how to plot a defined function ?

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reza hamzeh
reza hamzeh on 22 Oct 2019
Commented: Christine Tobler on 28 Oct 2019
hi. i coded 2 functions. now i want to plot N(t) versus T. but it gives me errors. plz help me to do that.
clear;
T=0:0.1:14;
plot(T,N(t))
function pa = partialtranspos(T)
J=1;B=4;d=4;
s0=[1 0;0 1];
sx=[0 1;1 0];
sy=[0 -1i;1i 0];
sz=[1 0;0 -1];
H = 2*J*kron(sz,sz)+B*(kron(sz,s0)+kron(s0,sz))+d*(kron(sx,sy)-kron(sy,sx));
ro = expm(-H/T)/trace(expm(-H/T));
pa = [ro(1,1) ro(2,1) ro(1,3) ro(2,3);ro(1,2) ro(2,2) ro(1,4) ro(2,4);
ro(3,1) ro(4,1) ro(3,3) ro(4,3);ro(3,2) ro(4,2) ro(3,4) ro(4,4)];
end
function ne = N(T)
ne=0.5*(sum(abs(eig(partialtranspose(T))))-1);
end
  1 Comment
Adam
Adam on 22 Oct 2019
If it gives you errors then post the error messages here to make it easier for people to help.

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Answers (1)

reza hamzeh
reza hamzeh on 22 Oct 2019
these are the errors. plz help me.
Error using /
Matrix dimensions must agree.
Error in fortest>partialtranspose (line 13)
ro = expm(-H/T)/trace(expm(-H/T));
Error in fortest>N (line 20)
ne=0.5*(sum(abs(eig(partialtranspose(T))))-1);
Error in fortest (line 4)
plot(T,N(T))
  1 Comment
Christine Tobler
Christine Tobler on 28 Oct 2019
H is a square matrix, while T is a row vector. The operation H / T is not supported, because this is trying to compute X which solves the linear system X*T = H, which is not possible when H is of size 4-by-4 and T is of size 1-by-141.

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