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Milburn T.J.,Vienna University of Technology | Kim M.S.,Imperial College London | Kim M.S.,Korea Institute of Advanced Study | Vanner M.R.,University of Queensland | Vanner M.R.,University of Oxford
Physical Review A - Atomic, Molecular, and Optical Physics

Nonclassical-state generation is an important component throughout experimental quantum science for quantum information applications and probing the fundamentals of physics. Here, we investigate permutations of quantum nondemolition quadrature measurements and single quanta addition or subtraction to prepare quantum superposition states in bosonic systems. The performance of each permutation is quantified and compared using several different nonclassicality criteria including Wigner negativity, nonclassical depth, and optimal fidelity with a coherent-state superposition. We also compare the performance of our protocol using squeezing instead of a quadrature measurement and find that the purification provided by the quadrature measurement can significantly increase the nonclassicality generated. Our approach is ideally suited for implementation in light-matter systems such as quantum optomechanics and atomic spin ensembles, and offers considerable robustness to initial thermal occupation. © 2016 American Physical Society. Source

Chung H.S.,Korea University | Yu C.,Korea University | Kim S.,Sejong University | Kim S.,Korea Institute of Advanced Study | And 2 more authors.
Physical Review D - Particles, Fields, Gravitation and Cosmology

Within the framework of the nonrelativistic QCD (NRQCD) factorization approach, we compute the polarization of prompt J/ψ produced at the Brookhaven's Relativistic Heavy-Ion Collider from proton-proton collisions at the center-of-momentum energy √s=200GeV. The perturbative contributions are computed at leading order in the strong coupling constant. The prediction reveals that the color-singlet contribution severely underestimates the PHENIX preliminary data for the differential cross section integrated over the rapidity range |y|<0.35 and its contribution is strongly transversely polarized, which disagrees with the PHENIX preliminary data. After including the color-octet contributions, we find that the NRQCD predictions for both the cross section and polarization over the transverse-momentum range 1.5GeV Source

Baek S.K.,Sungkyunkwan University | Baek S.K.,Umea University | Um J.,Korea Institute of Advanced Study | Yi S.D.,Sungkyunkwan University | Kim B.J.,Sungkyunkwan University
Physical Review B - Condensed Matter and Materials Physics

In a number of classical statistical-physical models, there exists a characteristic dimensionality called the upper critical dimension above which one observes the mean-field critical behavior. Instead of constructing high-dimensional lattices, however, one can also consider infinite-dimensional structures, and the question is whether this mean-field character extends to quantum-mechanical cases as well. We therefore investigate the transverse-field quantum Ising model on the globally coupled network and on the Watts-Strogatz small-world network by means of quantum Monte Carlo simulations and the finite-size scaling analysis. We confirm that both of the structures exhibit critical behavior consistent with the mean-field description. In particular, we show that the existing cumulant method has difficulty in estimating the correct dynamic critical exponent and suggest that an order parameter based on the quantum-mechanical expectation value can be a practically useful numerical observable to determine critical behavior when there is no well-defined dimensionality. © 2011 American Physical Society. Source

Gupta S.,Yonsei University | Kim C.S.,Yonsei University | Sharma P.,Korea Institute of Advanced Study
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics

We systematically analyze the radiative corrections to the S3 symmetric neutrino mass matrix at high energy scale, say the GUT scale, in the charged lepton basis. There are significant corrections to the neutrino parameters both in the Standard Model (SM) and Minimal Supersymmetric Standard Model (MSSM) with large tan<>β, when the renormalization group evolution (RGE) and seesaw threshold effects are taken into consideration. We find that in the SM all three mixing angles and atmospheric mass squared difference are simultaneously obtained in their current 3σ ranges at the electroweak scale. However, the solar mass squared difference is found to be larger than its allowed 3σ range at the low scale in this case. There are significant contributions to neutrino masses and mixing angles in the MSSM with large tan<>β from the RGEs even in the absence of seesaw threshold corrections. However, we find that the mass squared differences and the mixing angles are simultaneously obtained in their current 3σ ranges at low energy when the seesaw threshold effects are also taken into account in the MSSM with large tan<>β. © 2014 The Authors. Source

Lee J.,Korea Institute of Advanced Study | Gross S.P.,University of California at Irvine
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics

We propose a modularity optimization method, Mod-CSA, based on stochastic global optimization algorithm, conformational space annealing (CSA). Our method outperforms simulated annealing in terms of both efficiency and accuracy, finding higher modularity partitions with less computational resources required. The high modularity values found by our method are higher than, or equal to, the largest values previously reported. In addition, the method can be combined with other heuristic methods, and implemented in parallel fashion, allowing it to be applicable to large graphs with more than 10 000 nodes. © 2012 American Physical Society. Source

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