devise authentication for other applications

I have a general question about Rails.

Currently I am responsible for developing a web, whose language is not determined yet.
But there has already been a Rails web app with devise authentication. My new web app is somewhat independent of this existing app, but authentications should be unified for user-convenience, I believe.

Is there anyway to use the authentication functionality of this Rails app for the new app? Kind of authentication API ?

I appreciate your help.