Heavy ion collisions present exciting opportunities to study the effects of quantum coherence in the formation of subatomic particle showers. We report on the first calculation of the momentum sharing and angular separation distributions between the leading subjets inside a reconstructed jet in such collisions. These observables are directly sensitive to the hardest branching within jets and can probe the early stage of the jet formation. We find that the leading-order medium-induced splitting functions, here obtained in the framework of soft-collinear effective theory with Glauber gluon interactions, capture the essential many-body physics, which is different from proton-proton reactions. Qualitative and in most cases quantitative agreement between theory and preliminary CMS measurements suggests that hard parton branching in strongly interacting matter can be dramatically modified. We also propose a new measurement that will illuminate its angular structure.

Effective cavities can be optically induced in atomic media and employed to strengthen optical nonlinearities. Here we study the integration of induced cavities with a photonic quantum gate based on Rydberg blockade. Accounting for loss in the atomic medium, we calculate the corresponding finesse and gate infidelity. Our analysis shows that the conventional limits imposed by the blockade optical depth are mitigated by the induced cavity in long media, thus establishing the total optical depth of the medium as a complementary resource.

The transport properties of nanostructured systems are deeply affected by the geometry of the effective connections to metallic leads. In this work we derive a conductance expression for a class of interacting systems whose connectivity geometries do not meet the Meir-Wingreen proportional coupling condition. As an interesting application, we consider a quantum dot connected coherently to tunable electronic cavity modes. The structure is shown to exhibit a well-defined Kondo effect over a wide range of coupling strengths between the two subsystems. In agreement with recent experimental results, the calculated conductance curves exhibit strong modulations and asymmetric behavior as different cavity modes are swept through the Fermi level. These conductance modulations occur, however, while maintaining robust Kondo singlet correlations of the dot with the electronic reservoir, a direct consequence of the lopsided nature of the device.

Motivated by recent experiments with proximitized nanowires, we study a mesoscopic $s$-wave superconductor connected via point contacts to normal-state leads. We demonstrate that at energies below the charging energy the system is described by the two-channel Kondo model, which can be brought to the quantum critical regime by varying the gate potential and conductances of the contacts.

In-plane hole $g$ factors measured in quantum point contacts based on $p$-type heterostructures strongly depend on the orientation of the magnetic field with respect to the electric current. This effect, first reported a decade ago and confirmed in a number of publications, has remained an open problem. In this work, we present systematic experimental studies to disentangle different mechanisms contributing to the effect and develop the theory which describes it successfully. We show that there is a new mechanism for the anisotropy related to the existence of an additional $B_{+}{k}_{-}^4{\sigma }_{+}$ effective Zeeman interaction for holes, which is kinematically different from the standard single Zeeman term $B_{-}{k}_{-}^2{\sigma }_{+}$ considered until now.

Using first-principles-based simulations merging an effective Hamiltonian scheme with scaling, symmetry, and topological arguments, we find that an overlooked Berezinskii-Kosterlitz-Thouless ($\mathsf{B}\mathsf{K}\mathsf{T}$) phase sustained by quasicontinuous symmetry emerges between the ferroelectric phase and the paraelectric one of ${\mathrm{BaTiO}}_3$ ultrathin film, being under tensile strain. Not only do these results provide an extension of $\mathsf{B}\mathsf{K}\mathsf{T}$ physics to the field of ferroelectrics, but they also unveil their nontrivial critical behavior in low dimensions.

We study associating polymer gels under steady shear using Brownian dynamics simulation to explore the interplay between the network structure, dynamics, and rheology. For a wide range of flow rates, we observe the formation of shear bands with a pronounced difference in shear rate, concentration, and structure. A striking increase in the polymer pressure in the gradient direction with shear, along with the inherently large compressibility of the gels, is shown to be a crucial factor in destabilizing homogeneous flow through shear-gradient concentration coupling. We find that shear has only a modest influence on the degree of association, but induces marked spatial heterogeneity in the network connectivity. We attribute the increase in the polymer pressure (and polymer mobility) to this structural reorganization.

There is a long-standing experimental observation that the melting of topologically constrained DNA, such as circular closed plasmids, is less abrupt than that of linear molecules. This finding points to an important role of topology in the physics of DNA denaturation, which is, however, poorly understood. Here, we shed light on this issue by combining large-scale Brownian dynamics simulations with an analytically solvable phenomenological Landau mean field theory. We find that the competition between melting and supercoiling leads to phase coexistence of denatured and intact phases at the single-molecule level. This coexistence occurs in a wide temperature range, thereby accounting for the broadening of the transition. Finally, our simulations show an intriguing topology-dependent scaling law governing the growth of denaturation bubbles in supercoiled plasmids, which can be understood within the proposed mean field theory.

We define a simple model of conformal field theory in random space-time environments, which we refer to as stochastic conformal field theory. This model accounts for the effects of dilute random impurities in strongly interacting critical many-body systems. On one hand, surprisingly, although impurities are separated by macroscopic distances, we find that the infinite-time steady state is factorized on microscopic lengths, a signature of the emergence of localization. The stationary state also displays vanishing energy current and strong uncorrelated spatial fluctuations of local observables. On the other hand, at finite times, the transient shows a crossover from ballistic to diffusive energy propagation. In this regime and a Markovian limit, concentrating on current-generating initial states with a temperature imbalance, we show that the energy current and density satisfy simple dissipative hydrodynamic equations. We describe the space-time scales at which nonequilibrium currents exist. We show that a light-cone effect subsists in the presence of impurities although a momentum burst propagates transiently on a diffusive scale only.

We calculate the effect of impurities on the superconducting phase diagram of transition metal dichalcogenide monolayers in the presence of an in-plane magnetic field. Because of strong intrinsic spin-orbit coupling, the upper critical field greatly surpasses the Pauli limit at low temperatures. We find that it is insensitive to intravalley scattering and, ultimately, limited by intervalley scattering.

We examine an electric double layer containing an antagonistic salt in an aqueous mixture, where the cations are small and hydrophilic but the anions are large and hydrophobic. In this situation, a strong coupling arises between the charge density and the solvent composition. As a result, the anions are trapped in an oil-rich adsorption layer on a hydrophobic wall. We then vary the surface charge density $\sigma$ on the wall. For $\sigma >0$ the anions remain accumulated, but for $\sigma <0$ the cations are attracted to the wall with increasing $|\sigma |$. Furthermore, the electric potential drop $\mathrm{\Psi }(\sigma )$ is nonmonotonic when the solvent interaction parameter $\chi (T)$ exceeds a critical value ${\chi }_c$ determined by the composition and the ion density in the bulk. This leads to a first-order phase transition between two kinds of electric double layers with different $\sigma$ and common $\mathrm{\Psi }$. In equilibrium such two-layer regions can coexist. The steric effect due to finite ion sizes is crucial in these phenomena.

We characterize general non-Markovian Gaussian maps which are covariant under Galilean transformations. In particular, we consider translational and Galilean covariant maps and show that they reduce to the known Holevo result in the Markovian limit. We apply the results to discuss measures of macroscopicity based on classicalization maps, specifically addressing dissipation, Galilean covariance and non-Markovianity. We further suggest a possible generalization of the macroscopicity measure defined by Nimmrichter and Hornberger [Phys. Rev. Lett. 110, 16 (2013)].

We present an efficient experimental procedure that certifies nonvanishing quantum capacities for qubit noisy channels. Our method is based on the use of a fixed bipartite entangled state, where the system qubit is sent to the channel input. A particular set of local measurements is performed at the channel output and the ancilla qubit mode, obtaining lower bounds to the quantum capacities for any unknown channel with no need of quantum process tomography. The entangled qubits have a Bell state configuration and are encoded in photon polarization. The lower bounds are found by estimating the Shannon and von Neumann entropies at the output using an optimized basis, whose statistics is obtained by measuring only the three observables ${\sigma }_x\otimes {\sigma }_x$, ${\sigma }_y\otimes {\sigma }_y$, and ${\sigma }_z\otimes {\sigma }_z$.

We consider a family of quantum spin systems which includes, as special cases, the ferromagnetic $XY$ model and ferromagnetic Ising model on any graph, with or without a transverse magnetic field. We prove that the partition function of any model in this family can be efficiently approximated to a given relative error $\epsilon$ using a classical randomized algorithm with runtime polynomial in ${\epsilon }^{-1}$, system size, and inverse temperature. As a consequence, we obtain a polynomial time algorithm which approximates the free energy or ground energy to a given additive error. We first show how to approximate the partition function by the perfect matching sum of a finite graph with positive edge weights. Although the perfect matching sum is not known to be efficiently approximable in general, the graphs obtained by our method have a special structure which facilitates efficient approximation via a randomized algorithm due to Jerrum and Sinclair.

We develop a hybrid semiclassical method to study the time evolution of one-dimensional quantum systems in and out of equilibrium. Our method handles internal degrees of freedom completely quantum mechanically by a modified time-evolving block decimation method while treating orbital quasiparticle motion classically. We can follow dynamics up to time scales well beyond the reach of standard numerical methods to observe the crossover between preequilibrated and locally phase equilibrated states. As an application, we investigate the quench dynamics and phase fluctuations of a pair of tunnel-coupled one-dimensional Bose condensates. We demonstrate the emergence of soliton-collision-induced phase propagation, soliton-entropy production, and multistep thermalization. Our method can be applied to a wide range of gapped one-dimensional systems.

We report on a measurement of the flavor-specific $B_s^0$ lifetime and of the $D_s^{-}$ lifetime using proton-proton collisions at center-of-mass energies of 7 and 8 TeV, collected by the LHCb experiment and corresponding to $3.0{\mathrm{fb}}^{-1}$ of integrated luminosity. Approximately 407 000 $B_s^0\to D_s^{(*)-}{\mu }^{+}{\nu }_{\mu }$ decays are partially reconstructed in the $K^{+}{K}^{-}{\pi }^{-}{\mu }^{+}$ final state. The $B_s^0$ and $D_s^{-}$ natural widths are determined using, as a reference, kinematically similar $B^0\to D^{(*)-}{\mu }^{+}{\nu }_{\mu }$ decays reconstructed in the same final state. The resulting differences between widths of $B_s^0$ and $B^0$ mesons and of $D_s^{-}$ and $D^{-}$ mesons are ${\mathrm{\Delta }}_{\mathrm{\Gamma }}(B)=-0.0115\pm 0.0053(\mathrm{stat})\pm 0.0041(\mathrm{syst}){\mathrm{ps}}^{-1}$ and ${\mathrm{\Delta }}_{\mathrm{\Gamma }}(D)=1.0131\pm 0.0117(\mathrm{stat})\pm 0.0065(\mathrm{syst}){\mathrm{ps}}^{-1}$, respectively. Combined with the known $B^0$ and $D^{-}$ lifetimes, these yield the flavor-specific $B_s^0$ lifetime, ${\tau }_{B_s^0}^{\mathrm{fs}}=1.547\pm 0.013(\mathrm{stat})\pm 0.010(\mathrm{syst})\pm 0.004({\tau }_B)\mathrm{ps}$ and the $D_s^{-}$ lifetime, ${\tau }_{D_s^{-}}=0.5064\pm 0.0030(\mathrm{stat})\pm 0.0017(\mathrm{syst})\pm 0.0017({\tau }_D)\mathrm{ps}$. The last uncertainties originate from the limited knowledge of the $B^0$ and $D^{-}$ lifetimes. The results improve upon current determinations.

The measurement of two-particle angular correlations is a powerful tool to study jet quenching in a $p_T$ region inaccessible by direct jet identification. In these measurements pseudorapidity ($\mathrm{\Delta }\eta$) and azimuthal ($\mathrm{\Delta }\phi$) differences are used to extract the shape of the near-side peak formed by particles associated with a higher $p_T$ trigger particle ($1<p_{T,\mathrm{trig}}<8\mathrm{GeV}/c$). A combined fit of the near-side peak and long-range correlations is applied to the data allowing the extraction of the centrality evolution of the peak shape in Pb-Pb collisions at $\sqrt{s_{NN}}=2.76\mathrm{TeV}$. A significant broadening of the peak in the $\mathrm{\Delta }\eta$ direction at low $p_T$ is found from peripheral to central collisions, which vanishes above $4\mathrm{GeV}/c$, while in the $\mathrm{\Delta }\phi$ direction the peak is almost independent of centrality. For the 10% most central collisions and $1<p_{T,\text{assoc}}<2\mathrm{GeV}/c$, $1<p_{T,\mathrm{trig}}<3\mathrm{GeV}/c$ a novel feature is observed: a depletion develops around the center of the peak. The results are compared to $pp$ collisions at the same center of mass energy and ampt model simulations. The comparison to the investigated models suggests that the broadening and the development of the depletion is connected to the strength of radial and longitudinal flow.

Autoresonance (AR) cooling of a bunch of ions oscillating inside an electrostatic ion beam trap is demonstrated for the first time. The relatively wide initial longitudinal velocity distribution is reduced by at least an order of magnitude using AR acceleration and ramping forces. The hot ions escaping the bunch are not lost from the system but continue to oscillate in the trap outside of the bunch and may be further cooled by successive AR processes. Ion-ion collisions inside the bunch close to the turning points in the trap’s mirrors contribute to the thermalization of the ions. This cooling method can be applied to any mass and any charge.