7,035 research outputs found
Multiple quasiparticle Hall spectroscopy investigated with a resonant detector
We investigate the finite frequency (f.f.) noise properties of edge states in
the quantum Hall regime. We consider the measurement scheme of a resonant
detector coupled to a quantum point contact in the weak-backscattering limit. A
detailed analysis of the difference between the "measured" noise, due to the
presence of the resonant detector, and the symmetrized f.f. noise is presented.
We discuss both the Laughlin and Jain sequences, studying the tunnelling
excitations in these hierarchical models. We argue that the measured noise can
better distinguish between the different excitations in the tunnelling process
with respect to the symmetrized f.f. counterpart in an experimentally relevant
range of parameters. Finally, we illustrate the effect of the detector
temperature on the sensibility of this measure.Comment: 24 pages, 8 figure
W-like states of N uncoupled spins 1/2
The exact dynamics of a disordered spin star system, describing a central
spin coupled to N distinguishable and non interacting spins 1/2, is reported.
Exploiting their interaction with the central single spin system, we present
possible conditional schemes for the generation of W-like states, as well as of
well-defined angular momentum states, of the N uncoupled spins. We provide in
addition a way to estimate the coupling intensity between each of the N spins
and the central one. Finally the feasibility of our procedure is briefly
discussed.Comment: 8 pages, 2 figures, accepted for publication in European Physical
Journal Special Topic
Finite frequency noise for edge states at filling factor
We investigate the properties of the finite frequency noise in a quantum
point contact geometry for the fractional quantum Hall state at filling factor
. The results are obtained in the framework of the Wen's hierarchical
model.
We show that the peak structure of the colored noise allows to discriminate
among different possible excitations involved in the tunneling. In particular,
optimal values of voltage and temperature are found in order to enhance the
visibility of the peak associated with the tunneling of a 2-agglomerate, namely
an excitation with charge double of the fundamental one associated to the
single quasiparticle.Comment: 5 pages, 1 figure, to be published in the Proceedings of the
Conference on the Frontiers of Quantum and Mesoscopic Thermodynamics (FQMT11
Entanglement sudden death and sudden birth in two uncoupled spins
We investigate the entanglement evolution of two qubits interacting with a
common environment trough an Heisenberg XX mechanism. We reveal the possibility
of realizing the phenomenon of entanglement sudden death as well as the
entanglement sudden birth acting on the environment. Such analysis is of
maximal interest at the light of the large applications that spin systems have
in quantum information theory
Anomalous charge tunneling in the fractional quantum Hall edge states at filling factor \nu = 5/2
We explain effective charge anomalies recently observed for fractional
quantum Hall edge states at [M. Dolev, Y. Gross, Y. C. Chung, M.
Heiblum, V. Umansky, and D. Mahalu, Phys.Rev. B. \textbf{81}, 161303(R)
(2010)]. The experimental data of differential conductance and excess noise are
fitted, using the anti-Pfaffian model, by properly take into account
renormalizations of the Luttinger parameters induced by the coupling of the
system with an intrinsic noise. We demonstrate that a peculiar
agglomerate excitation with charge , double of the expected charge,
dominates the transport properties at low energies.Comment: 5 pages, 2 figure
Reliable source of conditional non-Gaussian states from single-mode thermal fields
We address both theoretically and experimentally the generation of pulsed
non-Gaussian states from classical Gaussian ones by means of conditional
measurements. The setup relies on a beam splitter and a pair of linear
photodetectors able to resolve up to tens of photons in the two outputs. We
show the reliability of the setup and the good agreement with the theory for a
single-mode thermal field entering the beam splitter and present a thorough
characterization of the photon statistics of the conditional states.Comment: 18 pages, 12 figure
Environmental induced renormalization effects in quantum Hall edge states
We propose a general mechanism for renormalization of the tunneling exponents
in edge states of the fractional quantum Hall effect. Mutual effects of the
coupling with out-of-equilibrium 1/f noise and dissipation are considered both
for the Laughlin sequence and for composite co- and counter-propagating edge
states with Abelian or non-Abelian statistics. For states with
counter-propagating modes we demonstrate the robustness of the proposed
mechanism in the so called disorder-dominated phase. Prototypes of these
states, such as \nu=2/3 and \nu=5/2, are discussed in detail and the rich
phenomenology induced by the presence of a noisy environment is presented. The
proposed mechanism justifies the strong renormalizations reported in many
experimental observations carried out at low temperatures. We show how
environmental effects could affect the relevance of the tunneling excitations,
leading to important implications in particular for the \nu=5/2 case.Comment: 14 pages, 4 figure
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