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Comment by bostonsre | Hacker News Reader

Yea, I'm curious about this as well and what bit rate they were able to achieve. Wondering if it could be used for high frequency trading in the future since I would think neutrons going straight from source to destination would be faster than any other communication method (no idea if this would be too dangerous or not tho).

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Radio waves already travel at the speed of light, I'm curious what speed-up you're imagining? A shortcut through the earth is the only option I can think of to beat radio's latency.

Yeah, you would significant time on some routes (e.g. NYC to Sydney or whatever), but in practice, the modulation time is probably going to kill you even if the neutrinos make it there faster. In the most extreme case (antipodal communication), the neutrinos take 43 ms to traverse the Earth and radio takes 67 ms to go around the Earth (ok, in practice a bit more since your fastest path would be via LEO satellites, and each hop adds a bit of latency, but it could be made small). But RF signals have MHz-GHz of bandwidth and huge SNR.

To take advantage of being 20 ms early, you'd need to be able to detect neutrinos at greater than 50 Hz from the other side of the world. For context, the planned 40 kton DUNE far detector a mere 1300 km from the world's most powerful neutrino beam at Fermilab, will have a neutrino rate from the beam of a few a day. So yes, highly impractical.

If you managed to crack the detection problem, you’d still likely be so saturated with solar / background neutrinos as to confound any real prospect of a signal.

There are two handles on this: reconstructing the energy/direction and making sure it's consistent with the beam and gating on the beam duty cycle (since at least the beams I'm familiar with produce neutrinos in short bunches, but I'm no expert).

You can also add modulation to the beam to encode more information to help discriminate against backgrounds but that might require even more rate...

You're taking about neutrinos, but the original comment was about neutrons; I think that must add another layer of infeasibility (or was a typo).

indeed, a sibling was talking about neutrinos and somehow I got mixed up where it started.

Radio waves in a vacuum travel at c. They move more slowly in things like copper. Light in fiber cables travel at about 2/3 c so a neutrino beam would be faster and potentially have a shorter distance by going through the earth. Actually designing and implementing a communications system using neutrinos is an exercise left to the reader.

With neutrons, no. They’re slow, isotropic and thermalize easily.

With neutrinos that’d be a different story. They travel at the speed of light (or just below it - depends who you ask) and they aren't readily absorbed by anything. Therefore they can travel through the earth instead of around it.

Problem?

Generation, modulation and detection of neutrinos.

> They’re slow, isotropic

Not necessarily, if produced with an accelerator. (Potentially a nuisance to gamma-ray spectroscopists, generating spurious anisotropic scattering peaks.) Otherwise, yes.

https://arxiv.org/abs/1203.2847

Yep, I was still asleep, good call.

I would be very surprised if neutrons travel faster than a microwave beam.

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