Take the 2-minute tour ×  I've recently been introduced to the
basics of finite-dimensional quantum mechanics from a purely
mathematical point of view (with a quantum-information theme to
it). When discussing quantum teleportation, the professor made a
remark about how the fact that the probability of each Bell
state measurement outcome is 1/4 independently of the measured
state is fundamental for the protocol to work.  However, I fail
to see what the mathematical reason for this is. Is there an
easy explanation for this fact?  share|improve this question add
comment  1 Answer  When the probability is the same for all
teleported states, the Bell state measurement does not give us
any information about the teleported state. That is an important
feature of the quantum teleportation protocols. If we got some
partial information about the state, the teleportation fidelity
would be lower than in the case of no information being
revealed.  share|improve this answer Certainly it is not allowed
for the measurement to