242 research outputs found
Decoherence due to telegraph and 1/f noise in Josephson qubits
We study decoherence due to random telegraph and 1/f noise in Josephson
qubits. We illustrate differences between gaussian and non gaussian effects at
different working points and for different protocols. Features of the
intrinsically non-gaussian and non-Markovian low-frequency noise may explain
the rich physics observed in the spectroscopy and the dynamics of charge based
devices.Comment: 6 pages, 4 figures. Proceedings of the International Symposium on
Mesoscopic Superconductivity and Spintronics 2004 (MS+S2004), Atsugi, Japa
Effects of low-frequency noise cross-correlations in coupled superconducting qubits
We study the effects of correlated low frequency noise sources acting on a
two qubit gate in a fixed coupling scheme. A phenomenological model for the
spatial and cross-talk correlations is introduced. The decoherence inside the
SWAP subspace is analysed by combining analytic results based on the adiabatic
approximation and numerical simulations. Results critically depend on amplitude
of the low frequency noise with respect to the qubits coupling strength.
Correlations between noise sources induce qualitative different behaviors
depending on the values of the above parameters. The possibility to reduce
dephasing due to correlated low frequency noise by a recalibration protocol is
discussed.Comment: 18 pages, 7 figure
Parity Effect in a Small Superconducting Particle
Matveev and Larkin calculated the parity effect on the ground state energy of
a small superconducting particle in the regimes where the mean level spacing is
either large or small compared to the bulk gap. We perform a numerical
calculation which extends their results into the intermediate regime, where the
level spacing is of the same order as the bulk gap.Comment: 6 LaTeX pages, including 2 EPS figures; corrected reference and
spellin
Different carbohydrate sources affect swine performance and post-prandial glycaemic response
The type of starch and fibre in the diet affects several parameters, including glycaemic and insulin response, that are involved in pig growth performance. Four experimental diets for growing pigs differing for carbohydrates source (corn, barley, faba bean and pea) were tested. The diets were analysed in vitro to assess the carbohydrates characteristics, and they were administered to 56 crossbreed growing pigs (Landrace × Large White) randomly divided into four groups (mean age of 95 ± 6 days; body weight 80 kg ± 4 days). Clinical examination and average daily gain were performed before recruitment and after 40 days of experiment. The metabolic effects were investigated by blood count and serum biochemical parameters and by the glycaemic and insulin post-prandial response. The study revealed substantial differences among the diets, suggesting that alternative feedstuffs for swine affect several parameters, including glycaemic and insulin response, with no negative effects on growing performance. The Barley group showed the highest daily weight gain (p <.05) associated with the highest glycaemic (p <.05) and insulin response at 1 and 2 h post-prandial (p <.01), suggesting that the barley-based diet can support performance comparable to that of the corn-based diet in growing pig. By contrast, the lowest glycaemia was observed in the Faba bean group (p <.05), confirming the capacity of this legume to modulate post-prandial glucose levels. Moreover, the ability of some ingredients in lowering glucose and insulin response enriches the knowledge on functional nutrients for animal diets and to prevent the incidence of enteric diseases.Highlights The type of starch and fibre used in the diet highly affected some blood parameters, such as glycaemic and insulin responses. The Barley group showed the highest daily weight gain. Lower glycaemia levels were observed in the Faba bean group compared to the Corn one. Alternative protein sources for swine diets can limit the glycaemic and insulin response with no negative effects on growing performance
Broadband noise decoherence in solid-state complex architectures
Broadband noise represents a severe limitation towards the implementation of
a solid-state quantum information processor. Considering common spectral forms,
we propose a classification of noise sources based on the effects produced
instead of on their microscopic origin. We illustrate a multi-stage approach to
broadband noise which systematically includes only the relevant information on
the environment, out of the huge parametrization needed for a microscopic
description. We apply this technique to a solid-state two-qubit gate in a fixed
coupling implementation scheme.Comment: Proceedings of Nobel Symposium 141: Qubits for Future Quantum
Informatio
Interplay between pairing and exchange in small metallic dots
We study the effects of the mesoscopic fluctuations on the competition
between exchange and pairing interactions in ultrasmall metallic dots when the
mean level spacing is comparable or larger than the BCS pairing energy. Due to
mesoscopic fluctuations, the probability to have a non-zero spin ground state
may be non-vanishing and shows universal features related to both level
statistics and interaction. Sample to sample fluctuations of the renormalized
pairing are enlightened.Comment: 10 pages, 5 figure
Electrostatic analogy for integrable pairing force Hamiltonians
For the exactly solved reduced BCS model an electrostatic analogy exists; in
particular it served to obtain the exact thermodynamic limit of the model from
the Richardson Bethe ansatz equations. We present an electrostatic analogy for
a wider class of integrable Hamiltonians with pairing force interactions. We
apply it to obtain the exact thermodynamic limit of this class of models. To
verify the analytical results, we compare them with numerical solutions of the
Bethe ansatz equations for finite systems at half-filling for the ground state.Comment: 14 pages, 6 figures, revtex4. Minor change
Dynamical suppression of telegraph and 1/f noise due to quantum bistable fluctuator
We study dynamical decoupling of a qubit from non gaussian quantum noise due
to discrete sources, as bistable fluctuators and 1/f noise. We obtain analytic
and numerical results for generic operating point. For very large pulse
frequency, where dynamic decoupling compensates decoherence, we found universal
behavior. At intermediate frequencies noise can be compensated or enhanced,
depending on the nature of the fluctuators and on the operating point. Our
technique can be applied to a larger class of non-gaussian environments.Comment: Revtex 4, 5 pages, 3 figures. Title revised and some other minor
changed. Final version as published in PR
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