Rydberg atoms field sensors: The quest for weak field detection

Rydberg atom-based radio frequency (RF) electrical (E) fields sensors are actively enabling new applications and techniques. One common goal in the development of atom-based sensors is to improve the minimal detectable field and sensitivity.  The majority of the work on Rydberg-atom sensors relies on spectroscopy of highly excited atoms using electromagnetically induced transparency (EIT) and their interaction with external electric fields in the form of Autler-Townes (AT) splitting.  Using standard EIT/AT techniques, E-field strengths down to a few V/m can routinely be measured. Even lower fields, down to tenths of V/m, can be measured depending on the frequency and atomic states used.  In this talk we will discuss various techniques to improve the detection of weak fields. These approaches will include: (1) optical re-pumping techniques, (2) RF heterodyne Rydberg atom-based mixer approaches, (3) optical homodyne techniques, (4) three-photon techniques, and (5) the use of RF resonators for field enhancements. The most important aspect here is the complimentary nature of these approaches.