Vaccum-chamber quantum sensor device could allow GPS-free navigation • Hacker News Board

Re: Vaccum-chamber quantum sensor device could allow GPS-free navigation

#81

Post by avsteele » Sun, Nov 14, 2021, 5:46 PM UTC

brabel wrote: post #60

chana_masala wrote: post #27

Earlier quoted context omitted.

HackerNews amazes me with how for nearly any topic there will be deep expertise in the thread. Thank you for sharing

The OP seems to know something, but I wouldn't go as far as taking the comment above as coming from an "expert"... the fact they feel confident to make recommendations about improvements on the chamber without even reading the paper actually tells me they are just armchair expert.

I am an expert. I have a PhD in experimental atomic physics. My work thesis work was on laser cooled atoms and ions. I have multiple publications in this topic area^. I started and run a company that is making the first commercial instruments that rely on laser-cooled atoms.^^

There is nothing wrong with making few conversational comments without being aware of the details in a particular paper. This is how scientists talk to each other BTW. If I was at a conference with the authors I'd say something similar to the OP above, then they'd agree or disagree.

^https://scholar.google.com/citations?user=mBN1xwcAAAAJ&hl=en

^^https://www.zerok.com

Re: Vaccum-chamber quantum sensor device could allow GPS-free navigation

#82

Post by avsteele » Sun, Nov 14, 2021, 6:09 PM UTC

horstbort wrote: post #69

avsteele wrote: post #25

The innovation here appear to be the chamber. (caveat: I still need to read the paper). A few thoughts follow. They are going for a UHV***, probably Still a lot of other work to do though. I see a table full of optics to make the MOT*. Also see a pair of anti-Helmholtz coils for the magnetic field. They could maybe replace those coils (which probably drive a few amps) with permanent magnets (assuming they don't need…

Permanent magnets are typically a no-go, because these sensors employ matter-wave interferometry, i.e. interference between atoms. Those unfortunately do not only react to gravity, but also to magnet fields, so these need to be suppressed as far as possible, especially gradients. And yes, this will absolutely be a pulsed design. I think, the breakthrough here is that they maintain a decent vacuum even without NEGs, w…

Great, thanks for the info

Re: Vaccum-chamber quantum sensor device could allow GPS-free navigation

#83

Post by errcorrectcode » Sun, Nov 14, 2021, 11:45 PM UTC

rjeli wrote: post #40

errcorrectcode wrote: post #16

How is this an improvement over other INS like LRG? INS mechanisms suffer from the same problem: that they only detect linear or rotational acceleration. To reach position, double integration must be performed, which rapidly accumulates error (drift) because velocity and position both have to be maintained to calculate the next position. Disclaimer: Trimble Nav alum

even worse, your (single) integrated gyro estimate must then be fed back into your double integrated accel filter to subtract gravity and further compound errors :)

Relativistic effects suck. GPS has to consider it when determining a fix too.

Re: Vaccum-chamber quantum sensor device could allow GPS-free navigation

#84

Post by kragen » Mon, Nov 15, 2021, 12:57 AM UTC

Fronzie wrote: post #53

kragen wrote: post #45

Earlier quoted context omitted.

Does passive pumping mean a chamber full of baked zeolite or something that's then chilled to adsorb all the gas? I guess I should read the paper too, but I don't have a copy.

Or even without the chilling. CRT televisions had zeolite as vacuum pump as well. They kept vacuum for up to decades.

I think CRTs were mostly manufactured using conventional high-vacuum pumps with moving parts or liquids, not sorption pumps. They didn't normally include a pump in the cathode-ray tube itself; the pump stayed at the factory. And I think you're mistaken that the CRTs ever included any zeolite. Perhaps you're confusing zeolites with getters, which react irreversibly with any stray molecules that manage to get into the vacuum?

Re: Vaccum-chamber quantum sensor device could allow GPS-free navigation

#85

Post by sbierwagen » Mon, Nov 15, 2021, 4:33 AM UTC

TheOtherHobbes wrote: post #73

baq wrote: post #65

Earlier quoted context omitted.

Civilian GPS. Milspec encrypted FHSS or whatever are they using not so much unless you flood the whole spectrum.

"The whole spectrum" for GPS FHSS being a relatively tiny frequency range. So still trivial to jam. There are physical restrictions on transmitter aerials which make really wide FHSS impossibly difficult. Especially from a satellite. So GPS still transmits on the same standard 5 frequencies, with some special codings. The antijamming features work a little differently. If you know a random code sequence you can use v…

In the military context, violence is an option. Powerful radio transmitters are vulnerable to anti-radiation missiles: https://en.wikipedia.org/wiki/Anti-radiation_missile In a free fire zone a GPS jammer would have a lifespan measured in minutes. A hypothetical conflict with a near-peer would involve a lot of jam and counter-jam drones destroying each other, until both sides run out of equipment.

A more interesting attack would be jamming the M code and then spoofing the data on the civilian band, which is one hypothesis for what happened to the RQ-170 that Iran soft-ish landed: https://en.wikipedia.org/wiki/Iran%E2%80%93U.S._RQ-170_incid...