Control Decoherence by Quantum Generalized Measurement

G. Mack, Sascha Wallentowitz, P. E. Toschek

Ming Zhang, Hong‐Yi Dai, Xiaocai Zhu +2 more

For any specified pure state of quantum open system, we can construct a kind of quantum generalized measurement (QGM) that the state of the system after measurement will be deterministically collapsed into the specified pure state from any initial state. In other words, any pure state of quantum open system is reachable by QGM. Subsequently, whether the qubit is density matrix controllable is discussed in the case of pure dephasing. Our results reveal that combining QGM with coherent control will enhance the ability of controlling the quantum open system. Furthermore, it is found that the ability to perform QGM on the quantum open system, combined with the ability of coherence control and conditions of decoherence-free subspace, allows us to suppress quantum decoherence.

Michael B. Mensky

Ming Zhang

We propose a method to overcome phase damping decoherence by periodically performing open loop tracking control and generalized measurement. Although it is impossible to stabilize a qubit subject to Markovian dynamics only by open loop coherent control, one can attain a dasiasoftenedpsila control goal with the help of periodical generalized measurement. The dasiasoftenedpsila control objective in our scheme is to keep the state of the controlled qubit to stay near a reference pure state all the time. Two sub-optimal control problems are given in the sense of trace distance and fidelity, respectively, and they are eventually reduced to the choice of a period T.

Михаил Борисович Менский

Paul Meuffels