1,766 research outputs found

    Exploring the Optimal Sensitivity of Sum-Variance Nonseparability Criteria for Spin-1/2 Systems

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    We report on experimental and theoretical studies on recently introduced entanglement measures which use a sum of spin-variance criteria for two spin-1∕2 particles. Three inequalities are explored which exhibit useful concatenating properties. They are each shown to have greater sensitivities than a Bell’s measurement, while each requiring fewer measurements than a Bell’s measurement to obtain. The simplest inequality, requiring just four measurements, is shown to be efficient at testing for entanglement in down-conversion sources which naturally exhibit maximally polarized noise. The most complex inequality, requiring just 12 measurements, is shown to have a sensitivity equal to that of the Peres separability criterion for maximally polarized and Werner noise. This increased sensitivity implies optimality of the measure

    Experimental Demonstration of High Two-Photon Time-Energy Entanglement

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    We report on the experimental demonstration of high energy-time entanglement in two-photon states created in the process of spontaneous parametric down-conversion. We show that the classical variance product, which we violate by three orders of magnitude, actually represents a lower bound estimate of the number of information eigenmodes K. Explicit measurements estimate K to be greater than 100, with theoretical estimates predicting a value of as high as 1×106. These results provide incentive for the practical feasibility of large bandwidth quantum information processing, particularly in cryptography over large distances

    Hong-Ou-Mandel Cloning: Quantum Copying Without an Ancilla

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    In this paper we report an experimental realization of an ancilla-free 1→2 phase-covariant quantum cloner. The cloner is realized by interfering a linearly polarized photon, which we wish to clone with a circularly polarized photon at a beam splitter. The two-photon effect can be understood in light of Hong-Ou-Mandel interference. The fidelity of the cloner was measured as 0.829±0.008 for the 0∕90 basis and 0.835±0.006 for the 45∕135 basis, which is in good agreement with the theoretical prediction of 5∕6 fidelity. The experimental scheme is straightforward and has a high cloning success rate

    Knowledge about asthma: A cross-sectional survey in 4 major hospitals of Karachi, Pakistan

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    Objective: To determine knowledge and misconceptions about asthma among the local population..Methods: This cross-sectional study was conducted at four tertiary care hospitals; Aga Khan University Hospital, Civil Hospital Karachi, Jinnah Postgraduate Medical Centre and Ojha Institute of Chest Diseases, Karachi, from October to November 2016, and comprised hospital attendants. The questionnaire used in the study comprised 26 questions answered with a true, false or not sure answer.SPSS 20 was used for data analysis.Results: There were 400 participants. The overall mean age was 41.2±14.2 years, and 214(53.5%) of the participants were males. Moreover, 75(19%) participants thought that asthma was a psychological disorder while 181(45%) considered it an infectious disease. Nearly 174(43.5%) believed that inhaled medications had significant side effects. Besides, 264(66%) participants considered steam inhalation to be an effective treatment for asthma, 269(67%) thought that patients with asthma should avoid rice in their diet and 167(42%) considered milk as a common trigger.CONCLUSIONS: Participants\u27 knowledge about asthma was poor and misconceptions were common about the condition

    Large-Alphabet Quantum Key Distribution Using Energy-Time Entangled Bipartite States

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    We present a protocol for large-alphabet quantum key distribution (QKD) using energy-time entangled biphotons. Binned, high-resolution timing measurements are used to generate a large-alphabet key with over 10 bits of information per photon pair, albeit with large noise. QKD with 5% bit error rate is demonstrated with 4 bits of information per photon pair, where the security of the quantum channel is determined by the visibility of Franson interference fringes. The protocol is easily generalizable to even larger alphabets, and utilizes energy-time entanglement which is robust to transmission over large distances in fiber