7,389 research outputs found
Final-state read-out of exciton qubits by observing resonantly excited photoluminescence in quantum dots
We report on a new approach to detect excitonic qubits in semiconductor
quantum dots by observing spontaneous emissions from the relevant qubit level.
The ground state of excitons is resonantly excited by picosecond optical
pulses. Emissions from the same state are temporally resolved with picosecond
time resolution. To capture weak emissions, we greatly suppress the elastic
scattering of excitation beams, by applying obliquely incident geometry to the
micro photoluminescence set-up. Rabi oscillations of the ground-state excitons
appear to be involved in the dependence of emission intensity on excitation
amplitude.Comment: 4 pages, 4 figures, to appear in Appl. Phys. Let
Mechanical quality factor of a sapphire fiber at cryogenic temperatures
A mechanical quality factor of was obtained for the 199
Hz bending vibrational mode in a monocrystalline sapphire fiber at 6 K.
Consequently, we confirm that pendulum thermal noise of cryogenic mirrors used
for gravitational wave detectors can be reduced by the sapphire fiber
suspension.Comment: To be published to Physiscs Letters A. Number of pages: 10 Number of
figures: 5 Number of tables:
Migration and Settlement: 13. Japan
In this report, authors from three Japanese institutions discuss changing migration patterns in their country. Emphasizing the current population shifts away from metropolitan areas, they analyze recent demographic dynamics in Japan, first with a 15-region and then an 8-region disaggregation of national population data. The report ends with a brief survey of major population policies that have been adopted in the last 30 years
Force measurements of a superconducting-film actuator for a cryogenic interferometric gravitational-wave detector
We measured forces applied by an actuator with a YBCO film at near 77 K for
the Large-scale Cryogenic Gravitational-wave Telescope (LCGT) project. An
actuator consisting of both a YBCO film of 1.6 micrometers thickness and 0.81
square centimeters area and a solenoid coil exerted a force of up to 0.2 mN on
a test mass. The presented actuator system can be used to displace the mirror
of LCGT for fringe lock of the interferometer.Comment: 9 pages, 3 figure
Core-collapse supernova simulations and the formation of neutron stars, hybrid stars, and black holes
We investigate observable signatures of a first-order quantum chromodynamics (QCD) phase transition in the context of core collapse supernovae. To this end, we conduct axially symmetric numerical relativity simulations with multi-energy neutrino transport, using a hadron-quark hybrid equation of state (EOS). We consider four non-rotating progenitor models, whose masses range from to \,M. We find that the two less massive progenitor stars (9.6 and 11.2\,M) show a successful explosion, which is driven by the neutrino heating. They do not undergo the QCD phase transition and leave behind a neutron star (NS). As for the more massive progenitor stars (50 and 70\,M), the proto-neutron star (PNS) core enters the phase transition region and experiences the second collapse. Because of a sudden stiffening of the EOS entering to the pure quark matter regime, a strong shock wave is formed and blows off the PNS envelope in the 50\,M model. Consequently the remnant becomes a quark core surrounded by hadronic matters, leading to the formation of the hybrid star. However for the 70\,M model, the shock wave cannot overcome the continuous mass accretion and it readily becomes a black hole. We find that the neutrino and gravitational wave (GW) signals from supernova explosions driven by the hadron-quark phase transition are detectable for the present generation of neutrino and GW detectors. Furthermore, the analysis of the GW detector response reveals unique kHz signatures, which will allow us to distinguish this class of supernova explosions from failed and neutrino-driven explosions
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