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Ionization of Rydberg atoms embedded in an ultracold plasma  [PDF]
Nicolas Vanhaecke,Daniel Comparat,Duncan A. Tate,Pierre Pillet
Physics , 2004, DOI: 10.1103/PhysRevA.71.013416
Abstract: We have studied the behavior of cold Rydberg atoms embedded in an ultracold plasma. We demonstrate that even deeply bound Rydberg atoms are completely ionized in such an environment, due to electron collisions. Using a fast pulse extraction of the electrons from the plasma we found that the number of excess positive charges, which is directly related to the electron temperature Te, is not strongly affected by the ionization of the Rydberg atoms. Assuming a Michie-King equilibrium distribution, in analogy with globular star cluster dynamics, we estimate Te. Without concluding on heating or cooling of the plasma by the Rydberg atoms, we discuss the range for changing the plasma temperature by adding Rydberg atoms.
Experimental Research of Spontaneous Evolution from Ultracold Rydberg Atoms to Plasma

ZHANG Lin-Jie,FENG Zhi-Gang,LI An-Ling,ZHAO Jian-Ming,LI Chang-Yong,JIA Suo-Tang,

中国物理快报 , 2008,
Abstract: The spontaneous evolution from ultracold Rydberg atoms to plasma is investigated in a caesium MOT by using the method of field ionization. The plasma transferred from atoms in different Rydberg states (n=22--32) are obtained experimentally. Dependence of the threshold time of evolving toplasma and the threshold number of initial Rydberg atoms on the principal quantum number of initial Rydberg states is studied. The experimental results are in agreement with hot--cold Rydberg--Rydberg atom collision ionization theory.
An experimental approach for investigating many-body phenomena in Rydberg-interacting quantum systems  [PDF]
C. S. Hofmann,G. Günter,H. Schempp,N. L. M. Müller,A. Faber,H. Busche,M. Robert-de-Saint-Vincent,S. Whitlock,M. Weidemüller
Physics , 2013,
Abstract: Recent developments in the study of ultracold Rydberg gases demand an advanced level of experimental sophistication, in which high atomic and optical densities must be combined with excellent control of external fields and sensitive Rydberg atom detection. We describe a tailored experimental system used to produce and study Rydberg-interacting atoms excited from dense ultracold atomic gases. The experiment has been optimized for fast duty cycles using a high flux cold atom source and a three beam optical dipole trap. The latter enables tuning of the atomic density and temperature over several orders of magnitude, all the way to the Bose-Einstein condensation transition. An electrode structure surrounding the atoms allows for precise control over electric fields and single-particle sensitive field ionization detection of Rydberg atoms. We review two experiments which highlight the influence of strong Rydberg--Rydberg interactions on different many-body systems. First, the Rydberg blockade effect is used to pre-structure an atomic gas prior to its spontaneous evolution into an ultracold plasma. Second, hybrid states of photons and atoms called dark-state polaritons are studied. By looking at the statistical distribution of Rydberg excited atoms we reveal correlations between dark-state polaritons. These experiments will ultimately provide a deeper understanding of many-body phenomena in strongly-interacting regimes, including the study of strongly-coupled plasmas and interfaces between atoms and light at the quantum level.
Strongly Coupled Plasmas via Rydberg-Blockade of Cold Atoms  [PDF]
G. Bannasch,T. C. Killian,T. Pohl
Physics , 2013, DOI: 10.1103/PhysRevLett.110.253003
Abstract: We propose and analyze a new scheme to produce ultracold neutral plasmas deep in the strongly coupled regime. The method exploits the interaction blockade between cold atoms excited to high-lying Rydberg states and therefore does not require substantial extensions of current ultracold plasma experiments. Extensive simulations reveal a universal behavior of the resulting Coulomb coupling parameter, providing a direct connection between the physics of strongly correlated Rydberg gases and ultracold plasmas. The approach is shown to reduce currently accessible temperatures by more than an order of magnitude, which opens up a new regime for ultracold plasma research and cold ion-beam applications with readily available experimental techniques.
Angular Momentum of Supersymmetric Cold Rydberg Atoms  [PDF]
Jian-Zu Zhang
Physics , 2009, DOI: 10.1103/PhysRevLett.77.44
Abstract: Semiunitary transformation is applied to discuss supersymmetrization of cold Rydberg atoms. In the limit of vanishing kinetic energy the lowest angular momentum of the supersymmetric cold Rydberg atom is $3\hbar/2$. A possible experimental verification is suggested.
Coherent manipulation of cold Rydberg atoms near the surface of an atom chip  [PDF]
J. D. Carter,J. D. D. Martin
Physics , 2013, DOI: 10.1103/PhysRevA.88.043429
Abstract: Coherent superpositions of the 49s and 48s Rydberg states of cold Rb atoms were studied near the surface of an atom chip. The superpositions were created and manipulated using microwaves resonant with the two-photon 49s-48s transition. Coherent behavior was observed using Rabi flopping, Ramsey sequences, spin-echo and spin-locking. These results are discussed in the context of Rydberg atoms as electric field noise sensors. We consider the coherence of systems quadratically coupled to noise fields with 1/f^k power spectral densities (k \approx 1).
Controlling ultracold Rydberg atoms in the quantum regime  [PDF]
Bernd Hezel,Igor Lesanovsky,Peter Schmelcher
Physics , 2006, DOI: 10.1103/PhysRevLett.97.223001
Abstract: We discuss the properties of Rydberg atoms in a magnetic Ioffe-Pritchard trap being commonly used in ultracold atomic physics experiments. The Hamiltonian is derived and it is demonstrated how tight traps alter the coupling of the atom to the magnetic field. We solve the underlying Schroedinger equation of the system within a given n-manifold and show that for a sufficiently large Ioffe field strength the 2n^2-dimensional system of coupled Schroedinger equations decays into several decoupled multicomponent equations governing the center of mass motion. An analysis of the fully quantized center of mass and electronic states is undertaken. In particular, we discuss the situation of tight center of mass confinement outlining the procedure to generate a low-dimensional ultracold Rydberg gas.
Electric field sensing near the surface microstructure of an atom chip using cold Rydberg atoms  [PDF]
J. D. Carter,O. Cherry,J. D. D. Martin
Physics , 2012, DOI: 10.1103/PhysRevA.86.053401
Abstract: The electric fields near the heterogeneous metal/dielectric surface of an atom chip were measured using cold atoms. The atomic sensitivity to electric fields was enhanced by exciting the atoms to Rydberg states that are 10^8 times more polarizable than the ground state. We attribute the measured fields to charging of the insulators between the atom chip wires. Surprisingly, it is observed that these fields may be dramatically lowered with appropriate voltage biasing, suggesting configurations for the future development of hybrid quantum systems.
Ultracold Rydberg Atoms in a Ioffe-Pritchard Trap  [PDF]
Bernd Hezel,Igor Lesanovsky,Peter Schmelcher
Physics , 2007, DOI: 10.1103/PhysRevA.76.053417
Abstract: We discuss the properties of ultracold Rydberg atoms in a Ioffe-Pritchard magnetic field configuration. The derived two-body Hamiltonian unveils how the large size of Rydberg atoms affects their coupling to the inhomogeneous magnetic field. The properties of the compound electronic and center of mass quantum states are thoroughly analyzed. We find very tight confinement of the center of mass motion in two dimensions to be achievable while barely changing the electronic structure compared to the field free case. This paves the way for generating a one-dimensional ultracold quantum Rydberg gas.
Dressing of Ultracold Atoms by their Rydberg States in a Ioffe-Pritchard Trap  [PDF]
Michael Mayle,Igor Lesanovsky,Peter Schmelcher
Physics , 2010, DOI: 10.1088/0953-4075/43/15/155003
Abstract: We explore how the extraordinary properties of Rydberg atoms can be employed to impact the motion of ultracold ground state atoms. Specifically, we use an off-resonant two-photon laser dressing to map features of the Rydberg states on ground state atoms. It is demonstrated that the interplay between the spatially varying quantization axis of the considered Ioffe-Pritchard field and the fixed polarizations of the laser transitions provides the possibility of substantially manipulating the ground state trapping potential.
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