The details of the technology are not very clear. One possibility to understand it is that they are using some quantum device to detect magnetic fields, and the quantum part makes it less noisy. This is possible, but a transistor already has a lot of quantum mechanics effect. It's like saying "a plane can fly because it has metals", it is true, but a locomotive also has a lot of metals.
From the article:
> China has also famously made breakthroughs in using quantum entanglement for encrypted communications by teleporting molecules over long distances. This could conceivably have application to communications with submerged submarines, a technically challenging task—with implications particularly for transmission of orders from a national command authority to launch nuclear weapons.
The quantum entanglement is useful to agree about a "one time pad" securely, but you need a somewhat direct communication for this and you also need a conventional communication channel to send the encrypted info, so it does not solve the problem of the submarine under water.
> A quantum radar functions by using a crystal to split a photon into two entangled photons. (Reportedly, finding a “fast, on-demand source of entangled photons” is the technical hurdle Canadian researchers are focusing on.) Then the radar beams one half of the entangled pair outwards, and monitors the corresponding effects on their entangled partners. If the beamed particles bump into, say, a stealth fighter, the effect on the beamed photon would be visible on the un-beamed partner photon as well. Then the photons which register a ‘ping’ are sorted out from the unaffected photons to form a sort of radar image.
It's impossible to measure any effect in the unbeamed photon https://en.wikipedia.org/wiki/No-communication_theorem , so I'd take any other article about quantum mechanic applications by this author with a grain of salt.
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.
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.)
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.
From the article:
> China has also famously made breakthroughs in using quantum entanglement for encrypted communications by teleporting molecules over long distances. This could conceivably have application to communications with submerged submarines, a technically challenging task—with implications particularly for transmission of orders from a national command authority to launch nuclear weapons.
The quantum entanglement is useful to agree about a "one time pad" securely, but you need a somewhat direct communication for this and you also need a conventional communication channel to send the encrypted info, so it does not solve the problem of the submarine under water.
From another article by the same author, linked in this post https://nationalinterest.org/blog/the-buzz/quantum-radars-co...
> A quantum radar functions by using a crystal to split a photon into two entangled photons. (Reportedly, finding a “fast, on-demand source of entangled photons” is the technical hurdle Canadian researchers are focusing on.) Then the radar beams one half of the entangled pair outwards, and monitors the corresponding effects on their entangled partners. If the beamed particles bump into, say, a stealth fighter, the effect on the beamed photon would be visible on the un-beamed partner photon as well. Then the photons which register a ‘ping’ are sorted out from the unaffected photons to form a sort of radar image.
It's impossible to measure any effect in the unbeamed photon https://en.wikipedia.org/wiki/No-communication_theorem , so I'd take any other article about quantum mechanic applications by this author with a grain of salt.