Quantum Teleportation Achieved Over Internet For The First Time

I thought the whole point of entangled communication is that you didn’t need to “send” anything. It automatically flips the entangled bit on the other end, all that “spooky action at a distance” bidness. Why do the need to “send” entangled photons?
- I've heard this explanation of it once from a physicist: Imagine you have a photograph. You rip that photograph in half. Now you put both halves into envelopes and mix them up. At this point, you don't know which half is in which envelope. Now you send one of the envelopes to Australia. You open your half. Because you see that you have the left half of the photograph, you gain instant knowledge that the right half is in Australia.
  With quanta, you can for example have a subatomic particle which decays into two quanta and then you know those quanta to have certain similar properties. As Wikipedia puts it:
  For instance, a spin-zero particle could decay into a pair of spin-1/2 particles. If there is no orbital angular momentum, the total spin angular momentum after this decay must be zero (by the conservation of angular momentum). Whenever the first particle is measured to be spin up on some axis, the other, when measured on the same axis, is always found to be spin down.
  https://en.wikipedia.org/wiki/Quantum_entanglement#Meaning_of_entanglement
  
  are the ripped photographs duplicates since changes on one effects the other im confused, like does ripping create two of the same
- You need to prep by sending the entangled particles (photons in this case). The spooky action is when you act on 1, you also act on the other. The useful bit is the uniqueness of the link. It cannot be intercepted without it being obvious and detectable.
  Think of it like voodoo dolls. It works at a distance, but you need to make the voodoo doll using a bit of the target, then send/take it elsewhere to stab.
  
  I'm pretty ignorant of physics, but isn't it only certain kinds of ways of acting on the first particle that "affect" the other, namely actions that measure a property of one particle that is correlated with the same property's value on the other? At first you don't know the value of either but you know they're correlated; but then when you measure and collapse the wave function on one and discovered a value for the property, you have automatically collapsed the wave function on the other too, yielding a predictably correlated value. If it were just any kind of action that affects the other particle, you'd be able to use it to sent information instantaneously, which you can't do. So it's not quite like how people imagine voodoo dolls: do something to the doll (make a change to it) and the person feels the effect. But perhaps someone who studies this stuff can help clarify.
  
  but voodoo dolls dont really work, do they?
- The "spooky action" is really just the determination of a particle's spin on one side meaning you already know the other particle will have an opposite spin. This probably violates locality because you gain knowledge about something that's non-local from a quantum perspective, even though entangled particles have to start local (there are opposing interpretations, like the de Broglie-Bohm). While in fiction this might suggest that changing the state of one particle simultaneously changes the other, in real life this just means extra information you mathematically shouldn't have, and doesn't really lead to FTL information transmission. What it does mean is that if you want secure communications you can use entangled particles to generate a secret key, determining the spin of them on either side, and you can be sure that they haven't been tampered with and that the other side of the communication will be equal and opposite. It's essentially a one-time pad.
- Quantum physicist here. Your idea is effectively correct, but the issue lies in generating entanglement at a distance, which is a gargantuan task. You can't start with two qubits (in the current discussion the photons are qubits, holders of quantum information) and simply proclaim them to be entangled over long distances (even centimeters can be considered long in the quantum realm). One of the more promising methods to achieve entanglement at a distance is to create entangled photons locally in your friendly neighborhood lab, and send them on their merry way. Photons are incredibly good at travelling far. When they have reached their destination you are free to do the next complicated part, the 'spooky action at a distance' as you call it ;) I just call it magic.
  The two standardized method of sending photons over earthly distances is either a) via air (e.g., lasers, radiowaves or satellite communication) or b) via fibre optics. Since the fibre optics network is so developed across the globe, quantum information engineers would love to tap into that infrastructure - which is the main motivation for the work done in the main article. Here, they proved that the entanglement survives the journey through the optical cable, which was expected (but not a given) for short distances. Entanglement is sensitive business and is lost very easily. 30 km of travel through an optical cable can be considered very, very long based on these premises - but also around the upper limit of what can be achieved without significant advances of quantum repeaters which replaces the functionality of amplifiers in traditional optical fibre networks.

Someone smarter than me, please go ahead and explain how this is going to be used to make life worse for all of us, probably in a deeply disturbing political reality that screams "the world Quinn from Sliders slid into and had to jump early because fuck this timeline"
- Monkeys learned to send signals faster. Now monkeys can bomb other monkeys they don't like faster.
- It could actually be a good thing, since it opens up the possibility of unsnoopable channels of communication, using encryption that would be disrupted by any attempt to intercept it.
  
  Also the ability to crack any of our current encryption almost instantly...
- You sound quite miserable, maybe you should stop thinking like this

TLDR: Researchers were able to send and receive entangled photons over a fiber optic cable that was simultaneously carrying a classical (non-quantum) signal typical of high speed telecommunications. They managed to accomplish this without the classical signal significantly interfering with the quantum measurements.
This was all done in a laboratory using a combination of standard telecommunications equipment for the classical signal and specialized equipment for the quantum signal. It was NOT done on a fiber carrying real internet traffic as the article would suggest.
- IIUC, quantum entanglement at a distance provides for faster than light/instant communication of state changes. High frequency trading, and dark orderbooks, is the only known economic application (space communications a far off application). I'm not sure why article avoided talking about this purpose.
  
  You don't understand correctly. Entangled particles do not allow for faster than light communication.
  
  While the entangled photons may be thought of as changing state simultaneously, in practice, it's not possible to use this to convey information, as doing so would break causality, and effect would be able to happen before its cause. Remember that what is commonly termed 'the speed of light' is actually better expressed as 'the speed of causality'. The most useful application of what this experiment performed would be in the area of quantum cryptography.
  
  that's not how that works, quantum entanglement can not be used to transmit information and thus doesn't violate causality
  
  it doesn’t work like that
- Correct, but still amazing because it means quantum internet is achievable over existing infrastructure. Not needing to lay down all new lines around the world for quantum transmissions will mean it gets adopted much faster. Even if specialized equipment is needed on either end of the cable, the hope/assumption would be that specialized equipment on either end will become cheaper as tech advances and scales upward - still a long ways off but cut down significantly.
  
  There are still massive hurdles for using optical fibre networks for quantum information transmission. The biggest lies in attenuation, where information is lost as the optical signal traverses the fibre. This is an exponential decay, so the signal is lost very quickly for longer distances. This is also the case for normal fibre communication, but these signals can be amplified using conventional amplifiers (aka repeaters in some fields), which are conveniently placed every 80 km or so in order to boost the signal. In contrast, quantum states can not be amplified in a similar manner and have to rely on quantum repeaters which, well, are more of a theoretical concept at this point in time.
  So, while the specialized equipment you refer to is indeed needed at both ends, the real challenge still lies in the quantum repeaters. Fortunately, satellite based communication is not as heavily punished by attenuation and would require fewer repeating steps (as compared to fibres) to transmit a quantum state from one end of the globe to the other. A handful of few repetition steps is a lot less daunting then the several hundreds that would be required for globe-scale quantum transmissions via fibre.
  
  Yeah it's absolutely an awesome accomplishment, it just bugs me whenever articles spread straight up false information.
- What's the upshot of this, even if the article's hyperbole is accurate? I'm assuming it's not as spooky or sci-fi as the terminology sounds to a monkey like me.
  
  It shows that it's possible to send entangled photons over existing fiber infrastructure without building something totally new, which as I understand it has applications in cryptography, secure communications, and quantum computing.
- That’s a common problem with these titles. If you want to make them short and snappy, you’ll either end up with something vague or straight up incorrect.

Bet
Edit: it seems I will be loosing that bet.