We demonstrate that the nonlinear mean-field shift in a multicomponent Bose-Einstein condensate may be eliminated by controlling the two-body interaction coefficients. This modification can be achieved by engineering the environment of the condensate. We consider the case of a two-component condensate in a quasi-one-dimensional atomic waveguide, achieving modification of the atom-atom interactions by varying the transverse wave functions of the components. Eliminating the density-dependent phase shift represents a promising potential application for multicomponent condensates in atom interferometry and precision measurements.

Can one construct a thermodynamics for compact, slowly moving powders and grains? A few years ago, Edwards proposed a possible step in this direction, raising the fascinating perspective that such systems have a statistical mechanics of their own, different from that of Maxwell, Boltzmann, and Gibbs, allowing us to have some information while still ignoring dynamic details. Recent developments in the theory of glasses have come to confirm these ideas within mean field. In order to go beyond, we explicitly generate Edwards' measure in a 3D model. Comparison of the results with the irreversible compaction data shows very good agreement. The present framework immediately suggests new experimental checks.

A search for sidereal variations in the frequency difference between co-located ${}^{129}\mathrm{Xe}$ and ${}^3\mathrm{He}$ Zeeman masers sets the most stringent limit to date on leading-order Lorentz and CPT violation involving the neutron, consistent with no effect at the level of ${10}^{-31\mathrm{}}\mathrm{GeV}$.

Consider a time-dependent Hamiltonian $H(Q,P;x(t\left)\right)$ with periodic driving $x\left(t\right)=A\sin \left(\Omega t\right)$. It is assumed that the classical dynamics is chaotic, and that its power spectrum extends over some frequency range $|\omega |<{\omega }_{\mathrm{cl}}$. Both classical and quantum-mechanical (QM) linear response theory (LRT) predict a relatively large response for $\Omega <{\omega }_{\mathrm{cl}}$, and a relatively small response otherwise, independent of the driving amplitude $A$. We define a nonperturbative regime in the $(\Omega ,A)$ space, where LRT fails, and demonstrate this failure numerically. For $A>\mathrm{}{A}_{\mathrm{prt}}$, where $A_{\mathrm{prt}}\propto ħ$, the system may have a relatively strong response for $\Omega >{\omega }_{\mathrm{cl}}$ due to QM nonperturbative effect.

We present a finite temperature field theory for collective excitations of trapped Bose condensates which includes the dynamics of the thermal cloud. In spherical traps we show that excitations couple strongly to a small number of modes, giving resonance structure in their frequency spectra. Where possible, we derive energy shifts and lifetimes of excitations. For the $l=0\mathrm{}$ mode we show that the simple picture of a decay rate fails, which should be observable in suitable experiments. It also suggests a possible explanation for the anomalous behavior of the $m=0\mathrm{}$ mode observed in anisotropic traps.

We study the properties of the “rigid Laplacian” operator; that is we consider solutions of the Laplacian equation in the presence of fixed truncation errors. The dynamics of convergence to the correct analytical solution displays the presence of a metastable set of numerical solutions, whose presence can be related to granularity. We provide some scaling analysis in order to determine the value of the exponents characterizing the process. We believe that this prototype model is also suitable to provide an explanation of the widespread presence of power law in a social and economic system where information and decision diffuse, with errors and delay from agent to agent.

We formulate the conditions under which the dynamics of a continuously measured quantum system becomes indistinguishable from that of the corresponding classical system. In particular, we demonstrate that even in a classically chaotic system the quantum state vector conditioned by the measurement remains localized and, under these conditions, follows a trajectory characterized by the classical Lyapunov exponent.

It is shown that, in dilute-gas Bose-Einstein condensates, there exist both dynamically stable and unstable configurations which, in the hydrodynamic limit, exhibit a behavior resembling that of gravitational black holes. The dynamical instabilities involve creation of quasiparticle pairs in positive and negative energy states, as in the well-known suggested mechanism for black-hole evaporation. We propose a scheme to generate a stable sonic black hole in a ring trap.

We show that the density profile of a Fermi gas in rapidly rotating potential will develop prominent features reflecting the underlying Landau-level–like energy spectrum. Depending on the aspect ratio of the trap, these features can be a sequence of ellipsoidal volumes or a sequence of quantized steps.

A novel kind of aperiodic stochastic resonance is experimentally studied in a vertical cavity surface emitting laser. We characterize the response of the system to a random, binary signal as a function of an applied external noise. A maximum in the input-output correlation is found for a nonzero added noise. We present analytic results with a good agreement with the measurements. We also discuss the physical meaning of the phenomenon using simple arguments, and we compare it to stochastic resonance.

Evidence of acceleration of a chemical reaction in a condensed phase due to the quantum anti-Zeno effect is presented by a quantum-mechanical calculation. The acceleration is caused by electronic decoherence. The mechanism clearly indicates the anti-Zeno effect and involves both delocalization of the electronic dynamics and a feedback loop by coupling to vibrations. Believed to be the first established example of the quantum anti-Zeno effect in chemistry, the observed phenomenon suggests the possibility of quantum control of chemical reactivity by choice of solvent.

Tests of local realism versus quantum mechanics based on Bell's inequality employ two entangled qubits. We investigate the general case of two entangled quantum systems defined in $N$-dimensional Hilbert spaces, or “ $\mathrm{qu}N\mathrm{its}$.” Via a numerical linear optimization method we show that violations of local realism are stronger for two maximally entangled $\mathrm{qu}N\mathrm{its}$ ( $3\le N\le 9$) than for two qubits and that they increase with $N$. The two $\mathrm{qu}N\mathrm{it}$ measurements can be experimentally realized using entangled photons and unbiased multiport beam splitters.

We propose an experiment, based on two consecutive Bragg pulses, to measure the momentum distribution of quasiparticle excitations in a trapped Bose gas at low temperature. With the first pulse one generates a bunch of excitations carrying momentum $q$, whose Doppler line is measured by the second pulse. We show that this experiment can provide direct access to the amplitudes $u_q$ and $v_q$ characterizing the Bogoliubov transformations from particles to quasiparticles. We simulate the behavior of the nonuniform gas by numerically solving the time dependent Gross-Pitaevskii equation.

We study the distributions of the resonance widths $P\left(\Gamma \right)$ and of delay times $P\left(\tau \right)$ in one-dimensional quasiperiodic tight-binding systems at critical conditions with one open channel. Both quantities are found to decay algebraically as ${\Gamma }^{-\alpha }$ and ${\tau }^{-\gamma }$ on small and large scales, respectively. The exponents $\alpha$ and $\gamma$ are related to the fractal dimension $D_0^E$ of the spectrum of the closed system as $\alpha {=1+D}_0^E$ and $\gamma {=2-D}_0^E$. Our results are verified for the Harper model at the metal-insulator transition and for Fibonacci lattices.

We simulate random sequential adsorption of tethered hard disks which undergo limited Monte Carlo surface diffusion to study kinetics and nonequilibrium phase behavior. Tethers allow the disks to move within a specified distance of their original adsorption locations, placing a control on the local entropy of each disk. As the surface coverage increases, systems with sufficiently long tethers form hexatic or crystalline lattices, while short tethers frustrate organization. Lattices form with surprisingly short tether lengths—on the order of one disk diameter.

A Comment on the Letter by Eloy Ayon-Beato and Alberto Garcia, Phys. Rev. Lett. 80, 5056 (1998).

We present a new model of Bose-Einstein condensate dynamics based on strong confinement near the ground state. The model is based on a combined particle-wave view of the condensate and predicts oscillations in a two-component condensate, based on interference of nonspreading wave packets moving within a pair of tilted nearly square potentials. The oscillations are similar to those recently reported for a magnetically trapped ${}^{87}\mathrm{Rb}$ condensate, and the model's predictions give good quantitative agreement with the experiments.

The evolution of a quantum wave function on a lattice with time-dependent random disorder is studied. It is found that the bound state wave function of a quantum system exhibits intrinsic instability with respect to noisy disorder in the statistical sense. Under the general scheme of time coarse graining, we show nonperturbatively that the stationary attractive potential is completely washed out at large time scales by the existence of the noisy disorder to any order of density correlations.

We present a scheme for creating quantum entangled atomic states through the coherent spin-exchange collision of a spinor Bose-Einstein condensate. The state generated possesses macroscopic Einstein-Podolsky-Rosen correlation and the fluctuation in one of its quasispin components vanishes. We show that an elongated condensate with large aspect ratio is most suitable for creating such a state.

We propose and analyze a scheme for generating entangled atomic beams out of a Bose-Einstein condensate using spin-exchanging collisions. In particular, we show how to create both atomic squeezed states and entangled states of pairs of atoms.