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Biomedical subjects

C Becher

Publications and source records attributed to C Becher.

11 recordsLinked to original sources
PubMed2003

Quantum information processing with trapped Ca(+) ions.

Quantum information processing is performed with single trapped Ca(+) ions, stored in a linear Paul trap and laser-cooled to the ground state of their harmonic quantum motion. Composite laser-pulse sequences were used to implement SWAP gate, phase gate and controlled-NOT gate operations. Stark shifts on the quantum-bit transitions were precisely measured and compensated. For a demonstration of quantum information processing, a Deutsch-Jozsa algorithm has been implemented using two quantum bits encoded on a single ion.

Journal Article↗
PubMed2003

Precision measurement and compensation of optical stark shifts for an ion-trap quantum processor.

Using optical Ramsey interferometry, we precisely measure the laser-induced ac-Stark shift on the S(1/2)-D(5/2) "quantum bit" transition near 729 nm in a single trapped 40Ca+ ion. We cancel this shift using an additional laser field. This technique is of particular importance for the implementation of quantum information processing with cold trapped ions. As a simple application we measure the atomic phase evolution during a n x 2 pi rotation of the quantum bit.

Journal Article↗
PubMed2002

Coupling a single atomic quantum bit to a high finesse optical cavity.

The quadrupole S(1/2)-D(5/2) optical transition of a single trapped Ca+ ion, well suited for encoding a quantum bit of information, is coherently coupled to the standing wave field of a high finesse cavity. The coupling is verified by observing the ion's response to both spatial and temporal variations of the intracavity field. We also achieve deterministic coupling of the cavity mode to the ion's vibrational state by selectively exciting vibrational state-changing transitions and by controlling the position of the ion in the standing wave field with nanometer precision.

Journal Article↗
PubMed2000

A quantum dot single-photon turnstile device.

Quantum communication relies on the availability of light pulses with strong quantum correlations among photons. An example of such an optical source is a single-photon pulse with a vanishing probability for detecting two or more photons. Using pulsed laser excitation of a single quantum dot, a single-photon turnstile device that generates a train of single-photon pulses was demonstrated. For a spectrally isolated quantum dot, nearly 100% of the excitation pulses lead to emission of a single photon, yielding an ideal single-photon source.

Journal Article↗
PubMed1998

Wards. Caring about sharing.

A small study of surgical patients in one hospital showed that most women preferred single-sex wards. But more than half the men had no preference. Most day-case patients wanted single-sex accommodation. Patients whose stay was seven days or longer showed greater tolerance of mixed-sex wards than others.

Adolescent↗
PubMed1996

Evaluation of commercial kits for quantitative identification and tests on antibiotic susceptibility of genital mycoplasmas.

In this study, commercial media and kits for identification and tests for antibiotic susceptibility of genital mycoplasmas were evaluated in comparison to standardized methods. A total of 298 specimens was routinely enrolled. Our results showed that all media corresponded for qualitative and semiquantitative identification with a specificity of 100% for both microorganisms and a sensitivity of 94% for U. urealyticum and of 88% for M. hominis. Standard methods were superior to commercial kits for qualitative and quantitative identification (sensitivity 85-97% for U. urealyticum and 79-83% for M. hominis). There were large discrepancies when testing antibiotic susceptibility.

Anti-Bacterial Agents↗
PubMed1987

[Microflora in a controlled caries model study in rats].

Changes of dental plaque were investigated in Osborne-Mendel-rats under the influence of a sucrose-containing diet as well as the inhibition of it by antibiotics (streptomycin, erythromycin, penicillin) in order to find out the optimal conditions of animal association with Str. mutans (OMZ 176). The cariogenic diet did not alter the isolated total germ numbers, but modified the flora to a streptococcal one. The application of an erythromycin/penicillin mixture caused a 100 fold decrease of the germ number and streptococcal elimination so that an association of the germ Str. mutans detectable by microbiological methods could take place at this moment. The obtained caries scores differed from the non-contaminated group. Mono-associated gnotobiotic Wistar rats developed more carious lesions than conventional animals of the same strain; therefore Str. mutans OMZ 176 was classified as high cariogenic.

Animals↗