We study the formation of Rydberg atoms in expanding plasmas at temperatures of 1-1000 K and densities from 10(5)-10(10) cm(-3). Up to 20% of the initially free charges recombine in about 100 micros, and the binding energy of the Rydberg atoms approximately equals the increase in the kinetic energy of the remaining free electrons. Three-body recombination is expected to dominate in this regime, yet most of our results are inconsistent with this mechanism.

We experimentally demonstrate interferometer-type guiding structures for neutral atoms based on dipole potentials created by micro-fabricated optical systems. As a central element we use an array of atom waveguides being formed by focusing a red-detuned laser beam with an array of cylindrical microlenses. Combining two of these arrays, we realize X-shaped beam splitters and more complex systems like the geometries for Mach-Zehnder and Michelson-type interferometers for atoms.

We study an experimentally feasible qubit system employing neutral atomic currents. Our system is based on bosonic cold atoms trapped in ring-shaped optical lattice potentials. The lattice makes the system strictly one dimensional and it provides the infrastructure to realize a tunable ring-ring interaction. Our implementation combines the low decoherence rates of neutral cold atoms systems, overcoming single site addressing, with the robustness of topologically protected solid state Josephson flux qubits. Characteristic fluctuations in the magnetic fields affecting Josephson junction based flux qubits are expected to be minimized employing neutral atoms as flux carriers. By breaking the Galilean invariance we demonstrate how atomic currents through the lattice provide an implementation of a qubit. This is realized either by artificially creating a phase slip in a single ring, or by tunnel coupling of two homogeneous ring lattices. The single qubit infrastructure is experimentally investigated with tailored optical potentials. Indeed, we have experimentally realized scaled ring-lattice potentials that could host, in principle, n ~ 10 of such ring-qubits, arranged in a stack configuration, along the laser beam propagation axis. An experimentally viable scheme of the two-ring-qubit is discussed, as well. Based on our analysis, we provide protocols to initialize, address, and read-out the qubit.

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We experimentally demonstrate novel structures for the realization of registers of atomic qubits: We trap neutral atoms in one- and two-dimensional arrays of far-detuned dipole traps obtained by focusing a red-detuned laser beam with a microfabricated array of microlenses. We are able to selectively address individual trap sites due to their large lateral separation of 125 microm. We initialize and read out different internal states for the individual sites. We also create two interleaved sets of trap arrays with adjustable separation, as required for many proposed implementations of quantum gate operations.

One way to focus the diffuse energy of a sound field in a liquid is by acoustically driving bubbles into nonlinear oscillation. A rapid and nearly adiabatic bubble collapse heats up the bubble interior and produces intense concentration of energy that is able to emit light (sonoluminescence) and to trigger chemical reactions (sonochemistry). Such phenomena have been extensively studied in bulk liquid. We present here a realization of sonoluminescence and sonochemistry created from bubbles confined within a narrow channel of polydimethylsiloxane-based microfluidic devices. In the microfluidics channels, the bubbles form a planar/pancake shape. During bubble collapse we find the formation of OH radicals and the emission of light. The chemical reactions are closely confined to gas-liquid interfaces that allow for spatial control of sonochemical reactions in lab-on-a-chip devices. The decay time of the light emitted from the sonochemical reaction is several orders faster than that in the bulk liquid. Multibubble sonoluminescence emission in contrast vanishes immediately as the sound field is stopped.cavitation | ultrasound | capillary waves

Atomtronics deals with matter-wave circuits of ultracold atoms manipulated through magnetic or laser-generated guides with different shapes and intensities. In this way, new types of quantum networks can be constructed in which coherent fluids are controlled with the know-how developed in the atomic and molecular physics community. In particular, quantum devices with enhanced precision, control, and flexibility of their operating conditions can be accessed. Concomitantly, new quantum simulators and emulators harnessing on the coherent current flows can also be developed. Here, the authors survey the landscape of atomtronics-enabled quantum technology and draw a roadmap for the field in the near future. The authors review some of the latest progress achieved in matter-wave circuits' design and atom-chips. Atomtronic networks are deployed as promising platforms for probing many-body physics with a new angle and a new twist. The latter can be done at the level of both equilibrium and nonequilibrium situations. Numerous relevant problems in mesoscopic physics, such as persistent currents and quantum transport in circuits of fermionic or bosonic atoms, are studied through a new lens. The authors summarize some of the atomtronics quantum devices and sensors. Finally, the authors discuss alkali-earth and Rydberg atoms as potential platforms for the realization of atomtronic circuits with special features.

We experimentally demonstrate and systematically study the stimulated revival (echo) of motional wave packet oscillations. For this purpose, we prepare wave packets in an optical lattice by non-adiabatically shifting the potential and stimulate their reoccurence by a second shift after a variable time delay. This technique, analogous to spin echoes, enables one even in the presence of strong dephasing to determine the coherence time of the wave packets. We find that for strongly bound atoms it is comparable to the cooling time and much longer than the inverse of the photon scattering rate.32.80. Pj, 42.50.Vk The process of decoherence, i.e. the collapse of superposition states due to the dissipative interaction with their environment is one of the basic concepts for our understanding of the connection between classical and quantum physics. In order to study the effect of decoherence unambiguously, one has to be able to distinguish it from other, non-dissipative effects. The macroscopic (i.e. ensemble-or time-averaged) response of a quantum system prepared in a superposition state typically decays not only due to the loss of coherence (homogeneous decay) but also due to dephasing resulting from local variations in the evolution of the quantum system (inhomogeneous decay). In many cases decoherence cannot be studied directly because the inhomogeneous decay is by far the dominating process.This limitation has been overcome in a famous series of experiments by introducing the techniques of spin echo for nuclear magnetic resonance (NMR) and photon echo for optical resonance, respectively [1][2][3]. These techniques are based on the observation that inhomogeneous decay due to dephasing is a reversible process. Thus, by appropriately modifying superposition states at a time ∆t after their preparation, the dephasing can be partially or fully reversed and a stimulated macroscopic response (echo) is induced at 2∆t. This effect enables one to measure the coherence time even in the presence of strong dephasing. We have, for the first time, applied this method to the investigation of the decoherence of motional wave packets of trapped atoms (Fig. 1). The method can be used independent of the specific experimental realization of the confining potential (e.g. a single dipole potential, periodic dipole potentials, magnetic trapping potentials, inhomogeneous arrays of atom traps, etc.).The specific system investigated here consists of motional wave packets of neutral atoms in a one-dimensional optical lattice. Optical lattices are periodic dipole potentials for atoms created by the interference of multiple laser beams [4]. Atoms can be trapped and cooled at the potential minima (mean position spread z rms =λ/18[5]). In optical lattices symmetrically and asymmetrically oscillating motional wave packets can be induced by nonadiabatically changing the lattice potential [6][7][8][9][10][11]. Quantum mechanically, the original atomic wave function is projected onto a coherent superposition of the eigenstates of the new potential a...