16 research outputs found
Imaging Coulomb Islands in a Quantum Hall Interferometer
In the Quantum Hall regime, near integer filling factors, electrons should
only be transmitted through spatially-separated edge states. However, in
mesoscopic systems, electronic transmission turns out to be more complex,
giving rise to a large spectrum of magnetoresistance oscillations. To explain
these observations, recent models put forward that, as edge states come close
to each other, electrons can hop between counterpropagating edge channels, or
tunnel through Coulomb islands. Here, we use scanning gate microscopy to
demonstrate the presence of quantum Hall Coulomb islands, and reveal the
spatial structure of transport inside a quantum Hall interferometer. Electron
islands locations are found by modulating the tunneling between edge states and
confined electron orbits. Tuning the magnetic field, we unveil a continuous
evolution of active electron islands. This allows to decrypt the complexity of
high magnetic field magnetoresistance oscillations, and opens the way to
further local scale manipulations of quantum Hall localized states
Anyonic interferometry and protected memories in atomic spin lattices
Strongly correlated quantum systems can exhibit exotic behavior called
topological order which is characterized by non-local correlations that depend
on the system topology. Such systems can exhibit remarkable phenomena such as
quasi-particles with anyonic statistics and have been proposed as candidates
for naturally fault-tolerant quantum computation. Despite these remarkable
properties, anyons have never been observed in nature directly. Here we
describe how to unambiguously detect and characterize such states in recently
proposed spin lattice realizations using ultra-cold atoms or molecules trapped
in an optical lattice. We propose an experimentally feasible technique to
access non-local degrees of freedom by performing global operations on trapped
spins mediated by an optical cavity mode. We show how to reliably read and
write topologically protected quantum memory using an atomic or photonic qubit.
Furthermore, our technique can be used to probe statistics and dynamics of
anyonic excitations.Comment: 14 pages, 6 figure
Fractional quantum Hall effect in a quantum point contact at filling fraction 5/2
Recent theories suggest that the excitations of certain quantum Hall states
may have exotic braiding statistics which could be used to build topological
quantum gates. This has prompted an experimental push to study such states
using confined geometries where the statistics can be tested. We study the
transport properties of quantum point contacts (QPCs) fabricated on a
GaAs/AlGaAs two dimensional electron gas that exhibits well-developed
fractional quantum Hall effect, including at bulk filling fraction 5/2. We find
that a plateau at effective QPC filling factor 5/2 is identifiable in point
contacts with lithographic widths of 1.2 microns and 0.8 microns, but not 0.5
microns. We study the temperature and dc-current-bias dependence of the 5/2
plateau in the QPC, as well as neighboring fractional and integer plateaus in
the QPC while keeping the bulk at filling factor 3. Transport near QPC filling
factor 5/2 is consistent with a picture of chiral Luttinger liquid edge-states
with inter-edge tunneling, suggesting that an incompressible state at 5/2 forms
in this confined geometry
Infinitesimal Idealization, Easy Road Nominalism, and Fractional Quantum Statistics
It has been recently debated whether there exists a so-called “easy road” to nominalism. In this essay, I attempt to fill a lacuna in the debate by making a connection with the literature on infinite and infinitesimal idealization in science through an example from mathematical physics that has been largely ignored by philosophers. Specifically, by appealing to John Norton’s distinction between idealization and approximation, I argue that the phenomena of fractional quantum statistics bears negatively on Mary Leng’s proposed path to easy road nominalism, thereby partially defending Mark Colyvan’s claim that there is no easy road to nominalism
Cuadernos de pedagogía
Se trata de un proyecto sobre formación científica aplicada a las aulas de Educación Infantil. Estudian, a través de la aplicación del método científico, las principales leyes que caracterizan el magnetismo. Se resumen las diferentes actividades realizadas.CataluñaMadrid (Comunidad Autónoma). Servicio de Formación del Profesorado. CRIF Las Acacias; Calle General Ricardos, 179; 28025 Madrid; Tel. +34915250893; Fax +34914660991; [email protected]
Correlation-induced single-flux-quantum penetration in quantum rings
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