29,241 research outputs found
Pumped spin-current and shot noise spectra in a single quantum dot
We exploit the pumped spin-current and current noise spectra under
equilibrium condition in a single quantum dot connected to two normal leads, as
an electrical scheme for detection of the electron spin resonance (ESR) and
decoherence. We propose spin-resolved quantum rate equations with correlation
functions in Laplace-space for the analytical derivation of the zero-frequency
atuo- and cross-shot noise spectra of charge- and spin-current. Our results
show that in the strong Coulomb blockade regime, ESR-induced spin flip
generates a finite spin-current and the quantum partition noises in the absence
of net charge transport. Moreover, spin shot noise is closely related to the
magnetic Rabi frequency and decoherence and would be a sensitive tool to
measure them.Comment: 4 pages, 3 figures, to be published in Phys. Rev. Lette
Shot noise in resonant tunneling through an interacting quantum dot with intradot spin-flip scattering
In this paper, we present theoretical investigation of the zero-frequency
shot noise spectra in electron tunneling through an interacting quantum dot
connected to two ferromagnetic leads with possibility of spin-flip scattering
between the two spin states by means of the recently developed bias-voltage and
temperature dependent quantum rate equations. For this purpose, a
generalization of the traditional generation-recombination approach is made for
properly taking into account the coherent superposition of electronic states,
i.e., the nondiagonal density matrix elements. Our numerical calculations find
that the Fano factor increases with increasing the polarization of the two
leads, but decreases with increasing the intradot spin-flip scattering.Comment: Some typos correction. 6 pages, 3 figures, based on work presented at
the 2004 IEEE NTC Quantum Device Technology Workshop, accepted for
publication by IEEE transactions on Nanotechnolog
Super-Poissonian shot noise in the resonant tunneling due to coupling with a localized level
We report our studies of the shot noise spectrum in tunneling through an
interacting quantum dot when an additional single-level quantum dot without
tunnel coupling to leads is coherently side-connected to it. We show that the
zero-frequency shot noise could reach a super-Poissonian value for appropriate
ratios between dot-dot hoppings and dot-lead couplings, but the current is
independent on the hopping. Moreover, the frequency spectrum of shot noise
shows an obvious peak at the Rabi frequency, which is controllable by tuning
the dot-lead couplings.Comment: 3 pages, 3 figures, Appl. Phys. Lett.(in press
Using schema transformation pathways for data lineage tracing
With the increasing amount and diversity of information available on the Internet, there has been a huge growth in information systems that need to integrate data from distributed, heterogeneous data sources. Tracing the lineage of the integrated data is one of the problems being addressed in data warehousing research. This paper presents a data lineage tracing approach based on schema transformation pathways. Our approach is not limited to one specific data model or query language, and would be useful in any data transformation/integration framework based on sequences of primitive schema transformations
Coulomb drag in double quantum wells with a perpendicular magnetic field
Momentum transfer due to electron-electron interaction (Coulomb drag) between
two quantum wells, separated by a distance , in the presence of a
perpendicular magnetic field, is studied at low temperatures. We find besides
the well known Shubnikov-de Haas oscillations, which also appear in the drag
effect, the momentum transfer is markedly enhanced by the magnetic field.Comment: 8 pages, Revtex, 4 Postscript figures are available upon request,
Accepted by Mod. Phys. Lett.
Improving the fairness of FAST TCP to new flows
It has been observed that FAST TCP, and the related protocol TCP Vegas, suffer unfairness when many flows arrive at a single bottleneck link, without intervening departures. We show that the effect is even more marked if a new flow arrives when existing flows share bandwidth fairly, and propose a simple method to ameliorate this effect
Topology of Entanglement in Multipartite States with Translational Invariance
The topology of entanglement in multipartite states with translational
invariance is discussed in this article. Two global features are foundby which
one can distinguish distinct states. These are the cyclic unit and the
quantised geometric phase. Furthermore the topology is indicated by the
fractional spin. Finally a scheme is presented for preparation of these types
of states in spin chain systems, in which the degeneracy of the energy levels
characterises the robustness of the states with translational invariance.Comment: major revision. accepted by EPJ
Berry's phase with quantized field driving: effects of inter-subsystem coupling
The effect of inter-subsystem couplings on the Berry phase of a composite
system as well as that of its subsystem is investigated in this paper. We
analyze two coupled spin- particles with one driven by a quantized
field as an example, the pure state geometric phase of the composite system as
well as the mixed state geometric phase for the subsystem is calculated and
discussed.Comment: 4 pages, 1 figur
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