Resource theories can be used to formalize the quantification and manipulation of resources in quantum information processing such as entanglement, asymmetry and coherence of quantum states, and incompatibility of quantum measurements. Given a certain state or measurement, one can ask whether there is a task in which it performs better than any resourceless state or measurement. Using conic programming, we prove that any general robustness measure (with respect to a convex set of free states or measurements) can be seen as a quantifier of such outperformance in some discrimination task. We apply the technique to various examples, e.g., joint measurability, positive operator valued measures simulable by projective measurements, and state assemblages preparable with a given Schmidt number.

We study the process of assisted work distillation. This scenario arises when two parties share a bipartite quantum state ${\rho }_{AB}$ and their task is to locally distill the optimal amount of work when one party is restricted to thermal operations, whereas the other can perform general quantum operations and they are allowed to communicate classically. We demonstrate that this question is intimately related to the distillation of classical and quantum correlations. In particular, we show that the advantage of one party performing global measurements over many copies of ${\rho }_{AB}$ is related to the nonadditivity of the entanglement of formation. We also show that there may exist work bound in the quantum correlations of the state that is only extractable under the wider class of local Gibbs-preserving operations.

The first measurement of heavy-flavor production by the LHCb experiment in its fixed-target mode is presented. The production of $J/\psi$ and $D^0$ mesons is studied with beams of protons of different energies colliding with gaseous targets of helium and argon with nucleon-nucleon center-of-mass energies of $\sqrt{s_{\mathrm{NN}}}=86.6$ and 110.4 GeV, respectively. The $J/\psi$ and $D^0$ production cross sections in $p\mathrm{He}$ collisions in the rapidity range [2, 4.6] are found to be ${\sigma }_{J/\psi }=652\pm 33(\text{stat})\pm 42(\text{syst})\mathrm{nb}/\text{nucleon}$ and ${\sigma }_{D^0}=80.8\pm 2.4(\text{stat})\pm 6.3(\text{syst})\mu \mathrm{b}/\text{nucleon}$, where the first uncertainty is statistical and the second is systematic. No evidence for a substantial intrinsic charm content of the nucleon is observed in the large Bjorken-$x$ region.

The propagation front of a crack generates large strain gradients and it is therefore a strong source of gradient-induced polarization (flexoelectricity). Herein, we demonstrate that, in piezoelectric materials, a consequence of flexoelectricity is that crack propagation is helped or hindered depending on whether it is parallel or antiparallel to the piezoelectric polar axis. The discovery of crack propagation asymmetry proves that fracture physics cannot be assumed to be symmetric in polar materials, and indicates that flexoelectricity should be incorporated in any realistic model.

The controlled generation and the protection of entanglement is key to quantum simulation and quantum computation. At the single-mode level, protocols based on photonic cat states hold strong promise as they present unprecedentedly long-lived coherence and may be combined with powerful error correction schemes. Here, we demonstrate that robust ensembles of “many-body photonic cat states” can be generated in a Bose-Hubbard model with pair hopping via a spontaneous $U(1)$ symmetry-breaking mechanism. We identify a parameter region where the ground state is a massively degenerate manifold consisting of local cat states which are factorized throughout the lattice and whose conserved individual parities can be used to make a register of qubits. This phenomenology occurs for arbitrary system sizes or geometries, as soon as long-range order is established, and it extends to driven-dissipative conditions. In the thermodynamic limit, it is related to a Mott insulator to pair-superfluid phase transition.

State of the art quantum sensing experiments targeting frequency measurements or frequency addressing of nuclear spins require one to drive the probe system at the targeted frequency. In addition, there is a substantial advantage to performing these experiments in the regime of high magnetic fields, in which the Larmor frequency of the measured spins is large. In this scenario we are confronted with a natural challenge of controlling a target system with a very high frequency when the probe system cannot be set to resonance with the target frequency. In this contribution we present a set of protocols that are capable of confronting this challenge, even at large frequency mismatches between the probe system and the target system, both for polarization and for quantum sensing.

The experimental detection of multipartite entanglement usually requires a number of appropriately chosen local quantum measurements that are aligned with respect to a previously shared common reference frame. The latter, however, can be a challenging prerequisite, e.g., for satellite-based photonic quantum communication, making the development of alternative detection strategies desirable. One possibility for avoiding the distribution of classical reference frames is to perform a number of local measurements with settings distributed uniformly at random. In this Letter, we follow such a treatment and show that an improved detection and characterization of multipartite entanglement is possible by combining statistical moments of different order. To do so, we make use of designs that are pseudorandom processes allowing us to link the present entanglement criteria to ordinary reference frame independent ones. The strengths of our methods are illustrated in various cases, starting with two qubits and followed by more involved multipartite scenarios.

Neutron-rich material ejected from neutron star–neutron star (NS-NS) and neutron star–black-hole (NS-BH) binary mergers is heated by nuclear processes to temperatures of a few hundred keV, resulting in a population of electron-positron pairs. Some of the positrons escape from the outer layers of the ejecta. We show that the population of low-energy positrons produced by NS-NS and NS-BH mergers in the Milky Way can account for the observed 511-keV line from the Galactic center (GC). Moreover, we suggest how positrons and the associated 511-keV emission can be used as tracers of recent mergers. Recent discovery of 511-keV emission from the ultrafaint dwarf galaxy Reticulum II, consistent with a rare NS-NS merger event, provides a smoking-gun signature of our proposal.

We compute the symbol of the full-color two-loop five-particle amplitude in $\mathcal{N}=4$ super Yang-Mills theory, including all nonplanar subleading-color terms. The amplitude is written in terms of permutations of Parke-Taylor tree-level amplitudes and pure functions to all orders in the dimensional regularization parameter, in agreement with previous conjectures. The answer has the correct collinear limits and infrared factorization properties, allowing us to define a finite remainder function. We study the multi-Regge limit of the nonplanar terms, analyze its subleading power corrections, and analytically present the leading logarithmic terms.

We compute the symbol of the two-loop five-point scattering amplitude in $\mathcal{N}=4$ supersymmetric Yang-Mills theory, including its full color dependence. This requires constructing the symbol of all two-loop five-point nonplanar massless master integrals, for which we give explicit results.

The axion is a promising dark matter candidate, which was originally proposed to solve the strong-$CP$ problem in particle physics. To date, the available parameter space for axion and axionlike particle dark matter is relatively unexplored, particularly at masses $m_a\lesssim 1\mu \mathrm{eV}$. ABRACADABRA is a new experimental program to search for axion dark matter over a broad range of masses, ${10}^{-12}\lesssim m_a\lesssim {10}^{-6}\mathrm{eV}$. ABRACADABRA-10 cm is a small-scale prototype for a future detector that could be sensitive to the QCD axion. In this Letter, we present the first results from a 1 month search for axions with ABRACADABRA-10 cm. We find no evidence for axionlike cosmic dark matter and set 95% C.L. upper limits on the axion-photon coupling between $g_{a\gamma \gamma }<1.4\times {10}^{-10}$ and $g_{a\gamma \gamma }<3.3\times {10}^{-9}{\mathrm{GeV}}^{-1}$ over the mass range $3.1\times {10}^{-10}–8.3\times {10}^{-9}\mathrm{eV}$. These results are competitive with the most stringent astrophysical constraints in this mass range.

This Letter describes a search for Higgs boson pair production using the combined results from four final states: $bb\gamma \gamma$, $bb\tau \tau$, $bbbb$, and $bbVV$, where $V$ represents a $W$ or $Z$ boson. The search is performed using data collected in 2016 by the CMS experiment from LHC proton-proton collisions at $\sqrt{s}=13\mathrm{TeV}$, corresponding to an integrated luminosity of $35.9{\mathrm{fb}}^{-1}$. Limits are set on the Higgs boson pair production cross section. A 95% confidence level observed (expected) upper limit on the nonresonant production cross section is set at 22.2 (12.8) times the standard model value. A search for narrow resonances decaying to Higgs boson pairs is also performed in the mass range 250–3000 GeV. No evidence for a signal is observed, and upper limits are set on the resonance production cross section.

If physics beyond the standard model enters well above the electroweak scale, its low-energy effects are described by standard model effective field theory. Already, at dimension 6, many operators involve the antisymmetric quark tensor $\overline{q}{\sigma }^{\mu \nu }q$, whose matrix elements are difficult to constrain from experiment, Ward identities, or low-energy theorems, in contrast to the corresponding vector and axial-vector or even scalar and pseudoscalar currents. However, with normalizations determined from lattice QCD, analyticity and unitarity often allow one to predict the momentum dependence in a large kinematic range. Starting from recent results in the meson sector, we extend this method to the nucleon case and, in combination with pole dominance, provide a comprehensive assessment of the current status of the nucleon form factors of the quark tensor.

The structure of the extremely proton-rich nucleus ${{}_8{}^{11}\mathrm{O}}_3$, the mirror of the two-neutron halo nucleus ${{}_3{}^{11}\mathrm{Li}}_8$, has been studied experimentally for the first time. Following two-neutron knockout reactions with a ${}^{13}\mathrm{O}$ beam, the ${}^{11}\mathrm{O}$ decay products were detected after two-proton emission and used to construct an invariant-mass spectrum. A broad peak of width $\sim 3.4\mathrm{MeV}$ was observed. Within the Gamow coupled-channel approach, it was concluded that this peak is a multiplet with contributions from the four lowest ${}^{11}\mathrm{O}$ resonant states: $J^{\pi }=3/2_1^{-}$, $3/2_2^{-}$, $5/2_1^{+}$, and $5/2_2^{+}$. The widths and configurations of these states show strong, nonmonotonic dependencies on the depth of the $p$-${}^9\mathrm{C}$ potential. This unusual behavior is due to the presence of a broad threshold resonant state in ${}^{10}\mathrm{N}$, which is an analog of the virtual state in ${}^{10}\mathrm{Li}$ in the presence of the Coulomb potential. After optimizing the model to the data, only a moderate isospin asymmetry between ground states of ${}^{11}\mathrm{O}$ and ${}^{11}\mathrm{Li}$ was found.

The high degree of control available over individual atoms enables precision tests of fundamental physical concepts. In this Letter, we experimentally study how precision measurements can be improved by preparing entangled states immune to the dominant source of decoherence. Using ${}^{40}{\mathrm{Ca}}^{+}$ ions, we explicitly demonstrate the advantage from entanglement on a precision test of local Lorentz invariance for the electron. Reaching the quantum projection noise limit set by quantum mechanics, we observe, for bipartite entangled states, the expected gain of a factor of two in the precision. Under specific conditions, multipartite entangled states may yield substantial further improvements. Our measurements improve the previous best limit for local Lorentz invariance of the electron using ${}^{40}{\mathrm{Ca}}^{+}$ ions by a factor of two to four to about $5\times {10}^{-19}$.

We demonstrate quantum control of ${}^9{\mathrm{Be}}^{+}$ ions directly implemented by an optical frequency comb. Based on numerical simulations of the relevant processes in ${}^9{\mathrm{Be}}^{+}$ for different magnetic field regimes, we demonstrate a wide applicability when controlling the comb’s spectral properties. We introduce a novel technique for the selective and efficient generation of a spectrally tailored narrow-bandwidth optical frequency comb near 313 nm. We experimentally demonstrate internal state control and internal-motional state coupling of ${}^9{\mathrm{Be}}^{+}$ ions implemented by stimulated-Raman manipulation using a spectrally optimized optical frequency comb. Our pulsed laser approach is a key enabling step for the implementation of quantum logic and quantum information experiments in Penning traps.

In quantum communication and photonic quantum information processing, the requirement of quantum repeaters and quantum memory often imposes a strict bandwidth prerequisite for the entangled photons. At the same time, there is ever more increasing demand for entangling more degrees of freedom, i.e., hyperentanglement, for a photon pair. In this Letter, we report the direct generation of narrow-band orbital angular momentum (OAM) and polarization hyperentangled photons from cold atoms. The narrow-band photon pair is naturally entangled in polarization and OAM, in addition to time-frequency, degrees of freedom due to spin and orbital angular momentum conservation conditions in the spontaneous four-wave mixing process in a cold atom ensemble. The narrow-band hyperentangled photon pair source reported here is expected to play important roles in quantum memory-based long-distance quantum communication.