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Advanced Tech: Ghost Murmur

Posted under Advanced Tech on April 26th, 2026 by Amaldev

You might have seen news a few weeks back about the rescue of a US pilot from Iran. Then came a media post from NewYorkPost about Ghost Murmur, a device that supposedly helped find him by detecting his heartbeat 60km away. There was a lot being said about it. I wanted to see if this was scientifically possible. It’s defense tech, so this will be slightly speculative from my end.

The claim made is that your heart creates a tiny magnetic field when current flows through it. A sensor picks it up and an “AI” software filters the noise and looks for a heartbeat pattern.

I deep-dived into it. There was a base technology that kind of enables it. It’s called Quantum Magnetometry. This was shown with NV centers in diamond. NV means nitrogen-vacancy. In simple terms, one carbon atom in diamond is replaced by nitrogen, and the neighbouring carbon atom is empty. When you shine laser light and apply microwaves, its quantum state changes slightly with the magnetic field around it. By reading that change in light, the diamond can act like a very sensitive magnetic-field probe.

So the probing tech is real. Many research groups work on NV-diamond magnetometry, and heart magnetic signals are also real. But heartbeat magnetic field is a very weak near-field signal. Near the chest, it may be in the picoTesla range, which is already tiny. A picoTesla is one trillionth of a Tesla. For reference, Earth’s magnetic field is usually around 25-65 microtesla.

And once you move away, that signal drops very fast. So I highly doubt they have somehow magically solved the problem that it survived kilometres of air, terrain and Earth’s magnetic field. They claim AI software, but AI can kick in only if the data capture is possible. So detecting one human heartbeat from 60 km away feels extremely unlikely based on public physics. I do think the claim is an overexaggeration from someone either to mislead or oversell.

Realistically it might be a sensor fusion. Maybe like a rescue beacon, GPS burst, thermal imaging and maybe some magnetic sensing all feeding one system.

What do you folks think?

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Advanced Tech: Rydberg Atom Receiver

Posted under Advanced Tech, Technology on April 5th, 2026 by Amaldev

I came across an unusual paper this week on a way to detect radio waves and to pull out speech data from normal walkie-talkie signals. It’s interesting, and I never knew this domain of detection. Let’s discuss.

A Rydberg atom is an atom with one electron pushed far from the nucleus into a very high energy state. Think of it as a weak, oversized atom. The distant electron makes the atom extremely sensitive to external electric fields.

So when a radio wave passes through, its electric field slightly shifts the atom’s energy levels. That shift is called the AC Stark shift. In simple terms, the RF field nudges the atom enough to change how it interacts with laser light. If you watch that laser with a photodetector, you can tell a radio signal is present.

In this paper, the team put rubidium (Atomic number 37) atoms in a vapour cell, shine lasers through it to create and probe the Rydberg state, and let a UHF(~460MHz) walkie-talkie transmit nearby. The incoming RF field changes the atoms, the optical signal changes with it, and that change is converted back into audio.

Since FM doesn’t directly show up in amplitude, they mix the signal with a nearby local oscillator and use a lock-in amplifier to extract the tiny beat signal. That’s how the audio is recovered cleanly.

So why does this matter? A normal radio uses an antenna, tuned RF circuits, mixers, and some DSP ICs. This approach uses atoms as the field-sensitive element instead. In this paper, they recovered real FM speech from a handheld radio and separated adjacent channels well. That’s a pretty nice trick to pull off.

It still does not beat a cheap radio chip on size, cost, power, or practicality. But I think the point is different. This work asks whether nature itself can be the sensor, and whether you can build a receiver around physics first and electronics later.

Anyway, if you are interested in these type of stuff give the paper a quick read at doi.org/10.1103/jlrg-6889

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