Quantum control of hybrid nuclear-electronic qubits

Pulsed magnetic resonance is a wide-reaching technology allowing the quantum state of electronic and nuclear spins to be controlled on the timescale of nanoseconds and microseconds respectively. The time required to flip either dilute electronic or nuclear spins is orders of magnitude shorter than their decoherence times, leading to several schemes for quantum information processing with spin qubits. We investigate instead the novel regime where the eigenstates approximate 50:50 superpositions of the electronic and nuclear spin states forming "hybrid nuclear-electronic" qubits. Here we demonstrate quantum control of these states for the first time, using bismuth-doped silicon, in just 32 ns: this is orders of magnitude faster than previous experiments where pure nuclear states were used. The coherence times of our states are five orders of magnitude longer, reaching 4 ms, and are limited by the naturally-occurring 29Si nuclear spin impurities. There is quantitative agreement between our experiments and no-free-parameter analytical theory for the resonance positions, as well as their relative intensities and relative Rabi oscillation frequencies. In experiments where the slow manipulation of some of the qubits is the rate limiting step, quantum computations would benefit from faster operation in the hybrid regime.Comment: 20 pages, 8 figures, new data and simulation

Forecasting the presidential primary vote: Viability, ideology and momentum

The presidential primary vote represents a unique electoral forecasting challenge, with multiple candidates and sequential voting. This study compares the leading primary vote forecast models by re-estimating them for a common set of candidates and nomination campaigns. A new forecast model is estimated to assess the predictive power of candidate ideology, controlling for the effects of variables found to be significant in prior studies. Finally, the study compares the early forecasts, based on data from before the Iowa caucus, with "momentum" models, which are the early models, updated with variables representing the results of the Iowa Caucus and New Hampshire Primary vote, predicting the remaining contested primary vote.

Following the Rules? Candidate Strategy in Presidential Primaries

The competitiveness of the 2008 presidential primaries in both the Republican and Democratic parties has prompted a reconsideration of the role of delegate-selection rules in influencing the strategic behavior of presidential candidates. Using advertising and candidate state-visit data from the 2004 and 2008 presidential nominating campaigns, we reexamine the strategies presidential candidates use when competing for the nomination of their party. Copyright (c) 2009 by the Southwestern Social Science Association.