic pressures up to 14.2 GPa in a cubic anvil cell apparatus, we find that its antiferromagnetic transition can be suppressed completely at a critical pressure of $P_c\approx 13\mathrm{GPa}$, around which bulk superconductivity emerges and displays a superconducting dome with the maximal $T_c^{\text{onset}}=9.3\mathrm{K}$ achieved at about 14 GPa. The close proximity of superconductivity to a magnetic instability in the temperature-pressure phase diagram of ${\mathrm{KMn}}_6{\mathrm{Bi}}_5$ and an unusually large ${\mu }_0{H}_{c2}(0)$ exceeding the Pauli paramagnetic limit suggests an unconventional magnetism-mediated paring mechanism. In contrast to the binary MnP, the flexibility of the crystal structure and chemical compositions in the ternary $A{\mathrm{Mn}}_6{\mathrm{Bi}}_5$ ($A=\text{alkali}$ metal) can open a new avenue for finding more Mn-based superconductors.

Two-dimensional electron gases (2DEGs) at the ${\mathrm{LaAlO}}_3/{\mathrm{SrTiO}}_3$ interface have attracted wide interest, and some exotic phenomena are observed, including 2D superconductivity, 2D magnetism, and diverse effects associated with Rashba spin-orbit coupling. Despite the intensive investigations, however, there are still hidden aspects that remain unexplored. For the first time, here we report on the circular photogalvanic effect (CPGE) for the oxide 2DEG. Spin polarized electrons are selectively excited by circular polarized light from the in-gap states of ${\mathrm{SrTiO}}_3$ to 2DEG and are converted into electric current via the mechanism of spin-momentum locking arising from Rashba spin-orbit coupling. Moreover, the CPGE can be effectively modified by the density and distribution of oxygen vacancies. This Letter presents an effective approach to generate and manipulate the spin polarized current, paving the way toward oxide spintronics.

Brillouin light spectroscopy is used to measure the elastic moduli of spherical polymer-grafted nanoparticle (GNP) melts as a function of chain length at fixed grafting density ($0.47\mathrm{chains}/{\mathrm{nm}}^2$) and nanoparticle radius (8 nm). While the moduli follow a rule of mixtures (Wood’s law) for long chains, they display enhanced elasticity and anomalous dissipation for graft chains $<100\mathrm{kDa}$. GNP melts with long polymers at high $\sigma$ have a dry zone near the GNP core, surrounded by a region where the grafts can interpenetrate with chain fragments from adjacent GNPs. We propose that the departures from Wood’s law for short chains are due to the effectively larger silica volume fraction in the region where sound propagates—this is caused by the short, interpenetrated chain fragments being pushed out of the way. We thus conclude that transport mechanisms (of gas, ions, sound, thermal phonons) in GNP melts are radically different if interpenetrated chain segments can be “pushed out of the way” or not. This provides a facile new means for manipulating the properties of these materials.

We propose a quantum-enhanced heat engine with entanglement. The key feature of our scheme is superabsorption, which facilitates enhanced energy absorption by entangled qubits. Whereas a conventional engine with $N$ separable qubits provides power with a scaling of $P=\mathrm{\Theta }(N)$, our engine uses superabsorption to provide power with a quantum scaling of $P=\mathrm{\Theta }(N^2)$. This quantum heat engine also exhibits a scaling advantage over classical ones composed of $N$-particle Langevin systems. Our work elucidates the quantum properties allowing for the enhancement of performance.

The ${}^{30}\mathrm{P}(p,\gamma ){}^{31}\mathrm{S}$ reaction plays an important role in understanding the nucleosynthesis of $A\ge 30$ nuclides in oxygen-neon novae. The Gaseous Detector with Germanium Tagging was used to measure ${}^{31}\mathrm{Cl}$ $\beta$-delayed proton decay through the key $J^{\pi }=3/2^{+}$, 260-keV resonance. The intensity $I_{\beta p}^{260}=8.3_{-0.9}^{+1.2}\times {10}^{-6}$ represents the weakest $\beta$-delayed, charged-particle emission ever measured below 400 keV, resulting in a proton branching ratio of ${\mathrm{\Gamma }}_p/\mathrm{\Gamma }=2.5_{-0.3}^{+0.4}\times {10}^{-4}$. By combining this measurement with shell-model calculations for ${\mathrm{\Gamma }}_{\gamma }$ and past work on other resonances, the total ${}^{30}\mathrm{P}(p,\gamma ){}^{31}\mathrm{S}$ rate has been determined with reduced uncertainty. The new rate has been used in hydrodynamic simulations to model the composition of nova ejecta, leading to a concrete prediction of ${}^{30}\mathrm{Si}$:${}^{28}\mathrm{Si}$ excesses in presolar nova grains and the calibration of nuclear thermometers.

The transition frequency of $(n,\ell )=(17,16)\to (16,15)$ in pionic helium-4 is calculated to an accuracy of 4 ppb (parts per billion), including relativistic and quantum electrodynamic corrections up to $O(R_{\infty }{\alpha }^5)$. Our calculations significantly improve the recent theoretical values [Hori et al., Phys. Rev. A 89, 042515 (2014)]. In addition, collisional effects between pionic helium and target helium on transition frequencies are estimated. Once measurements reach the ppb level, our Letter will improve the value of the ${\pi }^{-}$ mass by 2–3 orders of magnitude.

Photonic polarization qubits are widely used in quantum computation and quantum communication due to the robustness in transmission and the easy qubit manipulation. An integrated quantum memory for polarization qubits is a useful building block for large-scale integrated quantum networks. However, on-demand storing polarization qubits in an integrated quantum memory is a long-standing challenge due to the anisotropic absorption of solids and the polarization-dependent features of microstructures. Here we demonstrate a reliable on-demand quantum memory for polarization qubits, using a depressed-cladding waveguide fabricated in a ${{}^{151}\mathrm{Eu}}^{3+}:{\mathrm{Y}}_2{\mathrm{SiO}}_5$ crystal. The site-2 ${{}^{151}\mathrm{Eu}}^{3+}$ ions in ${\mathrm{Y}}_2{\mathrm{SiO}}_5$ crystal provides a near-uniform absorption for arbitrary polarization states and a new pump sequence is developed to prepare a wideband and enhanced absorption profile. A fidelity of $99.4\pm 0.6\%$ is obtained for the qubit storage process with an input of 0.32 photons per pulse, together with a storage bandwidth of 10 MHz. This reliable integrated quantum memory for polarization qubits reveals the potential for use in the construction of integrated quantum networks.

Fuzzy dark matter (FDM) made of ultralight bosonic particles is a viable alternative to cold dark matter with clearly distinguishable small-scale features in collapsed structures. On large scales, it behaves gravitationally like cold dark matter deviating only by a cutoff in the initial power spectrum and can be studied using $N$-body methods. In contrast, wave interference effects near the de Broglie scale result in new phenomena unique to FDM. Interfering modes in filaments and halos yield a stochastically oscillating granular structure which condenses into solitonic cores during halo formation. Investigating these highly nonlinear wave phenomena requires the spatially resolved numerical integration of the Schrödinger equation. In previous papers we introduced a hybrid zoom-in scheme that combines $N$-body methods to model the large-scale gravitational potential around and the mass accretion onto pre-selected halos with simulations of the Schrödinger-Poisson equation to capture wave-like effects inside these halos. In this work, we present a new, substantially improved reconstruction method for the wave function inside of previously collapsed structures. We demonstrate its capabilities with a deep zoom-in simulation of a well-studied sub-$L_{*}$-sized galactic halo from cosmological initial conditions. With a particle mass of $m=2.5\times {10}^{-22}\mathrm{eV}$ and halo mass $M_{\mathrm{vir}}=1.7\times {10}^{11}{M}_{\odot }$ in a $(60{\mathrm{h}}^{-1}\text{comoving Mpc}{)}^3$ cosmological box, it reaches an effective resolution of 20 comoving pc. This pushes the values of $m$ and $M$ accessible to simulations significantly closer to those relevant for studying galaxy evolution in the allowed range of FDM masses.

Collider experiments often exploit information about the quantum numbers of final state hadrons to maximize their sensitivity, with applications ranging from the use of tracking information (electric charge) for precision jet substructure measurements, to flavor tagging for nucleon structure studies. For such measurements, perturbative calculations in terms of quarks and gluons are insufficient, and nonperturbative track functions describing the energy fraction of a quark or gluon converted into a subset of hadrons (e.g., charged hadrons) must be incorporated. Unlike fragmentation functions, track functions describe correlations between hadrons and therefore satisfy complicated nonlinear evolution equations whose structure has so far eluded calculation beyond the leading order. In this Letter, we develop an understanding of track functions and their interplay with energy flow observables beyond the leading order, allowing them to be used in state-of-the-art perturbative calculations for the first time. We identify a shift symmetry in the evolution of their moments that fixes their structure, and we explicitly compute the evolution of the first three moments at next-to-leading order, allowing for the description of up to three-point energy correlations. We then calculate the two-point energy correlator on charged particles at $\mathcal{O}({\alpha }_s^2)$, illustrating explicitly that infrared singularities in perturbation theory are absorbed by moments of the track functions and also highlighting how these moments seamlessly interplay with modern techniques for perturbative calculations. Our results extend the boundaries of traditional perturbative QCD, enabling precision perturbative predictions for energy flow observables sensitive to the quantum numbers of hadronic states.

We propose a novel observable for the experimental detection of the gluon orbital angular momentum (OAM) that constitutes the proton spin sum rule. We consider longitudinal double spin asymmetry in exclusive dijet production in electron-proton scattering and demonstrate that the $\cos \varphi$ azimuthal angle correlation between the scattered electron and proton is a sensitive probe of the gluon OAM at small $x$ and its interplay with the gluon helicity. We also present a numerical estimate of the cross section for the kinematics of the Electron-Ion Collider.