Decoherence suppression by uncollapsing

We show that the qubit decoherence due to zero-temperature energy relaxation can be almost completely suppressed by using the quantum uncollapsing procedure. To protect a qubit state, a partial quantum measurement moves it towards the ground state, where it is kept during the storage period, while the second partial measurement restores the initial state. This procedure preferentially selects the cases without energy decay events. Stronger decoherence suppression requires smaller selection probability; a desired point in this trade-off can be chosen by varying the measurement strength. The experiment can be realized in a straightforward way using the superconducting phase qubit.Comment: 4 page

Divergence in seasonal hydrology across northern Eurasia: Emerging trends and water cycle linkages

Discharge from large Eurasia rivers increased during the 20th century, yet much remains unknown regarding details of this increasing freshwater flux. Here, for the three largest Eurasian basins (the Ob, Yenisei, and Lena) we examine the nature of annual and seasonal discharge trends by investigating the flow changes along with those for precipitation, snow depth, and snow water equivalent. On the basis of a multiperiod trend analysis and examination of station data, we propose two characteristic regimes to explain the long‐term discharge increase from these large Eurasian rivers. Over the early decades from approximately 1936 to 1965, annual precipitation correlates well with annual discharge, and positive discharge trends are concurrent with summer/fall discharge increases. The latter decades were marked by a divergence between winter/spring flows, which increased, amid summer/fall discharge declines. A comparison of cold season precipitation (CSP) and spring discharge trends across subbasins of the Ob, Yenisei, and Lena shows limited agreement with one precipitation data set but good agreement (R2 \u3e 0.90) when a second is used. While natural variability in the Arctic system tends to mask these emerging trends, spatial and temporal changes can generally be characterized by increased solid precipitation, primarily to the north, along with a drier hydrography during the warm season

Collision avoidance system optimization for closely spaced parallel operations through surrogate modeling

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2013.This electronic version was submitted and approved by the author's academic department as part of an electronic thesis pilot project. The certified thesis is available in the Institute Archives and Special Collections."June 2013." Cataloged from department-submitted PDF version of thesisIncludes bibliographical references (p. 103-106).The Traffic Alert and Collision Avoidance System (TCAS) is mandated worldwide to protect against aircraft mid-air collisions. One drawback of the current TCAS design is limited support for certain closely spaced parallel runway operations. TCAS alerts too frequently, leading pilots to often inhibit Resolution Advisories during approach. Research is underway on the Airborne Collision Avoidance System X (ACAS X), a next-generation collision avoidance system that will support new surveillance systems and air traffic control procedures. ACAS X has been shown to outperform TCAS for enroute encounter scenarios. However, the design parameters that are tuned for the enroute environment are not appropriate for closely spaced parallel operations (CSPO). One concept to enhance the safety of CSPO is a procedure-specific mode of the logic that minimizes nuisance alerts while still providing collision protection. This thesis describes the application of surrogate modeling and automated search for the purpose of tuning ACAS X for parallel operations. The performance of the tuned system is assessed using a data-driven blunder model and an operational performance model. Although collision avoidance system development normally relies on human judgment and expertise to achieve ideal behavior, surrogate modeling is efficient and effective in tuning ACAS X for CSPO as the tuned logic outperforms TCAS in terms of both safety and operational suitabilityby Kyle A. Smith.S.M

Simple quantum error detection and correction for superconducting qubits

We analyze simple quantum error detection and quantum error correction protocols relevant to current experiments with superconducting qubits. We show that for qubits with energy relaxation the repetitive N-qubit codes cannot be used for quantum error correction, but can be used for quantum error detection. In the latter case it is sufficient to use only two qubits for the encoding. In the analysis we demonstrate a useful technique of unraveling the qubit energy relaxation into "relaxation" and "no relaxation" scenarios. Also, we propose and numerically analyze several two-qubit algorithms for quantum error detection/correction, which can be readily realized at the present-day level of the phase qubit technology.Comment: 14 pages, 8 figure

ANALYZING KEY COMMUNICATORS

As history has shown, members of social groups trust select individuals who can access information and provide persuasive perspectives. Known by the Department of Defense as key communicators, these personalities maintain a great deal of influence deriving their authority from various official, cultural, religious, and social statuses within their respective communities. Although psychological operations and other national security personnel understand their value, current government training and processes do not adequately address the need for effective analysis of key communicators. The purpose of this research is to develop a foundational PSYOP analytical process to improve how practitioners select key communicators to support military objectives. Drawing from academic theories, scientific processes, and the experience of military service members, how can PSYOP personnel analyze key communicators to leverage their social networks? The research reviewed relevant theories, systems, processes, techniques, and procedures to develop the key communicator analytical process (KCAP). This process and its associated tool were designed to guide practitioners as they identify, categorize, organize, visualize, and evaluate relevant qualitative and quantitative communicator and audience variables to yield an appropriate index score with which to compare against others. Finally, this tool was applied to a historical case study to validate its functionality in future operational settings.Major, United States ArmyMajor, United States ArmyMajor, United States ArmyApproved for public release. Distribution is unlimited

Macroscopic constitutive model for ergodic and non-ergodic lead-free relaxors

A fully electromechanically coupled, three dimensional phenomenological constitutive model for relaxor ferroelectric materials was developed for the use in a finite-element-method (FEM) solution procedure. This macroscopic model was used to simulate the macroscopic electromechanical response of lead-free ergodic 0.94Na1/2Bi1/2TiO3−0.06BaTiO3 and non-ergodic 0.90Na1/2Bi1/2TiO3−0.06BaTiO3−0.04K0.5Na0.5NbO3 relaxor materials. The presented constitutive model is capable of accounting for the observed pinched hysteretic response as well as non-deviatoric polarization induced strain and internal order transitions. Time integration of the history dependent internal variables is done with a predictor-corrector integration scheme. The adaptability of the constitutive model regarding the pinching of the hystereses is shown. Simulations are compared to experimental observations

Human Vault Nanoparticle Targeted Delivery of Antiretroviral Drugs to Inhibit Human Immunodeficiency Virus Type 1 Infection.

"Vaults" are ubiquitously expressed endogenous ribonucleoprotein nanoparticles with potential utility for targeted drug delivery. Here, we show that recombinant human vault nanoparticles are readily engulfed by certain key human peripheral blood mononuclear cells (PBMC), predominately dendritic cells, monocytes/macrophages, and activated T cells. As these cell types are the primary targets for human immunodeficiency virus type 1 (HIV-1) infection, we examined the utility of recombinant human vaults for targeted delivery of antiretroviral drugs. We chemically modified three different antiretroviral drugs, zidovudine, tenofovir, and elvitegravir, for direct conjugation to vaults. Tested in infection assays, drug-conjugated vaults inhibited HIV-1 infection of PBMC with equivalent activity to free drugs, indicating vault delivery and drug release in the cytoplasm of HIV-1-susceptible cells. The ability to deliver functional drugs via vault nanoparticle conjugates suggests their potential utility for targeted drug delivery against HIV-1