22,058 research outputs found
Effects of uncertainties and errors on Lyapunov control
Lyapunov control (open-loop) is often confronted with uncertainties and
errors in practical applications. In this paper, we analyze the robustness of
Lyapunov control against the uncertainties and errors in quantum control
systems. The analysis is carried out through examinations of uncertainties and
errors, calculations of the control fidelity under influences of the
certainties and errors, as well as discussions on the caused effects. Two
examples, a closed control system and an open control system, are presented to
illustrate the general formulism.Comment: 4 pages, 5 figure
Pumped spin-current and shot noise spectra in a single quantum dot
We exploit the pumped spin-current and current noise spectra under
equilibrium condition in a single quantum dot connected to two normal leads, as
an electrical scheme for detection of the electron spin resonance (ESR) and
decoherence. We propose spin-resolved quantum rate equations with correlation
functions in Laplace-space for the analytical derivation of the zero-frequency
atuo- and cross-shot noise spectra of charge- and spin-current. Our results
show that in the strong Coulomb blockade regime, ESR-induced spin flip
generates a finite spin-current and the quantum partition noises in the absence
of net charge transport. Moreover, spin shot noise is closely related to the
magnetic Rabi frequency and decoherence and would be a sensitive tool to
measure them.Comment: 4 pages, 3 figures, to be published in Phys. Rev. Lette
Berry's phase with quantized field driving: effects of inter-subsystem coupling
The effect of inter-subsystem couplings on the Berry phase of a composite
system as well as that of its subsystem is investigated in this paper. We
analyze two coupled spin- particles with one driven by a quantized
field as an example, the pure state geometric phase of the composite system as
well as the mixed state geometric phase for the subsystem is calculated and
discussed.Comment: 4 pages, 1 figur
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