Oooooh. Very science fiction. Only real.

Sporky

TLDR - the Chinese have successfully built an Earth-to-orbit quantum entanglement system, which enables hack-proof instant communications over significant distances. Which is/was pretty much sci-fi.

https://eandt.theiet.org/content/articles/2017/06/quantum-communications-established-between-ground-and-space/

fields5069

Wow! The way they describe it, wouldn't the next step be to act on the photons to produce the communication? I guess that requires more work, but basically you would produce a message at one end which would appear at the other, without being transmitted.

Or something.

Sporky

Mebbe.

Though if you've established a provably secure genuine one-time-pad for the encryption then the message would be utterly secure even over an open channel.

Axe_meister

If this technology could be mass produced in a small size, it would change the IT world massively. You'd be able to build a single instance of a computer (rather than a cluster), with a massive amount of CPUs across multiple cabinets (distance of even a few meters has a massive effect on inter CPU communication).
Disaster recovery sites can be placed at any distance without latency implications,

Rickyd

I can't believe Albert Einstein ever said "spooky action at a distance", but if he did, good on him.

Sporky

I'm sure I remember reading (but not understanding) something about instant communication having potential causality issues.

FX_Munkee

Rickyd said:

I can't believe Albert Einstein ever said "spooky action at a distance", but if he did, good on him.

IIRC he was trying to goad Neils Bohr about his Quantum mechanics theories. Basically he was saying it was bullshit because if it worked like Bohr described you'd have "spooky action a t a distance".
So he was wrong.

TheBlueWolf

Oooh, interesting

Sporky

In related news, Apple have announced the Tachyonic Anti-iPhone, enabling users to speak and (more importantly) post social media updates to their past selves.

stickyfiddle

Between this and both China and India pushing full-speed into solar power there's a chance things are looking up!

Ravenous

This isn't about instantaneous communication though is it?

It's just about proving whether a signal has been interrupted or read by an unauthorised person.

(This entanglement stuff does not actually allow faster than light communication, in other words... because you're just reading a bit that has already been transmitted by normal means.)

Sporky

Ravenous said:

This isn't about instantaneous communication though is it?

Not at this stage, but the entangled photons do switch state at exactly the same time, so it's not entirely unreasonable to think that you could scale the system up to provide instantaneous communication.

TimmyO

Ravenous said:

This isn't about instantaneous communication though is it?

It's just about proving whether a signal has been interrupted or read by an unauthorised person.

(This entanglement stuff does not actually allow faster than light communication, in other words... because you're just reading a bit that has already been transmitted by normal means.)

I think the point here is that it isn't transmitted. The state in one place changes at the same time as in the other. 

Similar to how gravity acts instantly at a distance, hence research into communication by graviton. 

ICBM

Sporky said:

Ravenous said:

This isn't about instantaneous communication though is it?

Not at this stage, but the entangled photons do switch state at exactly the same time, so it's not entirely unreasonable to think that you could scale the system up to provide instantaneous communication.

No, because (at least as I understand how it works, which is admittedly from about thirty years ago) you still have to send the 'receiving' photon to the destination, which can only be at the speed of light - even though once it has arrived, a change in state of the 'sender' does change the state of the 'receiver' instantaneously.

TimmyO said:

Similar to how gravity acts instantly at a distance, hence research into communication by graviton. 

No it doesn't - gravity is propagated at the speed of light.

Ravenous

Yeah it's not instantaneous communication - because if you read the state to see if the other guy has transmitted, you break the state.

In other words you don't automatically know when the other party has sent you a message, and attempting to check it breaks the entanglement by collapsing his particle.

I'm not an expert on this, but plenty of physics guys have written that this particular method does not allow faster than light communication.

(To be fair, the article isn't about that anyway, it's about the security applications which are very real.)

ICBM

Breaking news: Theresa May introduces bill to ban quantum physics on the grounds that terrorists will know when GCHQ is listening in on them.

Bridgehouse

FTL travel is already available.

My wife manages it every time my debit card gets taken out my wallet to buy something guitar related - she instantaneously appears to check what I'm up to

Sporky

Well stuff you all. I still want my laser-propelled jetpack.

Ravenous

Sporky said:

Well stuff you all. I still want my laser-propelled jetpack.

And you will get it yesterday

thecolourbox

I threw a tennis ball at you at the speed of light just now

digitalscream

Ravenous said:

Yeah it's not instantaneous communication - because if you read the state to see if the other guy has transmitted, you break the state.

In other words you don't automatically know when the other party has sent you a message, and attempting to check it breaks the entanglement by collapsing his particle.

I'm not an expert on this, but plenty of physics guys have written that this particular method does not allow faster than light communication.

(To be fair, the article isn't about that anyway, it's about the security applications which are very real.)

Does it actually break the entanglement, though? My understanding is that entanglement is bi-directional (in the case of two entangled particles). Attempting to measure the state at the "receiver" end won't result in a totally random change of state in the entangled pair, so if the result of that measurement is predictable (whether with one result or one of several results), then it shouldn't be impossible to come up with a handshake protocol which can take that into account, with an included margin of error; even if the possible results of every measurement are a (finite) array of possibilities, you could use multiple entangled particles at each end for parallel measurement and calculate the most probable intended "transmission".