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

Double Electron−Electron Resonance Measured Between Gd³⁺ Ions and Nitroxide Radicals

Double electron−electron resonance has attracted growing attention as a technique to study structure and conformational changes of biomacromolecules. Here, a new combination of paramagnetic labels is experimentally tested, one being a commonly used nitroxide radical, and the other being a Gd³⁺ ion. The Gd³⁺−nitroxide spin pair can serve as a good substitute for the nitroxide−nitroxide pair of spin labels and potentially provides a link to other experimental approaches dealing with structural information

Distance measurements in Au nanoparticles functionalized with nitroxide radicals and Gd3+-DTPA chelate complexes

ISSN:1463-9084ISSN:1463-907

Multiple Pathway Relaxation Enhancement in the System Composed of Three Paramagnetic Species: Nitroxide Radical–Ln³⁺–O₂

Longitudinal relaxation of nitroxide spin-labels has been measured for a membrane-incorporated α-helical polypeptide in the presence and absence of residual amounts of membrane-dissolved O₂ and paramagnetic Dy³⁺ ions. Such a model system, containing three different types of paramagnetic species, provides an important example of nonadditivity of two different relaxation channels for the nitroxide spins

Clinical outcome and diagnostic methods of atypical mycobacteriosis due toMycobacterium aviumssp.hominissuisin a group of captive lowland tapirs (Tapirus terrestris)

Tapirs seem particularly susceptible to mycobacterial infections, especially to tuberculosis caused byM. tuberculosisorM. bovis. In this case series, we report an infection with the non-tuberculous mycobacteria (NTM) speciesM. aviumssp.hominissuis(MAH) in a group of four (2.2) captive lowland tapirs (Tapirus terrestris). Two female tapirs showed mild respiratory signs such as coughing and mucous sputum production for several years, one juvenile male tapir had to be euthanized due to severe dyspnoea, and the adult male only showed mild respiratory signs in 2010. Post-mortem histopathology of the euthanized animal revealed a chronic bronchopneumonia, and MAH was detected via culture. Subsequently, the three remaining tapirs were tested further: serologically, the tapirs had high antibody titres againstM. avium, but they showed no reaction in the comparative skin test (TST). At several time points, the animals were tested for the presence of mycobacteria in different sample matrices including sputum samples, pooled faecal samples as well as swabs from the tapir enclosure to identify potential environmental niches of the pathogen. Moreover, animals were directly sampled using nasal swabs, endoscopic broncho-alveolar (BAL) and gastric lavages. MAH was detected by culture in the sputum samples, in the BAL of the breeding pair, as well as in the swimming pool water and walls, and in swabs taken from the tapir's sleeping beds. We conclude that the TST is not a useful diagnostic tool to detect MAC infections in tapirs, whereas antibody ELISA and culture from BAL appear more sensitive