2,436 research outputs found
- and -spin relaxation time limitations of phosphorous donor electrons near crystalline silicon to silicon dioxide interface defects
A study of donor electron spins and spin--dependent electronic transitions
involving phosphorous (P) atoms in proximity of the (111) oriented
crystalline silicon (c-Si) to silicon dioxide (SiO) interface is
presented for [P] = 10 and [P] =
10 at about liquid He temperatures (
). Using pulsed electrically detected magnetic
resonance (pEDMR), spin--dependent transitions between the \Phos donor state
and two distinguishable interface states are observed, namely (i) \Pb centers
which can be identified by their characteristic anisotropy and (ii) a more
isotropic center which is attributed to E defects of the \sio bulk
close to the interface. Correlation measurements of the dynamics of
spin--dependent recombination confirm that previously proposed transitions
between \Phos and the interface defects take place. The influence of these
electronic near--interface transitions on the \Phos donor spin coherence time
as well as the donor spin--lattice relaxation time is then
investigated by comparison of spin Hahn--echo decay measurements obtained from
conventional bulk sensitive pulsed electron paramagnetic resonance and surface
sensitive pEDMR, as well as surface sensitive electrically detected inversion
recovery experiments. The measurements reveal that both and of
\Phos donor electrons spins in proximity of energetically lower interface
states at K are reduced by several orders of magnitude
Poor survival outcomes in HER2 positive breast cancer patients with low grade, node negative tumours
We present a retrospective analysis on a cohort of low-grade, node-negative patients showing that human epidermal growth factor receptor 2 (HER2) status significantly affects the survival in this otherwise very good prognostic group. Our results provide support for the use of adjuvant trastuzumab in patients who are typically classified as having very good prognosis, not routinely offered standard chemotherapy, and who as such do not fit current UK prescribing guidelines for trastuzumab
Comparison of coherence times in three dc SQUID phase qubits
We report measurements of spectroscopic linewidth and Rabi oscillations in
three thin-film dc SQUID phase qubits. One device had a single-turn Al loop,
the second had a 6-turn Nb loop, and the third was a first order gradiometer
formed from 6-turn wound and counter-wound Nb coils to provide isolation from
spatially uniform flux noise. In the 6 - 7.2 GHz range, the spectroscopic
coherence times for the gradiometer varied from 4 ns to 8 ns, about the same as
for the other devices (4 to 10 ns). The time constant for decay of Rabi
oscillations was significantly longer in the single-turn Al device (20 to 30
ns) than either of the Nb devices (10 to 15 ns). These results imply that
spatially uniform flux noise is not the main source of decoherence or
inhomogenous broadening in these devices.Comment: 4 pages, 5 figures, accepted for publication in IEEE Trans. Appl.
Supercon
Strong-field effects in the Rabi oscillations of the superconducting phase qubit
Rabi oscillations have been observed in many superconducting devices, and
represent prototypical logic operations for quantum bits (qubits) in a quantum
computer. We use a three-level multiphoton analysis to understand the behavior
of the superconducting phase qubit (current-biased Josephson junction) at high
microwave drive power. Analytical and numerical results for the ac Stark shift,
single-photon Rabi frequency, and two-photon Rabi frequency are compared to
measurements made on a dc SQUID phase qubit with Nb/AlOx/Nb tunnel junctions.
Good agreement is found between theory and experiment.Comment: 4 pages, 4 figures, accepted for publication in IEEE Trans. Appl.
Supercon
Detectability of gravitational wave events by spherical resonant-mass antennas
We have calculated signal-to-noise ratios for eight spherical resonant-mass
antennas interacting with gravitational radiation from inspiralling and
coalescing binary neutron stars and from the dynamical and secular bar-mode
instability of a rapidly rotating star. We find that by using technology that
could be available in the next several years, spherical antennas can detect
neutron star inspiral and coalescence at a distance of 15 Mpc and the dynamical
bar-mode instability at a distance of 2 Mpc.Comment: 39 pages, 4 EPS Figures, some additional SNRs for secular
instabilities, some changes to LIGO SNRs, Appendix added on the asymptotic
expansion of energy sensitivity, corrected supernova rates. Results available
at http://www.physics.umd.edu/rgroups/gen_rel_exp/snr.html Submitted to Phys.
Rev.
Multilevel effects in the Rabi oscillations of a Josephson phase qubit
We present Rabi oscillation measurements of a Nb/AlOx/Nb dc superconducting
quantum interference device (SQUID) phase qubit with a 100 um^2 area junction
acquired over a range of microwave drive power and frequency detuning. Given
the slightly anharmonic level structure of the device, several excited states
play an important role in the qubit dynamics, particularly at high power. To
investigate the effects of these levels, multiphoton Rabi oscillations were
monitored by measuring the tunneling escape rate of the device to the voltage
state, which is particularly sensitive to excited state population. We compare
the observed oscillation frequencies with a simplified model constructed from
the full phase qubit Hamiltonian and also compare time-dependent escape rate
measurements with a more complete density-matrix simulation. Good quantitative
agreement is found between the data and simulations, allowing us to identify a
shift in resonance (analogous to the ac Stark effect), a suppression of the
Rabi frequency, and leakage to the higher excited states.Comment: 14 pages, 9 figures; minor corrections, updated reference
Events trigger generator for resonant spherical detectors of gravitational waves
We have set up and tested a pipeline for processing the data from a spherical
gravitational wave detector with six transducers. The algorithm exploits the
multichannel capability of the system and provides a list of candidate events
with their arrival direction. The analysis starts with the conversion of the
six detector outputs into the scalar and the five quadrupolar modes of the
sphere, which are proportional to the corresponding gravitational wave
spherical components. Event triggers are then generated by an adaptation of the
WaveBurst algorithm. Event validation and direction reconstruction are made by
cross-checking two methods of different inspiration: geometrical (lowest
eigenvalue) and probabilistic (maximum likelihood). The combination of the two
methods is able to keep substantially unaltered the efficiency and can reduce
drastically the detections of fake events (to less than ten per cent). We show
a quantitative test of these ideas by simulating the operation of the resonant
spherical detector miniGRAIL, whose planned sensitivity in its frequency band
(few hundred Hertz's around 3 kHz) is comparable with the present LIGO one.Comment: 14 pages, 8 figures. Version accepted for publication on CQG.
Proceedings of the 12th Gravitational Wave Data Analysis Worksho
Assembly of Advanced Materials into 3D Functional Structures by Methods Inspired by Origami and Kirigami: A Review
Origami and kirigami, the ancient techniques for making paper works of art, also provide inspiration for routes to structural platforms in engineering applications, including foldable solar panels, retractable roofs, deployable sunshields, and many others. Recent work demonstrates the utility of the methods of origami/kirigami and conceptually related schemes in cutting, folding, and buckling in the construction of devices for emerging classes of technologies, with examples in mechanical/optical metamaterials, stretchable/conformable electronics, micro/nanoscale biosensors, and large‐amplitude actuators. Specific notable progress is in the deployment of functional materials such as single‐crystal silicon, shape memory polymers, energy‐storage materials, and graphene into elaborate 3D micro and nanoscale architectures. This review highlights some of the most important developments in this field, with a focus on routes to assembly that apply across a range of length scales and with advanced materials of relevance to practical applications.113Ysciescopu
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