Entangled Quantum States



John Bell brilliant theoretical physicist

He didnít 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 doesnít work with inequalities that any hidden variable theory would have to obey