6,958 research outputs found
Symmetry restrictions in chirality dependence of physical properties of single wall nanotubes
We investigate the chirality dependence of physical properties of nanotubes
which are wrapped by the planar hexagonal lattice including graphite and boron
nitride sheet, and reveal its symmetry origin. The observables under
consideration are of scalar, vector and tensor types. These exact chirality
dependence obtained are useful to verify the experimental and numerical results
and propose accurate empirical formulas. Some important features of physical
quantities can also be extracted by only considering the symmetry restrictions
without complicated calculations.Comment: 5 pages, 1 figure
1600 AD Huaynaputina Eruption (Peru), abrupt cooling, and epidemics in China and Korea
published_or_final_versio
Bell Inequalities Classifying Bi-separable Three-qubit States
We present a set of Bell inequalities that gives rise to a finer
classification of the entanglement for tripartite systems. These inequalities
distinguish three possible bi-separable entanglements for three-qubit states.
The three Bell operators we employed constitute an external sphere of the
separable cube.Comment: 8 page
A Note on Invariants and Entanglements
The quantum entanglements are studied in terms of the invariants under local
unitary transformations. A generalized formula of concurrence for
-dimensional quantum systems is presented. This generalized concurrence has
potential applications in studying separability and calculating entanglement of
formation for high dimensional mixed quantum states.Comment: Latex, 11 page
Fluctuation-Driven Vortex Fractionalization in Topologically Ordered Superfluids of Cold Atoms
We have studied spin structures of fluctuation-driven fractionalized vortices
and topological spin order in 2D nematic superfluids of cold sodium atoms. Our
Monte Carlo simulations suggest a softened pi-spin disclination structure in a
half-quantum vortex when spin correlations are short ranged; in addition,
calculations indicate that a unique non-local topological spin order emerges
simultaneously as cold atoms become a superfluid below a critical temperature.
We have also estimated fluctuation-dependent critical frequencies for
half-quantum vortex nucleation in rotating optical traps and discussed probing
these excitations in experiments.Comment: 5 pages, 2 figures; revised version accepted by Europhysics Letter
A Note on Normal Forms of Quantum States and Separability
We study the normal form of multipartite density matrices. It is shown that
the correlation matrix (CM) separability criterion can be improved from the
normal form we obtained under filtering transformations. Based on CM criterion
the entanglement witness is further constructed in terms of local orthogonal
observables for both bipartite and multipartite systems.Comment: 8 page
Controlling Excitations Inversion of a Cooper Pair Box Interacting with a Nanomechanical Resonator
We investigate the action of time dependent detunings upon the excitation
inversion of a Cooper pair box interacting with a nanomechanical resonator. The
method employs the Jaynes-Cummings model with damping, assuming different decay
rates of the Cooper pair box and various fixed and t-dependent detunings. It is
shown that while the presence of damping plus constant detunings destroy the
collapse/revival effects, convenient choices of time dependent detunings allow
one to reconstruct such events in a perfect way. It is also shown that the mean
excitation of the nanomechanical resonator is more robust against damping of
the Cooper pair box for convenient values of t-dependent detunings.Comment: 11 pages, 5 figure
Two-Setting Bell Inequalities for Many Qubits
We present a family of Bell inequalities involving only two measurement
settings of each party for N>2 qubits. Our inequalities include all the
standard ones with fewer than N qubits and thus gives a natural generalization.
It is shown that all the Greenberger-Horne-Zeilinger states violate the
inequalities maximally, with an amount that grows exponentially as
2^{{(N-2)}/2}. The inequalities are also violated by some states that do
satisfy all the standard Bell inequalities. Remarkably, our results yield in an
efficient and simple way an implementation of nonlocality tests of many qubits
favorably within reach of the well-established technology of linear optics.Comment: 4 pages, no figur
Finite density phase transition of QCD with and using canonical ensemble method
In a progress toward searching for the QCD critical point, we study the
finite density phase transition of and 2 lattice QCD at finite
temperature with the canonical ensemble approach. We develop a winding number
expansion method to accurately project out the particle number from the fermion
determinant which greatly extends the applicable range of baryon number sectors
to make the study feasible. Our lattice simulation was carried out with the
clover fermions and improved gauge action. For a given temperature, we
calculate the baryon chemical potential from the canonical approach to look for
the mixed phase as a signal for the first order phase transition. In the case
of , we observe an "S-shape" structure in the chemical potential-density
plane due to the surface tension of the mixed phase in a finite volume which is
a signal for the first order phase transition. We use the Maxwell construction
to determine the phase boundaries for three temperatures below . The
intersecting point of the two extrapolated boundaries turns out to be at the
expected first order transition point at with . This serves as a
check for our method of identifying the critical point. We also studied the
case, but do not see a signal of the mixed phase for temperature as
low as 0.83 .Comment: 28 pages, 11 figures,references added, final versio
Temporal Quantum Control with Graphene
We introduce a novel strategy for controlling the temporal evolution of a
quantum system at the nanoscale. Our method relies on the use of graphene
plasmons, which can be electrically tuned in frequency by external gates.
Quantum emitters (e.g., quantum dots) placed in the vicinity of a graphene
nanostructure are subject to the strong interaction with the plasmons of this
material, thus undergoing time variations in their mutual interaction and
quantum evolution that are dictated by the externally applied gating voltages.
This scheme opens a new path towards the realization of quantum-optics devices
in the robust solid-state environment of graphene.Comment: 5 pages, 2 figure
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