3 ms·

Success in teleporting light and solidifying it: Faster than the speed of light

8 points by rmason 2y ago

sinuhe69 2y ago
In sci-fi, a scene is well known: the departing spaceship keeps on board a collections of entangled particles with its peers on earth. Communications underway are realized through encoding and decoding the states of the entangled particles. This way they can communicate with command in real-time even over a vast distance, where the ship needed many years or even decades to go. It’s especially useful in battle scenarios.
- mr_toad 2y ago
  (Un)fortunately this doesn’t actually work - without the ability to control the waveform collapse all you can ‘transmit’ is random data.
  - kbrkbr 2y ago
    But couldn't you agree on a code in advance that does not rely on the content transmitted, but on the number of entangled particles for which the collapse takes place?
    - warpspin 2y ago
      And how would you test whether the collapse has taken place? This does not work. You either measure something and thereby collapse it, or you do not touch the stuff. You cannot find out via measurement whether the other side measured already.
ryankrage77 2y ago
I can't wrap my head around how you confirm the results, when any measurements are still limited by C. Even if you've got two atomic clocks in sync at each end of the experiment, surely you can only verify they are in sync as accurately as the latency between them? (e.g, if two clocks are 100 light-nanoseconds apart, you can only confirm they match to within 100 nanoseconds?). edit: If I'm understanding this article correctly, https://www.icfo.eu/news/2177/long-distance-quantum-teleportation-enabled-by-multiplexed-quantum-memories-/ https://www.icfo.eu/news/2177/long-distance-quantum-teleport..., they are still limited by 'classical hardware', and the measurement of the entangled particle takes time. So this doesn't yet allow transferring information faster than C?
- rcxdude 2y ago
  For the first part you can do much better if the travel time between them is symmetrical: then you can use the time it takes a signal to travel and return in order to calibrate for the difference between them. This is how NTP works, for example. The limitation is a) the degree to which the travel time is symmetrical (strictly speaking we don't know that c is the same in all directions, but the universe would look the same to us if it wasn't, and in practice you can have systematic errors which cause asymmetry). and b) the jitter of your time of arrival/departure measurements. For the second part, yes. The "spooky action" is faster-than-light but it doesn't allow any information transfer. The concept that's been talked about here is being able to transfer quantum states around like data (think allowing two quantum computers to communicate without needing to go via a classical conversion). Like quantum computers, applications are likely limited and it's not going to mean crazy fast information transfer or anything that would obselete classical computers, at least in the forseeable future.
renox 2y ago
BS you can't use teleportation to transfer information faster than the speed of light. Maybe they can use 'quantum teleportation' to do something useful but this article doesn't explain what..

8 points by rmason 2y ago

In sci-fi, a scene is well known: the departing spaceship keeps on board a collections of entangled particles with its peers on earth. Communications underway are realized through encoding and decoding the states of the entangled particles. This way they can communicate with command in real-time even over a vast distance, where the ship needed many years or even decades to go. It’s especially useful in battle scenarios.

mr_toad 2y ago
(Un)fortunately this doesn’t actually work - without the ability to control the waveform collapse all you can ‘transmit’ is random data.
- kbrkbr 2y ago
  But couldn't you agree on a code in advance that does not rely on the content transmitted, but on the number of entangled particles for which the collapse takes place?
  - warpspin 2y ago
    And how would you test whether the collapse has taken place? This does not work. You either measure something and thereby collapse it, or you do not touch the stuff. You cannot find out via measurement whether the other side measured already.

ryankrage77 2y ago

I can't wrap my head around how you confirm the results, when any measurements are still limited by C. Even if you've got two atomic clocks in sync at each end of the experiment, surely you can only verify they are in sync as accurately as the latency between them? (e.g, if two clocks are 100 light-nanoseconds apart, you can only confirm they match to within 100 nanoseconds?). edit: If I'm understanding this article correctly, https://www.icfo.eu/news/2177/long-distance-quantum-teleportation-enabled-by-multiplexed-quantum-memories-/ https://www.icfo.eu/news/2177/long-distance-quantum-teleport..., they are still limited by 'classical hardware', and the measurement of the entangled particle takes time. So this doesn't yet allow transferring information faster than C?

rcxdude 2y ago
For the first part you can do much better if the travel time between them is symmetrical: then you can use the time it takes a signal to travel and return in order to calibrate for the difference between them. This is how NTP works, for example. The limitation is a) the degree to which the travel time is symmetrical (strictly speaking we don't know that c is the same in all directions, but the universe would look the same to us if it wasn't, and in practice you can have systematic errors which cause asymmetry). and b) the jitter of your time of arrival/departure measurements. For the second part, yes. The "spooky action" is faster-than-light but it doesn't allow any information transfer. The concept that's been talked about here is being able to transfer quantum states around like data (think allowing two quantum computers to communicate without needing to go via a classical conversion). Like quantum computers, applications are likely limited and it's not going to mean crazy fast information transfer or anything that would obselete classical computers, at least in the forseeable future.

renox 2y ago

BS you can't use teleportation to transfer information faster than the speed of light. Maybe they can use 'quantum teleportation' to do something useful but this article doesn't explain what..