Entanglement does not send a message
Entangled particles show correlations that no local classical story can match. Those correlations cannot be used to send information faster than light.
Established2 min read
Bell’s inequality is a cap on how coordinated two distant measurements can be if nothing spooky is involved. Aspect’s experiments, and the loophole-free tests of 2015, broke the cap. The outcomes are more coordinated than any local hidden-variable theory allows.
The no-communication theorem is the other half. Each observer, alone, sees a random list. Only when the lists are compared, at ordinary speed or slower, does the correlation appear. You cannot steer the other list by choosing how to measure yours. Nature is nonlocal in the correlations and stubbornly local in the mail.
Caveats
- ‘Loophole-free’ belongs to the 2015 experiments (Delft, NIST, Vienna), not to every earlier Bell test.
Sources
- 1Hensen B. et al.. Loophole-free Bell Inequality Violation Using Electron Spins Separated by 1.3 Kilometres. Nature 526, 2015.