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Search Results: 1 - 10 of 2602 matches for " Andre Stefanov "
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Experimental realization of a quantum game on a one-way quantum computer
Robert Prevedel,Andre Stefanov,Philip Walther,Anton Zeilinger
Physics , 2007, DOI: 10.1088/1367-2630/9/6/205
Abstract: We report the first demonstration of a quantum game on an all-optical one-way quantum computer. Following a recent theoretical proposal we implement a quantum version of Prisoner's Dilemma, where the quantum circuit is realized by a 4-qubit box-cluster configuration and the player's local strategies by measurements performed on the physical qubits of the cluster. This demonstration underlines the strength and versatility of the one-way model and we expect that this will trigger further interest in designing quantum protocols and algorithms to be tested in state-of-the-art cluster resources.
Gas phase sorting of nanoparticles
Hendrik Ulbricht,Martin Berninger,Sarayut Deachapunya,Andre Stefanov,Markus Arndt
Physics , 2007,
Abstract: We discuss Stark deflectometry of micro-modulated molecular beams for the enrichment of biomolecular isomers as well as single-wall carbon nanotubes and we demonstrate the working principle of this idea with fullerenes. The sorting is based on the species-dependent polarizability-to-mass ratio $\alpha/m$. The device is compatible with a high molecular throughput, and the spatial micro-modulation of the beam permits to obtain a fine spatial resolution and a high sorting sensitivity.
Quantum correlations versus Multisimultaneity: an experimental test
Andre Stefanov,Nicolas Gisin,Antoine Suarez,Hugo Zbinden
Physics , 2001, DOI: 10.1103/PhysRevLett.88.120404
Abstract: Multisimultaneity is a causal model of relativistic quantum physics which assigns a real time ordering to any set of events, much in the spirit of the pilot-wave picture. Contrary to standard quantum mechanics, it predicts a disappearance of the correlations in a Bell-type experiment when both analysers are in relative motion such that, each one in its own inertial reference frame, is first to select the output of the photons. We tested this prediction using acousto-optic modulators as moving beam-splitters and interferometers separated by 55 m. We didn't observe any disappearance of the correlations, thus refuting Multisimultaneity.
A scalable optical detection scheme for matter wave interferometry
Alexander Stibor,Andre Stefanov,Fabienne Goldfarb,Elisabeth Reiger,Markus Arndt
Physics , 2006, DOI: 10.1088/1367-2630/7/1/224
Abstract: Imaging of surface adsorbed molecules is investigated as a novel detection method for matter wave interferometry with fluorescent particles. Mechanically magnified fluorescence imaging turns out to be an excellent tool for recording quantum interference patterns. It has a good sensitivity and yields patterns of high visibility. The spatial resolution of this technique is only determined by the Talbot gratings and can exceed the optical resolution limit by an order of magnitude. A unique advantage of this approach is its scalability: for certain classes of nano-sized objects, the detection sensitivity will even increase significantly with increasing size of the particle.
Faint laser quantum key distribution: Eavesdropping exploiting multiphoton pulses
Stephane Felix,Nicolas Gisin,Andre Stefanov,Hugo Zbinden
Physics , 2001, DOI: 10.1080/09500340108240903
Abstract: The technological possibilities of a realistic eavesdropper are discussed. Two eavesdropping strategies taking profit of multiphoton pulses in faint laser QKD are presented. We conclude that, as long as storage of Qubits is technically impossible, faint laser QKD is not limited by this security issue, but mostly by the detector noise.
Quantum entanglement with acousto-optic modulators: 2-photon beatings and Bell experiments with moving beamsplitters
Andre Stefanov,Hugo Zbinden,Antoine Suarez,Nicolas Gisin
Physics , 2002, DOI: 10.1103/PhysRevA.67.042115
Abstract: We present an experiment testing quantum correlations with frequency shifted photons. We test Bell inequality with 2-photon interferometry where we replace the beamsplitters by acousto-optic modulators, which are equivalent to moving beamsplitters. We measure the 2-photon beatings induced by the frequency shifts, and we propose a cryptographic scheme in relation. Finally, setting the experiment in a relativistic configuration, we demonstrate that the quantum correlations are not only independent of the distance but also of the time ordering between the two single-photon measurements.
Manipulating multi-photon entanglement in waveguide quantum circuits
Jonathan C. F. Matthews,Alberto Politi,Andre Stefanov,Jeremy L. O'Brien
Physics , 2009, DOI: 10.1038/nphoton.2009.93
Abstract: On-chip integrated photonic circuits are crucial to further progress towards quantum technologies and in the science of quantum optics. Here we report precise control of single photon states and multi-photon entanglement directly on-chip. We manipulate the state of path-encoded qubits using integrated optical phase control based on resistive elements, observing an interference contrast of 98.2+/-0.3%. We demonstrate integrated quantum metrology by observing interference fringes with 2- and 4-photon entangled states generated in a waveguide circuit, with respective interference contrasts of 97.2+/-0.4% and 92+/-4%, sufficient to beat the standard quantum limit. Finally, we demonstrate a reconfigurable circuit that continuously and accurately tunes the degree of quantum interference, yielding a maximum visibility of 98.2+/- 0.9%. These results open up adaptive and fully reconfigurable photonic quantum circuits not just for single photons, but for all quantum states of light.
Conformational flexibility of the pharmacologically important insulin analogues  [PDF]
Olga Ksenofontova, Vasily Stefanov
Advances in Biological Chemistry (ABC) , 2013, DOI: 10.4236/abc.2013.35056
Abstract: Understanding the conformational flexibility of the insulin drugs is of great importance for the treatment of diabetes mellitus. Once in the body, the drug must have a certain degree of mobility within a specified period of time for the manifestation of its pharmacological properties. This mobility ensures conformational states necessary for binding with the insulin receptor and activating specific biological processes. In this work we investigated conformational flexibility of the pharmacologically important insulin analogues—insulin lispro, insulin aspart, insulin glulisine, and insulin glargine, using the molecular dynamics simulation method. This study provides new insight into the nature of behaviour of A-and B-chains. It has been found out that B-chain substitutions result in rapid acting, while long-lasting action can be achieved by substitutions in both chains. The results of this study can be used for development of new insulin-based antidiabetic drugs.
Slow beams of massive molecules
Sarayut Deachapunya,Paul J. Fagan,Andras G. Major,Elisabeth Reiger,Helmut Ritsch,Andre Stefanov,Hendrik Ulbricht,Markus Arndt
Physics , 2007, DOI: 10.1140/epjd/e2007-00301-8
Abstract: Slow beams of neutral molecules are of great interest for a wide range of applications, from cold chemistry through precision measurements to tests of the foundations of quantum mechanics. We report on the quantitative observation of thermal beams of perfluorinated macromolecules with masses up to 6000 amu, reaching velocities down to 11 m/s. Such slow, heavy and neutral molecular beams are of importance for a new class of experiments in matter-wave interferometry and we also discuss the requirements for further manipulation and cooling schemes with molecules in this unprecedented mass range.
A simple scheme for expanding photonic cluster states for quantum information
Pruet Kalasuwan,Gabriel Mendoza,Anthony Laing,Tomohisa Nagata,Jack Coggins,Mark Callaway,Shigeki Takeuchi,Andre Stefanov,Jeremy L. O'Brien
Physics , 2010, DOI: 10.1364/JOSAB.27.00A181
Abstract: We show how an entangled cluster state encoded in the polarization of single photons can be straightforwardly expanded by deterministically entangling additional qubits encoded in the path degree of freedom of the constituent photons. This can be achieved using a polarization--path controlled-phase gate. We experimentally demonstrate a practical and stable realization of this approach by using a Sagnac interferometer to entangle a path qubit and polarization qubit on a single photon. We demonstrate precise control over phase of the path qubit to change the measurement basis and experimentally demonstrate properties of measurement-based quantum computing using a 2 photon, 3 qubit cluster state.
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