Can we see who voted our question's?
No, you can not. That would undermine the ability to vote without fear of retribution !
I would hope that in cases where someone downvotes, they would leave a comment - but we can't insist on this.
SE does keep track of votes. An example of this is reconciliation to correct REP when questions/answers are deleted or they close/merge accounts. Can this data not be found using the SE data queries tool? There are queries that some mods use to discover sock puppet accounts which includes looking up mass upvotes and/or the correlation of upvotes between two users.
I agree though, no one should know who up/down voted as it would just be bad for both the user and the community.