Curtains for locality in QM?
Posted: Thu Oct 17, 2019 6:38 am
Tried unsuccessfully, via both comment and private email, to get feedback from the presenter Derek Muller re the following vid at his YT Veritasium site:
Quantum Entanglement & Spooky Action at a Distance
https://www.youtube.com/watch?v=ZuvK-od647c
In particular, that portion from ~ 1:06 - 3:10. Just that from ~ 2:20-2:40 is most relevant here. Fixed detector angles - each orthogonal to incident particle spin. It's clear such an experiment cannot involve photons as annihilation of such (e.g. orthogonally oriented polarizers) would not allow continued propagation. So e.g. spin 1/2 massive particles are assumed. Presumably something involving say a cascaded Mach-Zender setup can achieve such a result.
Whatever the physical apparatus details, the claimed result - perfect anti-correlation of measured spins, yet purely random measurements at each detector, is NOT simply a consequence of overall angular momentum conservation of the particle pair, as Derek wrongly asserted. That's because momentum conservation should be independently obeyed during angular momentum exchange i.e. particle-detector interaction at each detector INDEPENDENT of what happens at the other one. IF locality in QM holds!
Directly implying zero average correlation of spin measurements. Contrary to experiment which (sans inevitable non-ideal detector efficiencies), yields perfect anti-correlation of measured spins - every time. Which result while consistent with overall conserved particle-pair angular momentum, also clearly transcends it.
NO SUBTLE STATISTICAL ARGUMENTS TO INVOKE HERE!!
So, either Derek has his facts wrong re the setup and measurement results claimed, or it's true and imo any hope of locality holding in QM has vanished for good.
Anyone here aware of a preferably non-paywalled article detailing and experimentally confirming in particular 2:20-2:40 in above linked vid?
Quantum Entanglement & Spooky Action at a Distance
https://www.youtube.com/watch?v=ZuvK-od647c
In particular, that portion from ~ 1:06 - 3:10. Just that from ~ 2:20-2:40 is most relevant here. Fixed detector angles - each orthogonal to incident particle spin. It's clear such an experiment cannot involve photons as annihilation of such (e.g. orthogonally oriented polarizers) would not allow continued propagation. So e.g. spin 1/2 massive particles are assumed. Presumably something involving say a cascaded Mach-Zender setup can achieve such a result.
Whatever the physical apparatus details, the claimed result - perfect anti-correlation of measured spins, yet purely random measurements at each detector, is NOT simply a consequence of overall angular momentum conservation of the particle pair, as Derek wrongly asserted. That's because momentum conservation should be independently obeyed during angular momentum exchange i.e. particle-detector interaction at each detector INDEPENDENT of what happens at the other one. IF locality in QM holds!
Directly implying zero average correlation of spin measurements. Contrary to experiment which (sans inevitable non-ideal detector efficiencies), yields perfect anti-correlation of measured spins - every time. Which result while consistent with overall conserved particle-pair angular momentum, also clearly transcends it.
NO SUBTLE STATISTICAL ARGUMENTS TO INVOKE HERE!!
So, either Derek has his facts wrong re the setup and measurement results claimed, or it's true and imo any hope of locality holding in QM has vanished for good.
Anyone here aware of a preferably non-paywalled article detailing and experimentally confirming in particular 2:20-2:40 in above linked vid?