50 research outputs found
Indistinguishability of quantum states and rotation counting
We propose a quantum system in which the winding number of rotations of a
particle around a ring can be monitored and emerges as a physical observable.
We explicitly analyze the situation when, as a result of the monitoring of the
winding number, the period of the orbital motion of the particle is extended to
full rotations, which leads to changes in the energy spectrum and in all
observable properties. In particular, we show that in this case, the usual
magnetic flux period of the Aharonov-Bohm effect is reduced to
.Comment: 5 pages, 3 embedded figure
Mach-Zehnder interferometer in the Fractional Quantum Hall regime
We consider tunneling between two edges of Quantum Hall liquids (QHL) of
filling factors , with , through
two point contacts forming Mach-Zehnder interferometer. Quasi-particle
description of the interferometer is derived explicitly through the instanton
duality transformation of the initial electron model. For , tunneling of quasiparticles of charge leads to non-trivial
-state dynamics of effective flux through the interferometer, which restores
the regular ``electron'' periodicity of the current in flux. The exact solution
available for equal propagation times between the contacts along the two edges
demonstrates that the interference pattern in the tunneling current depends on
voltage and temperature only through a common amplitude.Comment: five two-column pages in RevTex4, 1 eps figur
Violation of the fluctuation-dissipation theorem in time-dependent mesoscopic heat transport
We have analyzed the spectral density of fluctuations of the energy flux
through a mesoscopic constriction between two equilibrium reservoirs. It is
shown that at finite frequencies, the fluctuating energy flux is not related to
the thermal conductance of the constriction by the standard
fluctuation-dissipation theorem, but contains additional noise. The main
physical consequence of this extra noise is that the fluctuations do not vanish
at zero temperature together with the vanishing thermal conductance.Comment: 5 pages, 1 figur
Counting statistics and detector properties of quantum point contacts
Quantum detector properties of the quantum point contact (QPC) are analyzed
for arbitrary electron transparency and coupling strength to the measured
system and are shown to be determined by the electron counting statistics.
Conditions of the quantum-limited operation of the QPC detector which prevent
information loss through the scattering time and scattering phases are found
for arbitrary coupling. We show that the phase information can be restored and
used for the quantum-limited detection by inclusion of the QPC detector in the
electronic Mach-Zehnder interferometer.Comment: 4 pages, 2 figures, published versio
Quadratic Quantum Measurements
We develop a theory of quadratic quantum measurements by a mesoscopic
detector. It is shown that quadratic measurements should have non-trivial
quantum information properties, providing, for instance, a simple way of
entangling two non-interacting qubits. We also calculate output spectrum of a
quantum detector with both linear and quadratic response continuously
monitoring coherent oscillations in two qubits.Comment: 5 pages, 2 figure
FQHE interferometers in strong tunneling regime. The role of compactness of edge fields
We consider multiple-point tunneling in the interferometers formed between
edges of electron liquids with in general different filling factors in the
regime of the Fractional Quantum Hall effect (FQHE). We derive an effective
matrix Caldeira-Leggett models for the multiple tunneling contacts connected by
the chiral single-mode FQHE edges. It is shown that the compactness of the Wen-
Fr\"ohlich chiral boson fields describing the FQHE edge modes plays a crucial
role in eliminating the spurious non-locality of the electron transport
properties of the FQHE interferometers arising in the regime of strong
tunneling.Comment: 5 page