Understanding the relation between nonlocality and entanglement is one of the fundamental problems in quantum physics. In the bipartite case, it is known that these two phenomena are inequivalent, as there exist entangled states of two parties that do not violate any Bell inequality. However, except for a single example of an entangled three-qubit state that has a local model, almost nothing is known about such a relation in multipartite systems. We provide a general construction of genuinely multipartite entangled states that do not display genuinely multipartite nonlocality, thus proving that entanglement and nonlocality are inequivalent for any number of parties.

We construct a new class of rotating anti–de Sitter (AdS) black hole solutions with noncompact event horizons of finite area in any dimension and study their thermodynamics. In four dimensions these black holes are solutions to gauged supergravity. We find that their entropy exceeds the maximum implied from the conjectured reverse isoperimetric inequality, which states that for a given thermodynamic volume, the black hole entropy is maximized for Schwarzschild-AdS space. We use this result to suggest more stringent conditions under which this conjecture may hold.

We present a time-dependent quantum calculation of the van der Waals interaction between a pair of dissimilar atoms, one of which is initially excited while the other one is in its ground state. For small detuning, the interaction is predominantly mediated at all distances by the exchange of doubly resonant photons between the two atoms. We find that it presents both temporal and spatial oscillations. Spatially oscillating terms depend on the resonant frequencies of both atoms, while the frequency of the time oscillations is given by their detuning. We analyze the physical content of our findings and discuss to what extent previous conflicting stationary approaches provide compatible results. A proper account of causality is found essential in order to obtain the correct result.

An emerging route to nanostructured hybrid organic-metal interfaces with tailored properties is their manipulation by nanomechanical forces as exerted by STM and AFM tips. Yet, despite impressive experimental progress, close to nothing is known about the underlying atomistic mechanisms of such nanomechanical techniques, thus hindering predictive, rational approaches. Here, we identify “surface peeling” as an important new mechanism for the modification of surfaces. Using density-functional calculations of thiolate self-assembled monolayers at gold and silver, we find that this phenomenon is very sensitive to the force vector, resulting in a high anisotropy in the systems’ response that can be exploited for the selective creation of novel hybrid surfaces.

The Kondo lattice model describes a quantum phase transition between the antiferromagnetic state and heavy-fermion states. Applying the dual-fermion approach, we explore possible superconductivities emerging due to the critical antiferromagnetic fluctuations. The $d$-wave pairing is found to be the leading instability only in the weak-coupling regime. As the coupling is increased, we observe a change of the pairing symmetry into a $p$-wave spin-singlet pairing. The competing superconductivities are ascribed to crossover between small and large Fermi surfaces, which occurs with the formation of heavy quasiparticles.

Among the theoretically predicted two-dimensional topological insulators, $\mathrm{InAs}/\mathrm{GaSb}$ double quantum wells (DQWs) have a unique double-layered structure with electron and hole gases separated in two layers, which enables tuning of the band alignment via electric and magnetic fields. However, the rich trivial-topological phase diagram has yet to be experimentally explored. We present an in situ and continuous tuning between the trivial and topological insulating phases in $\mathrm{InAs}/\mathrm{GaSb}$ DQWs through electrical dual gating. Furthermore, we show that an in-plane magnetic field shifts the electron and hole bands relatively to each other in momentum space, functioning as a powerful tool to discriminate between the topologically distinct states.

In the field of spin caloritronics, spin-dependent transport phenomena are observed in a number of current experiments where a temperature gradient across a nanostructured interface is applied. The interpretation of these experiments is not clear as both phonons and electrons may contribute to thermal transport. Therefore, it still remains an open question how the temperature drop across a magnetic nanostructured interface arises microscopically. We answer this question for the case of a magnetic tunnel junction (MTJ) where the tunneling magneto-Seebeck effect occurs. Our explanation may be extended to other types of nanostructured interfaces. We explicitly calculate phonon and electron thermal conductance across $\mathrm{Fe}/\mathrm{MgO}/\mathrm{Fe}$ MTJs in an ab initio approach using a Green function method. Furthermore, we are able to calculate the electron and phonon temperature profile across the $\mathrm{Fe}/\mathrm{MgO}/\mathrm{Fe}$ MTJ by estimating the electron-phonon interaction in the Fe leads. Our results show that there is an electron-phonon temperature imbalance at the Fe-MgO interfaces. As a consequence, a revision of the interpretation of current experimental measurements may be necessary.

After colliding with a surface, microswimmers reside there during the detention time. They accumulate and may form complex structures such as biofilms. We introduce a general framework to calculate the distribution of detention times using the method of first-passage times and study how rotational noise and hydrodynamic interactions influence the escape from a surface. We compare generic swimmer models to the simple active Brownian particle. While the respective detention times of source dipoles are smaller, the ones of pullers are larger by up to several orders of magnitude, and pushers show both trends. We apply our results to the more realistic squirmer model, for which we use lubrication theory, and validate them by simulations with multiparticle collision dynamics.

Particle-particle interactions are of paramount importance in every multibody system as they determine the collective behavior and coupling strength. Many well-known interactions such as electrostatic, van der Waals, or screened Coulomb interactions, decay exponentially or with negative powers of the particle spacing $r$. Similarly, hydrodynamic interactions between particles undergoing Brownian motion decay as $1/r$ in bulk, and are assumed to decay in small channels. Such interactions are ubiquitous in biological and technological systems. Here we confine two particles undergoing Brownian motion in narrow, microfluidic channels and study their coupling through hydrodynamic interactions. Our experiments show that the hydrodynamic particle-particle interactions are distance independent in these channels. This finding is of fundamental importance for the interpretation of experiments where dense mixtures of particles or molecules diffuse through finite length, water-filled channels or pore networks.

Quantum discord is the quantitative difference between two alternative expressions for bipartite mutual information, given respectively in terms of two distinct definitions for the conditional entropy. By constructing a stochastic model of shared states, classical discord can be similarly defined, quantifying the presence of some stochasticity in the measurement process. Therefore, discord can generally be understood as a quantification of the system’s state disturbance due to local measurements, be it quantum or classical. We establish an operational meaning of classical discord in the context of state merging with noisy measurement and thereby show the quantum-classical separation in terms of a negative conditional entropy.

Device-independent quantum communication will require a loophole-free violation of Bell inequalities. In typical scenarios where line of sight between the communicating parties is not available, it is convenient to use energy-time entangled photons due to intrinsic robustness while propagating over optical fibers. Here we show an energy-time Clauser-Horne-Shimony-Holt Bell inequality violation with two parties separated by 3.7 km over the deployed optical fiber network belonging to the University of Concepción in Chile. Remarkably, this is the first Bell violation with spatially separated parties that is free of the postselection loophole, which affected all previous in-field long-distance energy-time experiments. Our work takes a further step towards a fiber-based loophole-free Bell test, which is highly desired for secure quantum communication due to the widespread existing telecommunication infrastructure.

Quantum resources can be more powerful than classical resources—a quantum computer can solve certain problems exponentially faster than a classical computer, and computing a function of two parties’ inputs can be done with exponentially less communication with quantum messages than with classical ones. Here we consider a task between two players, Alice and Bob where quantum resources are infinitely more powerful than their classical counterpart. Alice is given a string of length $n$, and Bob’s task is to exclude certain combinations of bits that Alice might have. If Alice must send classical messages, then she must reveal nearly $n$ bits of information to Bob, but if she is allowed to send quantum bits, the amount of information she must reveal goes to zero with increasing $n$. Next, we consider a version of the task where the parties may have access to entanglement. With this assistance, Alice only needs to send a constant number of bits, while without entanglement, the number of bits Alice must send grows linearly with $n$. The task is related to the Pusey-Barrett-Rudolph theorem which arises in the context of the foundations of quantum theory.

We analyze how preexisting entanglement between two Unruh-DeWitt particle detectors evolves when one of the detectors falls through a Rindler firewall in ($1+1$)-dimensional Minkowski space. The firewall effect is minor and does not wash out the detector-detector entanglement, in some regimes even preserving the entanglement better than Minkowski vacuum. The absence of cataclysmic events should continue to hold for young black hole firewalls. A firewall’s prospective ability to resolve the information paradox must hence hinge on its detailed gravitational structure, presently poorly understood.

Measurements are presented of the $CP$ violation observables $S$ and $C$ in the decays of $B^0$ and ${\overline{B}}^0$ mesons to the $J/\psi K_S^0$ final state. The data sample corresponds to an integrated luminosity of $3.0{\mathrm{fb}}^{-1}$ collected with the LHCb experiment in proton-proton collisions at center-of-mass energies of 7 and 8 TeV, and contains a total of 41 560 selected $B^0$ and ${\overline{B}}^0$ decays. The analysis of the time evolution of these decays yields $S=0.731\pm 0.035(\text{stat})\pm 0.020(\text{syst})$ and $C=-0.038\pm 0.032(\text{stat})\pm 0.005(\text{syst})$. In the standard model, $S$ equals $\sin (2\beta )$ to a good level of precision. The values are consistent with the current world averages and with the standard model expectations.

This Letter presents a search for a heavy neutral particle decaying into an opposite-sign different-flavor dilepton pair, $e^{\pm }{\mu }^{\mp }$, $e^{\pm }{\tau }^{\mp }$, or ${\mu }^{\pm }{\tau }^{\mp }$ using $20.3{\mathrm{fb}}^{-1}$ of $pp$ collision data at $\sqrt{s}=8\mathrm{TeV}$ collected by the ATLAS detector at the LHC. The numbers of observed candidate events are compatible with the standard model expectations. Limits are set on the cross section of new phenomena in two scenarios: the production of ${\tilde{\nu }}_{\tau }$ in $R$-parity-violating supersymmetric models and the production of a lepton-flavor-violating $Z^{\prime }$ vector boson.

We study the dynamics of paramagnetic molecular superrotors in an external magnetic field. An optical centrifuge is used to create dense ensembles of oxygen molecules in ultrahigh rotational states. In is shown, for the first time, that the gas of rotating molecules becomes optically birefringent in the presence of a magnetic field. The discovered effect of “magneto-rotational birefringence” indicates the preferential alignment of molecular axes along the field direction. We provide an intuitive qualitative model, in which the influence of the applied magnetic field on the molecular orientation is mediated by the spin-rotation coupling. This model is supported by the direct imaging of the distribution of molecular axes, the demonstration of the magnetic reversal of the rotational Raman signal, and by numerical calculations.

The first absolute experimental determinations of the differential cross sections for the formation of ground-state positronium are presented for He, Ar, ${\mathrm{H}}_2$, and ${\mathrm{CO}}_2$ near 0°. Results are compared with available theories. The ratio of the differential and integrated cross sections for the targets exposes the higher propensity for forward emission of positronium formed from He and ${\mathrm{H}}_2$.