105,101 research outputs found
Experimentally realizable control fields in quantum Lyapunov control
As a hybrid of techniques from open-loop and feedback control, Lyapunov
control has the advantage that it is free from the measurement-induced
decoherence but it includes the system's instantaneous message in the control
loop. Often, the Lyapunov control is confronted with time delay in the control
fields and difficulty in practical implementations of the control. In this
paper, we study the effect of time-delay on the Lyapunov control, and explore
the possibility of replacing the control field with a pulse train or a
bang-bang signal. The efficiency of the Lyapunov control is also presented
through examining the convergence time of the controlled system. These results
suggest that the Lyapunov control is robust gainst time delay, easy to realize
and effective for high-dimensional quantum systems
Dynamics of quantum-classical hybrid system: effect of matter-wave pressure
Radiation pressure affects the kinetics of a system exposed to the radiation
and it constitutes the basis of laser cooling. In this paper, we study {\it
matter-wave pressure} through examining the dynamics of a quantum-classical
hybrid system. The quantum and classical subsystem have no explicit coupling to
each other, but affect mutually via a changing boundary condition. Two systems,
i.e., an atom and a Bose-Einstein condensate(BEC), are considered as the
quantum subsystems, while an oscillating wall is taken as the classical
subsystem. We show that the classical subsystem would experience a force
proportional to from the quantum atom, whereas it acquires an
additional force proportional to from the BEC due to the atom-atom
interaction in the BEC. These forces can be understood as the {\it matter-wave
pressure}.Comment: 7 pages, 6 figue
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