  This paper studies a class of complex-valued linear systems whose state
evolution dependents on both the state vector and its conjugate. The
complex-valued linear system comes from linear dynamical quantum control theory
and is also encountered when a normal linear system is controlled by feedback
containing both the state vector and its conjugate that can provide more design
freedom. By introducing the concept of bimatrix and its properties, the
considered system is transformed into an equivalent real-representation system
and a non-equivalent complex-lifting system, which are normal linear systems.
Some analysis and design problems including solutions, controllability,
observability, stability, eigenvalue assignment, stabilization, linear
quadratic regulation (LQR), and state observer design are then investigated.
Criterion, conditions, and algorithms are provided in terms of the coefficient
bimatrices of the original system. The developed approaches are also utilized
to investigate the so-called antilinear system which is a special case of the
considered complex-valued linear system. The existing results on this system
have been improved and some new results are established.
