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London Underground hosts tests for 'quantum compass' that could replace GPS

theguardian.com

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Re: London Underground hosts tests for 'quantum compass' that could replace GPS

#41

Post by Terr_ »

akira2501 wrote: post #34
Terr_ wrote: post #28

Earlier quoted context omitted.

Also changes in the status-quo of international politics: Russia has been chronically sabotaging non-Russian navigation systems in neighboring countries, beaming jamming and spoofing signals across the borders. Russian airplanes aren't affected because nobody has chosen to retaliate in kind... Yet.

Planes have inertial measurement units which are the primary source. GPS or GNSS are just backups. You can switch these off with zero consequence during the flight. It may cause your satellite TV and internet to stop working but no critical systems will be impacted. Russian airplanes are commercially purchased from the same sources as the rest of the world and are generally outfitted with identical equipment. The imp…

> Russian airplanes are

The simpler answer is that Russia is not directing the sabotaging signals into their domestic flight paths.

Re: London Underground hosts tests for 'quantum compass' that could replace GPS

#42

Post by refulgentis »

hi-v-rocknroll wrote: post #26
rob74 wrote: post #24

Earlier quoted context omitted.

... and GPS was initially developed for - right, the military.

GPS can and was miniaturized. LRGs and QGs aren't for retail use because they're very expensive, bulky, and largely unnecessary.

F(T) != F(T+1)

I, for one, am glad to see people working to innovate along well-trodden paths.

Re: London Underground hosts tests for 'quantum compass' that could replace GPS

#43

Post by gridspy »

contravariant wrote: post #38
porphyra wrote: post #9

I remember doing laser cooling of rubidium atoms in physics class. It's really cool how it works: * Rubidium will absorb photons of a certain wavelength and re-emit it in a random direction. Since photons have momentum, it will get some net momentum change from absorbing photons all coming from a particular direction, but the re-emissions are in random directions so they have net zero momentum. * Shine laser light at…

Maybe I'm missing something but hitting a gas just above absolute zero with lasers from every direction doesn't sound as something that could be miniaturised.

Most technology has a limit like this (for instance CPU transistor size in the past). However once this is a proven technology, money will be invested in solving these issues.

Re: London Underground hosts tests for 'quantum compass' that could replace GPS

#44

Post by lbourdages »

hi-v-rocknroll wrote: post #10

Journalists get it wrong, again. Sigh. It will never replace GNSS. It's quantum inertial navigation (QIN) that double-integrates acceleration like another method, requiring external position, heading, and velocity (re)calibration and drifts without them. It has absolutely no idea where it is from only itself.

So it doesn't solve the issue inherent will all inertial navigation approaches (error accumulates very quickly because of the double integration), it just has less error?

Seems like an incremental improvement at best.

Re: London Underground hosts tests for 'quantum compass' that could replace GPS

#45

Post by gridspy »

TooKool4This wrote: post #31
hi-v-rocknroll wrote: post #16

Earlier quoted context omitted.

That's an extremely niche application unlikely to be scaled down to anything smaller than a backpack like laser ring gyros. As such, this type of positioning gear isn't for consumer use and is targeted mostly for underground surveying. (I worked for Trimble.)

Why does it matter if it's not for consumer applications? GNSS is used for many more applications (and arguably more critical) than consumer applications (agriculture, mapping & surveying, aeronautics, shipping, etc.) Also just want to mention that, yes, integration errors accumulate when using intero-receptive sensors but if errors are small enough (white noise, various biases, sample rates, quantization, etc.) from…

nmi - Nautical mile (1 nmi/hour mentioned above)

Today the international nautical mile is defined as 1,852 metres (about 6,076 ft; 1.151 mi).

https://en.wikipedia.org/wiki/Nautical_mile

Re: London Underground hosts tests for 'quantum compass' that could replace GPS

#46

Post by gnatman »

hi-v-rocknroll wrote: post #16
sandworm101 wrote: post #15

Earlier quoted context omitted.

>>> It will never replace GNSS. It will have to. That is the point. This isn't about better in-car navigation. The big money behind quantum gyroscopes is the potential to guide submarines/aircraft/missiles in times of war when the GNSS systems are down or otherwise unreliable, just like the best of traditional gyroscopes. Dead reckoning is a legitimate means of navigation, but there are also some aspects where actual…

That's an extremely niche application unlikely to be scaled down to anything smaller than a backpack like laser ring gyros. As such, this type of positioning gear isn't for consumer use and is targeted mostly for underground surveying. (I worked for Trimble.)

When one of the potential customers in this "extremely niche" space has an $800 billion annual budget, you don't lose sleep over it.

Re: London Underground hosts tests for 'quantum compass' that could replace GPS

#47

Post by dekhn »

porphyra wrote: post #9

I remember doing laser cooling of rubidium atoms in physics class. It's really cool how it works: * Rubidium will absorb photons of a certain wavelength and re-emit it in a random direction. Since photons have momentum, it will get some net momentum change from absorbing photons all coming from a particular direction, but the re-emissions are in random directions so they have net zero momentum. * Shine laser light at…

There's a whole bunch of laser cooling science/applications: https://en.wikipedia.org/wiki/Laser_cooling

Re: London Underground hosts tests for 'quantum compass' that could replace GPS

#48

Post by actinium226 »

lawlessone wrote: post #19
sandworm101 wrote: post #15

Earlier quoted context omitted.

>>> It will never replace GNSS. It will have to. That is the point. This isn't about better in-car navigation. The big money behind quantum gyroscopes is the potential to guide submarines/aircraft/missiles in times of war when the GNSS systems are down or otherwise unreliable, just like the best of traditional gyroscopes. Dead reckoning is a legitimate means of navigation, but there are also some aspects where actual…

Fair point, this would fit quite snugly on a ship or a sub. the real ones will probably smaller. I wonder will having more than one improve accuracy.

You could combine it with another IMU using a Kalman filter and improve accuracy that way.

Re: London Underground hosts tests for 'quantum compass' that could replace GPS

#49

Post by hi-v-rocknroll »

refulgentis wrote: post #42
hi-v-rocknroll wrote: post #26

Earlier quoted context omitted.

GPS can and was miniaturized. LRGs and QGs aren't for retail use because they're very expensive, bulky, and largely unnecessary.

F(T) != F(T+1) I, for one, am glad to see people working to innovate along well-trodden paths.

Yes, for their relevant applications. If you were a commercial spelunker or were the Ukrainian army needing to lob missiles into Russia that were impervious to encrypted GPS jamming, then you would gladly welcome your quantum overlords. Neither LRG or QG are ever going to be made into MEMS devices shoved into an iPhone. Its application is dead reckoning. For the use-case of navigation underground useable by everyday people, Skyhook-like services that rely on 5G UWB microcells are the most likely evolution beyond relying on Wi-Fi SSIDs and conventional cell towers for tower-assisted GNSS.

Re: London Underground hosts tests for 'quantum compass' that could replace GPS

#50

Post by 4gotunameagain »

porphyra wrote: post #9

I remember doing laser cooling of rubidium atoms in physics class. It's really cool how it works: * Rubidium will absorb photons of a certain wavelength and re-emit it in a random direction. Since photons have momentum, it will get some net momentum change from absorbing photons all coming from a particular direction, but the re-emissions are in random directions so they have net zero momentum. * Shine laser light at…

Does it mean that using this mechanism you can only achieve cooling for a narrow temperature range ?

As I assume you cannot shine laser light at a spread spectrum to capture all the possible ΔT

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