35 research outputs found
Measurement of single electron spin with sub-micron Hall magnetometer
Submicron Hall magnetometry has been demonstrated as an efficient technique
to probe extremely weak magnetic fields. In this letter, we analyze the
possibility of employing it to detect single electron spin. Signal strength and
readout time are estimated and discussed with respect to a number of practical
issues.Comment: 4 pages, 2 figur
Non-Markovian correlation functions for open quantum systems
Beyond the conventional quantum regression theorem, a general formula for
non-Markovian correlation functions of arbitrary system operators both in the
time- and frequency-domain is given. We approach the problem by transforming
the conventional time-nonlocal master equation into dispersed time-local
equations-of-motion. The validity of our approximations is discussed and we
find that the non-Markovian terms have to be included for short times. While
calculations of the density matrix at short times suffer from the initial value
problem, a correlation function has a well defined initial state. The resulting
formula for the non-Markovian correlation function has a simple structure and
is as convenient in its application as the conventional quantum regression
theorem for the Markovian case. For illustrations, we apply our method to
investigate the spectrum of the current fluctuations of interacting quantum
dots contacted with two electrodes. The corresponding non-Markovian
characteristics are demonstrated.Comment: 11 pages, 5 figure
Optical Manipulation of Single Electron Spin in Doped and Undoped Quantum Dots
The optical manipulation of electron spins is of great benefit to solid-state
quantum information processing. In this letter, we provide a comparative study
on the ultrafast optical manipulation of single electron spin in the doped and
undoped quantum dots. The study indicates that the experimental breakthrough
can be preliminarily made in the undoped quantum dots, because of the
relatively less demand.Comment: 3 pages, 3 figure
Theoretical investigation of the dynamic electronic response of a quantum dot driven by time-dependent voltage
We present a comprehensive theoretical investigation on the dynamic
electronic response of a noninteracting quantum dot system to various forms of
time-dependent voltage applied to the single contact lead. Numerical
simulations are carried out by implementing a recently developed hierarchical
equations of motion formalism [J. Chem. Phys. 128, 234703 (2008)], which is
formally exact for a fermionic system interacting with grand canonical
fermionic reservoirs, in the presence of arbitrary time-dependent applied
chemical potentials. The dynamical characteristics of the transient transport
current evaluated in both linear and nonlinear response regimes are analyzed,
and the equivalent classic circuit corresponding to the coupled dot-lead system
is also discussed
Exact dynamics of dissipative electronic systems and quantum transport: Hierarchical equations of motion approach
A quantum dissipation theory is formulated in terms of hierarchically coupled
equations of motion for an arbitrary electronic system coupled with grand
canonical Fermion bath ensembles. The theoretical construction starts with the
second--quantization influence functional in path integral formalism, in which
the Fermion creation and annihilation operators are represented by Grassmann
variables. Time--derivatives on influence functionals are then performed in a
hierarchical manner, on the basis of calculus--on--path--integral algorithm.
Both the multiple--frequency--dispersion and the non-Markovian reservoir
parametrization schemes are considered for the desired hierarchy construction.
The resulting formalism is in principle exact, applicable to interacting
systems, with arbitrary time-dependent external fields. It renders an exact
tool to evaluate various transient and stationary quantum transport properties
of many-electron systems. At the second--tier truncation level the present
theory recovers the real--time diagrammatic formalism developed by Sch\"{o}n
and coworkers. For a single-particle system, the hierarchical formalism
terminates at the second tier exactly, and the Landuer--B\"{u}ttiker's
transport current expression is readily recovered.Comment: The new versio