Martin Gärttner
Max Planck Society
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Featured researches published by Martin Gärttner.
Nature Physics | 2017
Martin Gärttner; Justin G. Bohnet; Arghavan Safavi-Naini; Michael L. Wall; John J. Bollinger; Ana Maria Rey
Characterizing the correlations of quantum many-body systems is known to be hard, but there are ways around: for example, a new method for measuring out-of-time correlations demonstrated in a Penning trap quantum simulator with over 100 ions.
Physical Review Letters | 2014
H. Schempp; G. Günter; Martin Robert-de-Saint-Vincent; C. S. Hofmann; D. Breyel; A. Komnik; David W. Schönleber; Martin Gärttner; Jörg Evers; S. Whitlock; M. Weidemüller
We experimentally study the full counting statistics of few-body Rydberg aggregates excited from a quasi-one-dimensional atomic gas. We measure asymmetric excitation spectra and increased second and third order statistical moments of the Rydberg number distribution, from which we determine the average aggregate size. Estimating rates for different excitation processes we conclude that the aggregates grow sequentially around an initial grain. Direct comparison with numerical simulations confirms this conclusion and reveals the presence of liquidlike spatial correlations. Our findings demonstrate the importance of dephasing in strongly correlated Rydberg gases and introduce a way to study spatial correlations in interacting many-body quantum systems without imaging.
Physical Review Letters | 2013
C. S. Hofmann; G. Günter; H. Schempp; Martin Robert-de-Saint-Vincent; Martin Gärttner; Jörg Evers; S. Whitlock; M. Weidemüller
We observe individual dark-state polaritons as they propagate through an ultracold atomic gas involving Rydberg states coupled via an electromagnetically induced transparency resonance. Strong long-range interactions between Rydberg excitations give rise to a blockade between polaritons, resulting in large optical nonlinearities and modified polariton number statistics. By combining optical imaging and high-fidelity detection of the Rydberg polaritons we investigate both aspects of this coupled atom-light system. We map out the full nonlinear optical response as a function of atomic density and follow the temporal evolution of polaritons through the atomic cloud. In the blockade regime, the statistical fluctuations of the polariton number drop well below the quantum noise limit. The low level of fluctuations indicates that photon correlations modified by the strong interactions have a significant backaction on the Rydberg atom statistics.
Nature Communications | 2016
Jacob Covey; Steven Moses; Martin Gärttner; Arghavan Safavi-Naini; Matthew T. Miecnikowski; Zhengkun Fu; Johannes Schachenmayer; Paul S. Julienne; Ana Maria Rey; D. S. Jin; J. Ye
Polar molecules in an optical lattice provide a versatile platform to study quantum many-body dynamics. Here we use such a system to prepare a density distribution where lattice sites are either empty or occupied by a doublon composed of an interacting Bose-Fermi pair. By letting this out-of-equilibrium system evolve from a well-defined, but disordered, initial condition, we observe clear effects on pairing that arise from inter-species interactions, a higher partial-wave Feshbach resonance and excited Bloch-band population. These observations facilitate a detailed understanding of molecule formation in the lattice. Moreover, the interplay of tunnelling and interaction of fermions and bosons provides a controllable platform to study Bose-Fermi Hubbard dynamics. Additionally, we can probe the distribution of the atomic gases in the lattice by measuring the inelastic loss of doublons. These techniques realize tools that are generically applicable to studying the complex dynamics of atomic mixtures in optical lattices.
Science | 2018
Philipp Kunkel; Maximilian Prüfer; Helmut Strobel; Daniel Linnemann; Anika Frölian; Thomas Gasenzer; Martin Gärttner; M. K. Oberthaler
Splitting the entanglement When particles in a quantum mechanical system are entangled, a measurement performed on one part of the system can affect the results of the same type of measurement performed on another part—even if these subsystems are physically separated. Kunkel et al., Fadel et al., and Lange et al. achieved this so-called distributed entanglement in a particularly challenging setting: an ensemble of many cold atoms (see the Perspective by Cavalcanti). In all three studies, the entanglement was first created within an atomic cloud, which was then allowed to expand. Local measurements on the different, spatially separated parts of the cloud confirmed that the entanglement survived the expansion. Science, this issue p. 413, p. 409, p. 416; see also p. 376 Local measurements on spatially separated parts of a cold atom cloud confirm entanglement between the subsystems. A key resource for distributed quantum-enhanced protocols is entanglement between spatially separated modes. However, the robust generation and detection of entanglement between spatially separated regions of an ultracold atomic system remain a challenge. We used spin mixing in a tightly confined Bose-Einstein condensate to generate an entangled state of indistinguishable particles in a single spatial mode. We show experimentally that this entanglement can be spatially distributed by self-similar expansion of the atomic cloud. We used spatially resolved spin read-out to reveal a particularly strong form of quantum correlations known as Einstein-Podolsky-Rosen (EPR) steering between distinct parts of the expanded cloud. Based on the strength of EPR steering, we constructed a witness, which confirmed genuine 5-partite entanglement.
Physical Review A | 2013
Martin Gärttner; Kilian Peter Heeg; Thomas Gasenzer; Jörg Evers
The dynamics of a cloud of ultra-cold two-level atoms is studied at off-resonant laser driving to a Rydberg state. We find that resonant excitation channels lead to strongly peaked spatial correlations associated with the buildup of asymmetric excitation structures. These aggregates can extend over the entire ensemble volume, but are in general not localized relative to the system boundaries. The characteristic distances between neighboring excitations depend on the laser detuning and on the interaction potential. These properties lead to characteristic features in the spatial excitation density, the Mandel
Physical Review A | 2014
David W. Schönleber; Martin Gärttner; Jörg Evers
Q
Molecular Physics | 2013
Martin Gärttner; Juan J. Omiste; Peter Schmelcher; R. Gonzaález-Feárez
parameter, and the total number of excitations. As an application an implementation of the three-atom CSWAP or Fredkin gate with Rydberg atoms is discussed. The gate not only exploits the Rydberg blockade, but also utilizes the special features of an asymmetric geometric arrangement of the three atoms. We show that continuous-wave off-resonant laser driving is sufficient to create the required spatial arrangement of atoms out of a homogeneous cloud.
Physical Review A | 2014
Martin Gärttner; S. Whitlock; David W. Schönleber; Jörg Evers
We study the impact of dephasing on the excitation dynamics of a cloud of ultracold two-level Rydberg atoms for both resonant and off-resonant laser excitation, using the wave function Monte Carlo (MCWF) technique. We find that while for resonant laser driving, dephasing mainly leads to an increase of the Rydberg population and a decrease of the Mandel Q parameter, at off-resonant driving strong dephasing toggles between direct excitation of pairs of atoms and subsequent excitation of single atoms, respectively. These two excitation mechanisms can be directly quantified via the pair correlation function, which shows strong suppression of the two-photon resonance peak for strong dephasing. Consequently, qualitatively different dynamics arise in the excitation statistics for weak and strong dephasing in off-resonant excitation. Our findings show that time-resolved excitation number measurements can serve as a powerful tool to identify the dominating process in the systems excitation dynamics.
Physical Review Letters | 2018
Martin Gärttner; Philipp Hauke; Ana Maria Rey
We present a theoretical study of the impact of an electric field combined with a magnetic field on the rotational dynamics of open-shell diatomic molecules. Within the rigid rotor approximation, we solve the time-independent Schrödinger equation including the fine-structure interactions and the Λ-doubling effects. We consider three sets of molecule-specific parameters and several field regimes and investigate the interplay between the different interactions identifying the dominant one. The possibility of inducing couplings between the spin and rotational degrees of freedom is demonstrated.