To find a heartbeat, a quantum Ghost Murmur tool would have to contend not just with Earth’s magnetic field and magnetic noise from natural and human-made electric currents but also with “the heartbeats of the sheep and dogs and jackrabbits—whatever else is running around out there,” says Chad Orzel, a professor of physics at Union College in New York State and author of How to Teach Quantum Physics to Your Dog. He uses refrigerator magnets to illustrate the weakness of magnetic fields in general. “You have to get the magnet very, very close to the refrigerator before it snaps into place,” he says. “That field drops off very quickly.” Clinical sensors “are usually butted right up against your body ... at a distance of centimeters,” Orzel adds. Even pattern-matching using artificial intelligence, he says, couldn’t find a magnetic signal large enough to identify the presence of a person from kilometers away in a desert. At one kilometer away, the signal would diminish to about one trillionth of the strength.
Bradley Roth, a physicist at Oakland University and author of the 2023 review Biomagnetism: The First Sixty Years, agrees. “People have been measuring the magnetic field of the heart for 60 years, and usually it’s done in a lab with shielding, and it’s done just a few centimeters or a couple inches from the heart, and even then you can barely record it.” A helicopter-borne version, he says, “would be not just a small advance, but it’d be a revolutionary advance from the state of the art.”
Orzel struggles to see how a Ghost Murmur could work. “There is really fascinating work being done using quantum magnetometry to measure heart rates,” he says, and magnetic brain scans can now catch the tiny flickers of firing nerves. “But none of that is something that works over ranges of many miles.”
So why was this a story at all? Orzel has a guess: “Somebody yanking a reporter’s chain,” he says. It could be a “snarky, clever way to say, ‘Of course, I’m not going to tell you how we figured this out’”—or a piece of disinformation “to fool somebody into thinking that we actually have this secret technology.”