It is really a good idea but unfortunately directly mapping interfaces as an entity attribute is not supported by JPA.
You can only map top level classes directly annotated with @Entity. This top level class may implement an interface though.
This feature has been requested and discussed for a long time.
Also take a look at this and this.
Depending on what you’re trying to accomplish, @Inheritance annotation with table-per-class strategy could be an option.
I hope it helps.