Multimegawatt dynamic NEP PMAD study

The National Aeronautics and Space Administration Lewis Research Center (NASA LeRC) is developing a FORTRAN-based model of a complete nuclear electric propulsion (NEP) vehicle to be used for piloted or cargo missions to the Moon or Mars. The proposed vehicle will use either a Brayton or K-Rankine power conversion cycle, and either ion or magnetoplasmadynamic (MPD) thrusters. In support of this effort, Rocketdyne evaluated various power management and distribution (PMAD) approaches and selected a low-frequency design that is based on the direct use of the alternator voltage and frequency for power transmission. This approach was compared with dc and high-frequency ac designs, and selected on the basis of mass, efficiency, and qualitative assessment of power quality, reliability and development costs. This low-frequency architecture will be used as the reference in future NEP PMAD studies and for the subsequent FORTRAN model development

Quantifying the effectiveness of silver ring splints to correct swan-neck deformity

Swan-neck deformity is a common symptom of rheumatoid arthritis affecting the fingers. It can be classified by hyperextension of the proximal interphalangeal (PIP) joint and flexion of the distal interphalangeal joint [1]. Methods to correct hyperextension of the PIP joint range from surgery to splinting techniques [2]. Silver ring splints (SRSs) were recently identified as a possible alternative to surgery and traditional thermoplastic splints because patient adherence was improved by their appearance [3]. The objective of this study was to investigate whether the SRSs restrict PIP joint hyperextension during a fine dexterity task

Enhanced energy relaxation process of quantum memory coupled with a superconducting qubit

For quantum information processing, each physical system has different advantage for the implementation and so hybrid systems to benefit from several systems would be able to provide a promising approach. One of the common hybrid approach is to combine a superconducting qubit as a controllable qubit and the other quantum system with a long coherence time as a memory qubit. The superconducting qubit allows us to have an excellent controllability of the quantum states and the memory qubit is capable of storing the information for a long time. By tuning the energy splitting between the superconducting qubit and the memory qubit, it is believed that one can realize a selective coupling between them. However, we have shown that this approach has a fundamental drawback concerning energy leakage from the memory qubit. The detuned superconducting qubit is usually affected by severe decoherence, and this causes an incoherent energy relaxation from the memory qubit to the superconducting qubit via the imperfect decoupling. We have also found that this energy transport can be interpreted as an appearance of anti quantum Zeno effect induced by the fluctuation in the superconducting qubit. We also discuss a possible solution to avoid such energy relaxation process, which is feasible with existing technology

Coulomb crystallization in expanding laser-cooled neutral plasmas

We present long-time simulations of expanding ultracold neutral plasmas, including a full treatment of the strongly coupled ion dynamics. Thereby, the relaxation dynamics of the expanding laser-cooled plasma is studied, taking into account elastic as well as inelastic collisions. It is demonstrated that, depending on the initial conditions, the ionic component of the plasma may exhibit short-range order or even a superimposed long-range order resulting in concentric ion shells. In contrast to ionic plasmas confined in traps, the shell structures are built up from the center of the plasma cloud rather than from the periphery

Spatiotemporal dynamics of quantum jumps with Rydberg atoms

We study the nonequilibrium dynamics of quantum jumps in a one-dimensional chain of atoms. Each atom is driven on a strong transition to a short-lived state and on a weak transition to a metastable state. We choose the metastable state to be a Rydberg state so that when an atom jumps to the Rydberg state, it inhibits or enhances jumps in the neighboring atoms. This leads to rich spatiotemporal dynamics that are visible in the fluorescence of the strong transition.Comment: 10 page

Initializing a Quantum Register from Mott Insulator States in Optical Lattices

We propose and quantitatively develop two schemes to quickly and accurately generate a stable initial configuration of neutral atoms in optical microtraps by extraction from the Mott insulator state in optical lattices. We show that thousands of atoms may be extracted and stored in the ground states of optical microtrap arrays with one atom per trap in one operational process demonstrating massive scalability. The failure probability during extraction in the first scheme can be made sufficiently small (10^{-4}) to initialize a large scale quantum register with high fidelity. A complementary faster scheme with more extracted atoms but lower fidelity is also developed.Comment: 5 pages, 3 figure