215 research outputs found
A quantum computer using a trapped-ion spin molecule and microwave radiation
We propose a new design for a quantum information processor where qubits are
encoded into Hyperfine states of ions held in a linear array of individually
tailored microtraps and sitting in a spatially varying magnetic field. The
magnetic field gradient introduces spatially dependent qubit transition
frequencies and a type of spin-spin interaction between qubits. Single and
multi-qubit manipulation is achieved via resonant microwave pulses as in
liquid-NMR quantum computation while the qubit readout and reset is achieved
through trapped-ion fluorescence shelving techniques. By adjusting the
microtrap configurations we can tailor, in hardware, the qubit resonance
frequencies and coupling strengths. We show the system possesses a side-band
transition structure which does not scale with the size of the processor
allowing scalable frequency discrimination between qubits. By using large
magnetic field gradients, one can readout and reset the qubits in the ion chain
via frequency selective optical pulses avoiding the need for many tightly
focused laser beams for spatial qubit addressing.Comment: 7 pages, 2 figures. New references added, additional material on
quantum error correction and device tolerance
Hydrodynamic journal bearing program Quarterly progress report no. 1, 29 May - 29 Jul. 1965
Test assembly design requirements for space power systems journal bearing
Genetic associations between feed efficiency measured in a performance test station and performance of growing cattle in commercial beef herds
ABSTRACT: Interest in selection for improved feed efficiency is increasing, but before any steps are taken toward selecting for feed efficiency, correlations with other economically important traits must first be quantified. The objective of this study was to quantify the genetic associations between feed efficiency measured during performance testing and linear type traits, BW, live animal value, and carcass traits recorded in commercial herds. Feed efficiency data were available on 2,605 bulls from 1 performance test station. There were between 10,384 and 93,442 performance records on type traits, BW, animal value, or carcass traits from 17,225 commercial herds. (Co)variance components were estimated using linear mixed animal models. Genetic correlations between the muscular type traits in commercial animals and feed conversion ratio (−0.33 to −0.25), residual feed intake (RFI; −0.33 to −0.22), and residual BW gain (RG; 0.24 to 0.27) suggest that selection for improved feed efficiency should increase muscling. This is further evidenced by the genetic correlations between carcass conformation of commercial animals and feed conversion ratio (−0.46), RFI (−0.37), and residual BW gain (0.35) measured in performance-tested animals. Furthermore, the genetic correlations between RFI and both ultrasonic fat depth and carcass fat score (0.39 and 0.33, respectively) indicated that selection for improved RFI will result in leaner animals. It can be concluded from the genetic correlations estimated in this study that selection for feed efficiency will have no unfavorable effects on the performance traits measured in this study and will actually lead to an improvement in performance for some traits, such as muscularity, animal price, and carcass conformation. Conversely, this suggests that genetic selection for traits such as carcass quality, muscling traits, and animal value might also be indirectly selecting for more efficient animals
Quantum gates using electronic and nuclear spins of Yb in a magnetic field gradient
An efficient scheme is proposed to carry out gate operations on an array of
trapped Yb ions, based on a previous proposal using both electronic and
nuclear degrees of freedom in a magnetic field gradient. For this purpose we
consider the Paschen-Back regime (strong magnetic field) and employ a
high-field approximation in this treatment. We show the possibility to suppress
the unwanted coupling between the electron spins by appropriately swapping
states between electronic and nuclear spins. The feasibility of generating the
required high magnetic field is discussed
Quantum Gates and Memory using Microwave Dressed States
Trapped atomic ions have been successfully used for demonstrating basic
elements of universal quantum information processing (QIP). Nevertheless,
scaling up of these methods and techniques to achieve large scale universal
QIP, or more specialized quantum simulations remains challenging. The use of
easily controllable and stable microwave sources instead of complex laser
systems on the other hand promises to remove obstacles to scalability.
Important remaining drawbacks in this approach are the use of magnetic field
sensitive states, which shorten coherence times considerably, and the
requirement to create large stable magnetic field gradients. Here, we present
theoretically a novel approach based on dressing magnetic field sensitive
states with microwave fields which addresses both issues and permits fast
quantum logic. We experimentally demonstrate basic building blocks of this
scheme to show that these dressed states are long-lived and coherence times are
increased by more than two orders of magnitude compared to bare magnetic field
sensitive states. This changes decisively the prospect of microwave-driven ion
trap QIP and offers a new route to extend coherence times for all systems that
suffer from magnetic noise such as neutral atoms, NV-centres, quantum dots, or
circuit-QED systems.Comment: 9 pages, 4 figure
The Sound Sensation of Apical Electric Stimulation in Cochlear Implant Recipients with Contralateral Residual Hearing
BACKGROUND: Studies using vocoders as acoustic simulators of cochlear implants have generally focused on simulation of speech understanding, gender recognition, or music appreciation. The aim of the present experiment was to study the auditory sensation perceived by cochlear implant (CI) recipients with steady electrical stimulation on the most-apical electrode. METHODOLOGY/PRINCIPAL FINDINGS: Five unilateral CI users with contralateral residual hearing were asked to vary the parameters of an acoustic signal played to the non-implanted ear, in order to match its sensation to that of the electric stimulus. They also provided a rating of similarity between each acoustic sound they selected and the electric stimulus. On average across subjects, the sound rated as most similar was a complex signal with a concentration of energy around 523 Hz. This sound was inharmonic in 3 out of 5 subjects with a moderate, progressive increase in the spacing between the frequency components. CONCLUSIONS/SIGNIFICANCE: For these subjects, the sound sensation created by steady electric stimulation on the most-apical electrode was neither a white noise nor a pure tone, but a complex signal with a progressive increase in the spacing between the frequency components in 3 out of 5 subjects. Knowing whether the inharmonic nature of the sound was related to the fact that the non-implanted ear was impaired has to be explored in single-sided deafened patients with a contralateral CI. These results may be used in the future to better understand peripheral and central auditory processing in relation to cochlear implants
A dose ranging trial to optimize the dose of Rifampin in the treatment of tuberculosis
The study was funded by the EDCTP (European & Developing Countries Clinical Trials Partnership), NACCAP (Netherlands-African partnership for Capacity development and Clinical interventions Against Poverty-related diseases) and the Bill & Melinda Gates Foundation.Rationale: Rifampin at a dose of 10 mg/kg was introduced in 1971 based on pharmacokinetic, toxicity and cost considerations. Available data in mice and humans showed that an increase in dose may shorten the duration of tuberculosis treatment. Objectives: To evaluate the safety and tolerability, the pharmacokinetics and the extended early bactericidal activity of increasing doses of rifampin. Methods: Patients with drug-susceptible tuberculosis were enrolled into a control group of 8 patients receiving the standard dose of 10 mg/kg rifampin, followed by consecutive experimental groups with 15 patients each receiving rifampin 20 mg/kg, 25 mg/kg, 30 mg/kg and 35 mg/kg, respectively, for 14 days. In all patients isoniazid, pyrazinamide and ethambutol were added in standard doses for the second 7 days of treatment. Safety, pharmacokinetics of rifampin, and fall in bacterial load were assessed. Measurements and Main Results: Grade 1 and 2 adverse events were equally distributed between the five dose groups; there were 5 grade 3 events of which 1 was a possibly related hepatotoxicity. Areas under the time-concentration curves and peak serum concentrations of rifampin showed a more than proportional increase with dose. The daily fall in bacterial load over 14 days was 0.176, 0.168, 0.167, 0.265, and 0.261 log10CFU/ml sputum in the 10, 20, 25, 30 and 35 mg/kg groups respectively. Conclusions: Two weeks of rifampin up to 35 mg/kg was safe and well tolerated. There was a non-linear increase in exposure to rifampin without an apparent ceiling effect and a greater estimated fall in bacterial load in the higher dosing groups. Clinical trial registration available at www.clinicaltrials.gove, ID NCT01392911.PostprintPeer reviewe
Clinical utility of a nested nucleic acid amplification format in comparison to viral culture for the diagnosis of mucosal herpes simplex infection in a genitourinary medicine setting
BACKGROUND: Nested nucleic acid amplification tests are often thought too sensitive or prone to generatingfalse positive results for routine use. The current study investigated the specificity and clinicalutility of a routine multiplex nested assay for mucosal herpetic infections. METHODS: Ninety patients, categorised into those clinically diagnosed to (a) have and (b) not haveherpetic infection, were enrolled. Swabs from oral and ano-genital sites were assayed by thenested assay and culture and the results assessed against clinical evaluation for diagnosingherpetic infections; cell content was also recorded. RESULTS: Twenty-six and 64 patients were thought to (a) have and (b) not have mucosal herpeticinfection. Taking the clinical evaluation as indicating the presence of herpetic infection, thenested polymerase chain reaction and culture had respective sensitivities of 19/26 (73%) and12/26 (46%) (Χ(2) p = 0.02). There was no significant difference in specificities between nPCR62/64 (97%) and culture 63/64 (98%) (Χ(2) p = 1.0). Cell content was important for viraldetection by nPCR (Χ(2) p = 0.07) but not culture. Nesting was found necessary for sensitivity anddid not reduce specificity. Assay under-performance appeared related to sub-optimal cellcontent (20%) but may have reflected clinical over-diagnosis. The results suggest the need forvalidating specimen cell quality. CONCLUSIONS: This study questions the value of routine laboratory confirmation of mucosal herpetic infection. The adoption of a more discriminatory usage of laboratory diagnostic facilities for genital herpetic infection, taking account of cell content, and restricting it to those cases where it actually affects patient management, may be warranted
Thick-film technology for ultra high vacuum interfaces of micro-structured traps
We adopt thick-film technology to produce ultra high vacuum compatible
interfaces for electrical signals. These interfaces permit voltages of hundreds
of Volts and currents of several Amperes and allow for very compact vacuum
setups, useful in quantum optics in general, and especially for quantum
information and quantum simulations using miniaturized traps for ions or
neutral atoms. Such printed circuits can also be useful as pure in-vacuum
devices. We demonstrate a specific interface, which provides eleven current
feedthroughs, more than 70 dc feedthroughs and a feedthrough for radio
frequencies. We achieve a pressure in the low 1e-11mbar range and demonstrate
the full functionality of the interface by trapping chains of cold ytterbium
ions, which requires all of the signals mentioned above being present. In
addition, a versatile multi-channel device for supplying precise time-dependent
voltages has been developed.Comment: 8 pages, 7 figures added references to recent literature about
microwave anipulated ions and fast shuttlin
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