134 research outputs found
From megahertz to terahertz qubits encoded in molecular ions: theoretical analysis of dipole-forbidden spectroscopic transitions in N
Recent advances in quantum technologies have enabled the precise control of
single trapped molecules on the quantum level. Exploring the scope of these new
technologies, we studied theoretically the implementation of qubits and clock
transitions in the spin, rotational, and vibrational degrees of freedom of
molecular nitrogen ions including the effects of magnetic fields. The relevant
spectroscopic transitions span six orders of magnitude in frequency
illustrating the versatility of the molecular spectrum for encoding quantum
information. We identified two types of magnetically insensitive qubits with
very low ("stretched"-state qubits) or even zero ("magic" magnetic-field
qubits) linear Zeeman shifts. The corresponding spectroscopic transitions are
predicted to shift by as little as a few mHz for an amplitude of magnetic-field
fluctuations on the order of a few mG translating into Zeeman-limited coherence
times of tens of minutes encoded in the rotations and vibrations of the
molecule. We also found that the Q(0) line of the fundamental vibrational
transition is magnetic-dipole allowed by interaction with the first excited
electronic state of the molecule. The Q(0) transitions, which benefit from
small systematic shifts for clock operation and high sensitivity to a possible
variation in the proton-to-electron mass ratio, were so far not considered in
single-photon spectra. Finally, we explored possibilities to coherently control
the nuclear-spin configuration of N through the magnetically enhanced
mixing of nuclear-spin states
Non-destructive State Detection and Spectroscopy of Single Molecules
We review our recent experimental results on the non-destructive quantum-state detection and spectroscopy of single trapped molecules. At the heart of our scheme, a single atomic ion is used to probe the state of a single molecular ion without destroying the molecule or even perturbing
its quantum state. This method opens up perspectives for new research directions in precision spectroscopy, for the development of new frequency standards, for tests of fundamental physical concepts and for the precise study of chemical reactions and molecular collisions with full control
over the molecular quantum state
Identification of molecular quantum states using phase-sensitive forces
Quantum-logic techniques used to manipulate quantum systems are now increasingly being applied to molecules. Previous experiments on single trapped diatomic species have enabled state detection with excellent fidelities and highly precise spectroscopic measurements. However, for complex molecules with a dense energy-level structure improved methods are necessary. Here, we demonstrate an enhanced quantum protocol for molecular state detection using state-dependent forces. Our approach is based on interfering a reference and a signal force applied to a single atomic and molecular ion. By changing the relative phase of the forces, we identify states embedded in a dense molecular energy-level structure and monitor state-to-state inelastic scattering processes. This method can also be used to exclude a large number of states in a single measurement when the initial state preparation is imperfect and information on the molecular properties is incomplete. While the present experiments focus on N[Formula: see text], the method is general and is expected to be of particular benefit for polyatomic systems
Evidence for a Ru Kondo Lattice in LaCuRuO
Rare -electron derived heavy-fermion properties of the solid-solution
series LaCuRuTiO were studied for by
resistivity, susceptibility, specific-heat measurements, and magnetic-resonance
techniques. The pure ruthenate () is a heavy-fermion metal characterized
by a resistivity proportional to at low temperatures . The coherent
Kondo lattice formed by the localized Ru 4 electrons is screened by the
conduction electrons leading to strongly enhanced effective electron masses. By
increasing titanium substitution the Kondo lattice becomes diluted resulting in
single-ion Kondo properties like in the paradigm -based heavy-fermion
compound CeLaCuSi [M. Ocko {\em et al.}, Phys. Rev. B
\textbf{64}, 195106 (2001)]. In LaCuRuTiO the
heavy-fermion behavior finally breaks down on crossing the metal-to-insulator
transition close to .Comment: 9 pages, 8 figure
Identification of molecular quantum states using phase-sensitive forces
Quantum-logic techniques used to manipulate quantum systems are now
increasingly being applied to molecules. Previous experiments on single trapped
diatomic species have enabled state detection with excellent fidelities and
highly precise spectroscopic measurements. However, for complex molecules with
a dense energy-level structure improved methods are necessary. Here, we
demonstrate an enhanced quantum protocol for molecular state detection using
state-dependent forces. Our approach is based on interfering a reference and a
signal force applied to a single atomic and molecular ion, respectively, in
order to extract their relative phase. We use this phase information to
identify states embedded in a dense molecular energy-level structure and to
monitor state-to-state inelastic scattering processes. This method can also be
used to exclude a large number of states in a single measurement when the
initial state preparation is imperfect and information on the molecular
properties is incomplete. While the present experiments focus on N, the
method is general and is expected to be of particular benefit for polyatomic
systems
Design and realization of a sputter deposition system for the \textit{in situ-} and \textit{in operando-}use in polarized neutron reflectometry experiments
We report on the realization of a sputter deposition system for the in situ-
and in operando-use in polarized neutron reflectometry experiments. Starting
with the scientific requirements, which define the general design
considerations, the external limitations and boundaries imposed by the
available space at a neutron beamline and by the neutron and vacuum
compatibility of the used materials, are assessed. The relevant aspects are
then accounted for in the realization of our highly mobile deposition system,
which was designed with a focus on a quick and simple installation and
removability at the beamline. Apart from the general design, the in-vacuum
components, the auxiliary equipment and the remote control via a computer, as
well as relevant safety aspects are presented in detail.Comment: Submitted for publication in Nuclear Inst. and Methods in Physics
Research, A. (1st revised version
State-selective coherent motional excitation as a new approach for the manipulation, spectroscopy and state-to-state chemistry of single molecular ions
We present theoretical and experimental progress towards a new approach for the precision spectroscopy, coherent manipulation and state-to-state chemistry of single isolated molecular ions in the gas phase. Our method uses a molecular beam for creating packets of rotationally cold neutrals from which a single molecule is state-selectively ionized and trapped inside a radiofrequency ion trap. In addition to the molecular ion, a single co-trapped atomic ion is used to cool the molecular external degrees of freedom to the ground state of the trap and to detect the molecular state using state-selective coherent motional excitation from a modulated optical-dipole force acting on the molecule. We present a detailed discussion and theoretical characterization of the present approach. We simulate the molecular signal experimentally using a single atomic ion, indicating that different rovibronic molecular states can be resolved and individually detected with our method. The present approach for the coherent control and non-destructive detection of the quantum state of a single molecular ion opens up new perspectives for precision spectroscopies relevant for, e.g., tests of fundamental physical theories and the development of new types of clocks based on molecular vibrational transitions. It will also enable the observation and control of chemical reactions of single particles on the quantum level. While focusing on N-2(+) as a prototypical example in the present work, our method is applicable to a wide range of diatomic and polyatomic molecules
Varicella-zoster virus infections in immunocompromised patients - a single centre 6-years analysis
Background: Infection with varicella-zoster virus (VZV) contemporaneously with malignant disease or immunosuppression represents a particular challenge and requires individualized decisions and treatment. Although the increasing use of varicella-vaccines in the general population and rapid initiation of VZVimmunoglobulins and acyclovir in case of exposure has been beneficial for some patients, immunocompromised individuals are still at risk for unfavourable courses. Methods: In this single center, 6-year analysis we review incidence, hospitalization and complication rates of VZVinfections in our center and compare them to published data. Furthermore, we report three instructive cases. Results: Hospitalization rate of referred children with VZV-infections was 45%, among these 17% with malignancies and 9% under immunosuppressive therapy. Rate of complications was not elevated in these two high-risk cohorts, but one ALL-patient died due to VZV-related complications. We report one 4-year old boy with initial diagnosis of acute lymphoblastic leukemia who showed a rapidly fatal outcome of his simultaneous varicella-infection, one 1.8-year old boy with an identical situation but a mild course of his disease, and an 8.5-year old boy with a steroiddependent nephrotic syndrome. This boy developed severe hepatic involvement during his varicella-infection but responded to immediate withdrawl of steroids and administration of acyclovir plus single-dose cidofovir after nonresponse to acyclovir after 48 h. Conclusion: Our data show that patients with malignant diseases or immunosuppressive therapy should be hospitalized and treated immediately with antiviral agents. Despite these measures the course of VZV-infections can be highly variable in these patients. We discuss aids to individual decision-making for these difficult situations
Effects of antiplatelet therapy on stroke risk by brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases: subgroup analyses of the RESTART randomised, open-label trial
Background
Findings from the RESTART trial suggest that starting antiplatelet therapy might reduce the risk of recurrent symptomatic intracerebral haemorrhage compared with avoiding antiplatelet therapy. Brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases (such as cerebral microbleeds) are associated with greater risks of recurrent intracerebral haemorrhage. We did subgroup analyses of the RESTART trial to explore whether these brain imaging features modify the effects of antiplatelet therapy
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