1,753 research outputs found
Toward high-fidelity coherent electron spin transport in a GaAs double quantum dot
In this paper, we investigate how to achieve high-fidelity electron spin
transport in a GaAs double quantum dot. Our study examines spin transport from
multiple perspectives. We first study how a double dot potential may
affect/accelerate spin relaxation. We calculate spin relaxation rate in a wide
range of experimental parameters and focus on the occurrence of spin hot spots.
A safe parameter regime is identified in order to avoid these spin hot spots.
We also study the non-adiabatic transitions in the Landau-Zener process of
sweeping the interdot detuning, and propose a scheme to take advantage of
possible Landau-Zener-St\"{u}kelburg interference to achieve high-fidelity spin
transport at a higher speed. Finally, we calculate the double-dot correction on
the effective -factor for the tunneling electron, and estimate the resulting
phase error between different spin states. Our results should provide a useful
guidance for future experiments on coherent electron spin transport.Comment: 10 pages, 7 figure
Nutational resonances, transitional precession, and precession-averaged evolution in binary black-hole systems
In the post-Newtonian (PN) regime, the timescale on which the spins of binary
black holes precess is much shorter than the radiation-reaction timescale on
which the black holes inspiral to smaller separations. On the precession
timescale, the angle between the total and orbital angular momenta oscillates
with nutation period , during which the orbital angular momentum
precesses about the total angular momentum by an angle . This defines
two distinct frequencies that vary on the radiation-reaction timescale: the
nutation frequency and the precession frequency
. We use analytic solutions for generic spin
precession at 2PN order to derive Fourier series for the total and orbital
angular momenta in which each term is a sinusoid with frequency for integer . As black holes inspiral, they can pass through
nutational resonances () at which the total angular momentum
tilts. We derive an approximate expression for this tilt angle and show that it
is usually less than radians for nutational resonances at binary
separations . The large tilts occurring during transitional precession
(near zero total angular momentum) are a consequence of such states being
approximate nutational resonances. Our new Fourier series for the total
and orbital angular momenta converge rapidly with providing an intuitive
and computationally efficient approach to understanding generic precession that
may facilitate future calculations of gravitational waveforms in the PN regime.Comment: 18 pages, 9 figures, version published in PR
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