169 research outputs found
Controlling fast transport of cold trapped ions
We realize fast transport of ions in a segmented micro-structured Paul trap.
The ion is shuttled over a distance of more than 10^4 times its groundstate
wavefunction size during only 5 motional cycles of the trap (280 micro meter in
3.6 micro seconds). Starting from a ground-state-cooled ion, we find an
optimized transport such that the energy increase is as low as 0.10 0.01
motional quanta. In addition, we demonstrate that quantum information stored in
a spin-motion entangled state is preserved throughout the transport. Shuttling
operations are concatenated, as a proof-of-principle for the shuttling-based
architecture to scalable ion trap quantum computing.Comment: 5 pages, 4 figure
On the Ground State of Two Flavor Color Superconductor
The diquark condensate susceptibility in neutral color superconductor at
moderate baryon density is calculated in the frame of two flavor
Nambu-Jona-Lasinio model. When color chemical potential is introduced to keep
charge neutrality, the diquark condensate susceptibility is negative in the
directions without diquark condensate in color space, which may be regarded as
a signal of the instability of the conventional ground state with only diquark
condensate in the color 3 direction.Comment: 4 pages, 2 figure
Cryogenic setup for trapped ion quantum computing
We report on the design of a cryogenic setup for trapped ion quantum
computing containing a segmented surface electrode trap. The heat shield of our
cryostat is designed to attenuate alternating magnetic field noise, resulting
in 120~dB reduction of 50~Hz noise along the magnetic field axis. We combine
this efficient magnetic shielding with high optical access required for single
ion addressing as well as for efficient state detection by placing two lenses
each with numerical aperture 0.23 inside the inner heat shield. The cryostat
design incorporates vibration isolation to avoid decoherence of optical qubits
due to the motion of the cryostat. We measure vibrations of the cryostat of
less than 20~nm over 2~s. In addition to the cryogenic apparatus, we
describe the setup required for an operation with
Ca and Sr ions.
The instability of the laser manipulating the optical qubits in
Ca is characterized yielding a minimum of its
Allan deviation of 2.410 at 0.33~s. To evaluate the
performance of the apparatus, we trapped Ca
ions, obtaining a heating rate of 2.14(16)~phonons/s and a Gaussian decay of
the Ramsey contrast with a 1/e-time of 18.2(8)~ms
Spin-one color superconductivity in compact stars?- an analysis within NJL-type models
We present results of a microscopic calculation using NJL-type model of
possible spin-one pairings in two flavor quark matter for applications in
compact star phenomenology. We focus on the color-spin locking phase (CSL) in
which all quarks pair in a symmetric way, in which color and spin states are
locked. The CSL condensate is particularly interesting for compact star
applications since it is flavor symmetric and could easily satisfy charge
neutrality. Moreover, the fact that in this phase all quarks are gapped might
help to suppress the direct Urca process, consistent with cooling models. The
order of magnitude of these small gaps (~1 MeV) will not influence the EoS, but
their also small critical temperatures (T_c ~800 keV) could be relevant in the
late stages neutron star evolution, when the temperature falls below this value
and a CSL quark core could form.Comment: 7 pages, 7 figures, revised version, accepted for the Conference
Proceedings of "Isolated Neutron Stars: from the Interior to the Surface",
London, 24-28. April 200
Quark Potential in a Quark-Meson Plasma
We investigate quark potential by considering meson exchanges in the two
flavor Nambu--Jona-Lasinio model at finite temperature and density. There are
two kinds of oscillations in the chiral restoration phase, one is the Friedel
oscillation due to the sharp quark Fermi surface at high density, and the other
is the Yukawa oscillation driven by the complex meson poles at high
temperature. The quark-meson plasma is strongly coupled in the temperature
region with being the critical temperature of
chiral phase transition. The maximum coupling in this region is located at the
critical point.Comment: 8 pages and 8 figure
Relation Between Chiral Susceptibility and Solutions of Gap Equation in Nambu--Jona-Lasinio Model
We study the solutions of the gap equation, the thermodynamic potential and
the chiral susceptibility in and beyond the chiral limit at finite chemical
potential in the Nambu--Jona-Lasinio (NJL) model. We give an explicit relation
between the chiral susceptibility and the thermodynamic potential in the NJL
model. We find that the chiral susceptibility is a quantity being able to
represent the furcation of the solutions of the gap equation and the
concavo-convexity of the thermodynamic potential in NJL model. It indicates
that the chiral susceptibility can identify the stable state and the
possibility of the chiral phase transition in NJL model.Comment: 21 pages, 6 figures, misprints are correcte
Ferromagnetic Semiconductors: Moving Beyond (Ga,Mn)As
The recent development of MBE techniques for growth of III-V ferromagnetic
semiconductors has created materials with exceptional promise in spintronics,
i.e. electronics that exploit carrier spin polarization. Among the most
carefully studied of these materials is (Ga,Mn)As, in which meticulous
optimization of growth techniques has led to reproducible materials properties
and ferromagnetic transition temperatures well above 150 K. We review progress
in the understanding of this particular material and efforts to address
ferromagnetic semiconductors as a class. We then discuss proposals for how
these materials might find applications in spintronics. Finally, we propose
criteria that can be used to judge the potential utility of newly discovered
ferromagnetic semiconductors, and we suggest guidelines that may be helpful in
shaping the search for the ideal material.Comment: 37 pages, 4 figure
Fibrosis in the kidney: is a problem shared a problem halved?
Fibrotic disorders are commonplace, take many forms and can be life-threatening. No better example of this exists than the progressive fibrosis that accompanies all chronic renal disease. Renal fibrosis is a direct consequence of the kidney's limited capacity to regenerate after injury. Renal scarring results in a progressive loss of renal function, ultimately leading to end-stage renal failure and a requirement for dialysis or kidney transplantation
25-Hydroxyvitamin D levels and chronic kidney disease in the AusDiab (Australian Diabetes, Obesity and Lifestyle) study
<p>Abstract</p> <p>Background</p> <p>Low 25-hydroxy vitamin D (25(OH)D) levels have been associated with an increased risk of albuminuria, however an association with glomerular filtration rate (GFR) is not clear. We explored the relationship between 25(OH)D levels and prevalent chronic kidney disease (CKD), albuminuria and impaired GFR, in a national, population-based cohort of Australian adults (AusDiab Study).</p> <p>Methods</p> <p>10,732 adults ≥25 years of age participating in the baseline survey of the AusDiab study (1999–2000) were included. The GFR was estimated using an enzymatic creatinine assay and the CKD-EPI equation, with CKD defined as eGFR <60 ml/min/1.73 m<sup>2</sup>. Albuminuria was defined as a spot urine albumin to creatinine ratio (ACR) of ≥2.5 mg/mmol for men and ≥3.5 for women. Serum 25(OH)D levels of <50 nmol/L were considered vitamin D deficient. The associations between 25(OH)D level, albuminuria and impaired eGFR were estimated using multivariate regression models.</p> <p>Results</p> <p>30.7% of the study population had a 25(OH)D level <50 nmol/L (95% CI 25.6-35.8). 25(OH)D deficiency was significantly associated with an impaired eGFR in the univariate model (OR 1.52, 95% CI 1.07-2.17), but not in the multivariate model (OR 0.95, 95% CI 0.67-1.35). 25(OH)D deficiency was significantly associated with albuminuria in the univariate (OR 2.05, 95% CI 1.58-2.67) and multivariate models (OR 1.54, 95% CI 1.14-2.07).</p> <p>Conclusions</p> <p>Vitamin D deficiency is common in this population, and 25(OH)D levels of <50 nmol/L were independently associated with albuminuria, but not with impaired eGFR. These associations warrant further exploration in prospective and interventional studies.</p
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