"Exercise 7.2" uu = (1,0,0,0) ud = (0,1,0,0) du = (0,0,1,0) dd = (0,0,0,1) sigmaz = ((1,0),(0,-1)) taux = ((0,1),(1,0)) I = ((1,0),(0,1)) S = kronecker(sigmaz,I) T = kronecker(I,taux) "Verify matrix elements" check(dot(uu,S,T,uu) == 0) check(dot(uu,S,T,ud) == 1) check(dot(uu,S,T,du) == 0) check(dot(uu,S,T,dd) == 0) check(dot(ud,S,T,uu) == 1) check(dot(ud,S,T,ud) == 0) check(dot(ud,S,T,du) == 0) check(dot(ud,S,T,dd) == 0) check(dot(du,S,T,uu) == 0) check(dot(du,S,T,ud) == 0) check(dot(du,S,T,du) == 0) check(dot(du,S,T,dd) == -1) check(dot(dd,S,T,uu) == 0) check(dot(dd,S,T,ud) == 0) check(dot(dd,S,T,du) == -1) check(dot(dd,S,T,dd) == 0) "ok" Run