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 $+P$ 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