We present experimental evidence for the spontaneous formation of a macroscopic spin polarization in overlapping regions of two independent Bose-Einstein condensates produced in different hyperfine states of ${}^{87}\mathrm{R}\mathrm{b}$. The condensates are independent in the sense that we do not explicitly introduce a relative phase between them. A single “spin-tip” pulse maps the transverse spin polarization into longitudinal spin polarization, and the atomic density distributions are measured with a Stern-Gerlach imaging method. The resulting matter-wave interference patterns are anticorrelated.

Chemical reactions on dust grains are of crucial importance in interstellar chemistry because they produce molecular hydrogen and various organic molecules. Because of the submicron size of the grains and the low flux, the surface populations of reactive species are small and strongly fluctuate. Under these conditions rate equations fail and the master equation is needed for modeling these reactions. However, the number of equations grows exponentially with the number of reactive species, severely limiting its feasibility. Here we present a method which dramatically reduces the number of equations, thus enabling the incorporation of the master equation in models of interstellar chemistry.

The comparison of different atomic transition frequencies over time can be used to determine the present value of the temporal derivative of the fine structure constant $\alpha$ in a model-independent way without assumptions on constancy or variability of other parameters, allowing tests of the consequences of unification theories. We have measured an optical transition frequency at 688 THz in ${}^{171}\mathrm{Y}\mathrm{b}^{+}$ with a cesium atomic clock at 2 times separated by 2.8 yr and find a value for the fractional variation of the frequency ratio $f_{\mathrm{Y}\mathrm{b}}/f_{\mathrm{C}\mathrm{s}}$ of $(-1.2\pm 4.4)\times {10}^{-15}{\mathrm{y}\mathrm{r}}^{-1}$, consistent with zero. Combined with recently published values for the constancy of other transition frequencies this measurement sets an upper limit on the present variability of $\alpha$ at the level of $2.0\times {10}^{-15}{\mathrm{y}\mathrm{r}}^{-1}$ $(1\sigma )$, corresponding so far to the most stringent limit from laboratory experiments.

We discuss a possible realization of a quantum register with controllable decoherence in terms of $|0⟩$ and $|1⟩$ photon number states of a micromaser field. It is shown how to create in the Jaynes-Cummings model a superposition state of $|0⟩$ and $|1⟩$ photon number states inside a closed micromaser cavity. The loss of phase coherence between these two states can subsequently be measured by a second probe atom monitoring the decoherence of the field. A technique is proposed for forming the superposition of number states $|0⟩$ and $|1⟩$ using the time structure of the Rabi oscillation. The proposed method avoids problems with stray fields at the cavity holes, which disturb the coherence of the atomic superposition, and offers a way to study how the coupling strength to the environment influences the decoherence rate, displaying the robustness of physical qubits and the fidelity of quantum computations.

The adiabatic theorem states that an initial eigenstate of a slowly varying Hamiltonian remains close to an instantaneous eigenstate of the Hamiltonian at a later time. We show that a perfunctory application of this statement is problematic if the change in eigenstate is significant, regardless of how closely the evolution satisfies the requirements of the adiabatic theorem. We also introduce an example of a two-level system with an exactly solvable evolution to demonstrate the inapplicability of the adiabatic approximation for a particular slowly varying Hamiltonian.

We present a direct experimental measurement of an effective temperature in a colloidal glass of laponite, using a micrometric bead as a thermometer. The nonequilibrium fluctuation-dissipation relation, in the particular form of a modified Einstein relation, is investigated with diffusion and mobility measurements of the bead embedded in the glass. We observe an unusual nonmonotonic behavior of the effective temperature: starting from the bath temperature, it is found to increase up to a maximum value, and then decrease back, as the system ages. We show that the observed deviation from the Einstein relation is related to the relaxation times previously measured in dynamic light scattering experiments.

Doubly quantized vortices were topologically imprinted in $|F=1⟩{}^{23}\mathrm{N}\mathrm{a}$ condensates, and their time evolution was observed using a tomographic imaging technique. The decay into two singly quantized vortices was characterized and attributed to dynamical instability. The time scale of the splitting process was found to be longer at higher atom density.

We examine the dependence of a thermodynamic potential of a fluid on the geometry of its container. If motion invariance, continuity, and additivity of the potential are satisfied, only four morphometric measures are needed to describe fully the influence of an arbitrarily shaped container on the fluid. These three constraints can be understood as a more precise definition for the conventional term extensive and have as a consequence that the surface tension and other thermodynamic quantities contain, aside from a constant term, only contributions linear in the mean and Gaussian curvature of the container and not an infinite number of curvatures as generally assumed before. We verify this numerically in the entropic system of hard spheres bounded by a curved wall.

We have experimentally explored and clarified the concept of noise suppression in intrinsically noisy systems by adding noise at the input using a microscopic bead held in a moving and intensity-modulated optical trap. By coupling the stiffness of the optical trap to its position, we have explicitly constructed an experimental model system in which added fluctuations in the trap position result in reduced variance of the observed bead position as compared to a stationary trap. This reduction in variance and the spectral properties of the observed output noise agree with theoretical predictions. Our experiment demonstrates that the essential aspect of noise reduction in such a system is that the added fluctuations drive the system into states with a reduced intensity of intrinsic noise sufficiently often.

We show that a dissipative current component is present in the dynamics generated by a Liouville-master equation, in addition to the usual component associated with Hamiltonian evolution. The dissipative component originates from coarse graining in time, implicit in a master equation, and needs to be included to preserve current continuity. We derive an explicit expression for the dissipative current in the context of the Markov approximation. Finally, we illustrate our approach with a simple numerical example, in which a quantum particle is coupled to a harmonic phonon bath and dissipation is described by the Pauli master equation.

We predict the existence of spatially localized nontrivial topological states of a Bose-Einstein condensate with repulsive atomic interactions confined by an optical lattice. These nonlinear localized states, matter-wave gap vortices, carry a vortexlike phase dislocation and exist in the gaps of the matter-wave band-gap spectrum due to the Bragg scattering. We discuss the structure, stability, and formation dynamics of the gap vortices in the case of two-dimensional optical lattices.

A new optical pumping method, “push-pull pumping,” can produce very nearly pure, coherent superposition states between the initial and the final sublevels of the important field-independent 0-0 clock resonance of alkali-metal atoms. The key requirement for push-pull pumping is the use of $D1$ resonant light which alternates between left and right circular polarization at the Bohr frequency of the state. The new pumping method works for a wide range of conditions, including atomic beams with almost no collisions, and atoms in buffer gases with pressures of many atmospheres.

Motivated by recent efforts to achieve cold fermions pairing, we study the nonadiabatic regime of the Bardeen-Cooper-Schrieffer state formation. After the interaction is turned on, at times shorter than the quasiparticle energy relaxation time, the system oscillates between the superfluid and normal state. The collective nonlinear evolution of the BCS-Bogoliubov amplitudes $u_p$, $v_p$, along with the pairing function $\Delta$, is shown to be an integrable dynamical problem which admits single soliton and soliton train solitons. We interpret the collective oscillations as Bloch precession of Anderson pseudospins, where each soliton causes a pseudospin $2\pi$ Rabi rotation.

We calculate the location of the quantum phase transitions of a Bose gas trapped in an optical lattice as a function of effective scattering length $a_{\mathrm{e}\mathrm{f}\mathrm{f}}$ and temperature $T$. Knowledge of recent high-loop results on the shift of the critical temperature at weak couplings is used to locate a nose in the phase diagram above the free Bose-Einstein critical temperature $T_c^{(0)}$, thus predicting the existence of a reentrant transition above $T_c^{(0)}$, where a condensate should form when increasing $a_{\mathrm{e}\mathrm{f}\mathrm{f}}$. At zero temperature, the transition to the normal phase produces the experimentally observed Mott insulator.

We show that for rotating harmonically trapped Bose gases in a fractional quantum Hall state, the anyonic excitation statistics in the rotating gas can effectively play a dynamical role. For particular values of the two-dimensional coupling constant $g=-2\pi {\hslash }^2(2k-1)/m$, where $k$ is a positive integer, the system becomes a noninteracting gas of anyons, with exactly obtainable solutions satisfying Bogomol'nyi self-dual order parameter equations. Attractive Bose gases under rapid rotation thus can be stabilized in the thermodynamic limit due to the anyonic statistics of their quasiparticle excitations.

We report the use of an atomic magnetometer based on nonlinear magneto-optical rotation with frequency-modulated light to detect nuclear magnetization of xenon gas. The magnetization of a spin-exchange-polarized xenon sample ($1.7{\mathrm{c}\mathrm{m}}^3$ at a pressure of 5 bars, natural isotopic abundance, polarization $1\%$), prepared remotely to the detection apparatus, is measured with an atomic sensor. An average magnetic field of $\sim 10\mathrm{n}\mathrm{G}$ induced by the xenon sample on the 10 cm diameter atomic sensor is detected with signal-to-noise ratio $\sim 10$, limited by residual noise in the magnetic environment. The possibility of using modern atomic magnetometers as detectors of nuclear magnetic resonance and in magnetic resonance imaging is discussed. Atomic magnetometers appear to be ideally suited for emerging low-field and remote-detection magnetic resonance applications.

Although molecular dynamics methods are commonly used to drive biomolecular simulations, the technique provides insufficient sampling to impact studies of the 200-300 residue proteins of greatest interest. One severe limitation of molecular dynamics is that the integrators are restricted by resonance phenomena to small time steps $(\Delta t<8\mathrm{f}\mathrm{s})$ much slower then the time scales of important structural and solvent rearrangements. Here, a novel set of equations of motion and a reversible, resonance-free, integrator are designed which permit step sizes on the order of 100 fs to be used.

We consider the effects of superfluidity on the light scattering properties of a two component gas of fermionic atoms, demonstrating that the scattered intensities of the Stokes and anti-Stokes lines exhibit a large maximum below the critical temperature when the gas is superfluid. This effect, the light scattering analog of the Hebel-Slichter effect in conventional superconductors, can be used to detect unambiguously the onset of pairing in an atomic gas in the BCS regime.

Mass measurements with a relative precision of better than $1.5\times {10}^{-8}$ were performed on ${}^{22}\mathrm{M}\mathrm{g}$ and its reaction partners ${}^{21}\mathrm{N}\mathrm{a}$ and ${}^{22}\mathrm{N}\mathrm{a}$ with the ISOLTRAP Penning trap mass spectrometer at CERN, yielding the mass excesses $D({}^{22}\mathrm{M}\mathrm{g})=-399.92(27)\mathrm{k}\mathrm{e}\mathrm{V}$, $D({}^{21}\mathrm{N}\mathrm{a})=-2184.71(21)\mathrm{k}\mathrm{e}\mathrm{V}$, and $D({}^{22}\mathrm{N}\mathrm{a})=-5181.56(16)\mathrm{k}\mathrm{e}\mathrm{V}$. The importance of these results is twofold. First, a comparative half-life ($Ft$ value) has been obtained for the superallowed $\beta$ decay of ${}^{22}\mathrm{M}\mathrm{g}$ to further test the conserved-vector-current hypothesis. Second, the resonance energy for the ${}^{21}\mathrm{N}\mathrm{a}$ proton capture reaction has been independently determined, allowing direct comparisons of observable $\gamma$ radiation in nova explosions with the yield expected from models.

We study one-dimensional disordered bosons at large commensurate filling. Using a real space renormalization group approach, we find a new random fixed point which controls a phase transition from a superfluid to an incompressible Mott glass. The transition can be tuned by changing the disorder distribution even with vanishing interactions. We derive the properties of the transition, which suggest that it is in the Kosterlitz-Thouless universality class.