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1.
Proc Natl Acad Sci U S A ; 112(46): 14202-5, 2015 Nov 17.
Artigo em Inglês | MEDLINE | ID: mdl-26578764

RESUMO

As a direct consequence of the no-cloning theorem, the deterministic amplification as in classical communication is impossible for unknown quantum states. This calls for more advanced techniques in a future global quantum network, e.g., for cloud quantum computing. A unique solution is the teleportation of an entangled state, i.e., entanglement swapping, representing the central resource to relay entanglement between distant nodes. Together with entanglement purification and a quantum memory it constitutes a so-called quantum repeater. Since the aforementioned building blocks have been individually demonstrated in laboratory setups only, the applicability of the required technology in real-world scenarios remained to be proven. Here we present a free-space entanglement-swapping experiment between the Canary Islands of La Palma and Tenerife, verifying the presence of quantum entanglement between two previously independent photons separated by 143 km. We obtained an expectation value for the entanglement-witness operator, more than 6 SDs beyond the classical limit. By consecutive generation of the two required photon pairs and space-like separation of the relevant measurement events, we also showed the feasibility of the swapping protocol in a long-distance scenario, where the independence of the nodes is highly demanded. Because our results already allow for efficient implementation of entanglement purification, we anticipate our research to lay the ground for a fully fledged quantum repeater over a realistic high-loss and even turbulent quantum channel.

2.
Chem Commun (Camb) ; 49(17): 1702-4, 2013 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-23340804

RESUMO

Here we report the facile formation of boron-containing cyclic (amino)(imino)carbene complexes by reaction of a chromium borylene complex [(OC)(5)Cr=B=N(SiMe(3))(2)] with isocyanides.

3.
Proc Natl Acad Sci U S A ; 110(4): 1221-6, 2013 Jan 22.
Artigo em Inglês | MEDLINE | ID: mdl-23288900

RESUMO

The counterintuitive features of quantum physics challenge many common-sense assumptions. In an interferometric quantum eraser experiment, one can actively choose whether or not to erase which-path information (a particle feature) of one quantum system and thus observe its wave feature via interference or not by performing a suitable measurement on a distant quantum system entangled with it. In all experiments performed to date, this choice took place either in the past or, in some delayed-choice arrangements, in the future of the interference. Thus, in principle, physical communications between choice and interference were not excluded. Here, we report a quantum eraser experiment in which, by enforcing Einstein locality, no such communication is possible. This is achieved by independent active choices, which are space-like separated from the interference. Our setup employs hybrid path-polarization entangled photon pairs, which are distributed over an optical fiber link of 55 m in one experiment, or over a free-space link of 144 km in another. No naive realistic picture is compatible with our results because whether a quantum could be seen as showing particle- or wave-like behavior would depend on a causally disconnected choice. It is therefore suggestive to abandon such pictures altogether.

4.
Opt Express ; 20(21): 23126-37, 2012 Oct 08.
Artigo em Inglês | MEDLINE | ID: mdl-23188277

RESUMO

We present a high-fidelity quantum teleportation experiment over a high-loss free-space channel between two laboratories. We teleported six states of three mutually unbiased bases and obtained an average state fidelity of 0.82(1), well beyond the classical limit of 2/3. With the obtained data, we tomographically reconstructed the process matrices of quantum teleportation. The free-space channel attenuation of 31 dB corresponds to the estimated attenuation regime for a down-link from a low-earth-orbit satellite to a ground station. We also discussed various important technical issues for future experiments, including the dark counts of single-photon detectors, coincidence-window width etc. Our experiment tested the limit of performing quantum teleportation with state-of-the-art resources. It is an important step towards future satellite-based quantum teleportation and paves the way for establishing a worldwide quantum communication network.


Assuntos
Dispositivos Ópticos , Telecomunicações/instrumentação , Desenho de Equipamento , Análise de Falha de Equipamento , Luz , Teoria Quântica , Espalhamento de Radiação
5.
Nature ; 489(7415): 269-73, 2012 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-22951967

RESUMO

The quantum internet is predicted to be the next-generation information processing platform, promising secure communication and an exponential speed-up in distributed computation. The distribution of single qubits over large distances via quantum teleportation is a key ingredient for realizing such a global platform. By using quantum teleportation, unknown quantum states can be transferred over arbitrary distances to a party whose location is unknown. Since the first experimental demonstrations of quantum teleportation of independent external qubits, an internal qubit and squeezed states, researchers have progressively extended the communication distance. Usually this occurs without active feed-forward of the classical Bell-state measurement result, which is an essential ingredient in future applications such as communication between quantum computers. The benchmark for a global quantum internet is quantum teleportation of independent qubits over a free-space link whose attenuation corresponds to the path between a satellite and a ground station. Here we report such an experiment, using active feed-forward in real time. The experiment uses two free-space optical links, quantum and classical, over 143 kilometres between the two Canary Islands of La Palma and Tenerife. To achieve this, we combine advanced techniques involving a frequency-uncorrelated polarization-entangled photon pair source, ultra-low-noise single-photon detectors and entanglement-assisted clock synchronization. The average teleported state fidelity is well beyond the classical limit of two-thirds. Furthermore, we confirm the quality of the quantum teleportation procedure without feed-forward by complete quantum process tomography. Our experiment verifies the maturity and applicability of such technologies in real-world scenarios, in particular for future satellite-based quantum teleportation.

6.
Opt Express ; 20(7): 8078-92, 2012 Mar 26.
Artigo em Inglês | MEDLINE | ID: mdl-22453479

RESUMO

LINC-NIRVANA is a near-infrared Fizeau interferometric imager that will operate at the Large Binocular Telescope. In preparation for the commissioning of this instrument, we conducted experiments for calibrating the high-layer wavefront sensor of the layer-oriented multi-conjugate adaptive optics system. For calibrating the multi-pyramid wavefront sensor, four light sources were used to simulate guide stars. Using this setup, we developed the push-pull method for calibrating the interaction matrix. The benefits of this method over the traditional push-only method are quantified, and also the effects of varying the number of push-pull frames over which aberrations are averaged is reported. Finally, we discuss a method for measuring mis-conjugation between the deformable mirror and the wavefront sensor, and the proper positioning of the wavefront sensor detector with respect to the four pupil positions.


Assuntos
Interferometria/instrumentação , Fotometria/instrumentação , Telescópios , Transdutores , Calibragem
7.
Opt Express ; 19(17): 16087-95, 2011 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-21934971

RESUMO

In the field of adaptive optics, multi-conjugate adaptive optics (MCAO) can greatly increase the size of the corrected field of view (FoV) and also extend sky coverage. By applying layer oriented MCAO (LO-MCAO) [4], together with multiple guide stars (up to 20) and pyramid wavefront sensors [7], LINC-NIRVANA (L-N for short) [1] will provide two AO-corrected beams to a Fizeau interferometer to achieve 10 milliarcsecond angular resolution on the Large Binocular Telescope. This paper presents first laboratory results of the AO performance achieved with the high layer wavefront sensor (HWS). This sensor, together with its associated deformable mirror (a Xinetics-349), is being operated in one of the L-N laboratories. AO reference stars, spread across a 2 arc-minute FoV and with aberrations resulting from turbulence introduced at specific layers in the atmosphere, are simulated in this lab environment. This is achieved with the Multi-Atmosphere Phase screen and Stars (MAPS) [2] unit. From the wavefront data, the approximate residual wavefront error after correction has been calculated for different turbulent layer altitudes and wind speeds. Using a somewhat undersampled CCD, the FWHM of stars in the nearly 2 arc-minute FoV has also been measured. These test results demonstrate that the high layer wavefront sensor of LINC-NIRVANA will be able to achieve uniform AO correction across a large FoV.

8.
Proc Natl Acad Sci U S A ; 107(46): 19708-13, 2010 Nov 16.
Artigo em Inglês | MEDLINE | ID: mdl-21041665

RESUMO

Bell's theorem shows that local realistic theories place strong restrictions on observable correlations between different systems, giving rise to Bell's inequality which can be violated in experiments using entangled quantum states. Bell's theorem is based on the assumptions of realism, locality, and the freedom to choose between measurement settings. In experimental tests, "loopholes" arise which allow observed violations to still be explained by local realistic theories. Violating Bell's inequality while simultaneously closing all such loopholes is one of the most significant still open challenges in fundamental physics today. In this paper, we present an experiment that violates Bell's inequality while simultaneously closing the locality loophole and addressing the freedom-of-choice loophole, also closing the latter within a reasonable set of assumptions. We also explain that the locality and freedom-of-choice loopholes can be closed only within nondeterminism, i.e., in the context of stochastic local realism.

9.
Chemistry ; 15(44): 12099-106, 2009 Nov 09.
Artigo em Inglês | MEDLINE | ID: mdl-19780118

RESUMO

We report on the hydroboration of 1-[bis(trimethylsilyl)amino]-2,3-diethylborirene (3) with 9-borabicyclo[3.3.1]nonane (9-BBN), which led through ring-opening to an amino(vinyl)borane. The viscous borane was subsequently converted into a crystalline borate on treatment with MeLi. Both compounds were fully characterized by multinuclear NMR spectroscopy and in case of the latter by single-crystal X-ray diffraction analysis. To elucidate the reaction mechanism of the unexpected boron-carbon bond cleavage, DFT calculations of energy minima and transition states for the hydroboration were carried out.

10.
Neurocrit Care ; 11(3): 377-80, 2009 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-19655277

RESUMO

OBJECTIVE AND IMPORTANCE: We report the histopathologic examination of Wingspan stent in acute ischemic stroke. CLINICAL PRESENTATION: A 75-year-old female presented with acute left-hemiplegia due to right carotid terminus occlusion. Mechanical embolectomy was unsuccessful. INTERVENTION: A Wingspan stent was placed from the distal intracranial carotid artery to the proximal middle cerebral artery stem and established partial antegrade flow. The patient died of malignant infarction on post-stroke day 7. At autopsy, embolized calcified atherosclerotic plaque fragments were noted within a non-occlusive thrombus over which the Wingspan stent was deployed. There was no evidence of intimal or media dissection or perforator ostium occlusion. CONCLUSION: Our case provides a rare pathological description of intracranial stent placement in the setting of acute ischemic stroke.


Assuntos
Angioplastia com Balão/instrumentação , Isquemia Encefálica/patologia , Stents , Acidente Vascular Cerebral/patologia , Doença Aguda , Idoso , Isquemia Encefálica/diagnóstico por imagem , Artérias Carótidas/diagnóstico por imagem , Artérias Carótidas/patologia , Angiografia Cerebral , Feminino , Humanos , Artéria Cerebral Média/diagnóstico por imagem , Artéria Cerebral Média/patologia , Acidente Vascular Cerebral/diagnóstico por imagem , Tomografia Computadorizada por Raios X
11.
Circulation ; 120(2): 141-9, 1-2, 2009 Jul 14.
Artigo em Inglês | MEDLINE | ID: mdl-19564562

RESUMO

BACKGROUND: Although both sirolimus (CYPHER) and paclitaxel (TAXUS) drug-eluting stents have demonstrated efficacy and safety in clinical trials, human autopsy data have raised concerns about long-term healing and the potential for local inflammatory reactions. METHODS AND RESULTS: Overlapping stents (CYPHER drug-eluting stents, Bx SONIC bare metal stents, TAXUS drug-eluting stents, and Liberté bare metal stents) were implanted in noninjured coronary arteries of 58 domestic swine. Histopathological evaluation of proximal, overlapped, and distal stented segments was determined with emphasis on inflammation at 30, 90, and 180 days. Circumferential granulomatous inflammation in all stented segments was defined as inflammation consisting of macrophages, multinucleated giant cells, lymphocytes, and granulocytes, including many eosinophils, adjacent to almost all struts. Circumferential granulomatous inflammation was more prevalent in CYPHER (9 of 23, 39%) compared with TAXUS (1 of 21, 5%; P=0.01) and control bare metal stents (0 of 44) in the combined 90- and 180-day cohorts. Only CYPHER specimens showed marked adventitial inflammation (P=0.0025) and fibrosis (P=0.0055) accompanied by extensive remodeling. Fibrin deposition within neointima and medial smooth muscle cell death were greater (both P<0.001) in TAXUS than CYPHER at 30 days, with more fibrin in TAXUS than CYPHER through 90 days (P<0.05). CONCLUSIONS: Although these data cannot be directly extrapolated to humans, the high prevalence in this porcine model of diffuse granulomatous inflammation seen with CYPHER stents, persisting at 180 days and associated with extensive remodeling of the artery, and persistent para-strut fibrin deposition with TAXUS stents emphasize the need for further investigation of biocompatibility with these and other novel combination drug/polymer drug-eluting stents.


Assuntos
Arterite/induzido quimicamente , Arterite/patologia , Vasos Coronários/patologia , Stents Farmacológicos/efeitos adversos , Paclitaxel/efeitos adversos , Sirolimo/efeitos adversos , Animais , Vasos Coronários/efeitos dos fármacos , Vasos Coronários/metabolismo , Modelos Animais de Doenças , Eosinófilos/patologia , Feminino , Fibrina/metabolismo , Fibrose/induzido quimicamente , Fibrose/patologia , Granuloma de Corpo Estranho/induzido quimicamente , Granuloma de Corpo Estranho/patologia , Paclitaxel/farmacologia , Sirolimo/farmacologia , Suínos , Túnica Íntima/efeitos dos fármacos , Túnica Íntima/metabolismo , Túnica Íntima/patologia
12.
J Am Chem Soc ; 131(25): 8989-99, 2009 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-19480461

RESUMO

Room temperature photolysis of aminoborylene complexes, [(CO)(5)M=B=N(SiMe(3))(2)] (1: M = Cr, 2: Mo) in the presence of a series of alkynes and diynes, 1,2-bis(4-methoxyphenyl)ethyne, 1,2-bis(4-(trifluoromethyl)phenyl)ethyne, 1,4-diphenylbuta-1,3-diyne, 1,4-bis(4-methoxyphenyl)buta-1,3-diyne, 1,4-bis(trimethylsilylethynyl)benzene and 2,5-bis(4-N,N-dimethylaminophenylethynyl)thiophene led to the isolation of novel mono and bis-bis-(trimethylsilyl)aminoborirenes in high yields, that is [(RC=CR)(mu-BN(SiMe(3))(2)], (3: R = C(6)H(4)-4-OMe and 4: R = C(6)H(4)-4-CF(3)); [{(mu-BN(SiMe(3))(2)(RC=C-)}(2)], (5: R = C(6)H(5) and 6: R = C(6)H(4)-4-OMe); [1,4-bis-{(mu-BN(SiMe(3))(2)(SiMe(3)C=C)}benzene], 7 and [2,5-bis-{(mu-BN(SiMe(3))(2) ((C(6)H(4)NMe(2))C=C)}-thiophene], 8. All borirenes were isolated as light yellow, air and moisture sensitive solids. The new borirenes have been characterized in solution by (1)H, (11)B, (13)C NMR spectroscopy and elemental analysis and the structural types were unequivocally established by crystallographic analysis of compounds 6 and 7. DFT calculations were performed to evaluate the extent of pi-conjugation between the electrons of the carbon backbone and the empty p(z) orbital of the boron atom, and TD-DFT calculations were carried out to examine the nature of the electronic transitions.

14.
Chem Commun (Camb) ; (4): 497-8, 2008 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-18188480

RESUMO

The first catalytic application of the Group VI metal borylene complexes [(CO)(5)M[double bond]BN(SiMe(3))(2)] involves the demercuration reaction of bis(alkynyl)mercurials, [Hg(C[triple bond]CR)(2)], with formation of a series of buta-1,3-diynes.

15.
Opt Express ; 15(23): 15377-86, 2007 Nov 12.
Artigo em Inglês | MEDLINE | ID: mdl-19550823

RESUMO

We demonstrate a wavelength-tunable, fiber-coupled source of polarization- entangled photons with extremely high spectral brightness and quality of entanglement. Using a 25 mm PPKTP crystal inside a polarization Sagnac interferometer we detect a spectral brightness of 273000 pairs (s mW nm)(-1), a factor of 28 better than comparable previous sources while state tomography showed the two-photon state to have a tangle of T = 0.987. This improvement was achieved by use of a long crystal, careful selection of focusing parameters and single-mode fiber coupling. We demonstrate that, due to the particular geometry of the setup, the signal and idler wavelengths can be tuned over a wide range without loss of entanglement.

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