1,441 research outputs found
Characterizing Quantum-Dot Blinking Using Noise Power Spectra
Fluctuations in the fluorescence from macroscopic ensembles of colloidal
semiconductor quantum dots have the spectral form of 1/f noise. The measured
power spectral density reflects the fluorescence intermittency of individual
dots with power-law distributions of "on" and "off" times, and can thus serve
as a simple method for characterizing such blinking behavior
Letter from E. W. Pelton to John Muir, 1863 Mar 22
Prairie du Chin Mar 22/63 3 - 30 PM Friend John There is no very partic- -ular change in Mrs Peltons case I think on the whole she has been more comfortable since my return from Madison than [illegible] you stay [illegible] But at times she is very bad, and seems to suffer greatly Her life is gradually ebling out [illegible]ful that I must surely soon past with her - that there is no [illegible] for her in this world She appeared much interested in the [illegible] wanted [me?] to bring them in and pick out the [illegible] ones Which I did, and file a salt sack with them, and put them away for her. As yet she has eaten but a few [meals?], and I fear she will eat very few more. She is having an uncomfortable afternoon, though getting a little [easier?] now. She has spoken your name many times in the wandering of her mind Since you were here she continues to have frequent fever, running very high some of the rime night & day Mrs Bassett is here with us. Yours Truly E [W?] Pelton 191 0032
Use of ERTS-1 data in the educational and applied research programs of agricultural extension
There are no author-identified significant results in this report
Theory and experiment of entanglement in a quasi-phase-matched two-crystal source
We report new results regarding a source of polarization entangled
photon-pairs created by the process of spontaneous parametric downconversion in
two orthogonally oriented, periodically poled, bulk KTiOPO4 crystals (PPKTP).
The source emits light colinearly at the non-degenerate wavelengths of 810 nm
and 1550 nm, and is optimized for single-mode optical fiber collection and
long-distance quantum communication. The configuration favors long crystals,
which promote a high photon-pair production rate at a narrow bandwidth,
together with a high pair-probability in fibers. The quality of entanglement is
limited by chromatic dispersion, which we analyze by determining the output
state. We find that such a decoherence effect is strongly material dependent,
providing for long crystals an upper bound on the visibility of the coincidence
fringes of 41% for KTiOPO4, and zero for LiNbO3. The best obtained raw
visibility, when canceling decoherence with an extra piece of crystal, was 91
\pm 0.2%, including background counts. We confirm by a violation of the
CHSH-inequality (S = 2.679 \pm 0.004 at 55 s^{-1/2} standard deviations) and by
complete quantum state tomography that the fibers carry high-quality entangled
pairs at a maximum rate of 55 x 10^3 s^{-1}THz^{-1}mW^{-1}.Comment: 12 pages, 10 figures, REVTeX
Practical quantum repeaters with linear optics and double-photon guns
We show how to create practical, efficient, quantum repeaters, employing
double-photon guns, for long-distance optical quantum communication. The guns
create polarization-entangled photon pairs on demand. One such source might be
a semiconducter quantum dot, which has the distinct advantage over parametric
down-conversion that the probability of creating a photon pair is close to one,
while the probability of creating multiple pairs vanishes. The swapping and
purifying components are implemented by polarizing beam splitters and
probabilistic optical CNOT gates.Comment: 4 pages, 4 figures ReVTe
A comparison between Gauss-Newton and Markov-chain Monte Carlo–based methods for inverting spectral induced-polarization data for Cole-Cole parameters
A calcium ion in a cavity as a controlled single-photon source
We present a single calcium ion, coupled to a high-finesse cavity, as an almost ideal system for the controlled generation of single photons. Photons from a pump beam are Raman-scattered by the ion into the cavity mode, which subsequently emits the photon into a well-defined output channel. In contrast with comparable atomic systems, the ion is localized at a fixed position in the cavity mode for indefinite times, enabling truly continuous operation of the device. We have performed numeric calculations to assess the performance of the system and present the first experimental indication of single-photon emission in our set-up
Ranking ligand affinity for the DNA minor groove by experiment and simulation
The structural and thermodynamic basis for the strength and selectivity of the interactions of minor-groove binders (MGBs) with DNA is not fully understood. In 2003 we reported the first example of a thiazole containing MGB that bound in a phase shifted pattern that spanned 6 base-pairs rather than the usual 4 (for tricyclic distamycin-like compounds). Since then, using DNA footprinting, nuclear magnetic resonance spectroscopy, isothermal titration calorimetry and molecular dynamics, we have established that the flanking bases around the central 4 being read by the ligand have subtle effects on recognition. We have investigated the effect of these flanking sequences on binding and the reasons for the differences and established a computational method to rank ligand affinity against varying DNA sequences
Dumbbell transport and deflection in a spatially periodic potential
We present theoretical results on the deterministic and stochastic motion of
a dumbbell carried by a uniform flow through a three-dimensional spatially
periodic potential. Depending on parameters like the flow velocity, there are
two different kinds of movement: transport along a potential valley and
stair-like motion oblique to the potential trenches. The crossover between
these two regimes, as well as the deflection angle, depends on the size of the
dumbbell. Moreover, thermal fluctuations cause a resonance-like variation in
the deflection angle as a function of the dumbbell extension.Comment: 5 pages, 8 figure
An entangled two photon source using biexciton emission of an asymmetric quantum dot in a cavity
A semiconductor based scheme has been proposed for generating entangled
photon pairs from the radiative decay of an electrically-pumped biexciton in a
quantum dot. Symmetric dots produce polarisation entanglement, but
experimentally-realised asymmetric dots produce photons entangled in both
polarisation and frequency. In this work, we investigate the possibility of
erasing the `which-path' information contained in the frequencies of the
photons produced by asymmetric quantum dots to recover polarisation-entangled
photons. We consider a biexciton with non-degenerate intermediate excitonic
states in a leaky optical cavity with pairs of degenerate cavity modes close to
the non-degenerate exciton transition frequencies. An open quantum system
approach is used to compute the polarisation entanglement of the two-photon
state after it escapes from the cavity, measured by the visibility of
two-photon interference fringes. We explicitly relate the two-photon visibility
to the degree of Bell-inequality violation, deriving a threshold at which
Bell-inequality violations will be observed. Our results show that an ideal
cavity will produce maximally polarisation-entangled photon pairs, and even a
non-ideal cavity will produce partially entangled photon pairs capable of
violating a Bell-inequality.Comment: 16 pages, 10 figures, submitted to PR
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