1,073 research outputs found
Non-universal weak antilocalization effect in cubic topological Kondo insulators
We study the quantum correction to conductivity on the surface of cubic
topological Kondo insulators with multiple Dirac bands. We consider the model
of time-reversal invariant disorder which induces the scattering of the
electrons within the Dirac bands as well as between the bands. When only
intraband scattering is present we find three long-range diffusion modes which
lead to weak antilocalization correction to conductivity, which remains
independent of the microscopic details such as Fermi velocities and relaxation
times. Interband scattering gaps out two diffusion modes leaving only one
long-range mode. We find that depending on the value of the phase coherence
time, either three or only one long-range diffusion modes contribute to weak
localization correction rendering the quantum correction to conductivity
non-universal. We provide an interpretation for the results of the recent
transport experiments on samarium hexaboride where weak antilocalization has
been observed.Comment: 15 pages, 7 figure
Effect of Ohmic environment on optimally controlled flux-biased phase qubit
We analyze the effect of environment on the gate operation of flux-biased
phase qubits. We employ the master equation for a reduced density matrix of the
qubit system coupled to an Ohmic environment, described by the Caldeira-Leggett
model. Numerically solving this equation, we evaluate the gate error as a
function of energy splitting between qubit states, junction capacitance, and
temperature. The analysis is presented for single-quadrature microwave
(control) pulses as well as for two-quadrature pulses, which lower the gate
error significantly for idealized systems in the absence of environment. Our
results indicate that two-quadrature pulses outperform single quadrature pulses
even in the presence of environment.Comment: 5 pages and 4 figure
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