Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

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

theguardian.com

Post reply on HN
Print view View original

31–40 of 146 posts

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

#31

Post by TooKool4This »

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.)

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 the inertial sensors an odometry solution might be adequate until an extero-receptive sensor can localize the sensor within an external frame.

This can shift the discussion from solving a problem that has no solution (i.e. how do I integrate a signal with white noise without any error) to an engineering problem (i.e. what error parameters allow the odometry to be accurate within x% over some timeframe).

There was interesting work DARPA was sponsoring around the above idea that you can read more about here: https://www.darpa.mil/program/micro-technology-for-positioni...

>The end goals of the TIMU program are the demonstration of a single-chip IMU which maintains an accumulated position error of less than 1 nmi/hour with device volume of less than 10 mm3 and power consumption of less than 200 mW.

(My job is related to estimating location of things).

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

#32

Post by akira2501 »

ForHackernews wrote: post #17
hi-v-rocknroll wrote: post #14

Earlier quoted context omitted.

Because it can't. There are always cumulative errors in INS. There is no way around this without external references, but then it's no longer inertial navigation and it's inertial-assisted navigation. An underground navigation system based on triangulation of UWB cells would be a better solution than some nonstarter project the size of a refrigerator that requires liquid nitrogen.

> There are always cumulative errors in INS. Is that necessarily true of this quantum thing? I know nothing about it except this article, theoretically if it kept track of exact Plank lengths or something, then there would be no errors to accumulate, right? Lots of the things that seem intuitively true break down in weird ways when dealing with quantum effects.

> theoretically if it kept track of exact Plank lengths or something,

Sure, just show me a way to measure something in terms of "exact Planck lengths" and we're money.

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

#33

Post by lxgr »

Even as somebody relatively familiar with inertial navigation, it took me almost the entire article to figure out that that's what this is doing.

I really wish the words "inertial navigation" or "dead reckoning" would have occurred at least once in the article, but obviously "quantum navigation" sounds much cooler and as an added bonus makes it sound more like magic than technology.

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

#34

Post by akira2501 »

Terr_ wrote: post #28
surfingdino wrote: post #20

Earlier quoted context omitted.

Russia launched a satellite capable of destroying GPS satellites and suddenly funding became available?

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 impacts to flights has to do with certain types of GPS coordinated instrument approaches for landings. Most of these runways have alternative approach strategies that can be used during jamming or other unavailability.

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

#35

Post by refulgentis »

akira2501 wrote: post #32
ForHackernews wrote: post #17

Earlier quoted context omitted.

> There are always cumulative errors in INS. Is that necessarily true of this quantum thing? I know nothing about it except this article, theoretically if it kept track of exact Plank lengths or something, then there would be no errors to accumulate, right? Lots of the things that seem intuitively true break down in weird ways when dealing with quantum effects.

> theoretically if it kept track of exact Plank lengths or something, Sure, just show me a way to measure something in terms of "exact Planck lengths" and we're money.

stares at TFA

Not really sure what to say, here.

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

#36

Post by contingencies »

hi-v-rocknroll wrote: post #14
matt123456789 wrote: post #12

Earlier quoted context omitted.

From the article: "This information, combined with the starting point of that object, allows its future positions to be calculated." It doesn’t go into the details of recalibration, I’ll give you that.

Because it can't. There are always cumulative errors in INS. There is no way around this without external references, but then it's no longer inertial navigation and it's inertial-assisted navigation. An underground navigation system based on triangulation of UWB cells would be a better solution than some nonstarter project the size of a refrigerator that requires liquid nitrogen.

Actually, in a train context, inertial is pretty damn high accuracy because you already have the world's best odometer showing (A) how many times your known size wheel has turned on your known track; and (B) you can test many axels simultaneously to ensure no slippage (I guess you wouldn't test the wheels as they move faster creating a higher frequency sampling requirement for ~no benefit whereas a dedicated axel feature could live within an environmental enclosure protected from dust and grime); (C) you are constantly doing exactly the same trip-segments over and over again.

So for a train with an offline positioning requirement, I'd suggest that an odometer based solution is close to ideal.

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

#37

Post by [deleted] »

sandworm101 wrote: post #15
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.

>>> 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…

[deleted]

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

#38

Post by contravariant »

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.

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

#39

Post by Terr_ »

surfingdino wrote: post #30
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.

There is no need to jam GLONASS. Russian planes are affected using other means--sanctions have cut them off from access to parts and maintenance. It's more impactful because all planes are affected by this, not just those that fly near the border of NATO countries.

I feel like that is mixing separate issues. The sanctions aren't because of the jamming and spoofing. If some other country started foisting the same pollution/sabotage onto its neighbors, those neighbors would still have a problem deciding on how to respond.

The main point is that the bar for someone breaking your navigation system has been lowered. It's not just something you'd expect in a small area or for a short time around an imminent violent confrontation, chronic disruption in a peaceful country is now A Thing That Happens.

That, in turn, changes the engineering considerations for how robust a product needs to be.

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

#40

Post by refulgentis »

hi-v-rocknroll wrote: post #25
ForHackernews wrote: post #17

Earlier quoted context omitted.

> There are always cumulative errors in INS. Is that necessarily true of this quantum thing? I know nothing about it except this article, theoretically if it kept track of exact Plank lengths or something, then there would be no errors to accumulate, right? Lots of the things that seem intuitively true break down in weird ways when dealing with quantum effects.

There is no magic involved, so there will still be errors and limitations. https://physics.stackexchange.com/questions/679991/which-is-...

TL;DR-TL;DR: says the opposite of your implied claim, "atom-gyros are set to outperform light-based gyros"

TL;DR: this is a StackExchange question with 1 answer, noting it is indeterminate if a quantum gyroscope would be more accurate than a laser-atom-based one.

It looks like you rushed through and missed that in this context, TFA is describing an atom gyro.

That leaves conversation at a point where either A) we assume the scientist interviewed knows what they're doing, or B) following your unstated lead, assume they're a crackpot and the whole article is irrelevant because they're untrustworthy, and thus in an ideal world, there's 0 comments on the article.

Post reply on HN