Frozen Quantum Coherence for a Central Two-Qubit System in a Spin-Chain Environment**Supported by the National Natural Science Foundation of China under Grant No 11404246, and the Shandong Provincial Natural Science Foundation under Grant No ZR2017MF040.

Abstract

We investigate the dynamics of coherence for a central two-qubit system coupled to an XY spin chain with the Dzyaloshinsky–Moriya interaction. It is found that a sudden transition of coherence exists near the critical point in the weak-coupling case, and an oscillatory envelope appears in the strong-coupling case. In both cases the freezing phenomenon of coherence can be found.