Please turn on javascript in your browser to play chess.
Science Forum

Science Forum

  1. 25 Apr '18 10:07 / 1 edit
    https://phys.org/news/2018-04-quantum-radar-expose-stealth-aircraft.html
    "...
    In the Arctic, space weather such as geomagnetic storms and solar flares interfere with radar operation and make the effective identification of objects more challenging.
    ...
    By moving from traditional radar to quantum radar, we hope to not only cut through this noise, but also to identify objects that have been specifically designed to avoid detection.
    ...
    The method works by sending one of the photons to a distant object, while retaining the other member of the pair. Photons in the return signal are checked for telltale signatures of entanglement, allowing photons from the noisy environmental background to be discarded. This can greatly improve the radar signal-to-noise in certain situations.
    ..."

    Interesting but I don't think being able to detect stealth aircraft would be necessarily a good thing because what is stopping our enemies use this? -it works both ways.
    However, quantum radar would also be useful for peace time purposes. So I guess it is still worth developing.
  2. Subscriber sonhouse
    Fast and Curious
    25 Apr '18 10:27 / 1 edit
    Originally posted by @humy
    https://phys.org/news/2018-04-quantum-radar-expose-stealth-aircraft.html
    "...
    In the Arctic, space weather such as geomagnetic storms and solar flares interfere with radar operation and make the effective identification of objects more challenging.
    ...
    By moving from traditional radar to quantum radar, we hope to not only cut through this noise, but also t ...[text shortened]... tum radar would also be useful for peace time purposes. So I guess it is still worth developing.
    Might make radio astronomy detectors more sensitive, microwave radar signals quantum linked. Do you know of experiments quantum entangled at microwave frequencies?
    The piece talks about entangled photons and microwave EM are photons, just a bit bigger, eh. I wonder if what they are talking about is not strictly radar but lidar instead. Laser radar.
    Sounds intensely technological, rejecting all photons not entangled, automatically.
  3. Standard member uzless
    The So Fist
    26 Apr '18 01:14 / 1 edit
    Originally posted by @humy

    Interesting but I don't think being able to detect stealth aircraft would be necessarily a good thing because what is stopping our enemies use this?
    they can already detect stealth aircraft by altering their radar to look for atmospheric turbulence on the linear axis...ie they can track a stealth plane by the wake it leaves.
  4. Standard member DeepThought
    Losing the Thread
    05 May '18 18:28
    Originally posted by @humy
    https://phys.org/news/2018-04-quantum-radar-expose-stealth-aircraft.html
    "...
    In the Arctic, space weather such as geomagnetic storms and solar flares interfere with radar operation and make the effective identification of objects more challenging.
    ...
    By moving from traditional radar to quantum radar, we hope to not only cut through this noise, but also t ...[text shortened]... tum radar would also be useful for peace time purposes. So I guess it is still worth developing.
    I see a couple of difficulties with this. The first problem, which the article alludes to, is that a functional radar uses a lot of power - to the extent that you simply cannot get too close to a military radar if you do not want to be cooked. I do not see how they can generate a signal with an adequate amount of power which is quantum entangled, store half of it, and unravel which photon is entangled with which on their return. In fact, I'd be a little surprised if entanglement effects survive the interaction with the environment of the outgoing photon. It might work in ideal laboratory conditions at incredibly low power, but I can't see it working at high power when it's raining.

    It's not going to help against passive stealth technology, since the signal doesn't return to the antenna if it's been absorbed by a stealth coating or deflected in an arbitrary direction, in the same way that it doesn't return to the antenna if there is no target. So the only benefit seems to me to be against jamming, but if they are sending out a jamming signal they're telling you where they are.

    The possibility that an adversary might develop a similar system is not a reason not to develop it. The spur for them to proceed is not the potential development of a quantum radar system, but the existence of NATO stealth aircraft. I can't see any non-military applications that classical RADAR isn't adequate for - jamming and stealth coatings not being a huge feature of civilian airtraffic.
  5. Subscriber sonhouse
    Fast and Curious
    05 May '18 22:12 / 2 edits
    Originally posted by @deepthought
    I see a couple of difficulties with this. The first problem, which the article alludes to, is that a functional radar uses a lot of power - to the extent that you simply cannot get too close to a military radar if you do not want to be cooked. I do not see how they can generate a signal with an adequate amount of power which is quantum entangle ...[text shortened]... n't adequate for - jamming and stealth coatings not being a huge feature of civilian airtraffic.
    If the high power part was solved, maybe it would be best used in radio astronomy say on the moon with no atmosphere to screw things up, also makes for a better beam with the same antenna dish.

    When I was in the USAF as a kid of 21, I had a full blown working radar in our shop, it was rated at 1 megawatt pulsed but average power was more like 50 watts average.

    I was assigned night duty once and had the test set up and running.

    One night a janitor came in carrying an armful of 4 foot florescent tubes, maybe 20 of them destined for the trash.

    So I (stupid for sure) saw him across the room and he did not see me fortunately for me, but I aimed the small dish at his lights and I was very surprised by how brightly the glowed and the janitor jumped about 3 feet in the air, tubes flying and smashing into pieces. I VERY quietly turned off the radar and bugged out before anyone knew I was there.

    But it was a really vivid demo of how much power even 50 watts could be when it is squished in time to a sub-microsecond pulse with a PRF of about 4 milliseconds which allowed the beam to go out about 600 km, 1200 Km round trip time of about 4 milliseconds (3.33 milliseconds per Km). Of course only in air at ten thousand meters altitude could you achieve such a range in real life) but at 30 meters away......

    I only did that particular stunt once and very glad I wasn't caught, I imagine I would have washed out of the force right then and there if they had known my stupid pet trick.

    It was funny ATT though