We employ the concept of a dynamical, activity order parameter to study the Ising model in a transverse magnetic field coupled to a Markovian bath. For a certain range of values of the spin-spin coupling, magnetic field and dissipation rate, we identify a first order dynamical phase transition between active and inactive dynamical phases. We demonstrate that dynamical phasecoexistence becomes manifest in an intermittent behavior of the bath quanta emission. Moreover, we establish the connection between the dynamical order parameter that quantifies the activity, and the longitudinal magnetization that serves as static order parameter. The system that we consider can be implemented in current experiments with Rydberg atoms and trapped ions.

Alkaline-earth-metal atoms can exhibit long-range dipolar interactions, which are generated via the coherent exchange of photons on the (3)P(0) - (3)D(1) transition of the triplet manifold. In the case of bosonic strontium, which we discuss here, this transition has a wavelength of 2.6 μm and a dipole moment of 4.03 D, and there exists a magic wavelength permitting the creation of optical lattices that are identical for the states (3)P(0) and (3)D(1). This interaction enables the realization and study of mixtures of hard-core lattice bosons featuring long-range hopping, with tunable disorder and anisotropy. We derive the many-body master equation, investigate the dynamics of excitation transport, and analyze spectroscopic signatures stemming from coherent long-range interactions and collective dissipation. Our results show that lattice gases of alkaline-earth-metal atoms permit the creation of long-lived collective atomic states and constitute a simple and versatile platform for the exploration of many-body systems with long-range interactions. As such, they represent an alternative to current related efforts employing Rydberg gases, atoms with large magnetic moment, or polar molecules.

Citation for published item:fettlesD oert tF nd win¡ § rD ti § r¡ % nd edmsD ghrles F nd vesnovskyD sgor nd ylmosD fetriz @PHIUA 9opologil properties of dense tomi lttie gsF9D hysil review eFD WT @RAF HRITHQ@AF Further information on publisher's website: eprinted with permission from the emerin hysil oietyX fettlesD oert tFD win¡ § rD ti § r¡ %D edmsD ghrles FD vesnovskyD sgor ylmosD fetriz @PHIUAF opologil properties of dense tomi lttie gsF hysil eview e WT@RAX HRITHQ@A PHIU y the emerin hysil oietyF eders my viewD rowseD ndGor downlod mteril for temporry opying purposes onlyD provided these uses re for nonommeril personl purposesF ixept s provided y lwD this mteril my not e further reproduedD distriutedD trnsmittedD modi(edD dptedD performedD displyedD pulishedD or sold in whole or prtD without prior written permission from the emerin hysil oietyF Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. We investigate the existence of topological phases in a dense two-dimensional atomic lattice gas. The coupling of the atoms to the radiation field gives rise to dissipation and a nontrivial coherent long-range exchange interaction whose form goes beyond a simple power law. The far-field terms of the potential-which are particularly relevant for atomic separations comparable to the atomic transition wavelength-can give rise to energy spectra with one-sided divergences in the Brillouin zone. The long-ranged character of the interactions has another important consequence: it can break the standard bulk-boundary relation in topological insulators. We show that topological properties such as the transport of an excitation along the edge of the lattice are robust with respect to the presence of lattice defects and dissipation. The latter is of particular relevance as dissipation and coherent interactions are inevitably connected in our setting. DOI: 10.1103/PhysRevA.96.041603 Introduction. Recently, the pursuit of topological phases in quantum many-body systems has been the focus of intense research. The potential application of these topological states for robust quantum computation [1,2] is one of the driving forces for this increased interest. So-called topological insulators are usually characterized by bulk bands separated by a gap and the presence of gapless edge states whose properties are topologically protected against local perturbations such as external disorder or noise [3,4]. Paradigmatic examples of these include the integer and fractional quantum Hall effects, which were initially realized on two...

We introduce a class of dissipative quantum spin models with local interactions and without quenched disorder that show glassy behaviour. These models are the quantum analogs of the classical facilitated spin models. Just like their classical counterparts, quantum facilitated models display complex glassy dynamics despite the fact that their stationary state is essentially trivial. In these systems, dynamical arrest is a consequence of kinetic constraints and not of static ordering. These models display a quantum version of dynamic heterogeneity: the dynamics towards relaxation is spatially correlated despite the absence of static correlations. Associated dynamical fluctuation phenomena such as decoupling of timescales is also observed. Moreover, we find that close to the classical limit quantum fluctuations can enhance glassiness, as recently reported for quantum liquids.Introduction. A central problem in condensed-matter science is that of the glass transition. Many body systems with excluded volume interactions, such as molecular liquids, experience pronounced dynamical slowdown at high densities and/or low temperatures, to the extent that they eventually cease to relax and form the amorphous solid we call glass. The glass transition as observed experimentally is not a phase transition but a very rapid kinetic arrest. At low enough temperature or high enough density glass formers relax too slowly to be observed experimentally in equilibrium and thus behave as (non-equilibrium) solids. This solidification occurs in the absence of any evident structural ordering, in contrast to more conventional condensed matter systems: in glass formers thermodynamics changes apparently very little but dynamics changes dramatically. Dynamic arrest like that of glasses is a generic phenomenon in condensed matter; for recent reviews see [1][2][3][4].While the first hallmark of glass formers is kinetic arrest, the second is dynamical heterogeneity [5]. Glass formers appear structurally homogeneous, but their dynamics is highly heterogeneous: as they slow down spatial dynamical correlations emerge and these become more pronounced the longer the relaxation times. One theoretical perspective on glasses in which dynamical heterogeneity appears naturally is that of dynamical facilitation, which posits that the origin of glassy slowing down is not to be found in thermodynamic ordering [6] but in effective constraints in the dynamics (see [2] for a review). From this perspective, slowdown, heterogeneity and other fluctuation features of glasses are rooted in the complex structure of trajectory space. This theory has emerged from the study of a class of idealized lattice systems, so-called kinetically constrained models, of which the simplest representatives are the facilitated spin models [7].Quantum glasses, just like their classical counterparts, are of much current interest, among other reasons due to their relevance to issues like supersolidity [8], quantum annealing [9], glassiness in electronic systems [10], thermalization and man...

We present a method for amplifying a single or scattered impurities immersed in a background gas of ultracold atoms so that they can be optically imaged and spatially resolved. Our approach relies on a Raman transfer between two stable atomic hyperfine states that is conditioned on the presence of an impurity atom. The amplification is based on the strong interaction among atoms excited to Rydberg states. We perform a detailed analytical study of the performance of the proposed scheme with particular emphasis on the influence of inevitable many-body effects.Impurities inside interacting quantum fluids provide a variety of interesting physical effects in fields such as high-T c superconductivity or plasma physics. Recent experimental advances in creating and controlling impurities in ultracold quantum gases have demonstrated that these systems are ideally suited for studying impurity phenomena such as transport in strongly correlated one-dimensional (1D) Bose gases [1], polaron physics in highly imbalanced Fermi-gas mixtures [2], or Rydberg-excitation saturation in Bose-Einstein condensates [3]. Since detection of single (neutral) impurities in a quantum gas poses severe experimental challenges, these experiments all rely on measuring either ensemble averages or effects of the impurities on the bulk host medium. Here, we develop a single-shot detection scheme for single impurity atoms, based on strong amplification of the detectable signal by converting the impurity into an internal state change of a large number of nearby background atoms, as shown in Fig. 1(a). Our scheme is applicable to any form of neutral impurity in an ultracold gas and can be implemented with standard absorption-imaging techniques available in virtually every existing experiment; for example, one possible application is the visualization of Rydberg crystals in a Bose gas [4].In the experimental situation we have in mind the background gas is initially polarized with all atoms being in a stable hyperfine state |A . The average distance R b between the impurities, which can be atoms of the same species in other internal states or a different atomic species altogether, is much larger than the average distance between background atoms. As illustrated in Fig. 1(b), our amplification scheme performs a conversion of background atoms from |A to a second hyperfine state |B only within a sphere of radius R c centered at the impurity. These atoms can be detected via state-selective absorption imaging in a single shot and, provided that R b > 2R c , a discrimination of the positions of the impurities can be achieved. We show that our scheme can be directly implemented in current experiments with ultracold rubidium gases yielding amplification factors of ∼10 to 100 atoms per impurity.We start from a setting where all impurity atoms have been electronically excited to a Rydberg n S state. Such a situation can be easily achieved by a resonant π pulse from the ground state. As an example, one can consider the case of strongly interacting Rydberg atoms in a...

We investigate the many-body quantum states of a laser-driven gas of Rydberg atoms confined to a large spacing ring lattice. If the laser driving is much stronger than the van der Waals interaction among the Rydberg atoms, these many-body states are collective fermionic excitations. The first excited state is a spin wave that extends over the entire lattice. We demonstrate that our system permits us to study fermions in the presence of disorder although no external atomic motion takes place. We analyze how this disorder influences the excitation properties of the fermionic states. Our work shows a route towards the creation of complex many-particle states with atoms in lattices.

We study the excitation dynamics of Rydberg atoms in a one-dimensional lattice with periodic boundary conditions where the atomic Rydberg states are resonantly excited from the electronic ground state. Our description of the corresponding dynamics is numerically exact within the perfect blockade regime, i.e. no two atoms in a given range can be excited. The time-evolution of the mean Rydberg density, density-density correlations as well as entanglement properties are analyzed in detail. We demonstrate that the short time dynamics is universal and dominated by quantum phenomena, while for larger time the characteristics of the lattice become important and the classical features determine the dynamics. The results of the perfect blockade approach are compared to the predictions of an effective Hamiltonian which includes the interaction of two neighboring Rydberg atoms up to second order perturbation theory.

The theory of continuous phase transitions predicts the universal collective properties of a physical system near a critical point, which for instance manifest in characteristic power-law behaviours of physical observables. The well-established concept at or near equilibrium, universality, can also characterize the physics of systems out of equilibrium. The most fundamental instance of a genuine non-equilibrium phase transition is the directed percolation (DP) universality class, where a system switches from an absorbing inactive to a fluctuating active phase. Despite being known for several decades it has been challenging to find experimental systems that manifest this transition. Here we show theoretically that signatures of the DP universality class can be observed in an atomic system with long-range interactions. Moreover, we demonstrate that even mesoscopic ensembles-which are currently studied experimentally-are sufficient to observe traces of this non-equilibrium phase transition in one, two and three dimensions.