3 ms·

>this happens at less than the speed of light. Why can't it happen simultaneously? Why is distance relevant in this case?

by josu 10y ago

tgb 10y ago
As I always bring up in these threads, quantum teleportation requires the transmission of classical bits, which of course is done slower than the speed of light.
- jdmichal 10y ago
  As far as I know, ctrl-j [0] is correct. The quantum entangled state transfer may be instantaneous. However, this merely results in a correlation of measurements. In order to determine a correlation, you need to have both measurements to compare. This is the part that must be transferred classically. See my top-level post for more information [1]. [0] https://news.ycombinator.com/item?id=12548712 https://news.ycombinator.com/item?id=12548712 [1] https://news.ycombinator.com/item?id=12548733 https://news.ycombinator.com/item?id=12548733
  - tgb 10y ago
    The second photon that the first's state is being teleported to is constructed by performing certain operations on it and which ones are performed are determined by the two classical bits that are measured from the first photon (hence destroying the firsts's state). So from the first photon being destroyed to the second gaining its state, there must be a speed of light delay as those two classical bits are transmitted.
    - jdmichal 10y ago
      > So from the first photon being destroyed to the second gaining its state, there must be a speed of light delay as those two classical bits are transmitted. This is the part where you are potentially wrong. Entanglement is about correlation. In order to derive the original message, you need the local entangled state, along with data from the remote actor. You could then correlate this information to derive the original remote entangled state -- ie, some message. Of course, this is now useless to you, as they could have simply sent the original message and saved you the correlation step. However, I don't know of any reason that the local quantum state could not be measured prior to the arrival of the data from the remote actor. The math says that the measurable effect should happen instantaneously. But that data alone is not sufficient to derive a message.

>this happens at less than the speed of light. Why can't it happen simultaneously? Why is distance relevant in this case?

by josu 10y ago

>this happens at less than the speed of light. Why can't it happen simultaneously? Why is distance relevant in this case?

tgb 10y ago

As I always bring up in these threads, quantum teleportation requires the transmission of classical bits, which of course is done slower than the speed of light.

jdmichal 10y ago
As far as I know, ctrl-j [0] is correct. The quantum entangled state transfer may be instantaneous. However, this merely results in a correlation of measurements. In order to determine a correlation, you need to have both measurements to compare. This is the part that must be transferred classically. See my top-level post for more information [1]. [0] https://news.ycombinator.com/item?id=12548712 https://news.ycombinator.com/item?id=12548712 [1] https://news.ycombinator.com/item?id=12548733 https://news.ycombinator.com/item?id=12548733
- tgb 10y ago
  The second photon that the first's state is being teleported to is constructed by performing certain operations on it and which ones are performed are determined by the two classical bits that are measured from the first photon (hence destroying the firsts's state). So from the first photon being destroyed to the second gaining its state, there must be a speed of light delay as those two classical bits are transmitted.
  - jdmichal 10y ago
    > So from the first photon being destroyed to the second gaining its state, there must be a speed of light delay as those two classical bits are transmitted. This is the part where you are potentially wrong. Entanglement is about correlation. In order to derive the original message, you need the local entangled state, along with data from the remote actor. You could then correlate this information to derive the original remote entangled state -- ie, some message. Of course, this is now useless to you, as they could have simply sent the original message and saved you the correlation step. However, I don't know of any reason that the local quantum state could not be measured prior to the arrival of the data from the remote actor. The math says that the measurable effect should happen instantaneously. But that data alone is not sufficient to derive a message.