4,885 research outputs found
Experimental Hamiltonian identification for controlled two-level systems
We present a strategy to empirically determine the internal and control Hamiltonians for an unknown two-level system (black box) subject to various (piecewise constant) control fields when direct readout by measurement is limited to a single, fixed observable
Controlled phase gate for solid-state charge qubits
We describe a mechanism for realizing a controlled phase gate for solid-state
charge qubits. By augmenting the positionally defined qubit with an auxiliary
state, and changing the charge distribution in the three-dot system, we are
able to effectively switch the Coulombic interaction, effecting an entangling
gate. We consider two architectures, and numerically investigate their
robustness to gate noise.Comment: 14 pages, 11 figures, 2 tables, RevTeX
Fidelity and coherence measures from interference
By utilizing single particle interferometry, the fidelity or coherence of a pair of quantum states is identified with their capacity for interference. We consider processes acting on the internal degree of freedom (e.g., spin or polarization) of the interfering particle, preparing it in states ρA or ρB in the respective path of the interferometer. The maximal visibility depends on the choice of interferometer, as well as the locality or nonlocality of the preparations, but otherwise depends only on the states ρA and ρB and not the individual preparation processes themselves. This allows us to define interferometric measures which probe locality and correlation properties of spatially or temporally separated processes, and can be used to differentiate between processes that cannot be distinguished by direct process tomography using only the internal state of the particle
Description of superdeformed bands in light N=Z nuclei using the cranked HFB method
Superdeformed states in light nuclei are studied by means of the
self-consistent cranking calculation (i.e., the P + QQ model based on the
cranked Hartree-Fock-Bogoliubov method). Analyses are given for two typical
cases of superdeformed bands in the mass region, that is, bands
where backbending is absent (Ca) and present (Ar). Investigations
are carried out, particularly for the following points: cross-shell excitations
in the sd and pf shells; the role of the g and d orbitals; the
effect of the nuclear pairing; and the interplay between triaxiality and band
termination.Comment: 17 pages, 18 figures, accepted in Phys. Rev.
Fundamental Speed Limits on Quantum Coherence and Correlation Decay
The study and control of coherence in quantum systems is one of the most
exciting recent developments in physics. Quantum coherence plays a crucial role
in emerging quantum technologies as well as fundamental experiments. A major
obstacle to the utilization of quantum effects is decoherence, primarily in the
form of dephasing that destroys quantum coherence, and leads to effective
classical behaviour. We show that there are universal relationships governing
dephasing, which constrain the relative rates at which quantum correlations can
disappear. These effectively lead to speed limits which become especially
important in multi-partite systems
Systematic analyses of the t t clustering effect in He isotopes
A systematic study on the ground state structure of He isotopes including 10He is presented through a new method developed on the basis of antisymmetrized molecular dynamics AMD , the generator coordinate method GCM , and the stochastic variational method SVM . In this approach, variational calculations are carried out by means of the GCM with the AMD wave functions produced by means of the SVM. A role of the t t cluster component is examined with the present method, allowing the wider configuration space containing simultaneously the t t valence neutrons structure and 4He valence neutrons strucutur
Interference of Quantum Channels
We show how interferometry can be used to characterise certain aspects of
general quantum processes, in particular, the coherence of completely positive
maps. We derive a measure of coherent fidelity, maximum interference visibility
and the closest unitary operator to a given physical process under this
measure.Comment: 4 pages, 5 figures, REVTeX 4, typographical corrections and added
acknowledgemen
Geometric phases for mixed states in interferometry
We provide a physical prescription based on interferometry for introducing
the total phase of a mixed state undergoing unitary evolution, which has been
an elusive concept in the past. We define the parallel transport condition that
provides a connection-form for obtaining the geometric phase for mixed states.
The expression for the geometric phase for mixed state reduces to well known
formulas in the pure state case when a system undergoes noncyclic and unitary
quantum evolution.Comment: Two column, 4 pages, Latex file, No figures, Few change
Changes in Serum Electrolytes and Lipid Profile in Diabetes Subjects in Freetown Sierra Leone
Background: Measurement of blood electrolytes level and lipid profile usually
give good indications of the disease progression in a number of non communicable
diseases.
Objective: To investigate the effect of diabetes on electrolyte and lipid status of
male and female diabetics in Freetown, Sierra Leone.
Subjects and Methods: Serum concentrations of electrolytes and lipids in one hundred and twenty (120) adult diabetics attending some diagnostic centers in Freetown Sierra Leone were measured and compared with those of one hundred and twenty (120) non-diabetic individuals.
Results: Total cholesterol, LDL-cholesterol, triglycerides and coronary heart disease (CHD) risk ratio in diabetic patients were significantly higher (
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