1,397 research outputs found
Role of hyperfine interaction for cavity-mediated coupling between spin qubits
We consider two qubits interacting by means of an optical cavity, where each
qubit is represented by a single electron spin confined to a quantum dot. It is
known that electron spins in III-V semiconductor quantum dots are affected by
the decoherence due to the hyperfine interaction with nuclear spins. Here we
show that the interaction between two qubits is influenced by the Overhauser
field as well. Starting from an unpolarizied nuclear ensemble, we investigate
the dependance of the fidelities for two-qubit gates on the Overhauser field.
We include the hyperfine interaction perturbatively to second order in our
analytical results, and to arbitrary precision numerically.Comment: 7 pages, 7 figure
The Republic of The Philippines: Epidemiology and Epigenetics
A brief, yet concise investigation was conducted on the Republic of the Philippines, with a keen interest in the epidemiology of the current urban areas of the nation (+150,000 inhabitants), as well as possible epigenetic change that may be induced from disease or environmental stressors upon these same groups of people. G6PD deficiency, a common disorder among persons in urban dwellings within the Republic of the Philippines (Hsia 1993) was found to have a strong correlation of incidence with members of other nations in localized proximity to the equator. Additionally, low birth weight in infants has been identified as a potential epigenetic cue in those of the emerging, current population (Kuzawa 2012).https://scholarscompass.vcu.edu/uresposters/1111/thumbnail.jp
Weak measurement of quantum dot spin qubits
The theory of weak quantum measurements is developed for quantum dot spin
qubits. Building on recent experiments, we propose a control cycle to prepare,
manipulate, weakly measure, and perform quantum state tomography. This is
accomplished using a combination of the physics of electron spin resonance,
spin blockade, and Coulomb blockade, resulting in a charge transport process.
We investigate the influence of the surrounding nuclear spin environment, and
find a regime where this environment significantly simplifies the dynamics of
the weak measurement process, making this theoretical proposal realistic with
existing experimental technology. We further consider spin-echo refocusing to
combat dephasing, as well as discuss a realization of "quantum undemolition",
whereby the effects of quantum state disturbance are undone.Comment: 8 pages, 2 figure
Datta-Das transistor with enhanced spin control
We consider a two-channel spin transistor with weak spin-orbit induced
interband coupling. We show that the coherent transfer of carriers between the
coupled channels gives rise to an \textit{additional} spin rotation. We
calculate the corresponding spin-resolved current in a Datta-Das geometry and
show that a weak interband mixing leads to enhanced spin control.Comment: Added ref. + corrected typo
Lesbian, Gay, and Bisexual Supervisees’ Experiences of LGB-Affirmative and Nonaffirmative Supervision
Lesbian, gay, and bisexual (LGB) supervisees were interviewed regarding their experiences of LGB affirmative and nonaffirmative supervision. Supervisees were asked to describe one of each type of event (i.e., affirmative, nonaffirmative) from their past supervision. In LGB-affirmative supervision, all supervisees felt supported in their LGB-affirmative work with clients. Supervisees perceived that the affirming events also positively affected the supervision relationship, client outcomes, and themselves as supervisees. In LGB nonaffirming supervision, supervisees perceived supervisors to be biased or oppressive toward supervisees’ clients or themselves on the basis of LGB concerns or identity. From supervisees’ perspectives, the nonaffirming events negatively affected the supervision relationship, client outcomes, and supervisees. Implications for research and supervision are discussed
Low-damping transmission of spin waves through YIG/Pt-based layered structures for spin-orbit-torque applications
We show that in YIG-Pt bi-layers, which are widely used in experiments on the
spin transfer torque and spin Hall effects, the spin-wave amplitude
significantly decreases in comparison to a single YIG film due to the
excitation of microwave eddy currents in a Pt coat. By introducing a novel
excitation geometry, where the Pt layer faces the ground plane of a microstrip
line structure, we suppressed the excitation of the eddy currents in the Pt
layer and, thus, achieved a large increase in the transmission of the
Damon-Eshbach surface spin wave. At the same time, no visible influence of an
external dc current applied to the Pt layer on the spin-wave amplitude in the
YIG-Pt bi-layer was observed in our experiments with YIG films of micrometer
thickness
Spin-Orbit Coupling and Time-Reversal Symmetry in Quantum Gates
We study the effect of spin-orbit coupling on quantum gates produced by
pulsing the exchange interaction between two single electron quantum dots.
Spin-orbit coupling enters as a small spin precession when electrons tunnel
between dots. For adiabatic pulses the resulting gate is described by a unitary
operator acting on the four-dimensional Hilbert space of two qubits. If the
precession axis is fixed, time-symmetric pulsing constrains the set of possible
gates to those which, when combined with single qubit rotations, can be used in
a simple CNOT construction. Deviations from time-symmetric pulsing spoil this
construction. The effect of time asymmetry is studied by numerically
integrating the Schr\"odinger equation using parameters appropriate for GaAs
quantum dots. Deviations of the implemented gate from the desired form are
shown to be proportional to dimensionless measures of both spin-orbit coupling
and time asymmetry of the pulse.Comment: 10 pages, 3 figure
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