119 research outputs found
Continuous variable entanglement distillation of Non-Gaussian Mixed States
Many different quantum information communication protocols such as
teleportation, dense coding and entanglement based quantum key distribution are
based on the faithful transmission of entanglement between distant location in
an optical network. The distribution of entanglement in such a network is
however hampered by loss and noise that is inherent in all practical quantum
channels. Thus, to enable faithful transmission one must resort to the protocol
of entanglement distillation. In this paper we present a detailed theoretical
analysis and an experimental realization of continuous variable entanglement
distillation in a channel that is inflicted by different kinds of non-Gaussian
noise. The continuous variable entangled states are generated by exploiting the
third order non-linearity in optical fibers, and the states are sent through a
free-space laboratory channel in which the losses are altered to simulate a
free-space atmospheric channel with varying losses. We use linear optical
components, homodyne measurements and classical communication to distill the
entanglement, and we find that by using this method the entanglement can be
probabilistically increased for some specific non-Gaussian noise channels
A pulsed source of continuous variable polarization entanglement
We have experimentally demonstrated polarization entanglement using
continuous variables in an ultra-short pulsed laser system at telecommunication
wavelengths. Exploiting the Kerr-nonlinearity of a glass fibre we generated a
polarization squeezed pulse with S2 the only non-zero Stokes parameter thus S1
and S3 being the conjugate pair. Polarization entanglement was generated by
interference of the polarization squeezed field with a vacuum on a 50:50 beam
splitter. The two resultant beams exhibit strong quantum noise correlations in
S1 and S3. The sum noise signal of S3 was at the respective shot noise level
and the difference noise signal of S1 fell 2.9dB below this value
Experimental entanglement distillation of mesoscopic quantum states
The distribution of entangled states between distant parties in an optical
network is crucial for the successful implementation of various quantum
communication protocols such as quantum cryptography, teleportation and dense
coding [1-3]. However, owing to the unavoidable loss in any real optical
channel, the distribution of loss-intolerant entangled states is inevitably
inflicted by decoherence, which causes a degradation of the transmitted
entanglement. To combat the decoherence, entanglement distillation, which is
the process of extracting a small set of highly entangled states from a large
set of less entangled states, can be used [4-14]. Here we report on the
mesoscopic distillation of deterministically prepared entangled light pulses
that have undergone non-Gaussian noise. The entangled light pulses [15-17] are
sent through a lossy channel, where the transmission is varying in time
similarly to light propagation in the atmosphere. By employing linear optical
components and global classical communication, the entanglement is
probabilistically increased.Comment: 13 pages, 4 figures. It's the first submitted version to the Nature
Physics. The final version is already published on Nature Physics vol.4,
No.12, 919 - 923 (2008
Assessing the Polarization of a Quantum Field from Stokes Fluctuation
We propose an operational degree of polarization in terms of the variance of
the projected Stokes vector minimized over all the directions of the Poincar\'e
sphere. We examine the properties of this degree and show that some problems
associated with the standard definition are avoided. The new degree of
polarization is experimentally determined using two examples: a bright squeezed
state and a quadrature squeezed vacuum.Comment: 4 pages, 2 figures. Comments welcome
Quantum reconstruction of an intense polarization squeezed optical state
We perform a reconstruction of the polarization sector of the density matrix
of an intense polarization squeezed beam starting from a complete set of Stokes
measurements. By using an appropriate quasidistribution, we map this onto the
Poincare space providing a full quantum mechanical characterization of the
measured polarization state.Comment: 4 pages, 4 eps color figure
Entanglement and squeezing in a two-mode system: theory and experiment
We report on the generation of non separable beams produced via the
interaction of a linearly polarized beam with a cloud of cold cesium atoms
placed in an optical cavity. We convert the squeezing of the two linear
polarization modes into quadrature entanglement and show how to find out the
best entanglement generated in a two-mode system using the inseparability
criterion for continuous variable [Duan et al., Phys. Rev. Lett. 84, 2722
(2000)]. We verify this method experimentally with a direct measurement of the
inseparability using two homodyne detections. We then map this entanglement
into a polarization basis and achieve polarization entanglement.Comment: submitted to J. Opt. B for a Special Issue on Foundations of Quantum
Optic
Simulations and Experiments on Polarisation Squeezing in Optical Fibre
We investigate polarisation squeezing of ultrashort pulses in optical fibre,
over a wide range of input energies and fibre lengths. Comparisons are made
between experimental data and quantum dynamical simulations, to find good
quantitative agreement. The numerical calculations, performed using both
truncated Wigner and exact phase-space methods, include nonlinear and
stochastic Raman effects, through coupling to phonons variables. The
simulations reveal that excess phase noise, such as from depolarising GAWBS,
affects squeezing at low input energies, while Raman effects cause a marked
deterioration of squeezing at higher energies and longer fibre lengths. The
optimum fibre length for maximum squeezing is also calculated.Comment: 19 pages, lots of figure
Teleportation of continuous variable polarisation states
This paper discusses methods for the optical teleportation of continuous
variable polarisation states. We show that using two pairs of entangled beams,
generated using four squeezed beams, perfect teleportation of optical
polarisation states can be performed. Restricting ourselves to 3 squeezed
beams, we demonstrate that polarisation state teleportation can still exceed
the classical limit. The 3-squeezer schemes involve either the use of quantum
non-demolition measurement or biased entanglement generated from a single
squeezed beam. We analyse the efficacies of these schemes in terms of fidelity,
signal transfer coefficients and quantum correlations
Polarization squeezing of intense pulses with a fiber Sagnac interferometer
We report on the generation of polarization squeezing of intense, short light
pulses using an asymmetric fiber Sagnac interferometer. The Kerr nonlinearity
of the fiber is exploited to produce independent amplitude squeezed pulses. The
polarization squeezing properties of spatially overlapped amplitude squeezed
and coherent states are discussed. The experimental results for a single
amplitude squeezed beam are compared to the case of two phase-matched,
spatially overlapped amplitude squeezed pulses. For the latter, noise variances
of -3.4dB below shot noise in the S0 and the S1 and of -2.8dB in the S2 Stokes
parameters were observed, which is comparable to the input squeezing magnitude.
Polarization squeezing, that is squeezing relative to a corresponding
polarization minimum uncertainty state, was generated in S1.Comment: v4: 2 small typos corrected v3: misc problems with Tex surmounted -
mysteriously missing text returned to results - vol# for Korolkova et al. PRA
v2: was a spelling change in author lis
Histologische Veränderungen im Hoden bei vom Klinefelter-Syndrom betroffenen, männlichen Individuen (Mensch und transgene Maus) : Untersuchung möglicher vaskulärer Umbauprozesse
Das Klinefelter-Syndrom ist eine der häufigsten chromosomalen Aneuploidien des männlichen Geschlechts, mit dem Karyotyp 47,XXY. Betroffene zeigen neben vielen Morbiditäten kardiovaskulärer, metabolischer und kognitiver Art als Hauptmerkmal einen Hypogonadismus mit gestörter Spermatogenese und Androgenmangel.
Diese Arbeit befasst sich besonders mit Untersuchungen der Gefäßstruktur innerhalb des Hodens beim Klinefelter-Syndrom. Durch zusätzliche Analysen anhand des 41,XXY*-Maus-Modells, das sich für Forschungszwecke etabliert hat, konnten zudem testikuläre Veränderungen während der postnatalen Entwicklung untersucht werden. In diesem Kontext waren Untersuchungen von Nestin, einem Intermediärfilament, das vorwiegend im Nervensystem vorkommt, jedoch auch den vaskulären Leydig-Vorläuferzellen zugeordnet wurde, Hauptgegenstand dieser Arbeit.
Biopsien von Männern mit Klinefelter-Syndrom zeigten eine im Gegensatz zu infertilen Vergleichs-Patienten erhöhte Zahl von Gefäßen, vornehmlich von denen mit 3 oder mehr Muskelschichten. Bei diesen größeren Gefäßen und testikulären Kapillaren konnten Nestin-exprimierende Zellen identifiziert werden. In Zusammenschau mit Vorarbeiten dürfte Nestin in den größeren Gefäßen an vaskulärem Umbau beteiligt sein und in den kleineren als Marker für Progenitor-Leydig-Zellen anzusehen sein. Ein Auftreten von Nestin in den kontraktilen Zellen des peritubulären Segmentes konnte durch Immunhistochemie ausgeschlossen werden.
Durch qPCR-Untersuchungen zeigte sich ergänzend, dass die testikuläre Nestin-Expression bei Klinefelter-Patienten höher ist als bei infertilen Patienten anderer Genese und fertilen Kontrollen.
In Bezug auf den zeitlichen Verlauf der Nestin-Expression in Gefäßen konnte im Maus-Hoden dargestellt werden, dass die Nestin-Lokalisation gehäuft mit dem Nachweis des Proliferationsmarkers PCNA einhergeht, wobei Nestin bei der 41,XXY*-Maus im Unterschied zu der 40,XY*-Maus postnatal länger vorhanden ist. Auf Proteinebene zeigte sich im Western Blot, dass Nestin bei den 41,XXY*-Mäusen stärker exprimiert wird. Korrelierend damit war auch die Expression des für die Markierung von Leydig-Zellen verwendbaren Enzyms Cytochrom P450scc bei 41,XXY*-Mäusen stark erhöht. Dies könnte darauf hindeuten, dass trotz verringertem Serum-Testosteron wahrscheinlich ein intratestikulär erhöhter Testosteron-Gehalt vorliegt, worauf bereits andere Studien hindeuteten.
Schlussfolgernd liefert die vorliegende Dissertation erstmalig Hinweise auf die Bedeutung von Nestin beim Klinefelter-Syndrom und 41,XXY*-Maus-Modell und unterstützt die Hypothese einer vaskulär-metabolischen Ursache für die bis heute nicht vollständig aufgeklärte Infertilität bei einer Erkrankung, die oftmals noch viel zu spät diagnostiziert wird.Klinefelter syndrome is one of the most common chromosomal aneuploidies of the male gender, with the karyotype 47,XXY. Beside cardiovascular, metabolic and cognitive morbidities, affected men exhibit hypogonadism with impaired spermatogenesis and androgen deficiency as key features.
This work particularly deals with investigations of the vascular structure in the testis in case of Klinefelter syndrome. Further analyses comprised the 41,XXY* mouse model, that was established for research. In this model testicular changes during postnatal development could be examined. The characterization of nestin expression, an intermediate filament proteine that primarily occurs in the nervous system, but was also assigned to vascular Leydig cell progenitors, was the main subject of this work. Biopsies of Klinefelter syndrome patients showed an increased number of vessels, especially of those with 3 or more smooth muscle cell layers, in contrast to infertile male controls. Nestin-expressing cells could be identified in these larger vessels and also in testicular capillaries. As can be deduced by this and previous investigations, in larger vessels nestin might be involved in vascular remodeling, whereas nestin in smaller vessels might indicate Leydig cell progenitors. As shown by immunohistochemistry, Nestin staining was absent in contractile cells of the peritubular segment.
Additional qPCR results demonstrated higher testicular nestin expression in Klinefelter syndrome patients in comparison to other infertile patients and fertile controls.
Developmental studies in the mouse model revealed a co-localization of nestin and the proliferation marker PCNA. Reduction of nestin expressing cells towards adulthood was delayed in 41,XXY* mice compared to controls. Western Blot analyses indicated higher nestin expression in the tesis of 41,XXY* mice. In agreement, the expression of the enzyme Cytochrome P450scc, used as marker for Leydig cells, was also higher in 41,XXY* mice. This data might reflect increased intratesticular testosterone (despite low serum testosterone) confirming previous findings.
For the first time this study provides evidence for a special significance of nestin in Klinefelter syndrome and the 41,XXY* mouse model, thereby supporting the hypothesis of a vascular-metabolic reason of the infertility in this disease
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