Could the CIA really track your heartbeat from kilometers away? On April 3rd, 2026, Iranian forces shot down an American fighter plane just over Isfahan. Inside were a pilot and a weapon system officer, and both ejected successfully. The US forces located the pilot quickly and rescued him only seven hours after the crash, but they couldn't rescue the weapon system officer. He landed elsewhere deep within hostile territory. And, worst of all, he was injured. With the Iranian forces on his tail, the officer needed to hide quickly, so he disappeared into the mountains. Fortunately, the officer had a rescue beacon that could signal his location to the US. The problem was that he not only had to step out of his hiding spot to transmit the signal, Iran could potentially intercept it and get to him first. So he could only use the beacon sparingly. With enemy forces getting closer every hour, how is the US going to pinpoint his location inside hundreds of square kilometers of the desert? It's like finding a needle in a haystack.

A blind sweep of the entire area could take days or even weeks, but, surprisingly, just 40 hours after the crash, the US announced the officer was rescued. Still invisible to the enemy, but not to the CIA. So how did they do it? Well, according to a New York Post article, the CIA deployed a futuristic device to rescue him. Reportedly they were able to detect the magnetic field produced by his heartbeat from kilometers away. Such a device would have to overcome the magnetic signatures from other soldiers, vehicles, and animals in the region, let alone Earth's magnetic field. It's like listening for a murmur in a crowd. So the technology was appropriately called Ghost Murmur. Immediately this kicked off a media frenzy. All of this sounds too good to be true, and there seemed to be no other sources beyond this New York Post article. So we dug deep to find out whether this supposed technology really exists and what its limits are. I very rarely believe things I read in the New York Post. Many of these researchers in the NV diamond area, are having to sign NDAs.

There are two lines in this New York Post article that hint at what this device can be. First, normally this signal is so weak that it can only be measured in a hospital setting with sensors pressed nearly against the chest, the source said. But advances in a field known as quantum magnetometry, specifically sensors built around microscopic defects in synthetic diamonds, have apparently made it possible to detect these signals at dramatically greater distances. First, does the heart actually create detectable magnetic fields? Whenever current flows through a conductor, it generates a magnetic field around it. And since our bodies run on electrical impulses traveling through neurons, our tissues and organs generate faint magnetic signals. But because the heart muscles fire in a coordinated way, the magnetic field they produce is the strongest in the body. It's around 50 to 100 pico Teslas, 10 to 100 times more than the next strongest field produced by the brain. But even then, this is still a million times weaker than Earth's magnetic field.

So it's no surprise that we only detected the magnetic field of the heart in 1963. It had to be done in a remote field away from the magnetic noise produced by lab equipment, elevators, and cars. By the 1970s, we got superconducting quantum interference devices, or SQUIDs. These magnetometers were incredibly sensitive, detecting fields as weak as a few femto Tesla. To no surprise, the US military quickly strapped these SQUIDs to planes and helicopters, and they tried to use them to detect large magnetic signatures like submarines in the ocean. But the project never really picked up. They typically need to be operated under a very tightly controlled conditions, often inside of shielded rooms. They can't handle large dynamic range of background fields and electromagnetic interference. Future magnetometers offered solutions, but they also had their own drawbacks. Until the 1990s when physicists started looking into diamonds that might eventually be able to sense magnetic fields while potentially getting around the drawbacks. These new quantum magnetometers work at room temperature operation, and that's what's really exciting about them. They're also a solid state sensor.

Well, for something to function as a magnetometer, it needs to respond to a magnetic field in a way that we can detect. Now, a pure diamond is just an ordered lattice of carbon atoms, so it doesn't react to magnetic fields in a meaningful way. But this changes when you start adding defects to the lattice. You can replace one of the carbon atoms in the lattice with, say, a nitrogen. And if you remove one of the carbons next to it completely, well, that creates a vacancy. This defect is called a nitrogen vacancy or an NV center. And these NV centers become particularly useful when they trap two unpaired electrons. That's because electrons have this intrinsic property called spin. A simple and flawed analogy is that spin is kind of like a tiny bar magnet that gives electrons their own magnetic signature and it can point either up or down.

When you shine light at an atom, an absorbed photon of light will excite an electron within the atom to a higher energy level. In a pure diamond, the band gap is big, around 5.5 electron volts. All lower energy light will mostly be ignored by the diamond and just pass through. But if you start adding defects, they unlock different energy levels. Secret platforms within this band gap for nearby electrons to jump to. The NV center can adopt one of three ms numbers, 0, -1, or 1. If we slowly turn up the field strength, you'll see that the +1 and -1 levels are starting to shift. This phenomenon is called Zeeman splitting. It's described by a simple formula that gives you a direct link between the energy split and the magnetic field strength. So in the presence of a periodic magnetic field like that generated by the heart, we would theoretically see a rhythmic separation of these lines. By measuring how spaced apart these lines are, you get the field strength. This is how an NV diamond magnetometer works.

Could it pick up a heartbeat from kilometers away? In 2022, researchers were able to pick up the magnetic field of a rat's heart, but it was done with the diamond less than two millimeters away from the heart. Well, the strength of a magnetic field falls off with the cube of the distance from the source. At 50 to 100 kilometers, this could drop to as little as 10 to the -30 Tesla. The most sensitive measurement ever made is at the 10 to the -15 Tesla level. You'd need a system that is 15 orders of magnitude more sensitive than SQUIDs and 18 orders of magnitude more sensitive than diamond NV sensors. Finally, there's the fact that a magnetic field of 10 to the -30 Tesla is weaker than a magnetic field an electron will give you a meter away. The New York Post is notoriously a very good place for amusing fiction.

Why would they make this up? During World War II, UK officials told the press that the pilots were able to find bombers in the dark because they ate a lot of carrots. But this was actually a cover story meant to distract the Germans from the fact the British installed radars on their planes. Well, these NV centers and diamonds are also used for quantum computing. But the more interesting, probably confidential way they could be used is as navigation devices. The Earth's magnetic field creates a unique pattern all across the globe. You can infer where you are without having any GPS reception anymore. With the rise of GPS spoofing and jamming, that could be incredibly powerful. So NV magnetometers do exist, and they do have potential military applications. It's just that detecting heartbeats kilometers away probably isn't one of them.