Entangled Quantum States

John Bell brilliant theoretical physicist

He didn’t like quantum mechanics (thought it was rotten)

John wheeler thought that it was beautiful

Feynman: Quantum Mechanics deals with amplitudes for initial to final state

What's the amplitude for us to go from one to the other and specify the final state

Bohr: different experimental arrangements are part of the specification of the quantum mechanical process

Decoherence- as soon as you a macroscopic system with quantum mech. System, the state is much more complicated

EPR paradox- some system with angular momentum that can decay into an electron and a positron

Thought that quantum mechanics was incomplete

If we can determine a value of a property of that system then that was an element of reality

If electron is spin up, then positron is spin down

Sz is real

Sx is real

Spooky action at a distance, reality

Depends on what the other experimenter does

Bell shows that it doesn’t work with inequalities that any hidden variable theory would have to obey