Unable to perform assignment because the size of the left side is 4-by-4 and the size of the right side is 2-by-4.

Hello,

I am trying to create block diagonal if dimension d is greater than 2. However I have this error:

Unable to perform assignment because the size of the left side is 4-by-4 and the size of the right side is 2-by-4.

My code is here:

function [A,B] = CH2d(d)
    A=zeros(d,d,2,d);
    B=A;
    projectors_of_sigma_x = [1/sqrt(2)*[1;1],1/sqrt(2)*[1;-1]];
    for k = 1:d
        for l =1:d 
           if d > 2 
             A(:,:,1,k) = blkdiag(A(:,:,1,k));
          end   
           A(:,:,1,k)=repmat(projectors_of_sigma_x(:,k),1,d);
        end
    end
end

[Ameer Hamza]

What are you trying to do at this line

A(:,:,1,k)=repmat(projectors_of_sigma_x(:,k),1,d);

If you add a breakpoint at this line, you can see that the dimensions on right side are different from dimension of A(:,:,1,k).

[Gözde Üstün]

I am trying to give the value (1/sqrt(2)*[1;1]) to element of matrix A(:,:,1,1) value (1/sqrt(2)*[1;-1]) to element of matrix A(:,:,1,2)

For d = 2 everything is great And my output is correct, you can see my output here:

a(:,:,1,1) =

    0.7071    0.7071
   0.7071     0.7071

Now I want to do that : if d is even and greater than 2 (for instance d =4), my output should be this:

   0.7071     0,7071    0       0
   0,7071     0.7071    0       0
   0          0         0.7071  0.7071
   0          0         0.7071  0.7071

[Ameer Hamza]

See my answer to your other similar question.

[Gözde Üstün]

Thanks and I replied you via other similar question