1,786 research outputs found
Silicon materials task of the low cost solar array project. Phase 3: Effect of impurities and processing on silicon solar cells
The 13th quarterly report of a study entitled an Investigation of the Effects of Impurities and Processing on Silicon Solar Cells is given. The objective of the program is to define the effects of impurities, various thermochemical processes and any impurity-process interactions on the performance of terrestrial silicon solar cells. The Phase 3 program effort falls in five areas: (1) cell processing studies; (2) completion of the data base and impurity-performance modeling for n-base cells; (3) extension of p-base studies to include contaminants likely to be introduced during silicon production, refining or crystal growth; (4) anisotropy effects; and (5) a preliminary study of the permanence of impurity effects in silicon solar cells. The quarterly activities for this report focus on tasks (1), (3) and (4)
Approaching Unit Visibility for Control of a Superconducting Qubit with Dispersive Readout
In a Rabi oscillation experiment with a superconducting qubit we show that a
visibility in the qubit excited state population of more than 90 % can be
attained. We perform a dispersive measurement of the qubit state by coupling
the qubit non-resonantly to a transmission line resonator and probing the
resonator transmission spectrum. The measurement process is well characterized
and quantitatively understood. The qubit coherence time is determined to be
larger than 500 ns in a measurement of Ramsey fringes.Comment: 4 pages, 5 figures, version with high resolution figures available at
http://www.eng.yale.edu/rslab/Andreas/content/science/PubsPapers.htm
Sideband Transitions and Two-Tone Spectroscopy of a Superconducting Qubit Strongly Coupled to an On-Chip Cavity
Sideband transitions are spectroscopically probed in a system consisting of a
Cooper pair box strongly but non-resonantly coupled to a superconducting
transmission line resonator. When the Cooper pair box is operated at the
optimal charge bias point the symmetry of the hamiltonian requires a two photon
process to access sidebands. The observed large dispersive ac-Stark shifts in
the sideband transitions induced by the strong non-resonant drives agree well
with our theoretical predictions. Sideband transitions are important in
realizing qubit-photon and qubit-qubit entanglement in the circuit quantum
electrodynamics architecture for quantum information processing.Comment: 4 pages, 5 figures, version with high resolution figures available at
http://qudev.ethz.ch/content/science/PubsPapers.htm
Comment on `Vacuum Rabi Splitting in a Semiconductor Circuit QED System' by Toida et al., Phys. Rev. Lett. 110, 066802 - Published 6 February 2013
Toida et al. claim in their recent article [Phys. Rev. Lett. 110, 066802
(2013)] that they `report a direct observation of vacuum Rabi splitting in a
GaAs/AlGaAs double quantum dot (DQD) based charge qubit coupled with a
superconducting coplanar waveguide (CPW) resonator'. In this comment, we
challenge the main claims made in their paper and show that their results: a)
do not provide any evidence of vacuum Rabi oscillations and b) do not provide
any direct evidence of vacuum Rabi splitting.Comment: 2 pages, 2 figure
An Introduction to Superconducting Qubits and Circuit Quantum Electrodynamics
A subset of the concepts of circuit quantum electrodynamics are reviewed as a
reference to the Axion Dark Matter Experiment (ADMX) community as part of the
proceedings of the 2nd Workshop on Microwave Cavities and Detectors for Axion
Research. The classical Lagrangians and Hamiltonians for an LC circuit are
discussed along with black box circuit quantization methods for a weakly
anharmonic qubit coupled to a resonator or cavity
Effect of impurities and processing on silicon solar cells. Volume 1: Characterization methods for impurities in silicon and impurity effects data base
Two major topics are treated: methods to measure and evaluate impurity effects in silicon and comprehensive tabulations of data derived during the study. Discussions of deep level spectroscopy, detailed dark I-V measurements, recombination lifetime determination, scanned laser photo-response, conventional solar cell I-V techniques, and descriptions of silicon chemical analysis are presented and discussed. The tabulated data include lists of impurity segregation coefficients, ingot impurity analyses and estimated concentrations, typical deep level impurity spectra, photoconductive and open circuit decay lifetimes for individual metal-doped ingots, and a complete tabulation of the cell I-V characteristics of nearly 200 ingots
Measurement-induced qubit state mixing in circuit QED from up-converted dephasing noise
We observe measurement-induced qubit state mixing in a transmon qubit
dispersively coupled to a planar readout cavity. Our results indicate that
dephasing noise at the qubit-readout detuning frequency is up-converted by
readout photons to cause spurious qubit state transitions, thus limiting the
nondemolition character of the readout. Furthermore, we use the qubit
transition rate as a tool to extract an equivalent flux noise spectral density
at f ~ 1 GHz and find agreement with values extrapolated from a
fit to the measured flux noise spectral density below 1 Hz.Comment: 5 pages, 4 figures. Final journal versio
Thermal Excitation of Multi-Photon Dressed States in Circuit Quantum Electrodynamics
The exceptionally strong coupling realizable between superconducting qubits
and photons stored in an on-chip microwave resonator allows for the detailed
study of matter-light interactions in the realm of circuit quantum
electrodynamics (QED). Here we investigate the resonant interaction between a
single transmon-type multilevel artificial atom and weak thermal and coherent
fields. We explore up to three photon dressed states of the coupled system in a
linear response heterodyne transmission measurement. The results are in good
quantitative agreement with a generalized Jaynes-Cummings model. Our data
indicates that the role of thermal fields in resonant cavity QED can be studied
in detail using superconducting circuits.Comment: ArXiv version of manuscript to be published in the Physica Scripta
topical issue on the Nobel Symposium 141: Qubits for Future Quantum
Computers(2009), 13 pages, 6 figures, hi-res version at
http://qudev.ethz.ch/content/science/PubsPapers.htm
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