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Optimal control of quantum systems with SU(1,1) dynamical symmetry
(Department of Automation, Tsinghua University, Beijing 100084, China)
Received:September 26, 2014Revised:May 06, 2015
Optimal control of quantum systems with SU(1,1) dynamical symmetry
W. Dong,R. Wu,J. Wu,C. Li,T. J. Tarn
(Department of Automation, Tsinghua University, Beijing 100084, China;Beijing Aerospace Automatic Control Institute, Beijing 100854, China;Center for Quantum Information Science and Technology, \\ Tsinghua National Laboratory for Information Science and Technology (TNlist), Beijing 100084, China)
$\SU(1,1)$ dynamical symmetry is of fundamental importance in analyzing unbounded quantum systems in theoretical and applied physics. In this paper, we study the control of generalized coherent states associated with quantum systems with $\SU(1,1)$ dynamical symmetry. Based on a pseudo Riemannian metric on the $\SU(1,1)$ group, we obtain necessary conditions for minimizing the field fluence of controls that steer the system to the desired final state. Further analyses show that the candidate optimal control solutions can be classified into normal and abnormal extremals. The abnormal extremals can only be constant functions when the control Hamiltonian is non-parabolic, while the normal extremals can be expressed by Weierstrass elliptic functions according to the parabolicity of the control Hamiltonian. As a special case, the optimal control solution that maximally squeezes a generalized coherent state is a sinusoidal field, which is consistent with what is used in the laboratory.
Key words:  Quantum control, optimal control, dynamical symmetry