12,663 research outputs found
High-fidelity ion-trap quantum computing with hyperfine clock states
We propose the implementation of a geometric-phase gate on
magnetic-field-insensitive qubits with -dependent forces for
trapped ion quantum computing. The force is exerted by two laser beams in a
Raman configuration. Qubit-state dependency is achieved by a small frequency
detuning from the virtually-excited state. Ion species with excited states of
long radiative lifetimes are used to reduce the chance of a spontaneous photon
emission to less than 10 per gate-run. This eliminates the main source
of gate infidelity of previous implementations. With this scheme it seems
possible to reach the fault tolerant threshold.Comment: 4 pages, 1 figur
Automated operation of a home made torque magnetometer using LabVIEW
In order to simplify and optimize the operation of our home made torque
magnetometer we created a new software system. The architecture is based on
parallel, independently running instrument handlers communicating with a main
control program. All programs are designed as command driven state machines
which greatly simplifies their maintenance and expansion. Moreover, as the main
program may receive commands not only from the user interface, but also from
other parallel running programs, an easy way of automation is achieved. A
program working through a text file containing a sequence of commands and
sending them to the main program suffices to automatically have the system
conduct a complex set of measurements. In this paper we describe the system's
architecture and its implementation in LabVIEW.Comment: 6 pages, 7 figures, submitted to Rev. Sci. Inst
Weighted Bergman kernels and virtual Bergman kernels
We introduce the notion of "virtual Bergman kernel" and apply it to the
computation of the Bergman kernel of "domains inflated by Hermitian balls", in
particular when the base domain is a bounded symmetric domain.Comment: 12 pages. One-hour lecture for graduate students, SCV 2004, August
2004, Beijing, P.R. China. V2: typo correcte
Quantum Simulation of Quantum Field Theories in Trapped Ions
We propose the quantum simulation of a fermion and an antifermion field modes
interacting via a bosonic field mode, and present a possible implementation
with two trapped ions. This quantum platform allows for the scalable add-up of
bosonic and fermionic modes, and represents an avenue towards quantum
simulations of quantum field theories in perturbative and nonperturbative
regimes.Comment: To be published in Physical Review Letter
An experimental study of transonic flow about a supercritical airfoil. Static pressure and drag data obtained from tests of a supercritical airfoil and an NACA 0012 airfoil at transonic speeds, supplement
Surface static-pressure and drag data obtained from tests of two slightly modified versions of the original NASA Whitcomb airfoil and a model of the NACA 0012 airfoil section are presented. Data for the supercritical airfoil were obtained for a free-stream Mach number range of 0.5 to 0.9, and a chord Reynolds number range of 2 x 10 to the 6th power to 4 x 10 to the 6th power. The NACA 0012 airfoil was tested at a constant chord Reynolds number of 2 x 10 to the 6th power and a free-stream Mach number range of 0.6 to 0.8
A 16-channel Digital TDC Chip with internal buffering and selective readout for the DIRC Cherenkov counter of the BABAR experiment
A 16-channel digital TDC chip has been built for the DIRC Cherenkov counter
of the BaBar experiment at the SLAC B-factory (Stanford, USA). The binning is
0.5 ns, the conversion time 32 ns and the full-scale 32 mus. The data driven
architecture integrates channel buffering and selective readout of data falling
within a programmable time window. The time measuring scale is constantly
locked to the phase of the (external) clock. The linearity is better than 80 ps
rms. The dead time loss is less than 0.1% for incoherent random input at a rate
of 100 khz on each channel. At such a rate the power dissipation is less than
100 mw. The die size is 36 mm2.Comment: Latex, 18 pages, 13 figures (14 .eps files), submitted to NIM
Geometric phase gate on an optical transition for ion trap quantum computation
We propose a geometric phase gate of two ion qubits that are encoded in two
levels linked by an optical dipole-forbidden transition. Compared to hyperfine
geometric phase gates mediated by electric dipole transitions, the gate has
many interesting properties, such as very low spontaneous emission rates,
applicability to magnetic field insensitive states, and use of a co-propagating
laser beam geometry. We estimate that current technology allows for
infidelities of around 10.Comment: 4 pages, 2 figure
Irreversible nucleation in molecular beam epitaxy: From theory to experiments
Recently, the nucleation rate on top of a terrace during the irreversible
growth of a crystal surface by MBE has been determined exactly. In this paper
we go beyond the standard model usually employed to study the nucleation
process, and we analyze the qualitative and quantitative consequences of two
important additional physical ingredients: the nonuniformity of the
Ehrlich-Schwoebel barrier at the step-edge, because of the existence of kinks,
and the steering effects, due to the interaction between the atoms of the flux
and the substrate. We apply our results to typical experiments of second layer
nucleation.Comment: 11 pages. Table I corrected and one appendix added. To be published
in Phys. Rev. B (scheduled issue: 15 February 2003
Integrative DNA methylome analysis of pan-cancer biomarkers in cancer discordant monozygotic twin-pairs
BACKGROUND: A key focus in cancer research is the discovery of biomarkers that accurately diagnose early lesions in non-invasive tissues. Several studies have identified malignancy-associated DNA methylation changes in blood, yet no general cancer biomarker has been identified to date. Here, we explore the potential of blood DNA methylation as a biomarker of pan-cancer (cancer of multiple different origins) in 41 female cancer discordant monozygotic (MZ) twin-pairs sampled before or after diagnosis using the Illumina HumanMethylation450 BeadChip. RESULTS: We analysed epigenome-wide DNA methylation profiles in 41 cancer discordant MZ twin-pairs with affected individuals diagnosed with tumours at different single primary sites: the breast, cervix, colon, endometrium, thyroid gland, skin (melanoma), ovary, and pancreas. No significant global differences in whole blood DNA methylation profiles were observed. Epigenome-wide analyses identified one novel pan-cancer differentially methylated position at false discovery rate (FDR) threshold of 10 % (cg02444695, P = 1.8 × 10(-7)) in an intergenic region 70 kb upstream of the SASH1 tumour suppressor gene, and three suggestive signals in COL11A2, AXL, and LINC00340. Replication of the four top-ranked signals in an independent sample of nine cancer-discordant MZ twin-pairs showed a similar direction of association at COL11A2, AXL, and LINC00340, and significantly greater methylation discordance at AXL compared to 480 healthy concordant MZ twin-pairs. The effects at cg02444695 (near SASH1), COL11A2, and LINC00340 were the most promising in biomarker potential because the DNA methylation differences were found to pre-exist in samples obtained prior to diagnosis and were limited to a 5-year period before diagnosis. Gene expression follow-up at the top-ranked signals in 283 healthy individuals showed correlation between blood methylation and gene expression in lymphoblastoid cell lines at PRL, and in the skin tissue at AXL. A significant enrichment of differential DNA methylation was observed in enhancer regions (P = 0.03). CONCLUSIONS: We identified DNA methylation signatures in blood associated with pan-cancer, at or near SASH1, COL11A2, AXL, and LINC00340. Three of these signals were present up to 5 years prior to cancer diagnosis, highlighting the potential clinical utility of whole blood DNA methylation analysis in cancer surveillance
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