71 research outputs found
Shot noise in coupled dots and the "fractional charges"
We consider the problem of shot noise in resonant tunneling through double
quantum dots in the case of interacting particles. Using a many-body quantum
mechanical description we evaluate the energy dependent transmission
probability, the total average current and the shot noise spectrum. Our results
show that the obtained reduction of the noise spectrum, due to Coulomb
interaction, can be interpret in terms of non--interacting particles with
fractional charge like behavior.Comment: some clarifications added, to appear in Phys. Lett.
Resonant scattering on impurities in the Quantum Hall Effect
We develop a new approach to carrier transport between the edge states via
resonant scattering on impurities, which is applicable both for short and long
range impurities. A detailed analysis of resonant scattering on a single
impurity is performed. The results are used for study of the inter-edge
transport by multiple resonant hopping via different impurities' sites. It is
shown that the total conductance can be found from an effective Schroedinger
equation with constant diagonal matrix elements in the Hamiltonian, where the
complex non-diagonal matrix elements are the amplitudes of a carrier hopping
between different impurities. It is explicitly demonstrated how the complex
phase leads to Aharonov-Bohm oscillations in the total conductance. Neglecting
the contribution of self-crossing resonant-percolation trajectories, one finds
that the inter-edge carrier transport is similar to propagation in
one-dimensional system with off-diagonal disorder. We demonstrated that each
Landau band has an extended state , while all other states are
localized. The localization length behaves as .Comment: RevTex 41 pages; 3 Postscript figure on request; Final version
accepted for publication in Phys. Rev. B. A new section added contained a
comparison with other method
Hard-core Final State Interaction Effects in Deep Inelastic Scattering
Hard-core final state interaction effects in the response function are
investigated in the asymptotic limit of momentum transfer q->Infinity. A new
treatment of the response is presented, which displays the relevant scattering
contribution. A modification of the otherwise expected free response is
obtained for Fermi and Bose systems and smearing of the condensate peak is
shown in this limit. A comparison with other treatments of final state
interactions is made.Comment: 13 pages, in RevTex. To be published in Physics Letters A. Figures
can be obtained from [email protected]
Coulomb blockade double-dot Aharonov-Bohm interferometer: giant fluctuations
Electron transport through two parallel quantum dots is a kind of solid-state
realization of double-path interference. We demonstrate that the inter-dot
Coulomb correlation and quantum coherence would result in strong current
fluctuations with a divergent Fano factor at zero frequency. We also provide
physical interpretation for this surprising result, which displays its generic
feature and allows us to recover this phenomenon in more complicated systems.Comment: 5 pages, 4 figure
Coulomb effects in tunneling through a quantum dot stack
Tunneling through two vertically coupled quantum dots is studied by means of
a Pauli master equation model. The observation of double peaks in the
current-voltage characteristic in a recent experiment is analyzed in terms of
the tunnel coupling between the quantum dots and the coupling to the contacts.
Different regimes for the emitter chemical potential indicating different peak
scenarios in the tunneling current are discussed in detail. We show by
comparison with a density matrix approach that the interplay of coherent and
incoherent effects in the stationary current can be fully described by this
approach.Comment: 6 pages, 6 figure
Coulomb correlations effects on localized charge relaxation in the coupled quantum dots
We analyzed localized charge time evolution in the system of two interacting
quantum dots (QD) (artificial molecule) coupled with the continuous spectrum
states. We demonstrated that Coulomb interaction modifies relaxation rates and
is responsible for non-monotonic time evolution of the localized charge. We
suggested new mechanism of this non-monotonic charge time evolution connected
with charge redistribution between different relaxation channels in each QD.Comment: 10 pages, 10 figure
Many-body approach to proton emission and the role of spectroscopic factors
The process of proton emission from nuclei is studied by utilizing the
two-potential approach of Gurvitz and Kalbermann in the context of the full
many-body problem. A time-dependent approach is used for calculating the decay
width. Starting from an initial many-body quasi-stationary state, we employ the
Feshbach projection operator approach and reduce the formalism to an effective
one-body problem. We show that the decay width can be expressed in terms of a
one-body matrix element multiplied by a normalization factor. We demonstrate
that the traditional interpretation of this normalization as the square root of
a spectroscopic factor is only valid for one particular choice of projection
operator. This causes no problem for the calculation of the decay width in a
consistent microscopic approach, but it leads to ambiguities in the
interpretation of experimental results. In particular, spectroscopic factors
extracted from a comparison of the measured decay width with a calculated
single-particle width may be affected.Comment: 17 pages, Revte
Entanglement of a Double Dot with a Quantum Point Contact
Entanglement between particle and detector is known to be inherent in the
measurement process. Gurvitz recently analyzed the coupling of an electron in a
double dot (DD) to a quantum point contact (QPC) detector. In this paper we
examine the dynamics of entanglement that result between the DD and QPC. The
rate of entanglement is optimized as a function of coupling when the electron
is initially in one of the dots. It decreases asymptotically towards zero with
increased coupling. The opposite behavior is observed when the DD is initially
in a superposition: the rate of entanglement increases unboundedly as the
coupling is increased. The possibility that there are conditions for which
measurement occurs versus entanglement is considered
Fermionic Linear Optics Revisited
We provide an alternative view of the efficient classical simulatibility of
fermionic linear optics in terms of Slater determinants. We investigate the
generic effects of two-mode measurements on the Slater number of fermionic
states. We argue that most such measurements are not capable (in conjunction
with fermion linear optics) of an efficient exact implementation of universal
quantum computation. Our arguments do not apply to the two-mode parity
measurement, for which exact quantum computation becomes possible, see
quant-ph/0401066.Comment: 16 pages, submitted to the special issue of Foundation of Physics in
honor of Asher Peres' 70th birthda
Measurements with a noninvasive detector and dephasing mechanism
We study dynamics of the measurement process in quantum dot systems, where a
particular state out of coherent superposition is observed. The ballistic
point-contact placed near one of the dots is taken as a noninvasive detector.
We demonstrate that the measurement process is fully described by the
Bloch-type equations applied to the whole system. These equations clearly
reproduce the collapse of the density-matrix into the statistical mixture in
the course of the measurement process. The corresponding dephasing width is
uniquely defined. We show that the continuous observation of one of the states
in a coherent superposition may accelerate decay from this state -- in
contradiction with rapidly repeated observations, which slow down the
transitions between quantum states (the quantum Zeno effect).Comment: The difference between continuous and rapidly repeated observations
is elaborated. To appear in Phys. Rev.
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