4,644 research outputs found
Dynamics of quantum entanglement in the reservoir with memory effects
The non-Markovian dynamics of quantum entanglement is studied by the
Shabani-Lidar master equation when one of entangled quantum systems is coupled
to a local reservoir with memory effects. The completely positive reduced
dynamical map can be constructed in the Kraus representation. Quantum
entanglement decays more slowly in the non-Markovian environment. The
decoherence time for quantum entanglement can be markedly increased by the
change of the memory kernel. It is found out that the entanglement sudden death
between quantum systems and entanglement sudden birth between the system and
reservoir occur at different instants.Comment: 14 pages, 3 figure
Entanglement and quantum phase transitions
We examine several well known quantum spin models and categorize behavior of
pairwise entanglement at quantum phase transitions. A unified picture on the
connection between the entanglement and quantum phase transition is given.Comment: 4 pages, 3 figure
Fidelity susceptibility, scaling, and universality in quantum critical phenomena
We study fidelity susceptibility in one-dimensional asymmetric Hubbard model,
and show that the fidelity susceptibility can be used to identify the
universality class of the quantum phase transitions in this model. The critical
exponents are found to be 0 and 2 for cases of half-filling and away from
half-filling respectively.Comment: 4 pages, 4 figure
Fidelity, dynamic structure factor, and susceptibility in critical phenomena
Motivated by the growing importance of fidelity in quantum critical
phenomena, we establish a general relation between fidelity and structure
factor of the driving term in a Hamiltonian through a newly introduced concept:
fidelity susceptibility. Our discovery, as shown by some examples, facilitates
the evaluation of fidelity in terms of susceptibility using well developed
techniques such as density matrix renormalization group for the ground state,
or Monte Carlo simulations for the states in thermal equilibrium.Comment: 4 pages, 2 figures, final version accepted by PR
Proximity-induced superconductivity in nanowires: Mini-gap state and differential magnetoresistance oscillations
We study proximity-induced superconductivity in gold nanowires as a function
of the length of the nanowire, magnetic field, and excitation current. Short
nanowires exhibit a sharp superconducting transition, whereas long nanowires
show nonzero resistance. At intermediate lengths, however, we observe two sharp
transitions; the normal and superconducting regions are separated by what we
call the mini-gap phase. Additionally, we detect periodic oscillations in the
differential magnetoresistance. We provide a theoretical model for the mini-gap
phase as well as the periodic oscillations in terms of the coexistence of
proximity-induced superconductivity with a normal region near the center of the
wire, created either by temperature or application of a magnetic field.Comment: 11 pages, 4 figure
Quantum criticality of the Lipkin-Meshkov-Glick Model in terms of fidelity susceptibility
We study the critical properties of the Lipkin-Meshkov-Glick Model in terms
of the fidelity susceptibility. By using the Holstein-Primakoff transformation,
we obtain explicitly the critical exponent of the fidelity susceptibility
around the second-order quantum phase transition point. Our results provide a
rare analytical case for the fidelity susceptibility in describing the
universality class in quantum critical behavior. The different critical
exponents in two phases are non-trivial results, indicating the fidelity
susceptibility is not always extensive.Comment: 3 figure
Fidelity susceptibility and long-range correlation in the Kitaev honeycomb model
We study exactly both the ground-state fidelity susceptibility and bond-bond
correlation function in the Kitaev honeycomb model. Our results show that the
fidelity susceptibility can be used to identify the topological phase
transition from a gapped A phase with Abelian anyon excitations to a gapless B
phase with non-Abelian anyon excitations. We also find that the bond-bond
correlation function decays exponentially in the gapped phase, but
algebraically in the gapless phase. For the former case, the correlation length
is found to be , which diverges
around the critical point .Comment: 7 pages, 6 figure
The Kazhdan-Lusztig conjecture for W-algebras
The main result in this paper is the character formula for arbitrary
irreducible highest weight modules of W algebras. The key ingredient is the
functor provided by quantum Hamiltonian reduction, that constructs the W
algebras from affine Kac-Moody algebras and in a similar fashion W modules from
KM modules. Assuming certain properties of this functor, the W characters are
subsequently derived from the Kazhdan-Lusztig conjecture for KM algebras. The
result can be formulated in terms of a double coset of the Weyl group of the KM
algebra: the Hasse diagrams give the embedding diagrams of the Verma modules
and the Kazhdan-Lusztig polynomials give the multiplicities in the characters.Comment: uuencoded file, 29 pages latex, 5 figure
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