matrix exponntial

hello 

i am new to maxima and actually looking for a cas that is capable of
calculating matrix exponentials (exp(iHt)) like they  appear in time
evolution operations in quantum mechanics. can maxima do this for me. 

when i tried myself i.e.:   exp(%I*I_z);

                    with:   I_z:matrix([1,0],[0,-1]);
                
                   i get:   [   %I	       ]
                            [ %E	  1    ]
                            [	          - %I ]
                            [  1        %E     ]
                    
              but expect:   [   %I	       ]
                            [ %E	  0    ]
                            [	          - %I ]
                            [  0        %E     ]


thanks in advance 

matthias