SolutionQCQINielsenChuang

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Exercise 2.32

2

The proof here for Exercise 2.32 appears to assume P^2=P implies P is a projector. I am not certain this is true (the converse is certainly true, a projector satisfies...

archmageirvine

clarkmiyamoto

Exercise 2.76

2

 I'm not sure about the correctness of the formalism, but this is my main idea: extend the smaller bases with null coefficients in the expansion in order to reach...

antodbb

(Hope to help adding more solutions!)

JacobHA

In the box,  This is wrong. A positive operator makes sure that it has non-negative eigenvalues. When performing $\sqrt A$, you need to sqrt the eigenvalues under the expression...

kunliu7

Hi, I believe in the solution given for 2.72 (1), the 1/2 factor in a and d is forgotten. So I believe it should be: If $\rho$ is positive, all...

jcwang111

Chapter 1 also contains 2 exercises. Although they are quite open in nature, I would have liked to see someone's attempt on answering them.

Aerylia

I believe a more general treatment will consider repeated singular values. In that situation, it was useful for me to notice that unitary matrices form a group, so left multiplication...

jiahai-feng

Although the square of the density operator $\rho^2$ is positive, and thus permits a spectral decomposition, the eigenvalues associated with that spectral decomposition are not necessarily the squares of the...

jjeffrey

added exercise 5.2

stilnat