3 ms·

Here is a Wikipedia article about the superconducting magnetic anomaly detector they are talking about : https://en.m.wikipedia.org/wiki/SQUID https://en.m.wiki

Here is a Wikipedia article about the superconducting magnetic anomaly detector they are talking about : https://en.m.wikipedia.org/wiki/SQUID https://en.m.wikipedia.org/wiki/SQUID The quantum part is actually relevant and is what makes it useful. Normal magnetic anomaly detectors rely on classical physics. These ones have an order of magnitude more sensitivity, and if they can be outfitted on a drone for a reasonable price it's game over for submarines. The idea of quantum radar is of course not what the article says. The idea is that you will use the entanglement state to discriminate between photons sent from the radar, and noise or jamming. If it does work it is pretty huge.

gus_massa 5y ago
There is a list of magnetometers in https://en.wikipedia.org/wiki/Magnetometer#Magnetic_surveys https://en.wikipedia.org/wiki/Magnetometer#Magnetic_surveys . The only one that does not use QM effects is the "Rotating coil magnetometer". For the quantum radar, I read about it a few years ago, but IIRC they only had a model that works in a lab with a small distance (and probably not under sunlight). You must send the entangled photon, get it back and combine with the other photon of the pair. You can send too many photons, because it will be difficult to make the correct pairs. And there is fog, dust, air currents, and other stuff that will mess with the polarization of the photon while it's traveling. Color me very skeptic about using it outside a lab. (Perhaps on the Moon, at night, or other similar scenario where there is no nasty air in the path.)
- sudosysgen 5y ago
  The vast majority of magnetometers are a variation on coil magnetometers. And no, rotating coil magnetometer aren't the only ones. Quantum radar is not affected by the sun, it doesn't operate in the same wavelength. As for how far we are at decoherence issues, neither of us can know. The state of the art is assuredly massively classified.

gus_massa 5y ago

There is a list of magnetometers in https://en.wikipedia.org/wiki/Magnetometer#Magnetic_surveys https://en.wikipedia.org/wiki/Magnetometer#Magnetic_surveys . The only one that does not use QM effects is the "Rotating coil magnetometer". For the quantum radar, I read about it a few years ago, but IIRC they only had a model that works in a lab with a small distance (and probably not under sunlight). You must send the entangled photon, get it back and combine with the other photon of the pair. You can send too many photons, because it will be difficult to make the correct pairs. And there is fog, dust, air currents, and other stuff that will mess with the polarization of the photon while it's traveling. Color me very skeptic about using it outside a lab. (Perhaps on the Moon, at night, or other similar scenario where there is no nasty air in the path.)

sudosysgen 5y ago
The vast majority of magnetometers are a variation on coil magnetometers. And no, rotating coil magnetometer aren't the only ones. Quantum radar is not affected by the sun, it doesn't operate in the same wavelength. As for how far we are at decoherence issues, neither of us can know. The state of the art is assuredly massively classified.