240 research outputs found
Measurement of the Surface Gravity of Boo
Direct angular size measurements of the G0IV subgiant Boo from the
Palomar Testbed Interferometer are presented, with limb-darkened angular size
of mas, which indicate a linear
radius of . A bolometric flux estimate of erg cms is computed, which indicates
an effective temperature of K and luminosity of for this object. Similar data are established for a check
star, HD 121860. The Boo results are compared to, and confirm, similar
parameters established by the {\it MOST} asteroseismology satellite. In
conjunction with the mass estimate from the {\it MOST} investigation, a surface
gravity of [cm s] is established for
Boo.Comment: To appear in March 1, 2007 ApJ v657 n
Ultrashort dead time of photon-counting InGaAs avalanche photodiodes
We report a 1.036 GHz gated Geiger mode InGaAs avalanche photodiode with a
detection dead time of just 1.93 ns. This is demonstrated by full recovery of
the detection efficiency two gate cycles after a detection event, as well as a
measured maximum detection rate of 497 MHz. As an application, we measure the
second order correlation function of the emission from a diode laser
with a single detector which works reliably at high speed owing to the
extremely short dead time of the detector. The device is ideal for high bit
rate fiber wavelength quantum key distribution and photonic quantum computing.Comment: 10 pages, 4 figures. Updated to published versio
Efficient single-photon emission from electrically driven InP quantum dots epitaxially grown on Si(001)
The heteroepitaxy of III-V semiconductors on silicon is a promising approach
for making silicon a photonic platform for on-chip optical interconnects and
quantum optical applications. Monolithic integration of both material systems
is a long-time challenge, since different material properties lead to high
defect densities in the epitaxial layers. In recent years, nanostructures
however have shown to be suitable for successfully realising light emitters on
silicon, taking advantage of their geometry. Facet edges and sidewalls can
minimise or eliminate the formation of dislocations, and due to the reduced
contact area, nanostructures are little affected by dislocation networks. Here
we demonstrate the potential of indium phosphide quantum dots as efficient
light emitters on CMOS-compatible silicon substrates, with luminescence
characteristics comparable to mature devices realised on III-V substrates. For
the first time, electrically driven single-photon emission on silicon is
presented, meeting the wavelength range of silicon avalanche photo diodes'
highest detection efficiency
Statistical correlation for the composite Boson
It is well known that the particles in a beam of Boson obeying Bose-Einstein
statistics tend to cluster (bunching effect), while the particles in a
degenerate beam of Fermion obeying Fermi-Dirac statistics expel each other
(anti-bunching effect). Here we investigate, for the first time, the
statistical correlation effect for the composite Boson, which is formed from a
spin singlet entangled electron pair. By using nonequilibrium Green's function
technique, we obtain a positive cross correlation for this kind of the
composite Boson when the external voltage is smaller than the gap energy, which
demonstrates that a spin singlet entangled electron pair looks like a composite
Boson. In the larger voltage limit, the cross correlation becomes negative due
to the contribution of the quasiparticles. At large voltages, the oscillation
between Fermionic and Bosonic behavior of cross correlation is also observed in
the strong coupling regime as one changes the position of the resonant levels.
Our result can be easily tested in a three-terminal
normal-superconductor-superconductor (N-S-S) hybrid mesoscopic system
Bose-Einstein Correlations for Three-Dimensionally Expanding, Cylindrically Symmetric, Finite Systems
The parameters of the Bose-Einstein correlation function may obey an {\it
-scaling}, as observed in and reactions at CERN SPS.
This -scaling implies that the Bose-Einstein correlation functions view
only a small part of the big and expanding system. The full sizes of the
expanding system at the last interaction are shown to be measurable with the
help the invariant momentum distribution of the emitted particles. A vanishing
duration parameter can also be generated in the considered model-class with a
specific dependence.Comment: 35 pages, ReVTeX, LaTeX, no figures, discussion extende
Entangled-Photon Imaging of a Pure Phase Object
We demonstrate experimentally and theoretically that a coherent image of a
pure phase object may be obtained by use of a spatially incoherent illumination
beam. This is accomplished by employing a two-beam source of entangled photons
generated by spontaneous parametric down-conversion. Though each of the beams
is, in and of itself, spatially incoherent, the pair of beams exhibits
higher-order inter-beam coherence. One of the beams probes the phase object
while the other is scanned. The image is recorded by measuring the photon
coincidence rate using a photon-counting detector in each beam. Using a
reflection configuration, we successfully imaged a phase object implemented by
a MEMS micro-mirror array. The experimental results are in accord with
theoretical predictions.Comment: 11 pages, 3 figures, submittedto Phys. Rev. Let
Fluctuations of the Initial Conditions and the Continuous Emission in Hydrodynamic Description of Two-Pion Interferometry
Within hydrodynamic approach, we study the Bose-Einstein correlation of
identical pions by taking into account both event-by-event fluctuating initial
conditions and continuous pion emission during the whole development of the hot
and dense matter formed in high-energy collisions. Considerable deviations
occur, compared to the usual hydro calculations with smooth initial conditions
and a sudden freeze-out on a well defined hypersurface. Comparison with data at
RHIC shows that, despite rather rough approximation we used here, this
description can give account of the dependence of and and
improves considerably the one for with respect to the usual version.Comment: 5 pages, 4 figure
Anisotropic interactions of a single spin and dark-spin spectroscopy in diamond
The nitrogen-vacancy (N-V) center in diamond is a promising atomic-scale
system for solid-state quantum information processing. Its spin-dependent
photoluminescence has enabled sensitive measurements on single N-V centers,
such as: electron spin resonance, Rabi oscillations, single-shot spin readout
and two-qubit operations with a nearby 13C nuclear spin. Furthermore, room
temperature spin coherence times as long as 58 microseconds have been reported
for N-V center ensembles. Here, we have developed an angle-resolved
magneto-photoluminescence microscopy apparatus to investigate the anisotropic
electron spin interactions of single N-V centers at room temperature. We
observe negative peaks in the photoluminescence as a function of both magnetic
field magnitude and angle that are explained by coherent spin precession and
anisotropic relaxation at spin level anti-crossings. In addition, precise field
alignment unmasks the resonant coupling to neighboring dark nitrogen spins that
are not otherwise detected by photoluminescence. The latter results demonstrate
a means of investigating small numbers of dark spins via a single bright spin
under ambient conditions.Comment: 13 pages, 4 figure
Two Mode Photon Bunching Effect as Witness of Quantum Criticality in Circuit QED
We suggest a scheme to probe critical phenomena at a quantum phase transition
(QPT) using the quantum correlation of two photonic modes simultaneously
coupled to a critical system. As an experimentally accessible physical
implementation, a circuit QED system is formed by a capacitively coupled
Josephson junction qubit array interacting with one superconducting
transmission line resonator (TLR). It realizes an Ising chain in the transverse
field (ICTF) which interacts with the two magnetic modes propagating in the
TLR. We demonstrate that in the vicinity of criticality the originally
independent fields tend to display photon bunching effects due to their
interaction with the ICTF. Thus, the occurrence of the QPT is reflected by the
quantum characteristics of the photonic fields.Comment: 7 pages, 4 figure
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