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London Underground hosts tests for 'quantum compass' that could replace GPS
- mojomark 2y agoThis work proposes a more accurate means of dead reckoning using a quantum-level source for inertial measurement in an Inertial Navitagation System (INS). Useful for robotic navigation underground, inside RF-shielded structures, on other planetary bodies, or underwater. The issue of localization error drift reduction from INS's seems very much like a Moore's law challenge, though I haven't mapped out the advances in intertial measurement accuracy/precision by year to see if the projected rate is similar or not. In any event, pretty cool; we'll see if this one pans out.
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- tomtom1337 2y agoIs the idea here to accurately track the acceleration that the sensor is undergoing? So, if you started at a known location with velocity=0 and integrate the acceleration data wrt time twice, you get the relative change in position and can thus know your new location?
- Someone 2y agoLooks like it, given (FTA): “The aim of the Imperial College project […] is to create a device that […] does not rely on receiving external signals.” and “At the heart of the quantum compass – which could be ready for widespread use in a few years – is a device known as an accelerometer that can measure how an object’s velocity changes” So, it’s advanced dead reckoning (https://en.wikipedia.org/wiki/Dead_reckoning https://en.wikipedia.org/wiki/Dead_reckoning). I wonder whether they really don’t use external signals at all or occasionally use them to correct for accumulation of errors. For example, the ability to detect that velocity w.r.t. earth is zero would help with that. (Of course, for the London subway, the fact that trains tend to follow the tracks can help, if the system knows the track layout. That probably is the simplest way to prevent accumulation of errors, but then, do they really need such a complex accelerometer?)
- haiku2077 2y agoThey're just using the subway as a convenient moving lab. The real-world application of this technology is for military submarines and marine drones.
- gus_massa 2y agoMy guess is that calculating the initial velocity is hard, so it will drift slowly. Perhapa keep the device on a table for a minute to ensure v=0, or sync it at every subway stop.
- vsskanth 2y agoHighly accurate dead reckoning basically. I wonder how it compares to the other method of mapping subterranean patterns and matching to them.
- porphyra 2y agoI 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 it from all directions but at a wavelength slightly longer than the wavelength at which it will absorb. Now, if the rubidium atom is moving, the light hitting it head on will be Doppler shifted into the wavelength that it absorbs, slowing it down, whereas the other light wouldn't affect it. So, no matter how it is moving, it will slow down. Rubidium is a good material since it has an S shell on the outside as though it were a big hydrogen atom, but it is so massive that it is a lot nicer to work with for this application.
- tanseydavid 2y ago>> It's really cool how it works Pun intended? Please say yes.
- contravariant 2y agoMaybe 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.
- gridspy 2y agoMost 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.
- porphyra 2y agoTheoretically you might be able to do it with some VCSELs, not sure though...
- nine_k 2y agoMaybe not down to a pea size, but possibly down to an orange size. Lasers are tiny, and "every direction" does not involve many of them, it involves some fiber optics, I suppose. The bulk of the device would be thermal insulation, and a volume for liquid helium + some piping to let it evaporate, and to replenish it.
- hi-v-rocknroll 2y agoJournalists 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.
- matt123456789 2y agoFrom 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.
- hi-v-rocknroll 2y agoBecause 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.
- ForHackernews 2y ago> 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.
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- hi-v-rocknroll 2y agoThere is no magic involved, so there will still be errors and limitations. https://physics.stackexchange.com/questions/679991/which-is-more-accurate-a-quantum-gyroscope-or-ring-laser-gyroscope https://physics.stackexchange.com/questions/679991/which-is-...
- ben_w 2y agoSo far as I can tell, it's this accelerometer: https://www.imperial.ac.uk/news/188973/quantum-compass-could-allow-navigation-without/ https://www.imperial.ac.uk/news/188973/quantum-compass-could... (2018, I'm unclear what's changed since then?)
- surfingdino 2y agoRussia launched a satellite capable of destroying GPS satellites and suddenly funding became available?
- aeyes 2y agoThere has been constant development trying to improve accelerometer and gyros. There are even commercial products, for example: https://m2lasers.com/quantum-accelerometer.html https://m2lasers.com/quantum-accelerometer.html
- jiggawatts 2y agoThey claim 10E-7 m/s/s precision, which is is about 60cm of drift in an hour, and up to 375 meters after a day. Obviously this won't work without re-calibrating to a known location at least a few times per day.
- Terr_ 2y agoAlso 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.
- surfingdino 2y agoThere 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.
- dejj 2y agoRelated: South-pointing chariot, 5th century BC https://en.wikipedia.org/wiki/South-pointing_chariot https://en.wikipedia.org/wiki/South-pointing_chariot
- lxgr 2y agoEven 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.
- lucb1e 2y agoEspecially with the word "compass" in the title, I figured they made an accurate map of the earth's magnetic field and would use that to avoid needing any satellites. Then I opened the comment thread... Come to think of it, the earth's magnetic pole shifts so I guess this isn't possible? Either way, "London Underground tests new dead reckoning system" would have been more accurate it sounds like
- echoangle 2y agoRegarding pole shift: you maybe could have multiple static measurement stations spread around which measure the current values at known positions and synchronize the data once per day to the trains. I’m not sure how you could even determine position just from magnetic field alone, surely there are multiple positions with the same magnetic conditions?
- lucb1e 2y agoMaybe, I don't know enough about magnetic fields to say much. In my head they're directional so you'd know how it's aligned and can measure how strong it is, and that might function similar to a gravity map, especially if you know where you're coming from: there may be two places on earth with the same amount of gravity, or in this case, the same magnetic field strength, but if those places aren't next to each other that may still be tolerable depending on the system requirements.
- mizzao 2y agoSo, basically an extremely accurate dead reckoning system?
- rjeli 2y agoWith high enough accelerometer accuracy, you need to start adjusting your subtracted gravity vector with maps, right?
- greesil 2y agoIf this was developed in the US this would immediately be ITAR restricted
- pkaye 2y agoWhat are you implying? That the UK technology will be publicly available for others countries to use?
- gravescale 2y agoIt's a shame all the cool stuff is all hidden in a white box, but I suppose it does look a bit like a Hollywood depiction of a homemade nuclear bomb so the British Transport Police would be getting a few panicked calls if it were in a perspex box. There's also no step-free access at South Kensington or Gloucester Road, so that must be a fun struggle for a grad student!
- Havoc 2y agoRussian shenanigans was my first thought too, but the real game changer is probably: >under ground and under water Tunnels, fiber cables, pipelines, submarines, autonomous subs etc would all benefit from less location guessing. (Tunnels tbf you can do with lasers already)
- ysofunny 2y agoso this is how by the time of Dune they'll say the compass is english instead of chinese like i was told?
- dsign 2y agoThe science is cool, but I wonder if a specialized popular science magazine of yester-year would do a better job at presenting it? "We made a high-precision accelerometer that uses lasers and quantum effects; let me tell you everything about it." Right now, it reads more like "Dr. C has this very peculiar quirk when he goes to the London underground. Admittedly, it is not as bizarre as his habit of drinking coffee instead of tea, but going to the underground carrying an aluminum tube instead of a newspaper is just a tad flummoxing..."
- anovikov 2y agoThat smells like bs to me.
- justusthane 2y agoWhy? It's just an extremely accurate accelerometer. It still needs to be giving a known starting position. It doesn't replace GPS so much as augments it. Granted, the article isn't very clear on that.
- anovikov 2y agoYeah i understand the concept. But i am under an impression that those guys are just milking an easy source of dumb money this way.
- zafka 2y agoI realize no one would be allowed to tell me if I am correct, but this tech sounds like it is perfect for military use. I am guessing there is already a pretty polished version of this roaming the oceans now.
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- jdlyga 2y agomind the gap!
- guerby 2y agoThis will become more and more common, see https://rmi.org/insight/the-cleantech-revolution/ https://rmi.org/insight/the-cleantech-revolution/ Direct link to PDF: https://rmi.org/wp-content/uploads/dlm_uploads/2024/06/RMI-Cleantech-Revolution-pdf.pdf https://rmi.org/wp-content/uploads/dlm_uploads/2024/06/RMI-C...