|   | 1 |  initial version  | 
You should define Q as a QuaternionAlgebra over the symbolic ring SR instead of over the rationals:
sage: Q.<i,j,k> = QuaternionAlgebra(SR, -1, -1)
sage: q = a*i + b*j + c*k
sage: q
a*i + b*j + c*k
sage: q^2
-a^2 - b^2 - c^2
 Copyright Sage, 2010. Some rights reserved under creative commons license. Content on this site is licensed under a Creative Commons Attribution Share Alike 3.0 license.
 
                
                Copyright Sage, 2010. Some rights reserved under creative commons license. Content on this site is licensed under a Creative Commons Attribution Share Alike 3.0 license.