The idea behind making it easy to log into sites on your phone easily is nice.

But QR codes are probably a bad way of going about it. The average user just doesn't know what to do with QR codes, and they have poor engagement (at least if you're targeting this at non-Asian countries). How often have you ever seen someone scanning a QR code? They're particularly a waste of space on advertising--where that space could be used to place a URL that people know what to do with.

Perhaps a better way to go about enabling this login process is asking for their mobile number, and then just SMSing them a link to click.