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Results tagged with textbook-and-exercises
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user 26793
Applies to questions of primarily educational value - styled in the format similar to that found in textbook exercises. This tag should be applied to questions that are (1) stated in the form of an exercise and (2) at the level of basic quantum information textbooks.
1
vote
1
answer
75
views
How to take partial trace of a $n - 1$ qubit subsystem from a $n$ qubit system
I would like to calculate the expression
$$
\text{Tr}_2\left\{R^z \sigma\right\}\,,
$$
where
$$
\sigma = \rho \otimes |0\rangle \langle0|^{{\otimes}(n-1)}\,.
$$
Here
$$
R = \sum{\theta_m}G_m\,,$$
wher …
- 45
1
vote
1
answer
415
views
Can a unital channel not be mixed unitary?
How to prove that for a multi-qubit system a unital channel is not necessarily mixed unitary? This is Problem 8.3 in Nielsen and Chuang. Here's a snippet of the text:
Shall I need to take two paralle …
- 45