5,828 research outputs found
Efficient orthogonal control of tunnel couplings in a quantum dot array
Electrostatically-defined semiconductor quantum dot arrays offer a promising
platform for quantum computation and quantum simulation. However, crosstalk of
gate voltages to dot potentials and inter-dot tunnel couplings complicates the
tuning of the device parameters. To date, crosstalk to the dot potentials is
routinely and efficiently compensated using so-called virtual gates, which are
specific linear combinations of physical gate voltages. However, due to
exponential dependence of tunnel couplings on gate voltages, crosstalk to the
tunnel barriers is currently compensated through a slow iterative process. In
this work, we show that the crosstalk on tunnel barriers can be efficiently
characterized and compensated for, using the fact that the same exponential
dependence applies to all gates. We demonstrate efficient calibration of
crosstalk in a quadruple quantum dot array and define a set of virtual barrier
gates, with which we show orthogonal control of all inter-dot tunnel couplings.
Our method marks a key step forward in the scalability of the tuning process of
large-scale quantum dot arrays.Comment: 8 pages, 7 figure
Description of Pseudo-Newtonian Potential for the Relativistic Accretion Disk around Kerr Black Holes
We present a pseudo-Newtonian potential for accretion disk modeling around
the rotating black holes. This potential can describe the general relativistic
effects on accretion disk. As the inclusion of rotation in a proper way is very
important at an inner edge of disk the potential is derived from the Kerr
metric. This potential can reproduce all the essential properties of general
relativity within 10% error even for rapidly rotating black holes.Comment: 5 Latex pages including 1 figure. Version to appear in Astrophysical
Journal, V-581, N-1, December 10, 200
Automated tuning of inter-dot tunnel couplings in quantum dot arrays
Semiconductor quantum dot arrays defined electrostatically in a 2D electron
gas provide a scalable platform for quantum information processing and quantum
simulations. For the operation of quantum dot arrays, appropriate voltages need
to be applied to the gate electrodes that define the quantum dot potential
landscape. Tuning the gate voltages has proven to be a time-consuming task,
because of initial electrostatic disorder and capacitive cross-talk effects.
Here, we report on the automated tuning of the inter-dot tunnel coupling in a
linear array of gate-defined semiconductor quantum dots. The automation of the
tuning of the inter-dot tunnel coupling is the next step forward in scalable
and efficient control of larger quantum dot arrays. This work greatly reduces
the effort of tuning semiconductor quantum dots for quantum information
processing and quantum simulation
Scalar and Spinor Perturbation to the Kerr-NUT Spacetime
We study the scalar and spinor perturbation, namely the Klein-Gordan and
Dirac equations, in the Kerr-NUT space-time. The metric is invariant under the
duality transformation involving the exchange of mass and NUT parameters on one
hand and radial and angle coordinates on the other. We show that this
invariance is also shared by the scalar and spinor perturbation equations.
Further, by the duality transformation, one can go from the Kerr to the dual
Kerr solution, and vice versa, and the same applies to the perturbation
equations. In particular, it turns out that the potential barriers felt by the
incoming scalar and spinor fields are higher for the dual Kerr than that for
the Kerr. We also comment on existence of horizon and singularity.Comment: 31 pages including 20 figures, RevTeX style: Final version to appear
in Classical and Quantum Gravit
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