-1

So based on this thread : Why is quantum entanglement considered to be an active link between particles?

which was asked 7 years ago, the answer says

"Entanglement is being presented as an "active link" only because most people - including authors of popular (and sometimes even unpopular, using the very words of Sidney Coleman) books and articles - don't understand quantum mechanics"

if so, then how has china developed a technology where they transmitted data via Earth-to-space quantum entanglement?

https://phys.org/news/2017-07-physicists-transmit-earth-to-space-quantum-entanglement.html

also some other countries have said that they developed a technology where they transmitted data in a less of a distance

so am i missing something here?

also not sure how is this the duplicate of my previous question when my previous question is the duplicate of a thread that was posted 7 years ago and now I'm responding to that, basically if someone asks a question even after 7 years no one can ask a question about that thread?

Glorfindel
  • 1,424
  • 4
  • 17
  • 21
John P
  • 91

1 Answers1

4

China did not transmit information via quantum entanglement. Rather, they ensured that the same information existed at two places. There is a subtle difference between the two situations. Two entangled particles share a state. Observe the state of one, and you then know the state of the other -- but you do not change or affect the state of the other. The challenge in establishing quantum keys for encryption is to ensure that the transmitted particles: 1) are entangled with their partner particles that stay behind, and 2) retain their entanglement until their states are measured at their destination. Then, when the state of the transmitted particle and its stay-at-home partner are both measured, we know that the measured states will be the same (or opposite, depending on the type of entanglement).

S. McGrew
  • 25,240
  • 3
  • 32
  • 81