4 ms·

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

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.

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.