Why measuring the first qubit in a Bell state doesn't determine the second qubit's outcome

[Baggio]

The four bell states are

1: (|00>+|11>)(2)^-0.5
2: (|00>-|11>)(2)^-0.5
3: (|01>+|10>)(2)^-0.5
4: (|01>-|10>)(2)^-0.5

I'm looking at super dense coding and the way i thought of it at first was that if a measurement of the first qubit was made then if we consider the first bell state (1) if 0 is the value obtained then the system if forced into the state |00> so that measurement of the second qubit yields 0 with certainty..

Now take (2) if we measure the first qubit and we get 0 then apparently measurement of the 2nd qubit yields 1 with certainty.. So my way of thinking isn't correct lol

Can someone clarify?

 

[marlon]

Seems to me you are really into QIT...

Check out this site of John Preskill. All the answers are in the links to lecture notes, they are highly recommended. I studied quantum info theory from these lectures at college...
http://www.theory.caltech.edu/~preskill/ph219/
marlon

 

[Baggio]

I'm doing a project on Quantum computing :D

 

[marlon]

well, you will find everything in them notes...feel free to ask more questions though

marlon