Double rf-SQUIDs Operating in a Non-Adiabatic Regime: A Dream Comes True?

At a time when the supremacy of SQUIDs as the most sensitive magnetometers is being challenged by the recent progress of optically pumped atomic magnetometers operating at room temperature, looking into new opportunities to further improve SQUIDs sensitivity would probably be most welcomed by the SQUID community. By far the most promising such opportunity is to operate a double (D) rf SQUID (an rf-SQUID in which a dc-SQUID is used instead of a single Josephson junction) in a non-adiabatic regime at frequencies of about a few GHz. At these relatively high frequencies required to assure an ultra-high SQUID sensitivity the SQUID-design complexity and the cost of the electronics involved (current generator and SQUID amplifier) are still kept at reasonable levels. The advantages of using this concept, as presented in my contribution in more detail now, are overwhelming. Ironically, although this idea in its preliminary shape has been around for some time now [1], the opportunity has never been explored experimentally! I am just wondering what else needs to be done to get this message across the SQUID community and have this concept finally tested experimentally?