The use of "antithesis"

Your use of "to" is correct. However, one would take issue with your use of the article, 'an'.

The word 'antithesis' is to mean the exact opposite of something. Meaning, there can be only one exact opposite. So if you're going to use antithesis in a sentence, it should be written as 'the antithesis' rather than 'an antithesis', as there shouldn't exist more than one antithesis.

Yes, the expression an antithesis to is a correct expression meaning "the opposite of":

From Nietzsche and Ethics:

• I hope to show two things: that Nietzsche characterizes his immoralist position as an extension of rather than as an antithesis to a moralist one, and that Nietzsche offers a teleological position different from any of the familiar ones.

Usage note of "antithesis" from M-W :

• Writers and speechmakers use the traditional pattern known as antithesis for its resounding effect; John Kennedy's famous "ask not what your country can do for you—ask what you can do for your country" is an example.
• But antithesis normally means simply "opposite". Thus, war is the antithesis of peace, wealth is the antithesis of poverty, and love is the antithesis of hate. Holding two antithetical ideas in one's head at the same time—for example, that you're the sole master of your fate but also the helpless victim of your terrible upbringing—is so common as to be almost normal.