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Question: Since we know that quantum entanglement does not provide for FTL communication, then what _are_ some practical uses for it? Why does it continue to g

Question: Since we know that quantum entanglement does not provide for FTL communication, then what _are_ some practical uses for it? Why does it continue to get so much attention in research? This answer might be, "to learn more about quantum mechanics," but my impression is that entanglement is fairly well-understood in physics.

jxcole 15y ago
Imagine if this could be used for communication (probably not, but you never know). That means you could have communication between two mechanical entities at the opposite sides of the earth without worrying about pesky radio wave things like line of sight and increased signal strength requirements over a distance. But a more appropriate answer is that there probably could be some sort of application, but unless we start building stuff we won't know what we're capable of and will be unable to engineer cool gizmos that use it.
- pasbesoin 15y ago
  I'm just skimming comments and haven't fully absorbed the context, but even without FTL, being able to communicate "directly" (e.g. "through" the Earth) would significantly reduce signal travel time, compared to running around the Earth on fiber or, longer yet, via bounced radio waves. For one, financial market traders would have a field day with such.
ww520 15y ago
Secret communication channel? I don't know how easy to intercept quantum entanglement. I seem to remember the quantum state would collapse if it's eavesdropped.
JoeAltmaier 15y ago
how about sharing a private key? Share 256 quantum bits, both 'realize' the bits, now you share a private key.
jessriedel 15y ago
The experiments are cool for two reasons: First, they helps us learn about and control decoherence, which is the primary obstacle to building a quantum computer. Decoherence is the reason everything doesn't behave quantum mechanically all the time, and its strength generally grows exponentially with the size of the system being studied. Building a useful quantum computer will require suppressing decoherence for order 100 qubits. Second, these experiments test quantum mechanics in new physical regimes where it might break (to be superseded by new physics). Just like one will find a discrepancy with Newtonian mechanics if one starts doing experiments near the speed of light, the suspicion is that quantum mechanics might breakdown when applied to large objects. People who are unsatisfied with the interpretation of quantum mechanics are especially interested in this possibility.

jxcole 15y ago

Imagine if this could be used for communication (probably not, but you never know). That means you could have communication between two mechanical entities at the opposite sides of the earth without worrying about pesky radio wave things like line of sight and increased signal strength requirements over a distance. But a more appropriate answer is that there probably could be some sort of application, but unless we start building stuff we won't know what we're capable of and will be unable to engineer cool gizmos that use it.

pasbesoin 15y ago
I'm just skimming comments and haven't fully absorbed the context, but even without FTL, being able to communicate "directly" (e.g. "through" the Earth) would significantly reduce signal travel time, compared to running around the Earth on fiber or, longer yet, via bounced radio waves. For one, financial market traders would have a field day with such.

ww520 15y ago

Secret communication channel? I don't know how easy to intercept quantum entanglement. I seem to remember the quantum state would collapse if it's eavesdropped.

JoeAltmaier 15y ago

how about sharing a private key? Share 256 quantum bits, both 'realize' the bits, now you share a private key.

jessriedel 15y ago

The experiments are cool for two reasons: First, they helps us learn about and control decoherence, which is the primary obstacle to building a quantum computer. Decoherence is the reason everything doesn't behave quantum mechanically all the time, and its strength generally grows exponentially with the size of the system being studied. Building a useful quantum computer will require suppressing decoherence for order 100 qubits. Second, these experiments test quantum mechanics in new physical regimes where it might break (to be superseded by new physics). Just like one will find a discrepancy with Newtonian mechanics if one starts doing experiments near the speed of light, the suspicion is that quantum mechanics might breakdown when applied to large objects. People who are unsatisfied with the interpretation of quantum mechanics are especially interested in this possibility.