588 research outputs found
Superposition of photon- and phonon- assisted tunneling in coupled quantum dots
We report on electron transport through an artificial molecule formed by two
tunnel coupled quantum dots, which are laterally confined in a two-dimensional
electron system of an AlGaAs/GaAs heterostructure. Coherent
molecular states in the coupled dots are probed by photon-assisted tunneling
(PAT). Above 10 GHz, we observe clear PAT as a result of the resonance between
the microwave photons and the molecular states. Below 8 GHz, a pronounced
superposition of phonon- and photon-assisted tunneling is observed. Coherent
superposition of molecular states persists under excitation of acoustic
phonons.Comment: 5 pages, 4 figure
Adiabatic steering and determination of dephasing rates in double dot qubits
We propose a scheme to prepare arbitrary superpositions of quantum states in
double quantum--dots irradiated by coherent microwave pulses. Solving the
equations of motion for the dot density matrix, we find that dephasing rates
for such superpositions can be quantitatively infered from additional electron
current pulses that appear due to a controllable breakdown of coherent
population trapping in the dots.Comment: 5 pages, 4 figures. To appear in Phys. Rev.
The use of agreement measures and latent class models to assess the reliability of classifying thermally marked otoliths
Otolith thermal marking is an efficient method for mass marking hatchery-reared salmon and can be used to estimate the proportion of hatchery fish captured in a mixed-stock fishery. Accuracy of the thermal pattern classification depends on the prominence of the pattern, the methods used to prepare and view the patterns, and the training and experience of the personnel who determine the presence or absence of a particular pattern. Estimating accuracy rates is problematic when no secondary marking is available and no error-free standards exist. Agreement measures, such as kappa (κ), provide a relative measure of the reliability of the determinations when independent readings by two readers are available, but the magnitude of κ can be influenced by the proportion of marked fish. If a third reader is used or if two or more groups of paired readings are examined, latent class models can provide estimates of the error rates of each reader. Applications of κ and latent class models are illustrated by a program providing contribution estimates of hatchery-reared chum and sockeye salmon in Southeast Alaska
Anaplastic, T-cell, Non-Hodgkin's Lymphoma Presenting with Haematuria
Non-Hodgkin's lymphoma (NHL) represents about 3% of new cancer cases[1]. Bladder involvement has been found in approximately 3-13% of NHL patients when studied at postmortem[2]. Although accounting for only 0.2% of all primary bladder tumours, the majority of bladder lymphomas are B-cell lymphomas. T-cell lymphoma of the bladder is incredibly rare. We describe a case of anaplastic, T-cell lymphoma presenting with haematuria and loin pain, with unilateral upper tract obstruction
Nuclear spin relaxation probed by a single quantum dot
We present measurements on nuclear spin relaxation probed by a single quantum
dot in a high-mobility electron gas. Current passing through the dot leads to a
spin transfer from the electronic to the nuclear spin system. Applying electron
spin resonance the transfer mechanism can directly be tuned. Additionally, the
dependence of nuclear spin relaxation on the dot gate voltage is observed. We
find electron-nuclear relaxation times of the order of 10 minutes
Tunable Fano effect in parallel-coupled double quantum dot system
With the help of the Green function technique and the equation of motion
approach, the electronic transport through a parallel-coupled double quantum
dot(DQD) is theoretically studied. Owing to the inter-dot coupling, the bonding
and antibonding states of the artificial quantum-dot-molecule may constitute an
appropriate basis set. Based on this picture, the Fano interference in the
conductance spectra of the DQD system is readily explained. The possibility of
manipulating the Fano lineshape in the tunnelling spectra of the DQD system is
explored by tuning the dot-lead coupling, the inter-dot coupling, the magnetic
flux threading the ring connecting dots and leads, and the flux difference
between two sub-rings. It has been found that by making use of various tuning,
the direction of the asymmetric tail of Fano lineshape may be flipped by
external fields, and the continuous conductance spectra may be magnetically
manipulated with lineshape retained. More importantly, by adjusting the
magnetic flux, the function of two molecular states can be exchanged, giving
rise to a swap effect, which might play a role as a qubit in the quantum
computation.Comment: 9 pages, 10 figure
A unique case of a malignant sertoli cell tumour with cutaneous metastasis
Pure Sertoli cell tumours (SCTs) represent less than 1% of testicular neoplasms and malignant forms are rare. We present a unique case of a 69-year-old man who initially underwent inguinal orchidectomy for a malignant SCT. He then subsequently developed a paraumbilical cutaneous lesion which was histologically identical to the primary tumour. SCTs rarely metastasise. This is the first case of SCT with cutaneous metastasis described in the literature
Spin blockade in ground state resonance of a quantum dot
We present measurements on spin blockade in a laterally integrated quantum
dot. The dot is tuned into the regime of strong Coulomb blockade, confining ~
50 electrons. At certain electronic states we find an additional mechanism
suppressing electron transport. This we identify as spin blockade at zero bias,
possibly accompanied by a change in orbital momentum in subsequent dot ground
states. We support this by probing the bias, magnetic field and temperature
dependence of the transport spectrum. Weak violation of the blockade is
modelled by detailed calculations of non-linear transport taking into account
forbidden transitions.Comment: 4 pages, 4 figure
- …