It's not a SQUID. There is new technology (quantum magnetometry) that measures slight shifts in molecular energy levels inside defects in synthetic diamonds. One of the google/alphabet spinouts from their quantum computing research is commercializing the technology (SandboxAQ).
The have a non contact MCG, like a EKG, but no electrical contacts. They can definitely "see" the heart beating from a few feet away.
SandboxAQ is also developing a navigation version. Put this sensitive magnetometer on a plane. You get very sensitive measurements of the local magnetic field. Once they have a region mapped, you can get exact positioning just from measuring magnetic fields.
You can extrapolate from SandboxAQ and get long range detection of a human heart. I don't know if it's real, but if so it's probably came out of that research effort.
You are correct, it is not based on SQUID. But, I think SQUID is technically a class of quantum magnetometer? Quantum magnetometry is pretty vague, since most high-end magnetometers use some sort of quantum mechanics.
I think the term you're looking for is atomic-optical magnetometer. Someone posted a DARPA project (AMBIIENT), that uses one. What's special about the atomic-optical magnetometer, is that it measures the gradient directly. With SQUID, if you have two SQUIDs in a uniform magnetic field, you can't determine the vector of the field. But, with atomic-optical magnetometry you can.
The photons arriving at the satellite from a ground target aren’t getting weaker due to distance in any way that defeats you, because the sun is illuminating the target and the NRO just needs to collect enough of the reflected photons.
SQUID sensors (the most sensitive magnetometers that exist) require magnetically shielded rooms to record cardiac signals at centimeter range.
They require a shielded room to increase the SNR. SQUID sensors are sensitive enough to record cardiac signals at distance. The issue is SNR.
What they are saying is that they produced a low noise sensor array and managed to increase the SNR through computation. They also stated that it was an ideal environment with no other electrical/magnetic interference.
AMBIIENT’s goal was biological imaging.. sensors near a body for medical/neuroscience applications. The range being discussed is still on the order of meters at best, not miles.
But perhaps the underlying technology is a superconducting SQUID.
The ability to detect a heartbeat from distance is far fetched though.