It seems that the majority of the skepticism comes from the classical understanding of magnetism and magnetic fields. It seems incredulous that you can detect

It seems that the majority of the skepticism comes from the classical understanding of magnetism and magnetic fields. It seems incredulous that you can detect the magnetic dipole of a heartbeat at distance because the magnetic field generated by a heart is essentially nonexistent. However, there /is/ a measurable effect from the magnetic vector potential even if the magnetic field is or is essentially 0. This seems counterintuitive, but has been experimentally verified [0, 1]. There are a myriad of quantum magnetometers with the main categories of superconducting (SQUID), atomic, and nitrogen-vacancy (NV) [2]. Superconducting magnetometers require cryogenics, so we can immediately discount its usage. Nitrogen-vacancy magnetometers can detect high frequency magnetic fields, which a heartbeat is not, and are less sensitive than atomic magnetometers. Therefore, NV magnetometers can be disregarded. Now, for atomic magnetometers. Optically pumped atomic magnetometers (OPAM). These are highly portable and extremely sensitive (fT/√Hz), with some OPAMs approaching the quantum noise limit [3]. Moreover, the detection of a magnetic vector potential is possible [4]. Another type of atomic magnetometer is the Spin Exchange Relaxation Free (SERF) magnetometer. SERFs are even more sensitive than standard OPAMs (aT/√Hz). So, likely, some form of atomic magnetometer is being used. Nonetheless, they most likely used a mixture of other methods to reduce the search area. [0] https://www.feynmanlectures.caltech.edu/II_15.html#Ch15-S5 https://www.feynmanlectures.caltech.edu/II_15.html#Ch15-S5 [1] https://www.youtube.com/watch?v=XKSjCOKDtpk https://www.youtube.com/watch?v=XKSjCOKDtpk [2] https://www.nist.gov/quantum-information-science/sensors-magnetic-world https://www.nist.gov/quantum-information-science/sensors-mag... [3] https://pubs.aip.org/aip/apl/article-abstract/89/21/214106/327733/Subfemtotesla-radio-frequency-atomic-magnetometer?redirectedFrom=fulltext https://pubs.aip.org/aip/apl/article-abstract/89/21/214106/3... [4] https://pubs.aip.org/aip/adv/article/13/2/025127/2877320/Differential-behavior-of-magnetic-field-and https://pubs.aip.org/aip/adv/article/13/2/025127/2877320/Dif...