Cooling classical many-spin systems using feedback control

Quantum feedback control and classical control theory

We introduce and discuss the problem of quantum feedback control in the context of established formulations of classical control theory, examining conceptual analogies and essential differences. We describe the application of state-observer-based control laws, familiar in classical control theory, to quantum systems and apply our methods to the particular case of switching the state of a partic...

Feedback control of coherent spin states using weak nondestructive measurements

Singular Perturbation Theory in Output Feedback Control of Pure-Feedback Systems

This paper studies output feedback control of pure-feedback systems with immeasurable states and completely non-affine property. Since availability of all the states is usually impossible in the actual process, we assume that just the system output is measurable and the system states are not available. First, to estimate the immeasurable states a state observer is designed. Relatively fewer res...

Non-classical Problems of Optimal Feedback Control

The paper is concerned with problems of optimal feedback control with “nonclassical” dynamics ẋ = f(t, x, u,Du), where the evolution of the state x depends also on the Jacobian matrix Du = (∂ui/∂xj) of the feedback control function u = u(t, x). Given a probability measure μ on the set of initial states, we seek feedback controls u(·) which minimize the expected value of a cost functional. After...

Symplectic integrators for classical spin systems

We suggest a numerical integration procedure for solving the equations of motion of certain classical spin systems which preserves the underlying symplectic structure of the phase space. Such symplectic integrators have been successfully utilized for other Hamiltonian systems, e. g. for molecular dynamics or non-linear wave equations. Our procedure rests on a decomposition of the spin Hamiltoni...