Is there a way to see who voted on your posts?
Is there any way for someone to find out who +1 a question or an answer?
Nope, voting on posts is anonymous.
Unless someone tells you explicitly that they voted, there is no way of finding out. Even moderators (diamonds next to their name) do not know who voted.
Theoretically, Stack Exchange employees can find out, as they have access to the underlying database, but as far as we know there is no UI that'll let anyone see voting breakdowns.
Votes are anonymous.
You can try to figure out who downvoted your question by correlating the exact time of the downvote with anyone who's reputation went down by 1 at the same time.