  Microwave electric field sensing is of importance for a wide range of
applications in areas of remote sensing, radar astronomy and communications.
Over the past decade, Rydberg atoms, owing to their exaggerated response to
microwave electric fields, plentiful optional energy levels and integratable
preparation methods, have been used in ultra-sensitive, wide broadband,
traceable, stealthy microwave electric field sensing. This review first
introduces the basic concept of quantum sensing, properties of Rydberg atoms
and principles of quantum sensing of microwave electric fields with Rydberg
atoms. Then an overview of this very active research direction is gradually
expanded, covering progresses of sensitivity and bandwidth in Rydberg atoms
based icrowavesensing,uperheterodyne quantum sensing with microwave-dressed
Rydberg atoms, quantum-enhanced sensing of microwave electric field, recent
advanced quantum measurement systems and approaches to further improve the
performance of microwave electric field sensing. Finally, a brief outlook on
future development directions is discussed.
