Rails 3.1 + Paperclip + jQuery fileupload

I've been looking for a way to set up Ruby on Rails 3.1 with Paperclip and jQuery fileupload. Looking at a tutorial at jQuery fileupload page I got the system set up but I can't find a way to make paperclip process the uploaded file.

Here's what I have (in short):

# model
has_attached_file :photo ...

# view
= form_for @user, :html => {:multipart => true} do |f|
  f.file_field :photo, :multiple => true
  f.submit

# controller
def create
  @user = User.new params[:user]
  if @user.save
    render :json => [...]
end

If I inspect submitted data I get all user properties in params[:user] and params[:user][:photo] which is ActionDispatch::Http::UploadedFile. When @user.save is called the image doesn't get processed or saved.

A clue, tutorial or a solution would be much appreciated!