First time user "can this optimization be solved with cvx"

Hello,

it is first time I use the software and I would like to know if this problem can be rewritten somehow to be solved with cvx, or otherway it would be awesome if you can indicate me a program to try to get the solution. I get the error message

   ??? Error using ==> maximize at 36
Disciplined convex programming error:
   Cannot maximize a(n) convex expression.

Error in ==> semi at 17
maximize(x1^2+x2^2+x3^2)

the code is the following

cvx_begin sdp

variables x0 x1 x2 x3 y1 y2 y3 y4 y5

x0==1/sqrt(3)

1/3+x1^2+x2^2+x3^2+y1^2+y2^2+y3^2+y4^2+y5^2<=1

x1==-x3 
y1==y5
y2==-y4 

x0*X0+x1*X1+x2*X2+x3*X3+y1*Y1+y2*Y2+y3*Y3+y4*Y4+y5*Y5>=0

maximize(x1^2+x2^2+x3^2)

cvx_end

X0, X1,…X3,Y1,…Y5,Z1…Z7 (in capital letters) are matrices (spherical tensors) I pretend the product with the variables in lowercase to be positive semidefinite a constraint as well as the other equalities/inequalities after the variable statement.

No, quadratic maximizations are not convex. Please see this answer) for more information on using CVX properly.

ok, you know if there are any other resources to try to solve a nonconvex problem like that or is it hopeless?