Results for "Tilman Pfau"

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Atomic vapor spectroscopy in integrated photonic structuresMay 04 2015We investigate an integrated optical chip immersed in atomic vapor providing several waveguide geometries for spectroscopy applications. The narrow-band transmission through a silicon nitride waveguide and interferometer is altered when the guided light ... More
Artificial atoms can do more than atoms: Deterministic single photon subtraction from arbitrary light fieldsMar 07 2011We study the interplay of photons interacting with an artificial atom in the presence of a controlled dephasing. Such artifical atoms consisting of several independent scatterer can exhibit remarkable properties superior to single atoms with a prominent ... More
A lattice of Magneto-Optical and Magnetic traps for cold atomsAug 30 2002Mar 13 2003We describe basic periodic trapping configurations for ultracold atoms above surfaces. The approach is based on a simple wire grid and can be scaled to provide large arrays of periodically arranged magnetic or magneto-optical traps. The unit cells of ... More
An ionic impurity in a Bose-Einstein condensate at sub-microkelvin temperaturesFeb 23 2018Apr 11 2018Rydberg atoms immersed in a Bose-Einstein condensate interact with the quantum gas via electron-atom and ion-atom interaction. To suppress the typically dominant electron-neutral interaction, Rydberg states with principal quantum number up to $n = 190$ ... More
Precision spectroscopy of negative-ion resonances in Rydberg moleculesApr 17 2019The level structure of negative-ions near the electron detachment limit dictates the low-energy scattering of an electron with the parent neutral atom. We demonstrate that a single ultracold atom bound inside a Rydberg orbit forming an ultralong-range ... More
Revivals and oscillations of the momentum of light in a planar multimode waveguideMay 30 2001The evolution of the transverse momentum of monochromatic light entering a multimode planar waveguide at large angle is investigated. We report on oscillations of the momentum caused by the beatings between the adjacent populated modes of the waveguide ... More
Universal scaling in a strongly interacting Rydberg gasFeb 26 2009Nov 25 2009We study a gas of ultracold atoms resonantly driven into a strongly interacting Rydberg state. The long distance behavior of the spatially frozen effective pseudospin system is determined by a set of dimensionless parameters, and we find that the experimental ... More
Observation of Rydberg Blockade Induced by a Single IonSep 04 2018We study the long-range interaction of a single ion with a highly excited ultracold Rydberg atom and report on the direct observation of ion-induced Rydberg excitation blockade mediated over tens of micrometer distances. Our hybrid ion-atom system is ... More
Production of a chromium Bose-Einstein condensateAug 18 2005Oct 12 2005The recent achievement of Bose-Einstein condensation of chromium atoms [1] has opened longed-for experimental access to a degenerate quantum gas with long-range and anisotropic interaction. Due to the large magnetic moment of chromium atoms of 6 {$\mu$}B, ... More
Mesoscopic ensembles of polar bosons in triple-well potentialsNov 27 2009Apr 29 2010Mesoscopic dipolar Bose gases in triple-well potentials offer a minimal system for the analysis of the long-range character of the dipole-dipole interactions. We show that this long-range character may be clearly revealed by a variety of possible ground-state ... More
Tuning the dipolar interaction in quantum gasesApr 16 2002Apr 26 2002We have studied the tunability of the interaction between permanent dipoles in Bose-Einstein condensates. Based on time-dependent control of the anisotropy of the dipolar interaction, we show that even the very weak magnetic dipole coupling in alkali ... More
Quantum correlations in dilute dipolar quantum droplets beyond the extended Gross-Pitaevskii equationApr 23 2019Dipolar quantum droplets are exotic quantum objects that are self-bound due to the subtle balance of attraction, repulsion and quantum correlations. Here we present a systematic study of the critical atom number of these self-bound droplets, comparing ... More
Proof of concept for an optogalvanic gas sensor for NO based on Rydberg excitationsJan 29 2018Jun 11 2018We demonstrate the applicability of 2-photon Rydberg excitations of nitric oxide (NO) at room temperature in a gas mixture with helium (He) as an optogalvanic gas sensor. The charges created initially from succeeding collisions of excited NO Rydberg molecules ... More
Ballistic expansion of a dipolar condensateNov 25 2002We have studied the free expansion of a Bose condensate in which both the usual s-wave contact interaction and the dipole-dipole interaction contribute considerably to the total interaction energy. We calculate corrections due to dipolar forces to the ... More
A fermionic impurity in a dipolar quantum dropletJul 02 2018In this article we develop the framework to describe Bose-Fermi mixtures of magnetic atoms, focusing on the interaction of bosonic self-bound dipolar quantum droplets with a small number of fermions. We find an attractive interaction potential due to ... More
Efficient demagnetization cooling of atoms and its limitsJun 14 2013May 25 2014Demagnetization cooling relies on spin-orbit coupling that brings motional and spin degrees of freedom into thermal equilibrium. In the case of a gas, one has the advantage that the spin degree of freedom can be cooled very efficiently using optical pumping. ... More
A proposal for continuous loading of an optical dipole trap with magnetically guided ultra cold atomsDec 11 2009The capture of a moving atom by a non-dissipative trap, such as an optical dipole trap, requires the removal of the excessive kinetic energy of the atom. In this article we develop a mechanism to harvest ultra cold atoms from a guided atom beam into an ... More
High Resolution Rydberg Spectroscopy of ultracold Rubidium AtomsAug 10 2005We present experiments on two-photon excitation of ${\rm ^{87}}$Rb atoms to Rydberg states. For this purpose, two continuous-wave (cw)-laser systems for both 780 nm and 480 nm have been set up. These systems are optimized to a small linewidth (well below ... More
Collective many-body interaction in Rydberg dressed atomsApr 14 2010Sep 17 2010We present a method to control the shape and character of the interaction potential between cold atomic gases by weakly dressing the atomic ground state with a Rydberg level. For increasing particle densities, a crossover takes place from a two-particle ... More
Quantum critical behavior in strongly interacting Rydberg gasesJun 24 2008Dec 16 2008We study the appearance of correlated many-body phenomena in an ensemble of atoms driven resonantly into a strongly interacting Rydberg state. The ground state of the Hamiltonian describing the driven system exhibits a second order quantum phase transition. ... More
Pulsed Rydberg four-wave mixing with motion-induced dephasing in a thermal vaporDec 15 2015We report on time-resolved pulsed four-wave mixing (FWM) signals in a thermal Rubidium vapor involving a Rydberg state. We observe FWM signals with dephasing times up to 7 ns, strongly dependent on the excitation bandwidth to the Rydberg state. The excitation ... More
Sisyphus cooling in a continuously loaded trapJun 07 2013We demonstrate continuous Sisyphus cooling combined with a continuous loading mechanism used to efficiently slow down and accumulate atoms from a guided beam. While the loading itself is based on a single slowing step, applying a radio frequency field ... More
Ground state of a two component dipolar Fermi gas in a harmonic potentialAug 02 2013Interacting two component Fermi gases are at the heart of our understanding of macroscopic quantum phenomena like superconductivity. Changing nature of the interaction is expected to head to novel quantum phases. Here we study the ground state of a two ... More
Critical Temperature of Weakly Interacting Dipolar CondensatesJun 22 2006Feb 26 2007We calculate perturbatively the effect of a dipolar interaction upon the Bose-Einstein condensation temperature. This dipolar shift depends on the angle between the symmetry axes of the trap and the aligned atomic dipole moments, and is extremal for parallel ... More
A two species trap for chromium and rubidium atomsJan 20 2004We realize a combined trap for bosonic chromium 52Cr and rubidium 87Rb atoms. First experiments focus on exploring a suitable loading scheme for the combined trap and on studies of new trap loss mechanisms originating from simultaneous trapping of two ... More
Bose-Einstein condensation of chromiumMar 02 2005We report on the generation of a Bose-Einstein condensate in a gas of chromium atoms, which will make studies of the effects of anisotropic long-range interactions in degenerate quantum gases possible. The preparation of the chromium condensate requires ... More
Rydberg polaritons in a thermal vaporMar 18 2016We present a pulsed four-wave mixing (FWM) scheme via a Rydberg state to create, store and retrieve collective Rydberg polaritons. The storage medium consists of a gas of thermal Rb atoms confined in a 220 {\mu}m thick cell, which are heated above room ... More
Correlations of quasi-2D dipolar ultracold gas at finite temperaturesApr 17 2013Apr 22 2013We study a quasi two dimensional dipolar gas at finite, but ultralow temperatures using the classical field approximation. The method, already used for a contact interacting gas, is extended here to samples with a weakly interacting long-range inter-atomic ... More
Driving Dipolar Fermions into the Quantum Hall Regime by Spin-Flip Induced Insertion of Angular MomentumFeb 06 2013Apr 03 2013A new method to drive a system of neutral dipolar fermions into the lowest Landau level regime is proposed. By employing adiabatic spin-flip processes in combination with a diabatic transfer, the fermions are pumped to higher orbital angular momentum ... More
Probing a scattering resonance in Rydberg molecules with a Bose-Einstein condensateOct 23 2015We present spectroscopy of a single Rydberg atom excited within a Bose-Einstein condensate. We not only observe the density shift as discovered by Amaldi and Segre in 1934, but a line shape which changes with the principal quantum number n. The line broadening ... More
Controlling Rydberg atom excitations in dense background gasesJul 05 2016We discuss the density shift and broadening of Rydberg spectra measured in cold, dense atom clouds in the context of Rydberg atom spectroscopy done at room temperature, dating back to the experiments of Amaldi and Segr\`e in 1934. We discuss the theory ... More
Mean-field description of dipolar bosons in triple-well potentialsJan 12 2012Oct 11 2012We investigate the ground state properties of a polarized dipolar Bose-Einstein condensate trapped in a triple-well potential. By solving the dipolar Gross-Pitaevskii equation numerically for different geometries we identify states which reveal the non-local ... More
Einstein's Working Sheets and His Search For a Unified Field TheoryJun 14 2019The Einstein Archives contain a considerable collection of calculations in the form of working sheets and scratch paper, documenting Einstein's scientific preoccupations during the last three decades of his life until his death in 1955. This paper provides ... More
Connecting Generative Adversarial Networks and Actor-Critic MethodsOct 06 2016Jan 18 2017Both generative adversarial networks (GAN) in unsupervised learning and actor-critic methods in reinforcement learning (RL) have gained a reputation for being difficult to optimize. Practitioners in both fields have amassed a large number of strategies ... More
Dynamical viscosity, contact correlations and pairing in attractive Fermi gasesApr 29 2019The dynamical bulk viscosity of a dilute Fermi gas is given exactly by the correlation function of the contact density of local pairs. Consequently, the breaking of scale invariance revealed by the bulk viscosity arises purely from pair fluctuations. ... More
Computation of the homotopy of the spectrum tmfNov 19 2003Apr 02 2009This paper contains a complete computation of the homotopy ring of the spectrum of topological modular forms constructed by Hopkins and Miller. The computation is done away from 6, and at the (interesting) primes 2 and 3 separately, and in each of the ... More
Formal plethoriesJul 28 2011Dec 21 2013Unstable operations in a generalized cohomology theory E give rise to a functor from the category of algebras over E to itself which is a colimit of representable functors and a comonoid with respect to composition of such functors. In this paper I set ... More
Connecting Generative Adversarial Networks and Actor-Critic MethodsOct 06 2016Oct 07 2016Both generative adversarial networks (GAN) in unsupervised learning and actor-critic methods in reinforcement learning (RL) have gained a reputation for being difficult to optimize. Practitioners in both fields have amassed a large number of strategies ... More
Self-bound droplets of a dilute magnetic quantum liquidJul 25 2016Self-bound many-body systems occur in different scenarios all across the fields of physics. For example in the astrophysical context the stellar classification is based on a detailed balance of attractive self-gravitating forces and repulsive terms e.g. ... More
Ultracold atom-electron interaction: from two to many-body physicsApr 23 2014The transition from a few-body system to a many-body system can result in new length scales, novel collective phenomena or even in a phase transition. Such a threshold behavior was shown for example in 4He droplets, where 4He turns into a superfluid for ... More
Comparing contact and dipolar interaction in a Bose-Einstein condensateAug 07 2006We have measured the relative strength $\epsilon_dd$ of the magnetic dipole-dipole interaction compared to the contact interaction in a chromium Bose-Einstein condensate. We analyze the asymptotic velocities of expansion of a dipolar chromium BEC with ... More
Liquid quantum droplets of ultracold magnetic atomsSep 13 2016The simultaneous presence of two competing inter-particle interactions can lead to the emergence of new phenomena in a many-body system. Among others, such effects are expected in dipolar Bose-Einstein condensates, subject to dipole-dipole interaction ... More
Triple stack glass-to-glass anodic bonding for optogalvanic spectroscopy cells with electrical feedthroughsMar 05 2014We demonstrate the use of an anodic bonding technique for building a vacuum tight vapor cell for the use of Rydberg spectroscopy of alkali atoms with thin film electrodes on the inside of the cell. The cell is fabricated by simultaneous triple stack glass-to-glass ... More
Evidence for coherent collective Rydberg excitation in the strong blockade regimeJan 17 2007Jun 19 2007Blockade effects on the single quantum level are at the heart of quantum devices like single-electron transistors. The blockade mechanisms are based on strong interactions like the Coulomb interaction in case of single electrons. Neutral atoms excited ... More
Observation of quantum droplets in a strongly dipolar Bose gasJan 13 2016Mar 18 2016Quantum fluctuations are the origin of genuine quantum many-body effects, and can be neglected in classical mean-field phenomena. Here we report on the observation of stable quantum droplets containing $\sim$ 800 atoms which are expected to collapse at ... More
Transient supersolid properties in an array of dipolar quantum dropletsJan 23 2019We study theoretically and experimentally the emergence of supersolid properties in a dipolar Bose-Einstein condensate. The theory reveals a ground state phase diagram with three distinct regimes - a regular Bose-Einstein condensate, incoherent and coherent ... More
Photo-association of trilobite Rydberg molecules via resonant spin-orbit couplingMar 03 2017May 04 2017We report on a novel method for photo-association of strongly polar trilobite Rydberg molecules. This exotic ultralong-range dimer, consisting of a ground-state atom bound to the Rydberg electron via electron-neutral scattering, inherits its polar character ... More
Rydberg dressing: Understanding of collective many-body effects and implications for experimentsDec 22 2013The strong interaction between Rydberg atoms can be used to control the strength and character of the interatomic interaction in ultracold gases by weakly dressing the atoms with a Rydberg state. Elaborate theoretical proposals for the realization of ... More
Rydberg excitation of Bose-Einstein condensatesOct 30 2007Rydberg atoms provide a wide range of possibilities to tailor interactions in a quantum gas. Here we report on Rydberg excitation of Bose-Einstein condensed 87Rb atoms. The Rydberg fraction was investigated for various excitation times and temperatures ... More
An echo experiment in a strongly interacting Rydberg gasJun 26 2007Oct 22 2007When ground state atoms are excited to a Rydberg state, van der Waals interactions among them can lead to a strong suppression of the excitation. Despite the strong interactions the evolution can still be reversed by a simple phase shift in the excitation ... More
Strong dipolar effects in a quantum ferrofluidJun 12 2007Mar 07 2008We report on the realization of a Chromium Bose-Einstein condensate (BEC) with strong dipolar interaction. By using a Feshbach resonance, we reduce the usual isotropic contact interaction, such that the anisotropic magnetic dipole-dipole interaction between ... More
Self-bound droplets of a dilute magnetic quantum liquidJul 25 2016Nov 10 2016Self-bound many-body systems are formed through a balance of attractive and repulsive forces and occur in many physical scenarios. Liquid droplets are an example of a self-bound system, formed by a balance of the mutual attractive and repulsive forces ... More
Continuous loading of cold atoms into a Ioffe-Pritchard magnetic trapNov 06 2002We present a robust continuous optical loading scheme for a Ioffe-Pritchard (IP) type magnetic trap. Atoms are cooled and trapped in a modified magneto-optical trap (MOT) consisting of a conventional 2D-MOT in radial direction and an axial molasses. The ... More
The interplay between thermal Rydberg gases and plasmasJan 23 2019We investigate the phenomenon of bistability in a thermal gas of cesium atoms excited to Rydberg states. We present both measurements and a numerical model of the phenomena based on collisions. By directly measuring the plasma frequency, we show that ... More
Scissors mode of dipolar quantum droplets of dysprosium atomsDec 19 2017Mar 25 2018We report on the observation of the scissors mode of a single dipolar quantum droplet. The existence of this mode is due to the breaking of the rotational symmetry by the dipole-dipole interaction, which is fixed along an external homogeneous magnetic ... More
Coupling a thermal atomic vapor to an integrated ring resonatorMay 19 2016Strongly interacting atom-cavity systems within a network with many nodes constitute a possible realization for a quantum internet which allows for quantum communication and computation on the same platform. To implement such large-scale quantum networks, ... More
Stable periodic density waves in dipolar Bose-Einstein condensates trapped in optical latticesFeb 01 2012Density-wave patterns in (quasi-) discrete media with local interactions are known to be unstable. We demonstrate that \emph{stable} double- and triple- period patterns (DPPs and TPPs), with respect to the period of the underlying lattice, exist in media ... More
An experimental and theoretical guide to strongly interacting Rydberg gasesFeb 10 2012We review experimental and theoretical tools to excite, study and understand strongly interacting Rydberg gases. The focus lies on the excitation of dense ultracold atomic samples close to, or within quantum degeneracy, to high lying Rydberg states. The ... More
Electromagnetically Induced Transparency in optically trapped rubidium atomsJan 09 2007Jan 10 2007We demonstrate electromagnetically induced transparency (EIT) in a sample of rubidium atoms, trapped in an optical dipole trap. Mixing a small amount of $\sigma^-$-polarized light to the weak $\sigma^+$-polarized probe pulses, we are able to measure the ... More
Apparatus for excitation and detection of Rydberg atoms in quantum gasesJun 18 2007We present and characterize a versatile experimental setup which allows for excitation and detection of Rydberg atoms in quantum gases. The novel concept of the setup features two charged particle detectors and eight electrical field plates inside the ... More
Onset of a modulational instability in trapped dipolar Bose-Einstein condensatesNov 20 2017Jan 23 2018We explore the phase diagram of a finite-sized dysprosium dipolar Bose-Einstein condensate in a cylindrical harmonic trap. We monitor the final state after the scattering length is lowered from the repulsive BEC regime to the quantum droplet regime. Either ... More
Striped states in a many-body system of tilted dipolesJun 28 2017Nov 28 2017We study theoretically and experimentally the behaviour of a strongly confined dipolar Bose-Einstein condensate, in the regime of quantum-mechanical stabilization by beyond-mean-field effects. Theoretically, we demonstrate that self-organized striped ... More
High- and low-frequency phonon modes in dipolar quantum gases trapped in deep latticesFeb 11 2013We study normal modes propagating on top of the stable uniform background in arrays of dipolar Bose-Einstein condensate (BEC) droplets trapped in a deep optical lattice. Both the on-site mean-field dynamics of the droplets and their displacement due to ... More
Transient supersolid properties in an array of dipolar quantum dropletsJan 23 2019Mar 08 2019We study theoretically and experimentally the emergence of supersolid properties in a dipolar Bose-Einstein condensate. The theory reveals a ground state phase diagram with three distinct regimes - a regular Bose-Einstein condensate, incoherent and coherent ... More
Photoassociation of spin polarized ChromiumDec 14 2015Dec 15 2015We report the homonuclear photoassociation (PA) of ultracold ${}^{52}\mathrm{Cr}$ atoms in an optical dipole trap. This constitutes the first measurement of PA in an element with total electron spin $\tilde{S}>1$. Although Cr, with its ${}^{7}\mathrm{S}_{3}$ ... More
Laser cooling of a magnetically guided ultra cold atom beamFeb 01 2010We report on the transverse laser cooling of a magnetically guided beam of ultra cold chromium atoms. Radial compression by a tapering of the guide is employed to adiabatically heat the beam. Inside the tapered section heat is extracted from the atom ... More
Continuous Loading of a Conservative Trap from an Atomic BeamFeb 04 2011We demonstrate the fast accumulation of Cr atoms in a conservative potential from a magnetically guided atomic beam. Without laser cooling on a cycling transition, a single dissipative step realized by optical pumping allows to load atoms at a rate of ... More
Doppler cooling of an optically dense cloud of trapped atomsAug 20 2002We have studied a general technique for laser cooling a cloud of polarized trapped atoms down to the Doppler temperature. A one-dimensional optical molasses using polarized light cools the axial motional degree of freedom of the atoms in the trap. Cooling ... More
Observing the Rosensweig instability of a quantum ferrofluidAug 20 2015Oct 08 2015Ferrofluids show unusual hydrodynamic effects due to the magnetic nature of their constituents. For increasing magnetization a classical ferrofluid undergoes a Rosensweig instability and creates self-organized ordered surface structures or droplet crystals. ... More
Fabrication and characterization of an electrically contacted vapor cellApr 11 2012We demonstrate the use of electrically contacted vapor cells to switch the transmission of a probe laser. The excitation scheme makes use of electromagnetically induced transparency involving a Rydberg state. The cell fabrication technique involves thinfilm ... More
Anisotropic Superfluid Behavior of a Dipolar Bose-Einstein CondensateApr 12 2018Jul 18 2018We present transport measurements on a dipolar superfluid using a Bose-Einstein condensate of Dy-162 with strong magnetic dipole-dipole interactions. By moving an attractive laser beam through the condensate we observe an anisotropy in superfluid flow. ... More
Coupling a single electron to a Bose-Einstein condensateJun 21 2013The coupling of electrons to matter is at the heart of our understanding of material properties such as electrical conductivity. One of the most intriguing effects is that electron-phonon coupling can lead to the formation of a Cooper pair out of two ... More
Probing a quantum gas with single Rydberg atomsJun 17 2015Jul 07 2016We present a novel spectroscopic method for probing the \insitu~density of quantum gases. We exploit the density-dependent energy shift of highly excited {Rydberg} states, which is of the order $10$\MHz\,/\,1E14\,cm$^{\text{-3}}$ for \rubidium~for triplet ... More
Higgs-Boson Production Induced by Bottom QuarksApr 03 2003Bottom quark-induced processes are responsible for a large fraction of the LHC discovery potential, in particular for supersymmetric Higgs bosons. Recently, the discrepancy between exclusive and inclusive Higgs boson production rates has been linked to ... More
Adjoint spaces and flag varieties of p-compact groupsFeb 20 2006For a compact Lie group $G$ with maximal torus $T$, Pittie and Smith showed that the flag variety $G/T$ is always a stably framed boundary. We generalize this to the category of $p$-compact groups, where the geometric argument is replaced by a homotopy ... More
Nice Restrictions of Reflection ArrangementsSep 22 2016In a recent paper, Hoge and the second author classified all nice and all inductively factored reflection arrangements. In this note we extend this classification by determining all nice and all inductively factored restrictions of reflection arrangements. ... More
Large deviations for the local times of a random walk among random conductances in a growing boxAug 21 2013We derive an annealed large deviation principle (LDP) for the normalised and rescaled local times of a continuous-time random walk among random conductances (RWRC) in a time-dependent, growing box in $\Z^d$. We work in the interesting case that the conductances ... More
The contact structure induced by a line fibration of R^3 is standardMay 08 2019Building on the work of and answering a question by Michael Harrison, we show that any contact structure on Euclidean 3-space induced by a line fibration is diffeomorphic to the standard contact structure.
Fractal curvatures and Minkowski content of self-conformal setsNov 14 2012For self-similar fractals, the Minkowski content and fractal curvature have been introduced as a suitable limit of the geometric characteristics of its parallel sets, i.e., of uniformly thin coatings of the fractal. For some self-conformal sets, the surface ... More
Dead leaves and the dirty ground: low-level image statistics in transmissive and occlusive imaging environmentsSep 14 2012Dec 05 2012The opacity of typical objects in the world results in occlusion --- an important property of natural scenes that makes inference of the full 3-dimensional structure of the world challenging. The relationship between occlusion and low-level image statistics ... More
W+Jets at CDF: Evidence for Top QuarksApr 20 2011Recently, an anomaly of W+jets events at large invariant masses has been reported by CDF. Many interpretations as physics beyond the Standard Model are being offered. We show how such an invariant mass peak can arise from a slight shift in the relative ... More
Exploring Gravitational LensingMay 17 2019In this article, we discuss the idea of gravitational lensing, from a systematic, historical and didactic point of view. We show how the basic lensing equation together with the concepts of geometrical optics opens a space of implications that can be ... More
Localizations of inductively factored arrangementsFeb 20 2016We show that the class of inductively factored arrangements is closed under taking localizations. We illustrate the usefulness of this with an application.
Counting chambers in restricted Coxeter arrangementsJun 29 2017Solomon showed that the Poincar\'e polynomial of a Coxeter group $W$ satisfies a product decomposition depending on the exponents of $W$. This polynomial coincides with the rank-generating function of the poset of regions of the underlying Coxeter arrangement. ... More
The realizability of some finite-length modules over the Steenrod algebra by spacesMar 25 2019The Joker is a finite cyclic module over the mod-$2$ Steenrod algebra $\mathcal A$ which appears frequently in Adams resolutions as well as in Picard groups. In a previous paper, the first author commenced a study of when the Joker and its iterated Steenrod ... More
A simplicial $A_\infty$-operad acting on $R$-resolutionsJan 07 2009We construct a combinatorial model of an A-infinity-operad which acts simplicially on the cobar resolution (not just its total space) of a simplicial set with respect to a ring R.
A-infinity monads and completionMay 20 2008Apr 02 2010Given an operad A of topological spaces, we consider A-monads in a topological category C . When A is an A-infinity-operad, any A-monad K : C -> C can be thought of as a monad up to coherent homotopies. We define the completion functor with respect to ... More
Precise asymptotics for the parabolic Anderson model with a moving catalyst or trapOct 07 2010Feb 17 2011We consider the solution $u\colon [0,\infty) \times\mathbb{Z}^d\rightarrow [0,\infty) $ to the parabolic Anderson model, where the potential is given by $(t,x)\mapsto\gamma\delta_{Y_t}(x)$ with $Y$ a simple symmetric random walk on $\mathbb{Z}^d$. Depending ... More
Alignment of D-state Rydberg moleculesJan 16 2014We report on the formation of ultralong-range Rydberg D-state molecules via photoassociation in an ultracold cloud of rubidium atoms. By applying a magnetic offset field on the order of 10 G and high resolution spectroscopy, we are able to resolve individual ... More
d-wave collapse and explosion of a dipolar Bose-Einstein condensateMar 17 2008Aug 22 2008We investigate the collapse dynamics of a dipolar condensate of 52Cr atoms when the s-wave scattering length characterizing the contact interaction is reduced below a critical value. A complex dynamics, involving an anisotropic, d-wave symmetric explosion ... More
The low-energy Goldstone mode in a trapped dipolar supersolidJun 11 2019A supersolid is a counter-intuitive state of matter that combines the frictionless flow of a superfluid with the crystal-like periodic density modulation of a solid. Since the first prediction in the 1950s, experimental efforts to realize this state have ... More
Broad universal Feshbach resonances in the chaotic spectrum of Dysprosium atomsJun 05 2015Oct 12 2015We report on the observation of weakly-bound dimers of bosonic Dysprosium with a strong universal s-wave halo character, associated with broad magnetic Feshbach resonances. These states surprisingly decouple from the chaotic backgound of narrow resonances, ... More
Condensate losses and oscillations induced by Rydberg atomsOct 12 2016We numerically analyze the impact of a single Rydberg electron onto a Bose-Einstein condensate. Both $S-$ and $D-$ Rydberg states are studied. The radial size of $S-$ and $D-$states are comparable, hence the only difference is due to the angular dependence ... More
Bose-Einstein condensation with magnetic dipole-dipole forcesJul 20 1999Mar 31 2000Ground-state solutions in a dilute gas interacting via contact and magnetic dipole-dipole forces are investigated. To the best of our knowledge, it is the first example of studies of the Bose-Einstein condensation in a system with realistic long-range ... More
Motion-induced signal revival in pulsed Rydberg four-wave mixing beyond the frozen gas limitOct 03 2014We present measurements on pulsed four-wave mixing involving a Rydberg state in an atomic vapor cell. The excitation to the Rydberg state is conducted by a pulsed two-photon excitation on the nanosecond timescale that is combined with a third CW laser ... More
Collective oscillations of dipolar Bose-Einstein condensates and accurate comparison between contact and dipolar interactionAug 13 2006We propose a scheme for the measurement of the s-wave scattering length $a$ of an atom or molecule with significant dipole-dipole interaction with an accuracy at the percent level. The frequencies of the collective oscillations of a Bose-Einstein condensate ... More
Curvature-direction measures of self-similar setsNov 18 2011Nov 14 2012We obtain fractal Lipschitz-Killing curvature-direction measures for a large class of self-similar sets F in R^d. Such measures jointly describe the distribution of normal vectors and localize curvature by analogues of the higher order mean curvatures ... More
Observation of mixed singlet-triplet Rb$_2$ Rydberg moleculesOct 05 2015Feb 22 2016We present high-resolution spectroscopy of Rb$_\text{2}$ ultralong-range Rydberg molecules bound by mixed singlet-triplet electron-neutral atom scattering. The mixing of the scattering channels is a consequence of the hyperfine interaction in the ground-state ... More
Evidence for strong van der Waals-type Rydberg-Rydberg interaction in thermal vaporDec 04 2012We present evidence for Rydberg-Rydberg interaction in a gas of rubidium atoms above room temperature. Rabi oscillations on the nanosecond timescale to different Rydberg states are investigated in a vapor cell experiment. Analyzing the atomic time evolution ... More
Spectral Inference Networks: Unifying Spectral Methods With Deep LearningJun 06 2018We present Spectral Inference Networks, a framework for learning eigenfunctions of linear operators by stochastic optimization. Spectral Inference Networks generalize Slow Feature Analysis to generic symmetric operators, and are closely related to Variational ... More