Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

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|cite|improve this question

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|cite|improve this answer
Certainly it is not allowed for the measurement to gain information about the state. However, this by itself doesn't necessarily require equally likely measurement outcomes. – Dan Stahlke Nov 5 '12 at 13:25

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.