196 research outputs found
Modular symmetry and non-Abelian discrete flavor symmetries in string compactification
We study the modular symmetry in magnetized D-brane models on .
Non-Abelian flavor symmetry in the model with magnetic flux (in a
certain unit) is a subgroup of the modular symmetry. We also study the modular
symmetry in heterotic orbifold models. The orbifold model has the
same modular symmetry as the magnetized brane model with , and its flavor
symmetry is a subgroup of the modular symmetry.Comment: 28 page
F-term Moduli Stabilization and Uplifting
We study K\"ahler moduli stabilization in IIB superstring theory. We propose
a new moduli stabilization mechanism by the supersymmetry-braking chiral
superfield which is coupled to K\"ahler moduli in K\"ahler potential. We also
study uplifting of the Large Volume Scenario (LVS) by it. In both cases, the
form of superpotential is crucial for moduli stabilization. We confirm that our
uplifting mechanism does not destabilize the vacuum of the LVS drastically.Comment: 22 pages, 2 figure
Quantum manipulation of two-electron spin states in metastable double quantum dots
We studied experimentally the dynamics of the exchange interaction between
two antiparallel electron spins in a so-called metastable double quantum dot
where coupling to the electron reservoirs can be ignored. We demonstrate that
the level of control of such a double dot is higher than in conventional double
dots. In particular, it allows to couple coherently two electron spins in an
efficient manner following a scheme initially proposed by Loss and DiVincenzo.
The present study demonstrates that metastable quantum dots are a possible
route to increase the number of coherently coupled quantum dots.Comment: 5 pages, 4 figure
Injection of a single electron from static to moving quantum dots
We study the injection mechanism of a single electron from a static quantum
dot into a moving quantum dot created in a long depleted channel with surface
acoustic waves (SAWs). We demonstrate that such a process is characterized by
an activation law with a threshold that depends on the SAW amplitude and the
dot-channel potential gradient. By increasing sufficiently the SAW modulation
amplitude, we can reach a regime where the transfer is unitary and potentially
adiabatic. This study points at the relevant regime to use moving dots in
quantum information protocols.Comment: 5 pages, 4 figure
量子干渉計における電子のコヒーレント制御と位相測定
学位の種別:課程博士University of Tokyo(東京大学
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