10 research outputs found
Lyapunov Control on Quantum Open System in Decoherence-free Subspaces
A scheme to drive and manipulate a finite-dimensional quantum system in the
decoherence-free subspaces(DFS) by Lyapunov control is proposed. Control fields
are established by Lyapunov function. This proposal can drive the open quantum
system into the DFS and manipulate it to any desired eigenstate of the free
Hamiltonian. An example which consists of a four-level system with three
long-lived states driven by two lasers is presented to exemplify the scheme. We
have performed numerical simulations for the dynamics of the four-level system,
which show that the scheme works good.Comment: 5 pages, 6 figure
Nonlinear effect on quantum control for two-level systems
The traditional quantum control theory focuses on linear quantum system. Here
we show the effect of nonlinearity on quantum control of a two-level system, we
find that the nonlinearity can change the controllability of quantum system.
Furthermore, we demonstrate that the Lyapunov control can be used to overcome
this uncontrollability induced by the nonlinear effect.Comment: 4 pages, 5 figure
The transfer function of generic linear quantum stochastic systems has a pure cascade realization
This paper establishes that generic linear quantum stochastic systems have a pure cascade realization of their transfer function, generalizing an earlier result established only for the special class of completely passive linear quantum stochastic systems. In particular, a cascade realization therefore exists for generic active linear quantum stochastic systems that require an external source of quanta to operate. The results facilitate a simplified realization of generic linear quantum stochastic systems for applications such as coherent feedback control and optical filtering. The key tools that are developed are algorithms for symplectic QR and Schur decompositions. It is shown that generic real square matrices of even dimension can be transformed into a lower 2×2 block triangular form by a symplectic similarity transformation. The linear algebraic results herein may be of independent interest for applications beyond the problem of transfer function realization for quantum systems. Numerical examples are included to illustrate the main results. In particular, one example describes an equivalent realization of the transfer function of a nondegenerate parametric amplifier as the cascade interconnection of two degenerate parametric amplifiers with an additional outcoupling mirror
The Kalman decomposition for linear quantum stochastic systems
2017 American Control Conference, May 24–26 2017, Seattle, WA, USA202305 bcchAccepted ManuscriptRGCPublishe