24,494 research outputs found
Interplay of charge and spin coherence in Landau-Zener-St\"uckelberg-Majorana interferometry
We study Landau-Zener dynamics in a double quantum dot filled with two
electrons, where the spin states can become correlated with charge states and
the level velocity can be tuned in a time-dependent fashion. We show that a
correct interpretation of experimental data is only possible when finite-time
effects are taken into account. In addition, our formalism allows the study of
partial adiabatic dynamics in the presence of phonon-mediated hyperfine
relaxation and charge-noise-induced dephasing. Our findings demonstrate that
charge noise severely impacts the visibility of
Landau-Zener-St\"uckelberg-Majorana interference fringes. This indicates that
charge coherence must be treated on an equal footing with spin coherence.Comment: 13 pages, 9 figure
Aperiodic Quantum Random Walks
We generalize the quantum random walk protocol for a particle in a
one-dimensional chain, by using several types of biased quantum coins, arranged
in aperiodic sequences, in a manner that leads to a rich variety of possible
wave function evolutions. Quasiperiodic sequences, following the Fibonacci
prescription, are of particular interest, leading to a sub-ballistic
wavefunction spreading. In contrast, random sequences leads to diffusive
spreading, similar to the classical random walk behaviour. We also describe how
to experimentally implement these aperiodic sequences.Comment: 4 pages and 4 figure
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