Phase transitions and the internal noise structure of nonlinear Schr\"odi nger equation solitons

We predict phase-transitions in the quantum noise characteristics of systems described by the quantum nonlinear Schr\"odinger equation, showing them to be related to the solitonic field transition at half the fundamental soliton amplitude. These phase-transitions are robust with respect to Raman noise and scattering losses. We also describe the rich internal quantum noise structure of the solitonic fields in the vicinity of the phase-transition. For optical coherent quantum solitons, this leads to the prediction that eliminating the peak side-band noise due to the electronic nonlinearity of silica fiber by spectral filtering leads to the optimal photon-number noise reduction of a fundamental soliton.Comment: 10 pages, 5 figure

Home Telemonitoring Program in Individuals with COPD During the Coronavirus Disease 2019 Pandemic: A Pilot Study

There has been significant interest in innovative ways to improve care of COPD patients. Remote patient monitoring (RPM), also called telemonitoring, is a method of healthcare delivery that gathers patient data outside of traditional healthcare settings. The COVID-19 pandemic has moved telemedicine to the forefront of care, accelerating the need to study remote monitoring in COPD patients. RPM tools including home spirometry, pulse oximetry and daily questionnaires have been shown to have potential to detect AECOPD earlier and improve patient-reported outcomes in COPD. Given the older age and numerous comorbid conditions of many COPD patients, it remains unclear if RPM interventions are feasible and acceptable by this patient population. To address this, we conducted a 12-week pilot study of a novel in-home telemonitoring system, consisting of three components: home spirometer, Bluetooth®-enabled home pulse oximeter, and tablet-based data collection system with avatar-assisted technology with the goal of determining impact on COPD Assessment Test (CAT) score and adherence to device measurements. The study was designed to be conducted entirely remotely given the Coronavirus disease-19 (COVID-19) pandemic

The N boson time dependent problem: an exact approach with stochastic wave functions

We present a numerically tractable method to solve exactly the evolution of a N boson system with binary interactions. The density operator of the system rho is obtained as the stochastic average of particular operators |Psi_1><Psi_2| of the system. The states |Psi_{1,2}> are either Fock states |N:phi_{1,2}> or coherent states |coh:phi_{1,2}> with each particle in the state phi_{1,2}. We determine the conditions on the evolution of phi_{1,2} -which involves a stochastic element- under which we recover the exact evolution of rho. We discuss various possible implementations of these conditions. The well known positive P-representation arises as a particular case of the coherent state ansatz. We treat numerically two examples: a two-mode system and a one-dimensional harmonically confined gas. These examples, together with an analytical estimate of the noise, show that the Fock state ansatz is the most promising one in terms of precision and stability of the numerical solution.Comment: 21 pages, 5 figures, submitted to Phys.Rev.

Superchemistry: dynamics of coupled atomic and molecular Bose-Einstein condensates

We analyze the dynamics of a dilute, trapped Bose-condensed atomic gas coupled to a diatomic molecular Bose gas by coherent Raman transitions. This system is shown to result in a new type of `superchemistry', in which giant collective oscillations between the atomic and molecular gas can occur. The phenomenon is caused by stimulated emission of bosonic atoms or molecules into their condensate phases

Dynamics of evaporative cooling in magnetically trapped atomic hydrogen

We study the evaporative cooling of magnetically trapped atomic hydrogen on the basis of the kinetic theory of a Bose gas. The dynamics of trapped atoms is described by the coupled differential equations, considering both the evaporation and dipolar spin relaxation processes. The numerical time-evolution calculations quantitatively agree with the recent experiment of Bose-Einstein condensation with atomic hydrogen. It is demonstrated that the balance between evaporative cooling and heating due to dipolar relaxation limits the number of condensates to 9x10^8 and the corresponding condensate fraction to a small value of 4% as observed experimentally.Comment: 5 pages, REVTeX, 3 eps figures, Phys. Rev. A in pres

Quantum dynamics of evaporatively cooled Bose-Einstein Condensates

We report on dynamical simulations of Bose-Einstein condensation via evaporative cooling in an atomic trap. The results show evidence for spontaneous vortex formation and quantum dynamics in small traps.Comment: 4 pages, 3 figure

Dynamical quantum noise in Bose-Einstein condensates

We introduce the study of dynamical quantum noise in Bose-Einstein condensates through numerical simulation of stochastic partial differential equations obtained using phase space representations. We derive evolution equations for a single trapped condensate in both the positive-$P$ and Wigner representations, and perform simulations to compare the predictions of the two methods. The positive-$P$ approach is found to be highly susceptible to the stability problems that have been observed in other strongly nonlinear, weakly damped systems. Using the Wigner representation, we examine the evolution of several quantities of interest using from a variety of choices of initial state for the condensate, and compare results to those for single-mode models.Comment: 8 figures, submitted to Phys. Rev.

Developing and applying heterogeneous phylogenetic models with XRate

Modeling sequence evolution on phylogenetic trees is a useful technique in computational biology. Especially powerful are models which take account of the heterogeneous nature of sequence evolution according to the "grammar" of the encoded gene features. However, beyond a modest level of model complexity, manual coding of models becomes prohibitively labor-intensive. We demonstrate, via a set of case studies, the new built-in model-prototyping capabilities of XRate (macros and Scheme extensions). These features allow rapid implementation of phylogenetic models which would have previously been far more labor-intensive. XRate's new capabilities for lineage-specific models, ancestral sequence reconstruction, and improved annotation output are also discussed. XRate's flexible model-specification capabilities and computational efficiency make it well-suited to developing and prototyping phylogenetic grammar models. XRate is available as part of the DART software package: http://biowiki.org/DART .Comment: 34 pages, 3 figures, glossary of XRate model terminolog

Bose-Einstein condensate collapse: a comparison between theory and experiment

We solve the Gross-Pitaevskii equation numerically for the collapse induced by a switch from positive to negative scattering lengths. We compare our results with experiments performed at JILA with Bose-Einstein condensates of Rb-85, in which the scattering length was controlled using a Feshbach resonance. Building on previous theoretical work we identify quantitative differences between the predictions of mean-field theory and the results of the experiments. Besides the previously reported difference between the predicted and observed critical atom number for collapse, we also find that the predicted collapse times systematically exceed those observed experimentally. Quantum field effects, such as fragmentation, that might account for these discrepancies are discussed.Comment: 4 pages, 2 figure