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

Tube trains could navigate the Underground using the rules of Quantum Physics

ianvisits.co.uk

Post reply on HN
Print view View original

41–50 of 83 posts

Re: Tube trains could navigate the Underground using the rules of Quantum Physics

#41

Post by defrost »

circuit10 wrote: post #27
ulfw wrote: post #21

Earlier quoted context omitted.

How about an RFID chip (costs nothing) on every sleeper. Little database and you know exactly where you are. Accurate a few centimeters

Or maybe a camera underneath the train? It could be the same kind of thing used in optical mice, or just count the sleepers

Not bad, but practically have you seen the underside of many trains?

The spit up of grease, leaves, metal particulate from rail and wheel grind, etc gets pretty thick.

The vision challenge is to cheaply and effectively keep a clean lens.

There's a similar challenge in monitoring production conveyor belts in mineral processing - vibration, tempreture, rocks kick about, dust make for a savage environment.

Re: Tube trains could navigate the Underground using the rules of Quantum Physics

#42

Post by avianlyric »

123pie123 wrote: post #31

Call me sceptical, but I suspect if this works very well it will be used in weapons. Which then leads me to think the whole thing is a smoke screen, not sure why

100%, but smoke screen is over selling it. From the article

> The project is being carried out in collaboration with Transport for London, QinetiQ, PA Consulting, Imperial College London and University of Sussex.

QinetiQ is a UK weapons developer, probably the UKs largest. So the defence angle isn’t really being hidden.

Older articles on this project from elsewhere outline the defence angle even more explicitly:

https://www.theguardian.com/science/article/2024/jun/15/lond...

But IanVisits is a transport focused blog, so the article has a transport focus, rather than a defence focus.

As to why any of this is happening on the underground, that’s pretty simple. Tube trains are a good real world test bed for this technology. Shove your quantum box on an existing train, drive it through the existing tunnels a few times as part of a normal tube service. Compare the run result and validate how accurate your technology is.

It’s a lot cheaper than putting it on a boat or a submarine. Not to mention Imperial College London is based in… London. They’re literally a five minute walk from a tube station.

Re: Tube trains could navigate the Underground using the rules of Quantum Physics

#44

Post by jojobas »

cameronh90 wrote: post #19
wiradikusuma wrote: post #14

Don't trains run on a fixed path, meaning we can use more traditional "positioning systems" like, umm, math? Or placing passive sensors or paint a big number on the wall?

Maths isn't a sensor technology. Wheels slip, air pressure fluctuates, rotary counters misread, errors accumulate, so better raw data could get you a more precise estimate of your current position. Various position technologies are already in use (e.g. "balise") but they have their limits if you're after cm-level accuracy. That said, I'm not buying that quantum INS is required for this over more established technique…

An experimental cryogenic device doesn't sound very good in terms of reliability. A train could have a few free rubber-coated wheels dedicated for precise odometry, there could be cameras with optical flow/reference markers on the tunnel walls every so often, virtually anything seems to be better than sinking millions in quantum devices.

Re: Tube trains could navigate the Underground using the rules of Quantum Physics

#46

Post by avianlyric »

dariosalvi78 wrote: post #25
Traster wrote: post #6

It's kind of annoying that they don't go into specifics about why this is good. The problem with traditional accelerometers is that the error accumulates, and so even small errors accumulate. The article doesn't really address what makes this different - and in fact I don't think it is different. You're still just measuring acceleration using a sensor and that sensor will have errors that accumulate. So the question…

the accumulation is due to integration when converting acceleration to distance, not the accelerometer itself

The accumulation might be from the integration, but the error is clearly from the accelerometers. Smaller error means smaller accumulated error, which means your magic box is usefully accurate for longer.

Re: Tube trains could navigate the Underground using the rules of Quantum Physics

#47

Post by avianlyric »

cameronh90 wrote: post #19
wiradikusuma wrote: post #14

Don't trains run on a fixed path, meaning we can use more traditional "positioning systems" like, umm, math? Or placing passive sensors or paint a big number on the wall?

Maths isn't a sensor technology. Wheels slip, air pressure fluctuates, rotary counters misread, errors accumulate, so better raw data could get you a more precise estimate of your current position. Various position technologies are already in use (e.g. "balise") but they have their limits if you're after cm-level accuracy. That said, I'm not buying that quantum INS is required for this over more established technique…

> so I wonder if the tube stuff is just a weak public cover for the military/civil emergency applications that make the technology actually interesting.

The project is quite explicitly a defence project. IanVisits is just a transport blog, so the article focus on the transport aspect of this project. But reporting else where makes it quite clear this a defence project.

https://www.theguardian.com/science/article/2024/jun/15/lond...

The only reasons for the Tube being involved is as a test bed for the technology. It’s cheaper to put this box on a train and test it, than it is to put it on a boat or a submarine. It’s also handy that the researchers involved are based in London, so the commute to their test bed is nice and short.

Re: Tube trains could navigate the Underground using the rules of Quantum Physics

#48

Post by 123pie123 »

avianlyric wrote: post #42
123pie123 wrote: post #31

Call me sceptical, but I suspect if this works very well it will be used in weapons. Which then leads me to think the whole thing is a smoke screen, not sure why

100%, but smoke screen is over selling it. From the article > The project is being carried out in collaboration with Transport for London, QinetiQ, PA Consulting, Imperial College London and University of Sussex. QinetiQ is a UK weapons developer, probably the UKs largest. So the defence angle isn’t really being hidden. Older articles on this project from elsewhere outline the defence angle even more explicitly: http…

I had missed the collaboration list,

being tested on trains makes complete sense

Re: Tube trains could navigate the Underground using the rules of Quantum Physics

#49

Post by y04nn »

This is a weird application for such sensors. The train may be used as a test platform. DARPA launched a program to develop quantum sensors that are reliable outside the lab recently [1].

[1] https://www.nextbigfuture.com/2025/10/darpa-developing-quant...

Re: Tube trains could navigate the Underground using the rules of Quantum Physics

#50

Post by rsynnott »

wewewedxfgdf wrote: post #40

You might be at Victoria Station, but there's a slim but tangible chance you are in fact in Paddington. We won't know until someone looks at you. Until then you are on every station possible in the underground sorted of smeared out into a probability wave.

... Mornington Crescent!
Post reply on HN