I don't think that will work. My public key is public. The ticket's public key is public. Right?
Thus, anyone can make QR codes that show the 2 public keys. It's trivial. This is the "showing a picture" scenerio I mentioned above. Anyone can show the right picture, especially since the picture that needs to be shown is public information.
Or just have your phone broadcast the public keys via radio to a turnstile.