7,184 research outputs found
Quantum walks on two kinds of two-dimensional models
In this paper, we numerically study quantum walks on two kinds of
two-dimensional graphs: cylindrical strip and Mobius strip. The two kinds of
graphs are typical two-dimensional topological graph. We study the crossing
property of quantum walks on these two models. Also, we study its dependence on
the initial state, size of the model. At the same time, we compare the quantum
walk and classical walk on these two models to discuss the difference of
quantum walk and classical walk
Generalized Hofstadter model on a cubic optical lattice: From nodal bands to the three-dimensional quantum Hall effect
We propose that a tunable generalized three-dimensional Hofstadter
Hamiltonian can be realized by engineering the Raman-assisted hopping of
ultracold atoms in a cubic optical lattice. The Hamiltonian describes a
periodic lattice system under artificial magnetic fluxes in three dimensions.
For certain hopping configurations, the bulk bands can have Weyl points and
nodal loops, respectively, allowing the study of both the two nodal semimetal
states within this system. Furthermore, we illustrate that with proper rational
fluxes and hopping parameters, the system can exhibit the three-dimensional
quantum Hall effect when the Fermi level lies in the band gaps, which is
topologically characterized by one or two nonzero Chern numbers. Our proposed
optical-lattice system provides a promising platform for exploring various
exotic topological phases in three dimensions.Comment: 10 pages, 5 figure
Orientation and Motion of Water Molecules at Air/Water Interface
Analysis of SFG vibrational spectra of OH stretching bands in four
experimental configurations shows that orientational motion of water molecule
at air/water interface is libratory within a limited angular range. This
picture is significantly different from the previous conclusion that the
interfacial water molecule orientation varies over a broad range within the
vibrational relaxation time, the only direct experimental evidence for
ultrafast and broad orientational motion of a liquid interface by Wei et al.
[Phys. Rev. Lett. 86, 4799, (2001)] using single SFG experimental
configuration
Bayesian Speaker Adaptation Based on a New Hierarchical Probabilistic Model
In this paper, a new hierarchical Bayesian speaker adaptation method called HMAP is proposed that combines the advantages of three conventional algorithms, maximum a posteriori (MAP), maximum-likelihood linear regression (MLLR), and eigenvoice, resulting in excellent performance across a wide range of adaptation conditions. The new method efficiently utilizes intra-speaker and inter-speaker correlation information through modeling phone and speaker subspaces in a consistent hierarchical Bayesian way. The phone variations for a specific speaker are assumed to be located in a low-dimensional subspace. The phone coordinate, which is shared among different speakers, implicitly contains the intra-speaker correlation information. For a specific speaker, the phone variation, represented by speaker-dependent eigenphones, are concatenated into a supervector. The eigenphone supervector space is also a low dimensional speaker subspace, which contains inter-speaker correlation information. Using principal component analysis (PCA), a new hierarchical probabilistic model for the generation of the speech observations is obtained. Speaker adaptation based on the new hierarchical model is derived using the maximum a posteriori criterion in a top-down manner. Both batch adaptation and online adaptation schemes are proposed. With tuned parameters, the new method can handle varying amounts of adaptation data automatically and efficiently. Experimental results on a Mandarin Chinese continuous speech recognition task show good performance under all testing conditions
Demonstration of Geometric Landau-Zener Interferometry in a Superconducting Qubit
Geometric quantum manipulation and Landau-Zener interferometry have been
separately explored in many quantum systems. In this Letter, we combine these
two approaches to study the dynamics of a superconducting phase qubit. We
experimentally demonstrate Landau-Zener interferometry based on the pure
geometric phases in this solid-state qubit. We observe the interference caused
by a pure geometric phase accumulated in the evolution between two consecutive
Landau-Zener transitions, while the dynamical phase is canceled out by a
spin-echo pulse. The full controllability of the qubit state as a function of
the intrinsically robust geometric phase provides a promising approach for
quantum state manipulation.Comment: 5 pages + 3 pages supplemental Materia
An Experimental Proposal to Test Dynamic Quantum Non-locality with Single-Atom Interferometry
Quantum non-locality based on the well-known Bell inequality is of kinematic
nature. A different type of quantum non-locality, the non-locality of the
quantum equation of motion, is recently put forward with connection to the
Aharonov-Bohm effect [Nature Phys. 6, 151 (2010)]. Evolution of the
displacement operator provides an example to manifest such dynamic quantum
non-locality. We propose an experiment using single-atom interferometry to test
such dynamic quantum non-locality. We show how to measure evolution of the
displacement operator with clod atoms in a spin-dependent optical lattice
potential and discuss signature to identify dynamic quantum non-locality under
a realistic experimental setting.Comment: 4 page
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