Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Qubits probability

  1. Apr 15, 2008 #1
    1. The problem statement, all variables and given/known data
    http://img249.imageshack.us/img249/4476/46715318ov5.jpg [Broken]

    3. The attempt at a solution

    I know to calculate the pr we square the number in front of the state.

    e.g) for state psi 00, the pr is (1/root(2))^2

    But for state psi 01, do I include the imaginary number part? That is, do I calculate the square of (1+i/2root(2))?

    Last edited by a moderator: May 3, 2017
  2. jcsd
  3. Apr 15, 2008 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    The probability is the square of the magnitude of the coefficient (if the wavefunction is normalized). So the formula is that the probability of measuring E_{01} for example is

    [tex] \vert C_{01} \vert^2 = C_{01} \times C_{01}^* [/tex]

    which is obviousy a rel number.
    This should be familiar to you. Of course, when the coefficient is real, this becomes simply the ordinary square of the coefficient.
    Last edited by a moderator: May 3, 2017
  4. Apr 16, 2008 #3
    Ah so its the complex conjugate. Makes sense!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook