1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Reduced density matrix

  1. Sep 15, 2008 #1
    At the thermal equilibrium, the density matrix of a 2 spin-half system is given by:

    \mathbf{\rho} =
    e^{-(1+c)/T} & 0 & 0 & 0\\
    0 & cosh[(1-c)/T] & -sinh[(1-c)/T] & 0\\
    0 & -sinh[(1-c)/T] & cosh[(1-c)/T] & 0\\
    0 & 0 & 0 & e^{-(1+c)/T}


    where c is a parameter.

    How to find the reduced density matrix by tracing out the other spin?
    i.e. [tex]\rho_{1} = tr_{2}\rho[/tex]

    I only know how to find the reduced density matrix for a pure state, say like [tex]\frac{1}{\sqrt{2}}(\left|\downarrow\uparrow> - \left|\uparrow\downarrow> )[/tex]
    But for this given density matrix, i have no idea. Are there any equations that i can use? What's the procedure?
  2. jcsd
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Can you help with the solution or looking for help too?

Similar Discussions: Reduced density matrix
  1. Flux density (Replies: 0)

  2. Matrix problem (Replies: 0)

  3. Density matrix (Replies: 0)