alt.hn

5/19/2025 at 9:34:23 AM

Mini-satellite paves the way for quantum messaging anywhere on Earth

 https://www.nature.com/articles/d41586-025-00581-7

by bookofjoe

5/22/2025 at 2:47:26 PM

"QKD is already used by banks and governments to transmit keys over fibre optics. But these cables absorb photons, limiting the distance over which the signal can travel."

Does hollow-core fibre suffer the same limitation?

by ortusdux

5/22/2025 at 3:18:13 PM

"QKD is already used by banks and governments to transmit keys over fibre optics."

I wonder what specific uses they mean. It's kind of hard to believe those are "serious" use-cases, going beyond demonstrations done for marketing reasons... Then again, as soon as you have a serious use-case, you don't tell anyone about it, so it's really hard to evaluate how much (if at all) this stuff is really used in practice.

by staunton

5/22/2025 at 4:08:36 PM

Quantum key distribution is a real thing. It's a very specific set of constraints that would make it generally attractive, though, namely not relying on networks of trust to function, maybe? Key distribution as a dumb pipe.

by rhdjsjebshjffn

5/22/2025 at 7:31:28 PM

I'm not asking if it's "a real thing". I'm asking if it's used anywhere, either commercially or -- in any case -- to encrypt actually sensitive data outside of tech demonstrations. I'm not aware of anything. China has a "qkd backbone" but if they're actually using it for anything is anyone's guess.

by staunton

5/22/2025 at 7:37:15 PM

This seems like a really dumb thing to emphasize for marketing ends outside of actual competency. But what else is new!

by rhdjsjebshjffn

5/22/2025 at 7:39:29 PM

I'm having trouble parsing your comment... What is a dumb thing? Who is emphasizing what?

by staunton

5/22/2025 at 10:57:45 PM

Ah, understandable.

> what is a dumb thing?

Emphasizing quantum key control. In the situations where it's really relevant you don't need buy-in from investors, the value is evident.

Sayonara!

by rhdjsjebshjffn

5/22/2025 at 2:56:55 PM

Yes, hollow-core fibers also attenuate light.

by 0_____0

5/22/2025 at 3:59:34 PM

Can someone else who’s more of an expert or well read in the area explain the following to me? I thought quantum computing requires very low temperatures and highly controlled environments, and that’s why it’s not commonly available (cost is, of course, another huge barrier). In this case, does the satellite conform to those requirements or is it something else? Do both the sending and receiving systems conform to those physical requirements? Can this system be deployed almost anywhere on earth at a low cost?

Other than money, what are the non-negotiable requirements for such a system to be deployed and to work as expected? What is the exact breakthrough here?

by AnonC

5/22/2025 at 4:07:59 PM

This is about quantum messaging not quantum computers. They don't have the same requirements.

However its pretty useless. QKD, does basically the same thing as the diffie-helman protocol, except with less math assumptions. Like diffie-helman it protects against passive evesdroppers but not active man in the middle. Any real system is going to have to use traditional crypto for active MITM protection, and if you are already using traditional crypto, might as well use it for the whole thing.

In essence this is a cool science experiment but doesn't really offer meaningful improvements over traditional crypto methods.

by bawolff

5/22/2025 at 3:58:46 PM

Key distribution is already solved until someone can actually solve a large discrete logarithm problem with a quantum computer.

You cannot use this mechanism to send messages, only to agree on a secret that neither party chooses.

by noqc

5/22/2025 at 6:54:58 PM

Even if someone can solve discrete log, we have other algorithms like kyber.

QKD also isn't safe against (active) MITM attacks, which is kind of important.

by bawolff

5/22/2025 at 3:50:32 PM

this is impressive stuff -- I wonder for military applications how it will change military logistics ?

by dzonga

5/22/2025 at 3:51:13 PM

one thing is for sure, the next world-war they are just going to take out every satellite in the first 5 minutes

the micro-debris will make orbits impossible for the next century

and that's assuming they don't use EMP from orbit to take out ground communications too like starfish prime

by ck2

5/23/2025 at 9:27:16 AM

Probably easier at some point to simply target the primary ground stations and operations rooms.

by verzali

5/22/2025 at 3:57:28 PM

That is a better case scenario than immediate nuclear annihilation.

by RajT88

5/22/2025 at 4:37:40 PM

I think there is a dangerous misunderstanding that the population of earth could survive even a small number of nukes being used anywhere on the planet

It would be a slow-moving but certain mass-extinction event

A single modern nuke is 30-80 times more powerful than Hiroshima

And then look at the socio-economic devastation of something like Covid

by ck2

5/22/2025 at 7:46:03 PM

I guess you're talking about "nuclear winter", where the ash from the nuclear explosions gets into the upper atmosphere, blocks some of the sunlight and leads to a global famine.

I'm not sure what's "a small number of nukes" in your book. Last I read about it, estimates suggest e.g. India and Pakistan dropping their entire arsenals on each other would indeed cause a nuclear winter.

by staunton

5/22/2025 at 5:48:42 PM

Go look at the Nevada Test Site on Google maps. About 1000 nukes were set off there. Las Vegas is only about 100 miles away and by all accounts seems to be thriving.

In a nuclear attack, it's unlikely "we'll" be fine, but someone will be.

by nancyminusone

5/23/2025 at 4:04:55 PM

What on earth are you downplaying

There never ever has been an above-ground test of a modern enhanced hydrogen bomb in the USA

The Bikini Atoll test in the 1950s using 75 year old technology killed people via radiation over 130 miles away

Modern ICBMs carry several much more powerful warheads than that

Even a few of them would make life on earth a permanent hell like peak covid pandemic but forever

Even the "smallest" nuclear war would be one-and-we're-done event

Eventually some tyrant on their deathbed will do it though

by ck2

5/23/2025 at 5:14:48 PM

So hold on. You are saying Tsar Bomba would have potentially been an extinction event at ground level?

Holy shit.

by RajT88

5/22/2025 at 4:20:44 PM

That's nothing new really, late cold war wargames have satellites like the RORSATs playing a big role, and that's when anti-satellite weapon development really became a thing.

Low LEO will mostly clear out in a few years. And for really important satellites that matter a lot no matter what the cost, they can still be used. You just have to accept a higher rate of attrition.

by lupusreal