Protecting quantum coherence of two-level atoms from vacuum fluctuations of electromagnetic field

• We study the dynamics of a two-level atom interacting with a bath of fluctuating vacuum electromagnetic field.
• For both a single and two-qubit systems, the quantum coherence cannot be protected from noise without a boundary.
• The insusceptible of the quantum coherence can be fulfilled only when the atom is close to the boundary and is transversely polarizable.
• Otherwise, the quantum coherence can only be protected in some degree in other polarizable direction.

In the framework of open quantum systems, we study the dynamics of a static polarizable two-level atom interacting with a bath of fluctuating vacuum electromagnetic field and explore under which conditions the coherence of the open quantum system is unaffected by the environment. For both a single-qubit and two-qubit systems, we find that the quantum coherence cannot be protected from noise when the atom interacts with a non-boundary electromagnetic field. However, with the presence of a boundary, the dynamical conditions for the insusceptible of quantum coherence are fulfilled only when the atom is close to the boundary and is transversely polarizable. Otherwise, the quantum coherence can only be protected in some degree in other polarizable direction.