In the four maximally entangled two-qubit Bell states, what is the difference between the first and the second states, similarly, the difference between the third and the fourth states. What the different in signs mean( +,-)...
What does it mean when we say that the in the case of absence of a phase reference, the laser would produce a Poissonian mixture of number states?.. I got confused actually between the meaning of the phase in classical sense and quantum in this regard. Regards