77 research outputs found
Detection of single-electron heat transfer statistics
We consider a quantum dot system whose charge fluctuations are monitored by a
quantum point contact allowing for the detection of both charge and transferred
heat statistics. Our system consists of two nearby conductors that exchange
energy via Coulomb interaction. In interfaces consisting of capacitively
coupled quantum dots, energy transfer is discrete and can be measured by charge
counting statistics. We investigate gate dependent deviations away from a
charge fluctuation theorem in the presence of local temperature gradients (hot
spots). Non universal relations are found for state dependent charge counting.
A fluctuation theorem holds for coupled dot configurations with heat exchange
and no net particle flow.Comment: 6 pages, 3 figures. Published version. Corrected after erratum
publicatio
Quantum to Classical Transition of the Charge Relaxation Resistance of a Mesoscopic Capacitor
We present an analysis of the effect of dephasing on the single channel
charge relaxation resistance of a mesoscopic capacitor in the linear low
frequency regime. The capacitor consists of a cavity which is via a quantum
point contact connected to an electron reservoir and Coulomb coupled to a gate.
The capacitor is in a perpendicular high magnetic field such that only one
(spin polarized) edge state is (partially) transmitted through the contact. In
the coherent limit the charge relaxation resistance for a single channel
contact is independent of the transmission probability of the contact and given
by half a resistance quantum. The loss of coherence in the conductor is modeled
by attaching to it a fictitious probe, which draws no net current. In the
incoherent limit one could expect a charge relaxation resistance that is
inversely proportional to the transmission probability of the quantum point
contact. However, such a two terminal result requires that scattering is
between two electron reservoirs which provide full inelastic relaxation. We
find that dephasing of a single edge state in the cavity is not sufficient to
generate an interface resistance. As a consequence the charge relaxation
resistance is given by the sum of one constant interface resistance and the
(original) Landauer resistance. The same result is obtained in the high
temperature regime due to energy averaging over many occupied states in the
cavity. Only for a large number of open dephasing channels, describing
spatially homogenous dephasing in the cavity, do we recover the two terminal
resistance, which is inversely proportional to the transmission probability of
the QPC. We compare different dephasing models and discuss the relation of our
results to a recent experiment.Comment: 10 pages, 8 figure
Two-particle non-local Aharonov-Bohm effect from two single-particle emitters
We propose a mesoscopic circuit in the quantum Hall effect regime comprising
two uncorrelated single-particle sources and two distant Mach-Zehnder
interferometers with magnetic fluxes, which allows in a controllable way to
produce orbitally entangled electrons. Two-particle correlations appear as a
consequence of erasing of which path information due to collisions taking place
at distant interferometers and in general at different times. The two-particle
correlations manifest themselves as an Aharonov-Bohm effect in noise while the
current is insensitive to magnetic fluxes. In an appropriate time-interval the
concurrence reaches a maximum and a Bell inequality is violated.Comment: 4 pages, 2 figures, published in Phys. Rev. Let
Quantum Nondemolition Measurement of a Kicked Qubit
We propose a quantum nondemolition measurement using a kicked two-state
system (qubit). By tuning the waiting time between kicks to be the qubit
oscillation period, the kicking apparatus performs a nondemolition measurement.
While dephasing is unavoidable, the nondemolition measurement can (1) slow
relaxation of diagonal density matrix elements, (2) avoid detector back-action,
and (3) allow for a large signal-to-noise ratio. Deviations from the ideal
behavior are studied by allowing for detuning of the waiting time, as well as
finite-time, noisy pulses. The scheme is illustrated with a double-dot qubit
measured by a gate-pulsed quantum point contact.Comment: 7 pages, 1 figur
Mesoscopic Capacitance Oscillations
We examine oscillations as a function of Fermi energy in the capacitance of a
mesoscopic cavity connected via a single quantum channel to a metallic contact
and capacitively coupled to a back gate. The oscillations depend on the
distribution of single levels in the cavity, the interaction strength and the
transmission probability through the quantum channel. We use a Hartree-Fock
approach to exclude self-interaction. The sample specific capacitance
oscillations are in marked contrast to the charge relaxation resistance, which
together with the capacitance defines the RC-time, and which for spin polarized
electrons is quantized at half a resistance quantum. Both the capacitance
oscillations and the quantized charge relaxation resistance are seen in a
strikingly clear manner in a recent experiment.Comment: 9 pages, 2 figure
Coherence of Single Electron Sources from Mach-Zehnder Interferometry
A new type of electron sources has emerged which permits to inject particles
in a controllable manner, one at a time, into an electronic circuit. Such
single electron sources make it possible to fully exploit the particles'
quantum nature. We determine the single-particle coherence length from the
decay of the Aharonov-Bohm oscillations as a function of the imbalance of a
Mach-Zehnder interferometer connected to a single electron source. The
single-particle coherence length is of particular importance as it is an
intrinsic property of the source in contrast to the dephasing length.Comment: 4 pages, 4 figure
Gap theory of rectification in ballistic three-terminal conductors
We introduce a model for rectification in three-terminal ballistic
conductors, where the central connecting node is modeled as a chaotic cavity.
For bias voltages comparable to the Fermi energy, a strong nonlinearity is
created by the opening of a gap in the transport window. Both noninteracting
cavity electrons at arbitrary temperature as well as the hot electron regime
are considered. Charging effects are treated within the transmission formalism
using a self-consistent analysis. The conductance of the third lead in a
voltage probe configuration is varied to also model inelastic effects. We find
that the basic transport features are insensitive to all of these changes,
indicating that the nonlinearity is robust and well suited to applications such
as current rectification in ballistic systems. Our findings are in broad
agreement with several recent experiments.Comment: 8 pages, 6 figure
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